Category Archives: Post World War II


Martin XB-51 Attack Bomber

By William Pearce

In February 1946, the United States Army Air Force (AAF) sought design proposals for an attack aircraft to replace the Douglas A-26 Invader. The Glenn L. Martin Company (Martin) responded with its Model 234, a straight-wing aircraft of a rather conventional layout, except that the engine nacelle on each wing housed a turboprop and a turbojet engine. The Model 234 had a crew of six and was forecasted to carry 8,000 lb (3,629 kg) of ordinance over 800 miles (1,287 km).


The Martin XB-51 was a unique attack bomber designed at the dawn of the jet age. The first prototype is seen here with its original tail. Note the inlet for the fuselage-mounted engine. The dark square behind the canopy is a window over the radio operator. (Martin/USAF image)

Martin was awarded a contract to develop the Model 234 on 23 May 1946, and the aircraft was designated XA-45. A few weeks later, the AAF decided to discard the “Attack” category, and the XA-45 was subsequently redesignated XB-51. The AAF then requested new requirements for the XB-51 with an emphasis on speed. The AAF’s new desired specifications for the A-26 replacement was a top speed of 640 mph (1,030 km/h) and the ability to carry 4,000 lb (1,814 kg) of ordinance over 600 miles (966 km). The new requirements necessitated a complete redesign of the XB-51, which Martin completed and submitted to the AAF in February 1947. After slight modifications, the design was somewhat finalized by July 1947. The AAF ordered two prototypes, which were assigned serial numbers 46-685 and 46-686.

The Martin XB-51 was a radical departure from the firm’s previous aircraft designs. The XB-51 was an all-metal aircraft that featured a relatively large fuselage supported by relatively small swept wings. The aircraft had a crew of two and was powered by three General Electric J47-GE-13 engines, each developing 5,200 lbf (23.13 kN) of thrust. Two of the engines were mounted on short pylons attached to the lower sides of the aircraft in front of the wings. The third engine was buried in the extreme rear of the fuselage.


The XB-51 with its flaps up and its wing at an incidence of three degrees as the aircraft is rolled out on 4 September 1949. The circle on the side of the fuselage just behind the cockpit is a side window for the radio operator. There is no window mirrored on the left side of the aircraft. Note that the intake for the fuselage-mounted engine has its cover rotated closed. (Martin/USAF image)

The pilot sat in the front of the aircraft under what appeared to be a small canopy in contrast to the large fuselage. Behind the pilot and completely within the fuselage was the radio operator, who was also in charge of the short range navigation and bombing (SHORAN) system. The crew compartment was pressurized, and access was provided by a door on the left underside of the fuselage, between the pilot and radio operator’s stations. In case of an emergency, both crew were provided with upward firing ejection seats.

The engine housed in the rear fuselage was fed by an inlet duct located atop the fuselage. A rotating assembly was installed forward of the inlet to either cover the inlet with an aerodynamic fairing when the engine was not in use, or rotate to provide a duct to feed air to the engine. The rear engine could be shut down in flight to extend the aircraft’s range. When not in use, a door in the intake duct prevented the back flow of air through the rear engine. Large doors swung open beneath the fuselage to access the rear engine.


The first XB-51 with flaps down and its wing at an incidence of 7.5 degrees. Note that only one of the wingtip outrigger gears is touching the ground. (Martin/USAF image)

Mounted above the rear engine was the vertical stabilizer, with the horizontal stabilizer mounted to its top. Originally, the XB-51’s design had the horizontal stabilizer mounted midway up the vertical stabilizer, but the aircraft was not built with this configuration. The horizontal stabilizer was swept back 35 degrees, and its incidence could be changed for trimming. Two rocket assisted takeoff (RATO) bottles could be fitted to each side of the rear fuselage. The RATO packs would be ignited to shorten the XB-51’s takeoff distance, then discarded once the aircraft was in flight. Each bottle provided 1,000 lbf (4.44 kN) of thrust. Hydraulically operated air brakes were located on each side of the fuselage, under the intake for the rear engine. A braking parachute was housed in the left side of a fairing located below the rudder.

The XB-51 used tandem (bicycle) main gear that consisted of front and aft trucks, and outrigger wheels that deployed from the aircraft’s wingtips for support. Martin had used a similar gear arrangement for the straight-wing XB-48 jet medium bomber and had initially tested the setup using the Martin XB-26H, a B-26 Marauder specially modified for to test the tandem landing gear. The main trucks could swivel to counteract the aircraft’s yaw while taking off or landing with a crosswind.


Ordinance for the XB-51 that would fit in the bomb bay. From left to right, four 1,600 lb (726 kg) bombs, eight 5 in (127 mm) High Velocity Aircraft Rockets (HAVR), one 4,000 lb (1,814 kg) bomb, four 2,000 lb (907 kg) bombs, four 1,000 lb (454 kg) bombs, and nine 500 lb (227 kg) bombs. The 4,000 lb (1,814 kg) bomb required an enlarged bomb bay door. (Martin/USAF image)

The aircraft’s bomb bay was located in the fuselage between the main wheels. The bomb bay had a single rotating door to which the bomb load was attached. Opening the rotating door did not create any buffeting or require any speed restriction normally required by two conventional doors. In addition, the rotating door was removable and could be quickly replaced with another door already loaded with ordinance. The standard door could accommodate nine 500 lb (227 kg) bombs, four 1,000 lb (454 kg) bombs; four 1,600 lb (726 kg) bombs; or two 2,000 lb (907 kg) bombs. Two additional 2,000 lb (907 kg) bombs could be accommodated on exterior bomb racks mounted on the bottom of the door. A special enlarged door could be fitted to carry a single 4,000 lb (1,814 kg) bomb or a Mk 5 or Mk 7 nuclear bomb. The XB-51’s maximum bomb load was 10,400 lb (4,717 kg). Eight 5 in (127 mm) High Velocity Aircraft Rockets (HAVR) could be carried in the bomb bay in place of internal bombs.

Three fuel tanks were installed in the aircraft’s fuselage. The forward tank was located above the front main gear and held 640 US gal (2,426 L). The center and aft tanks were both located above the bomb bay and held 745 US gal (2,820 L) and 1,450 US gal (5,489 L) respectively. All the standard fuel tanks could be filled via a single fueling receptacle. A 160.5 US gal (607.6 L) water/alcohol tank to boost engine performance during takeoff was mounted between the front and center fuel tanks. Two 350 US gal (1,325 L) tanks could be carried in the bomb bay for ferrying the aircraft over long distances. The XB-51 had a total normal fuel capacity of 2,835 US gal (10,732 L), and 3,535 US gal (13,381 L) with the bomb bay tanks.


The XB-51 executing a high-performance takeoff provides a good view of the aircraft’s leading-edge slats and large flaps. No RATO bottles are fitted. (Martin/USAF image)

In the nose of the XB-51 were eight fixed 20 mm cannons with 160 rpg and a forward strike camera. The nose of the second XB-51 was detachable, and different noses could be fitted depending on the aircraft’s mission. In addition to the standard gun nose, other noses featured equipment for precision bombing and equipment for photo-reconnaissance. As standard, the XB-51 had a reconnaissance camera installed under the cockpit and a strike assessment camera installed in the lower rear fuselage.

With fuel, engines, and the main landing gear all housed in the fuselage, the XB-51’s mid-mounted wings were very thin. The wings were swept back 35 degrees and had six degrees of anhedral. Outrigger wheels deployed from the wingtips to steady the aircraft on the tandem main gear. Slats extended along the outer 70 percent of the wing’s leading edge. Large, slotted flaps covered 75 percent of the wings trailing edge, with small ailerons taking up 15 percent of the trailing edge. While the ailerons contributed to aircraft’s roll control, their main purpose was to provide feedback for the pilot. The majority of roll control was provided by spoilers positioned on the wing’s upper surface, just forward of the flaps. The spoilers extended about 40 percent of the wing’s span. The incidence of the entire wing could vary from 2 to 7.5 degrees and would automatically change with deployment of the flaps. The wing incidence increased at lower speeds to decrease the aircraft’s stall speed and make the aircraft assume the correct attitude for landing, which was with the nose high approximately six degrees. The tandem landing gear required the simultaneous touchdown of both the forward and aft trucks. To prevent the accumulation of ice, hot air was bled off from the engines, directed through a passageway in the wing’s leading edge, and exhausted out the wingtip.

The Martin XB-51 had a 53 ft 1 in (16.18 m) wingspan, was 85 ft 1 in (25.93 m) long, and was 17 ft 4 in (5.28 m) tall. The track between the outrigger landing gear was 49 ft 5 in (15.06 m). The aircraft had a top speed of 645 mph (1,038 km/h) at sea level and 580 mph (933 km/h) at 35,000 ft (10,668 m). Cruising speed was 532 mph (856 mph) at 35,000 ft (10,668 m), and the aircraft’s landing speed was around 140 mph (225 km/h). The XB-51’s initial rate of climb was 6,980 ft (35.5 m/s) at maximum power and 3,600 ft (18.3 m/s) at normal power. The service ceiling was 40,500 ft (12,344 m); normal range was 980 miles (1,577 km), and ferry range was 1,445 miles (2,326 km). The XB-51 had an empty weight of 30,906 lb (14,019 kg), a combat weight of 44,000 (19,958 kg), and a gross weight of 55,930 lb (25,369 kg).


The first XB-51 undergoing an engine run. The bullet fairing has been added to the tail. Note the covered ports in the nose for the 20 mm cannons. (Martin/USAF image)

On 24 February 1948, a mockup of the XB-51 was inspected by the United States Air Force (USAF), which had become a separate branch of the US Armed Forces on 18 September 1947. Construction of the first prototype (46-685) proceeded swiftly at the Martin plant in Middle River, Maryland, and the completed aircraft was rolled out on 4 September 1949. After completing ground tests, aircraft 46-685 made is first flight on 28 October 1949, piloted by Orville Edward ‘Pat’ Tibbs. Initial flight testing went well until the rear main gear collapsed after landing on 28 December. The aircraft was repaired and returned to flight status in early 1950. High-speed testing had revealed some vibrations with the tail and a tendency to Dutch roll. A bullet faring was added at the intersection of the horizontal and vertical stabilizers in March 1950 to mitigate the issues.

The second prototype (46-686) made its first flight on 17 April 1950, piloted by Frank Earl ‘Chris’ Christofferson. Although 46-686 was initially flown with the original tail, bullet fairings were soon added. Both aircraft were involved in numerous landing accidents, mostly attributed to the tandem landing gear and the pilot’s lack of familiarity with its nuances. Nose high landings resulted in tail strikes that damaged the aft fuselage. Nose low and hard landings resulted in the collapse or shearing of the front main gear. Despite the landing difficulties, pilots seemed to like the aircraft and its performance. While the XB-51 could perform rolls and outpace some fighters, the aircraft was not stressed for aggressive maneuvers.


Another image of the first XB-51 with its bullet tail fairing. Note the RATO bottles attached to the rear fuselage. The shield painted under the cockpit says “Air Force Flight Test Center.” (Martin/USAF image)

The USAF considered putting the XB-51 into production, but the role for which the aircraft was intended had changed again with the outbreak of the Korean War. Speed was no longer the main focus, and the USAF now desired an aircraft that could loiter in an area until needed by ground forces. The USAF compared the XB-51 against the North American AJ-1 Savage and B-45 Tornado, the Avro Canada CF-100 Canuck, and the English Electric Canberra. Under the new criteria, the USAF selected the Canberra as the winner in February 1951, and the XB-51 program was essentially cancelled. The Canberra had more than twice the range and loiter time of the XB-51. The following month, Martin was awarded a contract to build the Canberra as the B-57, and the rotary-style bomb bay pioneered on the XB-51 was installed on the B-57. Ultimately, 403 B-57 aircraft would be produced. Both XB-51 aircraft continued to be evaluated and tested. The two XB-51s underwent performance and armament tests at Edwards Air Force Base (AFB) in California and Elgin AFB in Florida.

On 9 May 1952, the second prototype XB-51 was destroyed at Edwards AFB when Major Neal Lathrop executed a roll at low altitude and collided with the ground. Lathrop was the sole occupant on board. At the time of the accident, 46-686 had accumulated 151 hours of flight time and had made 193 flights.


The second (left) and first (right) XB-51 aircraft at the Martin plant in Middle River. Both aircraft have the bullet tail fairings, and the second prototype (left) has RATO bottles attached. The Martin plant in the background still has the camouflage paint scheme applied during World War II. Compare the different flap and wing positions between the two aircraft. (Martin/USAF image)

The first prototype played the role of the “Gilbert XF-120” fighter in the 1956 movie “Toward the Unknown.” The movie was shot mostly at Edwards AFB in 1955. On 25 March 1956 the 46-685 was destroyed while taking off from El Paso Municipal (now International) Airport in Texas. The stop in El Paso was to refuel as the aircraft traveled from Edwards AFB to Eglin AFB. The accident occurred due to a premature rotation and subsequent stall. The radio operator, Staff Sergeant Wilbur R. Savage, was killed in the crash, and the pilot, Major James O. Rudolph, died of his injuries on 16 April 1956. The first XB-51 prototype had accumulated 432 hours and made 453 flights.

Performance of the Martin XB-51 had exceeded the manufacturer’s guarantees. However, the aircraft was designed and built at a time when USAF’s desires and priorities were rapidly shifting, and it turned out that the service did not really want the aircraft they had originally asked for. Pilots held the XB-51 in a high regard despite its demanding landing characteristics. Ultimately, the XB-51 faded into history as a short-lived experimental aircraft investigating a new direction at the dawn of the jet age.


The second (right) and first (left) XB-51 aircraft make a low pass over Martin Field on 11 October 1950. Note the shadows of the aircraft on the runway. (Martin/USAF image)

The Martin XB-51 by Scott Libis (1998)
“Martin XB-51” by Clive Richards, Wings of Fame Volume 14 (1999)
Martin Aircraft 1909–1950 by John R. Breihan, Stan Piet, and Roger S. Mason (1995)
Standard Aircraft Characteristics XB-51 by U.S. Air Force (11 July 1952)
Jane’s All the World’s Aircraft 1951-1952 by Leonard Bridgman (1951)
U.S. Bombers 1928 to 1980s by Lloyd S. Jones (1980)

Latecoere 631-03

Latécoère 631 Flying Boat Airliner

By William Pearce

On 12 March 1936, the civil aeronautics department of the French Air Ministry requested proposals for a commercial seaplane with a maximum weight of 88,185 lb (40,000 kg) and capable of carrying at least 20 passengers (with sleeping berths) and 1,100 lb (500 kg) of cargo 3,730 miles (6,000 km) against a 37 mph (60 km/h) headwind. In addition, the aircraft needed a normal cruising speed of 155 mph (250 km/h). This large passenger aircraft was to be used on transatlantic service to both North and South America. Marcel Moine, head engineer at Latécoère (Société Industrielle Latécoère, SILAT) had already been working on an aircraft to meet similar goals. In late 1935, Moine had designed an aircraft for service across the North Atlantic with a maximum weight of 142,200 lb (64,500 kg). However, the design was seen as too ambitious. Moine modified the design to meet the request issued in 1936, and the aircraft was proposed to the Air Ministry as the Latécoère 630.

Latecoere 631-04

The Latécoère 631 was one of the most impressive flying boats ever built. Unfortunately, its time had already passed before the aircraft could enter service. Laté 631-04 (fourth aircraft) F-BDRA is seen here, and it was the second of the type in service for Air France. Note the configuration of the flaps and ailerons.

The Laté 630 was an all-metal, six-engine flying boat with retractable floats. The 930 hp (694 kW), liquid-cooled Hispano Suiza 12 Ydrs was selected to power the 98,860 lb (44,842 kg) aircraft, which had a 187 ft (57.0 m) wingspan, was 117 ft 9 in (35.9 m) long, and had a range of 4,909 miles (7,900 km). On 15 November 1936, order 575/6 was issued for detailed design work of the Laté 630 and a model for wind tunnel tests. This was followed by order number 637/7 for a single Laté 630 prototype on 15 April 1937. However, the Air Ministry cancelled the Laté 630 on 22 July 1937, stating that advancements in aeronautics enabled the design and construction of a larger and more capable aircraft. Construction of the Potez-CAMS 161, which was designed under the same specifications as the Laté 630, was allowed to continue.

Taking aeronautical advancements into consideration, the Air Ministry issued an updated request for an aircraft with a maximum weight of 154,323 lb (70,000 kg) and capable of transporting 40 passengers and 11,000 lb (5,000 kg) of cargo with a normal cruising speed of over 186 mph (300 km/h). To meet the new requirements, Moine and Latécoère enlarged and repowered the Laté 630 design, creating the Laté 631. In October 1937, detailed design work and a wind tunnel model of the Laté 631 were ordered. Order number 597/8 for a single prototype was issued on 1 July 1938. A Lioré et Olivier H-49 (which became the SNCASE SE.200) prototype was also ordered under the same specification as the Laté 631.

The Latécoère 631 was an all-metal flying boat with a two-step hull. The monocoque fuselage consisted of an aluminum frame covered with aluminum sheeting. The interior of the hull was divided into numerous passenger compartments and included a lounge/bar under the radio/navigation room (may have been in the nose in some configurations) and a kitchen at the rear. The cockpit and radio/navigation room were located above the main passenger compartment and just ahead of the wings. The cockpit was positioned rather far back from the nose of the aircraft. Numerous access doors were provided, including in the nose, side of the cockpit, and in the sides of the fuselage.

Latecoere 631 cockpit

The cockpit of the Laté 631 was rather spacious. Note the six throttle levers suspended above the pilot’s seat. The copilot could not reach the levers, but the flight engineer had another set of throttles. The central pylon contained the trim wheels and controls for the floats and flaps. At left in the foreground is the navigation station, and the radio station is at right.

The high-mounted wing was blended to the top of the fuselage and carried the aircraft’s six engines in separate nacelles. The wing had two main spars and a false spar. Each wing consisted of an inner section with the engine nacelles and an outer section beyond the nacelles. The outer engine nacelle on each wing incorporated a retractable float that extended behind the wing’s trailing edge. Due to interference, the float needed to be at least partially deployed before the flaps could be lowered. A passageway in the wing’s leading edge was accessible from the radio/navigation room and allowed access to the engine nacelles. Each nacelle had two downward-opening doors just behind the engine that served as maintenance platforms. A section of the firewall was removable, allowing access to the back of the engine from within the nacelle. Between the inboard engine and the fuselage was a compartment in the wing’s leading edge designed to hold mail cargo.

Originally, 1,500 hp (1,119 kW) Gnôme Rhône 18P radial engines were selected to power the Laté 631. However, the availability of these engines was in question, and a switch to 1,600 hp (1,193 kW) Wright R-2600 radial engines was made. The Gnôme Rhône 14R and the Pratt & Whitney R-2800 were also considered, but the 14R was also unavailable, and the export of R-2800 engines was restricted. Each engine turned a three-blade, variable-pitch propeller that was 14 ft 1 in (4.3 m) in diameter and built by Ratier. Later, larger propellers were used, but sources disagree on their diameter—either 14 ft 5 in or 15 ft 1 in (4.4 m or 4.6 m). It is possible that both larger diameters were tried at various times.

At the rear of the aircraft were twin tails mounted to a horizontal stabilizer that had 16.7 degrees of dihedral. All control surfaces had an aluminum frame with a leading edge covered by aluminum. The rest of the control surface was fabric covered. Movement of the control surfaces was boosted by a servo-controlled electrohydraulic system, which could be disengaged by the pilot. The slotted aileron on each wing was split in the middle and consisted of an outer and an inner section. The ailerons also had Flettner servo tabs that were used to trim the aircraft and could be engaged to boost roll control.

Latecoere 631-01 German 63-11

Laté 631-01 (F-BAHG) in German markings as 63+11. The openings for the large passenger windows existed in the airframe but were covered on Laté 631-01. The prototype aircraft was destroyed during an allied attack while in German hands on Lake Constance in April 1944.

Six wing tanks carried 7,582 gallons (28,700 L) of fuel, and each tank fed one engine. During flight, these tanks were replenished by pumping fuel from six tanks in the hull that carried 5,785 gallons (21,900 L) of fuel. The Laté 631’s total fuel capacity was 13,367 gallons (50,600 L). Each engine had its own 111-gallon (422-L) oil tank.

The Latécoère 631 had a 188 ft 5 in (57.43 m) wingspan, was 142 ft 7 in (43.46 m) long, and was 33 ft 11 in (10.35 m) tall. The aircraft had a maximum speed of 245 mph (395 km/h) at 5,906 ft (1,800 m) and 224 mph (360 km/h) at sea level. Its cruising speed was 183 mph (295 km/h) at 1,640 ft (500 m). The Laté 631 had an empty weight of 89,265 lb (40,490 kg) and a maximum weight of 163,347 lb (75,000 kg). The aircraft had a 3,766-mile (6,060-km) range with an airspeed of 180 mph (290 km/h) against a 37 mph (60 km) headwind.

Construction of the Laté 631 was started soon after the contract was issued. However, work was halted on 12 September 1939 so that Latécoère could focus on production of desperately needed military aircraft after war was declared on Germany. After the French surrender, work on the Laté 631 resumed in July 1940 but was halted again on 10 November by German order. The French and Germans negotiated over continuing work on the aircraft, which was purely for civil transportation. The Germans allowed construction to continue, and a second prototype was ordered under the same contract as the first (597/8) on 19 March 1941. The 35 Wright R-2600 engines that had been ordered were stranded in Casablanca, Morocco by the outbreak of the war in 1939. Amazingly, the hold on these engines was released, and they were delivered at the end of 1941.

Latecoere 631-02 stripes

Laté 631-02 (F-BANT) was finished at the end of the war and painted with invasion stripes for (hopefully) easy identification. The aircraft is at Biscarrosse undergoing tests, probably around the time of its first flight on 6 March 1945. Like on the prototype, the passenger windows are covered, but the windows were later added. Note the retractable float and that engine No. 5 is running.

The Laté 631-01, the first prototype, was registered as F-BAHG and completed at Toulouse, France in the summer of 1942. The aircraft was then disassembled and transported, with some difficulty, 310 miles (500 km) to Marignane in southern France. The aircraft was then reassembled for subsequent tests on Étang de Berre. The SNCASE SE.200, the Laté 631’s competitor, was built at Marignane and was nearing completion at the same time. The reassembly of Laté 631-01 was completed in October 1942, and the aircraft made its first flight on 4 November with Pierre Crespy as the pilot. Seven others, including Moine, were onboard as crew and observers. A second flight was made on 5 November, and flutter of the aileron and wing was encountered at 143 mph (230 km/h). The issues were traced to an improperly made part in the aileron control circuit that had subsequently failed.

Laté 631-01 was repaired, but German occupation of the French free zone on November 1942 brought a halt to further flight tests. On 23 November, order 280/42 was issued for two additional Laté 631s, bringing the total to four aircraft. The Germans lifted flight restrictions, and Laté 631-01 was flown again in December 1942. Test flights continued but were halted on several occasions by German orders. In April 1943, the tests were allowed to continue provided the aircraft was painted in German colors with German markings and a Lufthansa pilot was on board during the flights. Germany had essentially seized Laté 631-01 (and the SE.200) at this point and believed the aircraft could be used as a commercial transport once the “quick” war was concluded. The Germans were also interested in ways to add armament to the flying boat and make it a maritime patrol aircraft. Laté 631-01 was repainted and carried the German code 63+11 (for 631-01).

Laté 631-01 flight testing resumed in June 1943. On 20 January 1944, the aircraft took off on its 46th flight, and it was the first flight in which its gross weight exceeded 154,323 lb (70,000 kg). A second flight was made at 157,630 lb (71,500 kg). The tests had demonstrated that at 88,185 lb (40,000 kg), the Laté 631 could hold its course with three engines on the same side shut down. At 154,323 lb (70,000 kg), the course could be held with the outer two engines shut down on the same side. Some additional indications of flutter had been encountered but not understood.

Latecoere 631-02 Brazil

Laté 631-02 at Rio de Janeiro, Brazil in late October 1945. Note the open nacelle platforms, which were accessible through a wing passageway. A Brazilian flag is attached to the forward antenna mast.

Around 22 January 1944, Laté 631-01 was taken over by German forces and flown to Lake Constance (Bodensee) and moored offshore from Friedrichshafen, Germany. The SE.200 had already suffered the same fate on 17 January. On the night of 6 April 1944, Laté 631-01 and the SE.200 were destroyed at their moorings on Lake Constance by an Allied de Haviland Mosquito. The Laté 631 prototype had accumulated approximately 48 hours of flight time.

Construction of other Laté 631 aircraft had continued until early 1944, when German forces wanted Latécoère to focus on building the Junkers 488 bomber (which was never completed and was destroyed by the French Resistance). The disassembled second Laté 631 (631-02) was hidden in the French countryside until the end of the war. On 11 September 1944, order 51/44 was issued for five additional Laté 631 aircraft, which brought the total to nine. In December 1944, the components of Laté 631-02 were transported to Biscarrosse, where the aircraft was completed and assembled for testing on Lac de Biscarrosse et de Parentis. On 6 March 1945, Crespy took Laté 631-02 aloft for its first flight. While testing continued, the aircraft was christened Lionel de Marmier and was registered as F-BANT in April 1945. On 31 July, Laté 631-02 started a round trip of over 3,730 miles (6,000 km) to Dakar, Senegal, returning to Biscarrosse on 4 August. On 24 August, material for two additional Laté 631s was added to order 51/44, enabling the production of up to 11 aircraft.

On 28 September 1945, an issue with the autopilot in Laté 631-02 caused a violent roll to the right that damaged the wing, requiring the replacement of over 8,000 rivets to affect repairs. The aircraft was quickly fixed so that a scheduled propaganda flight to Rio de Janeiro, Brazil could be made on 10 October 1945. On that day, Laté 631-02 collided with a submerged concreate mooring block while taxiing and tore a 6 ft 7 in (2 m) gash in the hull. Upset over this incident, French authorities took the opportunity to nationalize the Latécoère factories. Production of the last six Laté 631 aircraft was spread between AECAT (which was formed from Latécoère), Breguet, SNCASO, and SNCAN. SNCASO at Saint-Nazaire would be primarily responsible for the production of aircraft No. 6, 8, and 10, and SNCAN at Le Havre would be primarily responsible for aircraft No. 7, 9, and 11. Laté 631-02 eventually made the flight to Rio de Janeiro, with 45 people on board, arriving on 25 October 1945.

Latecoere 631-03

Laté 631-03 (F-BANU) was the third aircraft completed. Its first flight was on 15 June 1946, and it crashed during a test flight on 28 March 1950 while investigating the loss (in-flight break up) of Laté 631-06 on 1 August 1948. Investigation of Laté 631-03’s crash revealed vibration issues with the engines and wings, and led to a solution to prevent further accidents.

On 31 October 1945, the first tragedy struck the Laté 631 program. While on a flight between Rio de Janeiro and Montevideo, Uruguay with 64 people on board, Laté 631-02 suffered a propeller failure on the No. 3 (left inboard) engine. The imbalance caused the No. 3 engine to rip completely away from the aircraft. A separated blade damaged the propeller on the No. 2 engine (left middle), which resulted in that engine almost being ripped from its mounts. Another separated blade flew through the fuselage, killed one passenger, and mortally wounded another (who later died in a hospital). An emergency landing was performed on Laguna de Rocha in Uruguay. The failure of the Ratier propeller was traced to its aluminum hub, which was subsequently replaced with a steel unit. The recovery of the aircraft was performed by replacing the missing engine with one from the right wing. The four-engine aircraft, with a minimal crew, was flown to Montevideo on 13 November for complete repairs, which took three months.

In February 1946, three Laté 631 aircraft were purchased by Argentina, but this deal ultimately fell through, with Argentina never paying for the aircraft. In May 1946, an agreement was reached in which Air France would take possession of three Laté 631 aircraft. On 15 June 1946, Jean Prévost made the first flight of Laté 631-03 at Biscarrosse. The aircraft was registered as F-BANU, christened as Henri Guillaumet, and soon transferred to Air France.

Laté 631-04 was registered as F-BDRA, and its first flight occurred on 22 May 1947 at Biscarrosse. The aircraft was the second Laté 631 to go to Air France. Laté 631-05 was registered as F-BDRB, and its first flight occurred on 22 May 1947. Laté 631-06, registered as F-BDRC, made its first flight on 9 November 1947, taking off from the Loire estuary near Saint-Nazaire, France. Laté 631-06 F-BDRC was the third aircraft for Air France.

Latecoere 631-05

Laté 631-05 (F-BDRB) first flew on 22 May 1947. The aircraft was slated to be converted into a cargo transport, but that never occurred. The aircraft was damaged beyond economical repair during a hangar collapse in February 1956.

Laté 631-07, registered as F-BDRD, made its first flight on 27 January 1948. The aircraft was lost on 21 February during a test flight from Le Havre to Biscarrosse. Laté 631-07 had taken off in poor weather and was not equipped for flying on instruments alone. It crashed into the English Channel (Bay of Seine) off Les-Dunes-de-Varreville (Utah Beach). A definitive cause was never found, but it was speculated that either the pilot lost spatial orientation and crashed into the sea, or that the pilot was flying very low or trying to land after the weather closed in and struck wreckage left behind from the D-Day landings at Utah Beach. Regardless, all 19 on board, which were the crew and Latécoère engineers, were killed.

On 1 August 1948, Air France Laté 631-06 F-BDRC was lost over the Atlantic flying between Fort-de-France, Martinique and Port-Etienne (now Nouadhibou), Mauritania. Wreckage was recovered that indicated an in-flight breakup that possibly involved a fire or explosion, but a definitive cause was never determined. None of the 52 people on board survived. F-BDRC had accumulated 185 flight hours at the time of the accident, and Air France subsequently withdrew its two other Laté 631s from service. Laté 631-04 F-BDRA participated in the search for survivors, flying a total of 75 hours, including a single 26-hour flight.

The flying boat era had ended during the 10 years between when the Latécoère 631 was ordered in 1938, and when the aircraft went into service with Air France in 1947. The advances in aviation during World War II had shown that landplanes were the future of commercial aviation. Following the accidents, there was no hope for the Laté 631 to be used as a commercial airliner. With four completed aircraft and another four under construction, the decision was made to convert the Laté 631 into a cargo aircraft.

Latecoere 631-06 Air France

Laté 631-06 (F-BDRC) made its first flight on 9 November 1947. It was the third (and final) aircraft to be received by Air France. On 1 August 1948, Laté 631-06 disappeared over the Atlantic with the loss of all 52 on board. Air France withdrew its remaining Laté 631 aircraft as a result. Note the access hatch atop the fuselage. Another hatch existed behind the wings.

On 28 November 1948, Laté 631-08 F-BDRE was flown for the first time, taking off from Saint-Nazaire. Laté 631-08 was originally intended as an additional aircraft for Air France but was orphaned after the crash of Laté 631-06. Laté 631-08, along with Laté 631-03, were eventually given to a new company, SEMAF (Société d’Exploitation du Matériel Aéronautique Français / French Aircraft Equipment Exploitation Company). SEMAF was founded in March 1949 and worked to develop the Laté 631 as an air freighter. Laté 631-08 F-BDRE was converted to a cargo aircraft by strengthening its airframe and installing a 9 ft 2 in x 5 ft 3 in (2.80 x 1.60 m) cargo door on the left side of the rear fuselage. The aircraft was first flown with the modifications on 8 June 1949. Laté 631-08 soon began hauling fabric and manufactured products between France and various places in Africa. The aircraft had completed 12 trips by March 1950.

Laté 631-09 F-BDRF preceded Laté 631-08 into the air. Laté 631-09’s first flight occurred on 20 November 1948 at Le Harve. Laté 631-10 F-BDRG made its first flight on 7 October 1949 from Saint-Nazaire. Both of these aircraft were flown to Biscarrosse and stored with the never completed Laté 631-11 F-BDRH. Laté 631-09 and -10 were later reregistered as F-WDRF and F-WDRG.

Laté 631-03 F-BANU was reregistered as F-WANU when it underwent tests to measure vibrations of the airframe and engines. This was done in part to discover what led to the loss of Laté 631-06 F-BDRC. On 28 March 1950, Laté 631-03 made its second flight of the day, taking off from Biscarrosse. With engine power pushed up, the left wing began to flutter, and the outer section of the left aileron broke away. Laté 631-03 began to spin, turned on its back, and continued to spin until it impacted the water inverted. The 12 people on board, which included the crew and engineers from Latécoère and Rotol, were killed instantly. Many witnessed the crash, and the wreckage of Laté 631-03 was recovered. Examination revealed that the engines with a .4375 gear reduction and operating at 1,925 rpm during cruise flight turned the propeller at 840 rpm. This resonated with a critical frequency of the wings, ailerons and Flettner tabs, which was 840 cycles per minute. The interaction rapidly fatigued parts in the outer aileron control system and caused them to fail. The damaged aileron system allowed the aileron to flutter, breaking the control system completely and leading to a complete loss of aircraft control.

Latecoere 631-08

Laté 631-08 (F-BDRE) is seen here with its updated registration of F-WDRE. Laté 631-08 was the only aircraft that operated as an air freighter.

At the time if the accident, Laté 631-03 had been reengined with R-2600 engines incorporating a .5625 gear reduction. These engines were installed on later Laté 631 aircraft and retrofitted on the earlier aircraft. However, nearly all of the Laté 631-03’s 1,001 hours were with the other engines, which was enough to have fatigued the aileron control to its breaking point. The loss of Laté 631-03 led to the collapse of SEMAF.

With the cause of the crash known, a new company was formed to upgrade the Laté 631 fleet and modify them for cargo service. La Société France Hydro (France Hydro Company) was given charge of Laté 631-02 and Laté 631-08, which was reregistered as F-WDRE. Modifications to prevent a reoccurrence of Laté 631-03’s crash were incorporated into the aircraft, and Laté 631-08 returned to cargo service in late 1951. Laté 631-08 flew a Biscarrosse-Bizerte-Bahrain-Trincomalee-Saigon route of some 7,460 miles (12,000 km) starting in March 1952. The aircraft departed Bizerte, Tunisia with a takeoff weight of 167,000 lb (75,750 kg), the highest recorded for a Laté 631. By 1953, Laté 631-08 was hauling cotton from Douala, Cameroon to Biscarrosse. This had proven somewhat lucrative, and a cargo-conversion of Laté 631-02 was started. Laté 631-05 was also transferred to France Hydro, but little was done with the aircraft. On 10 September 1955, Laté 631-08 broke apart during a violent thunderstorm while over Sambolabo, Cameroon. All 16 people on board were killed. The Latécoère 631 was withdrawn from service after this accident, and no further attempts were made to use the aircraft.

In February 1956, Laté 631-05, -10, and -11 were damaged beyond economical repair when the roof of the Biscarrosse hangar collapsed after heavy snowfall. All of the remaining Latécoère 631s were subsequently scrapped, most in late 1956. In 1961, the remains of Laté 631-01 and the SE.200 prototype were raised from Lake Constance by a Swiss recovery team and subsequently scrapped.

Latecoere 631-08 France-Hydro

Laté 631-08 while in service with France Hydro. The aircraft crashed in a storm on 10 September 1955; this was the last flight of any Laté 631. The remaining aircraft were later scrapped. Note the open door on the bow and the open hatch forward of the cockpit that led to a cargo hold.

Les Paquebots Volants by Gérard Bousquet (2006)
Latécoère: Les avions et hydravios by Jean Cuny (1992)

Lun MD-160 Ekranoplan cruiser

Lun-class / Spasatel Ekranoplans

By William Pearce

In March 1980, the Soviet government envisioned a fast-attack force utilizing missile-carrying ekranoplans. An ekranoplan (meaning “screen plane”), also known as wing-in-ground effect (WIG) or ground-effect-vehicle (GEV), is a form of aircraft that operates in ground effect for added lift. The machines typically operate over water because of their need for large flat surfaces.

Lun MD-160 Ekranoplan moored

The missile-carrying Lun ekranoplan at rest on the Caspian Sea. The craft exhibits worn paint in the undated photo. Note the gunner’s station just below the first missile launcher. A Mil Mi-14 helicopter is in the background.

When the missile-carrying ekranoplan was being considered, the huge KM (Korabl Maket) ekranoplan was being tested, and testing was just starting on the three production A-90 Orlyonok transport ekranoplans. Known as Project 903, the missile-carrying Lun-class ekranoplans would be built upon the lessons learned from the earlier machines. The word “lun” (лунь) is Russian for “harrier.” An order for four examples was initially considered, with the number soon jumping to 10 Lun-class machines.

The first Lun-class ekranoplan was designated S-31, with some sources stating the designation MD-160 was also applied. Most sources referred the craft simply as “Lun.” The Lun was designed by Vladimir Kirillovykh at the Alekseyev Central Hydrofoil Design Bureau in Gorky (now Nizhny Novgorod), Russia. The new craft differed from previous ekranoplans by not having dedicated cruise engines.

Lun MD-160 Ekranoplan at speed

The Lun at speed traveling over the water’s surface. Note the contoured, heat-resistant surface behind each missile tube to deflect the exhaust of the launching missile. The large domes on the tail are evident in this image.

The Lun’s all-metal fuselage closely resembled that of a flying boat with a stepped hull. Mounted just behind the cockpit were eight Kuznetsov NK-87 turbojets, each capable of 28,660 lbf (127.5 kN) of thrust. The engines were mounted in sets of four on each side of the Lun. The nozzle of each jet engine rotated down during takeoff to increase the air pressure under the Lun’s wings (power augmented ram thrust). This helped the craft rise from the water’s surface and into ground effect. The nozzles were positioned straight back for cruise flight.

Lun MD-160 Ekranoplan ship

With flaps down, the Lun passes by a Soviet Navy ship. The rear gunner’s position is just visible at the rear of the craft.

The mid-mounted, short span wings had a wide cord and an aspect ratio of 3.0. Six large flaps made up the trailing edge of each wing, with the outer flaps most likely operating as flaperons (a combination flap and aileron). The tip of each wing was capped by a flat plate that extended down to form a float. A single hydro-ski was positioned under the fuselage, where the wings joined. The hydraulically-actuated ski helped lift the craft out of the water as it picked up speed. A swept T-tail with a split rudder at its trailing edge rose from the rear of the fuselage. Radomes in the tail’s leading edge housed equipment for navigational and combat electronics. The large, swept horizontal stabilizer had large elevators mounted to its trailing edges.

Lun MD-160 Ekranoplan cruiser

Looking more like an alien ship out of a science fiction movie than a cold-war experiment, the Lun was an impressive sight. Note the chines on the bow to help deflect water from the engines.

Mounted atop the Lun were three pairs of angled missile launchers. No cruise engines were mounted to the Lun’s tail over concerns that the engines would cut out when they ingested the exhaust plume from a missile launch. The launchers carried the P-270 (3M80) Moskit—a supersonic, ramjet-powered, anti-ship cruise missile. The P-270 traveled at 1,200 mph (1,930 km/h) and had a range of up to 75 miles (120 km). The belief was that the Lun-class ekranoplans would be able to close in on an enemy ship undetected and launch the P-270 missile, which would be nearly unstoppable to the enemy ships. The Lun also had two turrets, each with two 23 mm cannons. One turret was forward-facing and positioned below the first pair of missile launchers. The second turret was rear-facing and positioned behind the Lun’s tail.

Lun MD-160 Ekranoplan Kaspiysk

View of the Lun in March 2009 as it sits slowly deteriorating at the Kaspiysk base on the Caspian Sea. The special dock was made for the Lun. The dock was towed out to sea and submerged to allow the Lun to either float free for launch or be recovered.

The Lun had a wingspan of 144 ft 4 in (44.0 m), a length of 242 ft 2 in (73.8 m), and a height of 62 ft 11 in (19.2 m). The craft had a cruise speed of 280 mph (450 km/h) and a maximum speed of 342 mph (550 km/h). Operating height was from 3 to 16 ft (1 to 5 m), and the Lun had an empty weight of 535,723 lb (243,000 kg) and a maximum weight of 837,756 lb (380,000 kg). The craft had a range of 1,243 miles (2,000 km) and could operate in seas with 9.8 ft (3 m) waves. The Lun had a crew of 15 and could stay at sea for up to five days.

The Lun was launched on the Volga River on 16 July 1986. Operating from the base at Kaspiysk, Russia, testing occurred on the Caspian Sea from 30 October 1989 to 26 December. By that time, plans for the Lun-class of missile-carrying ekranoplans had faded, and the decision was made that only one of the type would be built. The Lun was withdrawn from service sometime in the 1990s and stored at Kaspiysk, where it remains today. In 2002, there was talk of reviving the missile-carrying ekranoplan, but no action was taken.

Lun MD-160 Ekranoplan Kaspiysk igor113

An interesting view of the Lun sitting at Kaspiysk in late-2009. Note the downward angle of the jet nozzles, and the flaps appear to be disconnected. The elements have taken a toll on the ekranoplan. (igor113 image)

The second machine (S-33), which was about 75-percent complete, was converted to serve as a Search and Rescue (SAR) craft. This decision was in part due to the loss of the K-278 Komsomolets submarine on 7 April 1989. A fire caused the loss of the submarine, and 42 of the 69-man crew died, many from hypothermia as they awaited rescue. This accident illustrated the need for a fast-response SAR craft.

Spasatel Ekranoplan Volga

The Spasatel in mid-2014 at the Volga Shipyard with a protective wrap to help preserve the craft. The wings and horizontal stabilizers are resting on the ekranoplan’s back. Note the machine’s reinforced spine. (rapidfixer image)

For its new purpose, S-33 was named Spasatel for “Rescuer.” Conversion work was started around 1992. The Spasatel had the same basic configuration as the Lun but had a reinforced spine and an observation deck placed atop its tail. The Spasatel possessed the same dimensions and performance as the Lun. However, sources state that the Spasatel would fly out of ground effect. For sea search missions, the craft would fly at an altitude of 1,640 ft (500 m), and it had a ceiling of 24,606 ft (7,500 m). The Spasatel had a range of 1,864 miles (3,000 km).

Spasatel Ekranoplan Volga Andrey Orekhov

The Spasatel seen in late 2018 at the Volga / Krasnoye Sormovo Shipyard in Nizhny Novgorod. The craft has been outside and exposed to the elements since 2016. Note the observation deck incorporated into the tail. (Андрей Орехов / Andrey Orekhov image)

The SAR ekranoplan would be quickly altered based on its mission. The Spasatel could carry up to 500 passengers, or temporarily hold 800 people for up to five days waiting for rescue. As a hospital ship, 80 patients could be treated on the Spasatel. A tank with 44,092 lb (20,000 kg) of fire retardant could be mounted atop the Spasatel for fighting fires on ships or oil platforms. Or, a submersible with space for 24 people could be mounted on the Spasatel for responding to submarine accidents. The Spasatel could even respond to oil spills and lay out 9,843 ft (3,000 m) of barriers. Even more ambitious was the noble plan to have several Spasatel ekranoplans in-service around the world ready to respond to any call of marine distress at a moment’s notice.

The Spasatel was about 80-percent complete when work was halted in the mid-1990s due to a lack of funds. In 2001, there was renewed hope that the Spasatel would be completed, but again, no money was forthcoming. The Spasatel was housed in the construction building at the Volga Shipyard until 2016, when it was moved outside. In 2017, there was again some hope that the Spasatel would be completed, now for SAR missions in the Arctic. Under this plan, work on the Spasatel would continue from 2018 until its completion around 2025. However, it does not appear that any work has been done, and the Spasatel continues to deteriorated as it sits exposed to the elements.

Spasatel Ekranoplan Model

Spasatel model from 2017 depicting its new purpose as an artic rescue craft. It does not appear that any work has been performed on the actual machine, but who knows what the future may hold. (Valery Matytsin/TASS image via The Drive)

Soviet and Russian Ekranoplans by Sergy Komissarov and Yefim Gordon (2010)
WIG Craft and Ekranoplan by Liang Lu, Alan Bliault, and Johnny Doo (2010)

Alexeyev A-90 Orlyonok top

Alexeyev SM-6 and A-90 Orlyonok Ekranoplans

By William Pearce

Rostislav Alexeyev (sometimes spelled Alekeyev) of the Central Hydrofoil Design Bureau (CHDB or Tsentral’noye konstruktorskoye byuro na podvodnykh kryl’yakh / TsKB po SPK) had been working out of the Krasnoye Sormovo Shipyard in Gorky (now Nizhny Novgorod), Russia since the 1940s. In the 1950s, Alexeyev began experimental work with ekranoplans (meaning “screen planes”), also known as wing-in-ground effect (WIG) or ground-effect-vehicle (GEV). His work led to the construction of the massive, experimental KM (Korabl Maket or ship prototype) ekranoplan in the mid-1960s.

Alexeyev SM-6 rear

The SM-6 was a 50-percent scale proof-of-concept vehicle for the A-90 Orlyonok ekranoplan. First flown in 1971, testing of the SM-6 continued until the mid-1980s.

As work on the KM was underway, the Soviet Navy expressed interest in a troop transport ekranoplan, and Alexeyev had started design studies of such a craft as early as 1964. In 1966, the decision was made to construct a 50-percent scale test model of the troop transport. The test ekranoplan was designated SM-6 (samokhodnaya model’-6 or self-propelled model-6).

The SM-6 had a flying boat-style stepped hull that was made of steel and aluminum. The two-place, side-by-side cockpit was near the front of the machine and covered with a large canopy. Two hydro-skis were placed under the hull: one under the nose (bow) and one under the wings. The hydraulically-actuated skis helped lift the craft out of the water as it picked up speed.

Alexeyev SM-6 square

An undated image of the SM-6 on display at Lenin Square in Kaspiysk, Russia. The ekranoplan has since been removed, and its fate is unknown. However, another undated image shows the its derelict fuselage (hull) in a sorry state.

Mounted in the SM-6’s nose were two Milkulin RD-9B jet engines, each of which produced 4,630 lbf (20.6 kN) of thrust. The inlets for the engines were in the upper surface of the nose, and the nozzles protruded out the sides of the SM-6, just behind and below the cockpit. For takeoff, the jet nozzle of each engine was rotated down to increase air pressure under the craft’s wings (power augmented ram thrust). In cruise flight, the nozzles were pointed back for forward thrust.

The low-mounted wing had a short span and a wide cord, and had an aspect ratio of 2.8. Five flaps were attached along each wing’s trailing edge. The outer flaps most likely acted as flaperons, a combination flap and aileron, but definitive proof has not been found. The tip of each wing extended down to form a float. A large vertical stabilizer extended from the rear of the craft. A rudder was positioned on the trailing edge of the vertical stabilizer. When the SM-6 was on the water’s surface, the bottom part of the rudder was submerged and helped steer the craft. Mounted atop the tail was a 3,750 shp (2,796 kW) Ivchenko AI-20K turboprop engine driving a four-blade propeller that was approximately 12 ft (3.65 m) in diameter. Behind the engine and atop the tail was the large horizontal stabilizer with swept leading and trailing edges. Large elevators were incorporated into the trailing edges of the horizontal stabilizer.

Alexeyev A-90 Orlyonok top

The A-90 Orlyonok cruising above the Caspian Sea. The jet intakes positioned atop the bow helped reduce the amount of water ingested into the engines and kept the craft rather streamlined.

The SM-6 had a wingspan of 48 ft 7 in (14.8 m), a length of 101 ft 8 in (31.0 m), and a height of 25 ft 9 in (7.85 m). The craft had a cruise speed of 186 mph (300 km/h) and a maximum speed of 217 mph (350 km/h). Its operating height was from 2 to 5 ft (.5 to 1.5 m), and the SM-6 had a maximum weight of 58,422 lb (26,500 kg). The craft had a range of 435 miles (700 km) and could operate in seas with 3.3 ft (1.0 m) waves.

Construction of the SM-6 started in October 1966 at the Krasnoye Sormovo Shipyard. Insufficient funding caused some delays, and the SM-6 was not finished until 30 December 1970. At that time, the Volga Shipyard was established as an experimental production facility of the CHDB and operated out of the same plant in which the SM-6 was built. The CHDB was also renamed the Alekseyev Central Hydrofoil Design Bureau.

Alexeyev A-90 Orlyonok cargo

The entire front of the Orlyonok swung open to allow access to the cargo hold. A 22,708 lb (10,300 kg) BTR-60PB armored personnel carrier is seen loaded on the Orlyonok. Note the engine’s exhaust nozzle and the machine gun turret.

In July 1971, the SM-6 was transported about 53 miles (85 km) up the Volga River to Chkalovsk, Russia. Initial tests of the craft were conducted in August 1971 on the Gorky Reservoir. In early 1972, the SM-6 was successfully tested on ice and snow. In 1973, modifications were made that included mounting wheels to the hydro-skis. The wheels were used as beaching gear, allowing the SM-6 to power itself out of the water and onto land, or vice versa. Having proven itself as a fully functioning ekranoplan, the SM-6 was transferred to the Kaspiysk base on the Caspian Sea in late 1974. The SM-6 continued to undergo modifications and testing until the mid-1980s. At different points in its career, the SM-6 was marked as 6M79 and 6M80. After it was withdrawn from service, the SM-6 was displayed for a number of years at a public square (Lenin Square?) in Kaspiysk. The elements took a toll on the ekranoplan, and it was eventually removed from the square. The derelict remains of the SM-6 sat near the shore of the Caspian Sea for a time, and mostly likely, the machine was later scrapped.

Following the successful tests of the SM-6 in 1971, plans moved forward for constructing a full-scale, troop transport ekranoplan. The full-size ekranoplan was known as the A-90 Orlyonok (Eaglet) or Project 904. Although twice its size, the Orlyonok had mostly the same configuration as the SM-6.

Alexeyev A-90 Orlyonok front

The Orlyonok’s beaching gear allowed the craft to propel itself out of the water and onto a hard surface. The turning arc of the nose wheel has not been found, but with the main wheels under the wing, the Orlyonok may have been able to turn rather sharply on land.

Mounted in the Orlyonok’s nose (bow) were two Kuznetsov NK-8-4K jet engines that provided 23,149 lbf (103.0 kN) of thrust each. Just behind the craft’s cockpit was a turret with two 12.7-mm (.50-Cal) machine guns. The entire nose of the Orlyonok, including its cockpit, swung open to the right a maximum of 92 degrees. A set of folding ramps allowed for direct entry into the machine’s cargo hold, which was 68 ft 11 in (21.0 m) long, 9 ft 10 in (3.0 m) wide, and 10 ft 6 in (3.2 m) tall. The hold could carry 250 troops or 44,092 lb (20,000 kg) of equipment, including armored vehicles.

The beaching gear mounted to the hydro-skis consisted of a steerable, two-wheel nose unit and a ten-wheel main unit under the hull. The low-mounted wing had a short span and a wide cord, with an aspect ratio of 3.0. The trailing edge of the wing had flaperons at its tips with flaps spanning the rest of the distance. The tip of each wing extended down to form a float. A large vertical stabilizer extended from the rear of the craft. Mounted atop the tail was a 15,000 ehp (11,186 kW) Kuznetsov NK-12MK turboprop engine driving an eight-blade, contra-rotating propeller that was approximately 19 ft 8 in (6.0 m) in diameter. The Orlyonok was equipped with a full-range of navigational and combat electronics.

Alexeyev A-90 Orlyonok slow

At low speed, a fair amount of spray enveloped the Orlyonok. The circular markings on the sides of the craft designated over-wing access doors, which were actually rectangular.

The Orlyonok had a wingspan of 103 ft 4 in (31.5 m), a length of 190 ft 7 in (58.1 m), and a height of 52 ft 2 in (15.9 m). The craft had a cruise speed of 224 mph (360 km/h) and a maximum speed of 249 mph (400 km/h). Operating height was from 2 to 16 ft (.5 to 5.0 m). The Orlyonok had an empty weight of 220,462 lb (100,000 kg) and a maximum weight of 308,647 lb (140,000 kg). The craft had a range of 932 miles (1,500 km) and could operate in seas with 6.6 ft (2.0 m) waves.

The Orlyonok prototype was built at the Volga Shipyard and made its first flight in 1972, taking off from the Volga River. The craft was later disguised as a Tupolev Tu-134 airliner fuselage and transported by barge to the Kaspiysk base on the Caspian Sea for further testing. In 1975, the prototype was accidently beached on a rocky sandbar. The craft was able to power itself back into the water, but the hull was damaged and its structural integrity was compromised. The damage went undetected until the rear fuselage and tail broke off during a landing on rough seas. Alexeyev was onboard and took control of the crippled ekranoplan. Using full-power of the bow jet engines, Alexeyev as able to keep the open back of the hull above water and return to base. The authorities attributed the accident to a design deficiency and blamed Alexeyev, who was removed as the chief designer and reassigned to experimental work.

Alexeyev A-90 Orlyonok GKS-13

The Orlyonok prototype flies past a Soviet Navy ship on the Caspian Sea. Unlike the SM-6, the Orlyonok’s rudder did not extend into the water when the craft was on the sea.

The Russian Navy had been sufficiently impressed by the Orlyonok to order three production machines and a static test article. The damaged prototype was returned to the Volga Shipyard and completely rebuilt as the first production Orlyonok, S-21 (610), which was completed in 1978 and delivered to the Navy on 3 November 1979. The second Orlyonok, S-25 (630), was completed in 1979 and delivered on 27 October 1981. The final Orlyonok, S-26 (650), was completed in 1980 and delivered on 30 December 1981. Plans to produce an additional eight units were ultimately abandoned.

The three Orlyonoks were tested and operated for several years on the Caspian Sea. The captain and crew of S-21 took it upon themselves to test the machine to its limits. Away from witnesses and in the middle of the Caspian Sea, S-21 was flown out of ground effect and up to 328 ft (100 m) for an extended time. At that height, the ekranoplan was sluggish, unstable, and a challenge to fly, but positive control was maintained.

Alexeyev A-90 Orlyonoks

Two production Orlyonoks at Kaspiysk on the Caspian Sea. Note the open over-wing doors and the open engine access panel of the first machine.

By 1989, the three Orlyonoks had performed a total of 438 flights and 118 beachings. On 12 September 1992, S-21 was lost when a control malfunction coupled with pilot error caused it to rise to 130 ft (40 m) and stall. One member of the ten-man crew was killed, and S-21 was eventually sunk by the Navy—the cost of salvaging the craft was too high. Reportedly, the last Orlyonok flight was made by S-26 in late 1993, after which, the Orlyonoks fell into a state of disuse followed by disrepair.

In 1998, the Navy wrote off the two remaining Orlyonoks. Around 2000, S-25 was scrapped, but S-26 was somehow preserved. In 2006, S-26 was given to the Museum and Memorial Complex of the History of the Navy of Russia (Muzeyno-Memorial’nyy Kompleks Istorii Vmf Rossii) located on the Volga River in Moscow. The S-26 was demilitarized in 2007 and restored and installed at the museum in 2008. The Orlyonok design inspired other military and commercial ekranoplan design, but none were built.

Alexeyev A-90 Orlyonok 2008

Orlyonok S-26 shortly after it was put on display at the Naval museum in Moscow. The wheels of the beaching gear are visible, although it appears the main set is missing two wheels. Sadly, the condition of the impressive ekranoplan has deteriorated over the years. (Alex Beltyukov image via Wikimedia Commons)

Soviet and Russian Ekranoplans by Sergy Komissarov and Yefim Gordon (2010)
WIG Craft and Ekranoplan by Liang Lu, Alan Bliault, and Johnny Doo (2010)

Alexeyev KM rear

Alexeyev KM Ekranoplan (Caspian Sea Monster)

By William Pearce

Rostislav Alexeyev (sometimes spelled Alekeyev) was born in Novozybkov, Russia on 18 December 1916. On 1 October 1941, he graduated from the Gorky Industrial Institute (now Gorky Polytechnic Institute) as a shipbuilding engineer. Alexeyev was sent to work at the Krasnoye Sormovo Shipyard in Gorky (now Nizhny Novgorod), Russia. In 1942, Alexeyev was tasked to develop hydrofoils for the Soviet Navy, work that was still in progress at the end of World War II. However, there was sufficient governmental interest for Alexeyev to continue his hydrofoil studies after the war. This work led to the development of the Raketa, Meteor, Kometa, Sputnik, Burevestnik, and Voskhod passenger-carrying hydrofoils spanning from the late 1940s to the late 1970s.

Alexeyev SM-2

The SM-2 was the first ekranoplan that possessed the same basic configuration later used on the KM. The nozzle of the bow (booster) engine is visible on the side of the SM-2. The intake for the rear (cruise) engine is below the vertical stabilizer. Note the three open cockpits.

Alexeyev appreciated the speed of the hydrofoil but realized that much greater speeds could be achieved if the vessel traveled just above the water’s surface. Wings with a short span and a wide cord could be attached to a vessel to lift its hull completely out of the water as it traveled at high speed, allowing it to ride on a cushion of air. Such a craft would take advantage of the ground (screen) effect as air is compressed between the craft and the ground. In Russian, this type of vessel is called an ekranoplan, meaning “screen plane.” They are also known as wing-in-ground effect (WIG) or a ground-effect-vehicle (GEV), since the craft’s wing must stay near the surface and in ground effect. Because ground effect vehicles fly without contacting the surface, they are technically classified as aircraft. However, ground effect vehicles need a flat surface over which to operate and are typically limited to large bodies of water, even though they can traverse very flat expanses of land. Because they operate from water, ground effect vehicles are normally governed by maritime rules.

In the late 1950s, Alexeyev and his team began work on several scale, piloted, test machines to better understand the ekranoplan concept. The first was designated SM-1 (samokhodnaya model’-1 or self-propelled model-1) and made its first flight on 22 July 1961. The SM-1 was powered by a single jet engine and had two sets (mid and rear) of lifting wings. Lessons learned from the SM-1 were incorporated into the SM-2, which was completed in March 1962. The SM-2 had a single main wing and a large horizontal stabilizer. The craft also incorporated a booster jet engine in its nose (bow) to blow air under the main wing to increase lift (power augmented ram thrust). The SM-2 was demonstrated to Premier of the Soviet Union Nikita Khrushchev, who then lent support for further ekranoplan development to Alexeyev and his team.

Alexeyev SM-5

The SM-5 was a 25-percent scale version of the KM. The craft followed the same basic configuration as the SM-2 but was more refined. The structure ahead of the dorsal intake was to deflect sea spray.

Ekranoplan design experimentation was expanded further with the SM-3. The craft had very wide-cord wings and was completed late in 1962. That same year, Alexeyev began working at the Central Hydrofoil Design Bureau (CHDB or Tsentral’noye konstruktorskoye byuro na podvodnykh kryl’yakh / TsKB po SPK). In 1963, the next test machine, the SM-4, demonstrated that a good understanding of ekranoplan design had been achieved. Also in 1963, the Soviet Navy placed an order for a large, experimental ekranoplan transport known as the KM (Korabl Maket or ship prototype).

While the CHDB began design work on the KM, the SM-5 was built in late 1963. The SM-5 was a 25-percent scale model of the KM and was powered by two Mikulin KR7-300 jet engines. The craft had a wingspan of 31 ft 2 in (9.5 m), a length of 59 ft 1 in (18.0 m), and a height of 18 ft 1 in (5.5 m). The SM-5 had a takeoff speed of 87 mph (140 km/h), a cruise speed of 124 mph (200 km/h), and a maximum speed of 143 mph (230 km/h). Its operating height was from 3 to 10 ft (1 to 3 m), and the craft had a maximum weight of 16,094 lb (7,300 kg). The SM-5 could operate in seas with 3.9 ft (1.2 m) waves. Initial tests of the SM-5 were so successful that the decision was made to construct the KM without building a larger scale test machine. Sadly, the SM-5 was destroyed, and its two pilots were killed in a crash on 24 August 1964. During a test, a strong wind was encountered that caused the craft to gain altitude. Rather than reduce power, the pilot added power. The SM-5 rose out of ground effect and stalled.

Alexeyev KM at speed

The KM (Korabl Maket) at speed on the Caspian Sea. Note the “04” tail number and the spray deflectors covering the cruise engine intakes on the vertical stabilizer.

The KM’s all-metal fuselage closely resembled that of a flying boat with a stepped hull. Mounted just behind the cockpit were eight Dobrynin VD-7 turbojets, with four engines mounted in parallel on each side of the KM. Each VD-7 was capable of 28,660 lbf (127.5 kN) of thrust. The jet nozzle of each engine rotated down during takeoff to increase the air pressure under the craft’s wings. These engines were known as boost engines.

The shoulder-mounted, short span wings had a wide cord and an aspect ratio of 2.0. Two large flaps made up the trailing edge of each wing. The tip of each wing was capped by a flat plate that extended down to form a float. Two additional VD-7 turbojets were mounted near the top of the KM’s large vertical stabilizer. These engines were known as cruise engines and were used purely for forward thrust. A heat-resistant panel covered the section of the rudder just behind the cruise engines. At low speeds, the rudder extended into the water and helped steer the KM. Atop the vertical stabilizer was the horizontal stabilizer, which had about 20 degrees of dihedral. A large elevator was mounted to the trailing edge of the horizontal stabilizer.

Alexeyev KM top

The servicemen atop the KM help illustrate the craft’s immense size. Note the access hatches in the wings. This view also shows the ekranoplan’s large control surfaces. The nozzles of the left engines are in the down (boost/takeoff) position while the nozzles on the right are in the straight (cruise flight) position.

The KM had a wingspan of 123 ft 4 in (37.6 m), a length of 319 ft 7 in (97.4 m), and a height of 72 ft 2 in (22.0 m). The craft had a cruise speed of 267 mph (430 km/h) and a maximum speed of 311 mph (500 km/h). Operating height was from 13 to 46 ft (4 to 14 m), and the KM had an empty weight of 529,109 lb (240,000 kg) and a maximum weight of 1,199,313 lb (544,000 kg). The craft had a range of 932 miles (1,500 km) and could operate in seas with 11.5 ft (3.5 m) waves. The KM had a crew of three and could carry 900 troops, but the craft was intended purely for experimental purposes.

The KM was built at the Krasnoye Sormovo Shipyard in Gorky. Alexeyev was the craft’s chief designer and V. Efimov was the lead engineer. The KM was launched on the Volga River on 22 June 1966 and was subsequently floated down the river to the Naval base at Kaspiysk, Russia on the Caspian Sea. To keep the KM hidden during the move, its wings were detached, it was covered, and it was moved only at night. After arriving at the Kaspiysk base, the KM was reassembled, and sea-going trials started on 18 October 1966. V. Loginov was listed as the pilot, but Alexeyev was actually at the controls. At 124 mph (200 km/h), the KM rose to plane on the water’s surface but did not take to the air. Planning tests were continued until 25 October 1966. The early tests revealed that the KM’s hull was not sufficiently rigid and that engine damage was occurring due to water ingestion. Stiffeners were added to the hull, and plans were made to modify the engines.

Alexeyev KM front

While at rest, the KM’s water-tight wings added to the craft’s stability on the water’s surface. Note the far-left engine’s open access panels. Covers are installed in all of the engine intakes.

The first true flight of the KM occurred on 14 August 1967 with Alexeyev at the controls. The flight lasted 50 minutes, and a speed of 280 mph (450 km/h) was reached. Further testing revealed good handling characteristics, and sharp turns were made with the inside wing float touching the water. At one point, the KM was mistakenly flown over a low-lying island for about 1.2 miles (2 km), proving the machine could operate over land, provided it was very flat.

The KM was discovered in satellite imagery by United States intelligence agencies in August 1967. Rather baffled by the craft’s type and intended purpose, the Central Intelligence Agency (CIA) began to refer to the enormous machine as the “Kaspian Monster,” in reference to the KM designation. The “Kaspian Monster” name slowly changed to “Caspian Sea Monster,” which is how the craft is generally known today. The sole KM was painted with at least five different numbers (01, 02, 04, 07, and 08) during its existence. Some sources state the numbers corresponded to different developmental phases, while others contend that the numbers were an attempt to obscure the actual number of machines built.

Alexeyev KM rear

The KM, now with an “07” tail number, cruises above the water. Note the heat resistant panel on the rudder, just behind the exhaust of the cruise jet engines.

While the KM was being built, a second 25-percent scale model was constructed. The model was designated SM-8, and its layout incorporated changes made to the KM’s design that occurred after the SM-5 was built. Like the SM-5, the SM-8 was powered by two Mikulin KR7-300 jet engines. The craft had a wingspan of 31 ft 2 in (9.5 m), a length of 60 ft 8 in (18.5 m), and a height of 18 ft 1 in (5.5 m). The SM-8 had a cruise speed of 137 mph (220 km/h). Operating height was from 3 to 10 ft (1 to 3 m), and the craft had a maximum weight of 16,094 lb (8,100 kg). The SM-8 could operate in seas with 3.9 ft (1.2 m) waves. The craft was first flown in 1968 and tested over a grassy bank in June 1969. The SM-8 also served to train pilots for the KM.

Alexeyev SM-8

The SM-8 was a second 25-percent scale model of the KM and constructed after the loss of SM-5. Its configuration more closely matched that of the KM. The stack above the wings surrounded the intake for the front (booster) engine and deflected sea spray. The front engine was installed so that its exhaust traveled forward to the eight outlets (four on each side) behind the cockpit.

By the late 1960s, the KM had proven that the ekranoplan was a viable means to quickly transport personnel or equipment over large expanses of water. Alexeyev’s focus had moved to another ekranoplan project, the A-90 Orlyonok. By 1979, the KM had been modified by relocating the cruise engines from the vertical stabilizer to a pylon mounted above the cockpit. All engines were fitted with covers to deflect water and prevent the inadvertent ingestion of the occasional unfortunate seabird.

In December 1980, the KM was lost after an accident occurred during takeoff. Excessive elevator was applied and resulted in a relatively high angle of attack. Rather than applying power and correcting the pitch angle, the angle was held and power was reduced. A stall occurred with the KM rolling to the left and impacting the water. The crew escaped unharmed, but the KM was left to slowly sink to the bottom of the Caspian Sea. Reportedly, the craft floated for a week before finally sinking. Either the Soviets were done with the KM, or its immense size prevented reasonable efforts to salvage the machine. From the time it first flew, the KM was the heaviest aircraft in the world until the Antonov An-225 Mriya made its first flight on 21 December 1988. The KM is still the longest aircraft to fly. Experience gained from the KM was applied to the Lun-class S-31 / MD-160.

Alexeyev KM 1979

The KM as seen in 1979 with the cruise engines relocated from the vertical stabilizer to a pylon above the cockpit. A radome is mounted above the engines. All of the engines have been fitted with spray deflectors.

Soviet and Russian Ekranoplans by Sergy Komissarov and Yefim Gordon (2010)
WIG Craft and Ekranoplan by Liang Lu, Alan Bliault, and Johnny Doo (2010)

NAA XA2J Super Savage top

North American XA2J Super Savage Medium Bomber

By William Pearce

At the close of World War II, the United States Navy lacked the ability to carry out a nuclear strike. The nuclear bombs of the time were large and heavy, and no aircraft operating from an aircraft carrier could accommodate the bomb’s size and weight. The Navy did not want nuclear strikes to be the sole responsibility of the Army Air Force (AAF). In addition, the Navy felt that launching an attack with a medium-sized aircraft from a carrier that was hundreds of miles from the target offered advantages compared to large AAF bombers traveling thousands of miles to the target. On 13 August 1945, the Navy sponsored a design competition for a carrier-based, nuclear-strike aircraft. The competition was won by the North American AJ Savage.

NAA AJ Savage

Typical example of a production North American AJ-1 Savage, with its R-2800 engines on the wings and J33 jet in the rear fuselage. The intake for the jet was just before the vertical stabilizer and was closed when the jet was not in use.

First flown on 3 July 1948, the AJ Savage was a unique aircraft that spanned the gap between the piston-engine and jet-engine eras. The Savage was powered by two Pratt & Whitney R-2800 engines and a single Allison J33 turbojet that was mounted in the rear fuselage. The jet engine was used for takeoff and to make a final, high-speed dash to the target. In December 1947, before the AJ prototype had even flown, North American Aviation (NAA) proposed an improved version of the Savage that benefited from the continued advancement of turboprop engines. Designated NA-158 by the manufacturer, a mockup was inspected in September 1948, and the Navy ordered two examples and a static test airframe in October 1948—only three months after the AJ Savage’s first flight. The new aircraft was designated XA2J Super Savage, and the two prototypes ordered were given Navy Bureau of Aeronautics (BuAer) serial numbers 124439 and 124440.

Originally, the North American XA2J Super Savage was to be very different from the AJ Savage, but the jet engine in the rear fuselage would be retained. As the project moved through 1949, emphasis was placed on improving the XA2J’s deck performance over that of its predecessor. As a result, the XA2J became an entirely new aircraft but still resembled the AJ Savage. A mockup of the updated XA2J design, the NA-163, was inspected by the Navy in September 1949, and approval was given for NAA to begin construction.

NAA XA2J Super Savage Apr 1949

Concept drawing of the XA2J Super Savage from April 1949. Note how the aircraft bears little resemblance to the AJ Savage. The intake for the jet engine can be seen just before the vertical stabilizer. The pilot sat alone under the canopy, and the co-pilot/bombardier and gunner sat in the fuselage, behind and below the pilot.

The XA2J had the same basic configuration as its predecessor but was a larger aircraft overall. The Super Savage was of all metal construction and utilized tricycle landing gear. The high-mounted, straight wing was equipped with a drooping leading edge and large trailing edge flaps. To be brought below deck on a carrier, the aircraft’s wings and tail folded hydraulically. The pressurized cockpit accommodated the three-man crew, which consisted of a pilot, a co-pilot/bombardier, and a gunner. The pilot and co-pilot/bombardier sat side-by-side, and the rear-facing gunner sat behind them. Cockpit entry was via a side door, and an escape chute provided emergency egress out of the bottom of the aircraft. The co-pilot/bombardier was responsible for the up to 10,500 lb (4,763 kg) of bombs stored in a large, internal bomb bay. The gunner managed the radar-equipped tail turret with its two 20 mm cannons and 1,000 rpg. The defensive armament was never fitted to the prototype.

The XA2J did away with the mixed propeller and jet propulsion of the earlier AJ Savage; instead, it relied on two wing-mounted Allison T40 turboprop engines. The T40 engine was made up of two Allison T38 engines positioned side-by-side and coupled to a common gear reduction for contra-rotating propellers. Either T38 power section could be decoupled from the gear reduction, and the remaining engine could drive the complete contra-rotating propeller unit. The engine produced 5,332 hp (3,976 kW) and 1,225 lbf (4.7 kN) of thrust, for a combined output equivalent to 5,850 hp (4,362 kW). The Aeroproducts propellers used on the XA2J had six-blades and were 15 ft (4.57 m) in diameter.

NAA XA2J Super Savage ground

The XA2J Super Savage as built only had turboprop engines. In this image, the wide propellers installed on the aircraft have different cuff styles. Markings on the propeller installed on the right engine would seem to indicate that the propeller (rounded cuff) is being tested. Note the cockpit entry side door and open bomb bay doors.

The Super Savage had a 71 ft 6 in (21.8 m) wingspan and was 70 ft 3 in (21.4 m) long and 24 ft 2 in (7.4 m) tall. Folded, the wingspan dropped to 46 ft (14 m), and height decreased to 16 ft (4.9 m). The aircraft had an empty weight of 35,354 lb (16,036 kg) and a maximum takeoff weight of 61,170 lb (27,746 kg). Two fuel tanks at each wing root and two fuselage fuel tanks gave the aircraft a total fuel capacity of 2,620 gallons (9,918 L). The XA2J’s estimated top speed was 451 mph (726 km/h) at 24,000 ft (7,315 m), and its cruise speed was 400 mph (644 km/h). The aircraft had a ceiling of 37,500 ft (11,430 m) and a combat range of 2,180 miles (3,508 km) with an 8,000 lb (3,629 kg) bomb load.

NAA believed that the Super Savage airframe could be more than just a carrier-based medium bomber. The company developed designs in which various equipment packages could be installed in the aircraft’s bomb bay. The XA2J could be changed into a photo-recon platform with the installation of a camera package. Or the aircraft could become a tanker once it was outfitted with a 1,400 gallon (5,300 L) fuel tank in the bomb bay and a probe-and-drogue refueling system. A target tug system was also designed.

NAA XA2J Super Savage top

The Super Savage over the desert of California. The Allison T40 engine created trouble for every aircraft in which it was installed. The jet exhaust divider between the T38 engine sections can just be seen at the rear of the engine nacelle. Both propellers installed on the aircraft have square cuffs.

Construction of the first XA2J Super Savage prototype (BuAer 124439) began in late 1949 and progressed rapidly. However, Allison experienced massive technological problems developing the T40 engines, and they were not delivered until late 1951. The XA2J finally made its first flight on 4 January 1952 and was piloted by Robert Baker. The aircraft took off from Los Angeles International Airport and was ferried to Edwards Air Force Base (Edwards) for testing. By the time of the XA2J’s first flight, superior aircraft designs, namely the Douglas A3D (A-3) Skywarrior, were nearing completion. In addition, Allison never solved all of the T40’s issues, and the engines were limited to 5,035 hp (3,755 kW).

Testing at Edwards revealed some difficulties with the Super Savage. All aircraft powered by the complex T40 experienced numerous power plant failures, and the XA2J was no exception. The Super Savage was around 4,000 lb (1,814 kg) overweight and was never tested to its full potential. The highest speed obtained during testing was just over 400 mph (644 km/h). Even the aircraft’s estimated performance did not offer a significant advantage over that of the AJ Savage already in service. The XA2J project was cancelled in mid-1953, and the second prototype (BuAer 124440) was never completed.

NAA XA2J Super Savage in flight

The Super Savage had an aggressive appearance that gave the impression that the aircraft could live up to its name. However, it was outclassed by the Douglas A3D (A-3) Skywarrior and had performance on par with the AJ Savage it was intended to replace.

North American Aircraft 1934-1999 Volume 2 by Kevin Thompson (1999)
Aircraft Descriptive Data for North American XA2J-1 (June 1953)
American Attack Aircraft Since 1926 by E.R. Johnson (2008)
The Allison Engine Catalog 1915–2007 by John M. Leonard (2008)
– “They didn’t quit… 5: Turbine-Driven Savage,” Air Pictorial Vol. 21 No. 12. (December 1959);all

Sikorsky S-67 Blackhawk airbrakes

Sikorsky S-67 Blackhawk Attack Helicopter

By William Pearce

In the late 1960s, Sikorsky Aircraft had many helicopter models in production, but they had lost contracts to develop new helicopters. In 1966, the United States Army’s Advanced Aerial Fire Support System (AAFSS) contract was awarded to Lockheed, but their AH-56 Cheyenne attack helicopter ran into serious design issues. On 20 November 1969, Sikorsky initiated development of a new helicopter to be used primarily as a gunship, but it could also be used in other roles. This helicopter was designated S-67 Blackhawk, and its design and construction was self-funded by Sikorsky.

Sikorsky S-67 Blackhawk airbrakes

The Sikorsky S-67 Blackhawk was a very versatile helicopter that exhibited great performance, but it also had various shortcomings that the US Army could not overlook. The helicopter’s narrow fuselage and air brakes are illustrated in this image.

The Sikorsky S-67 Blackhawk was designed as a high-speed attack helicopter with a small wing to generate lift. The pilot and copilot/gunner sat in tandem in the helicopter’s cockpit, with the copilot in the front seat and the pilot in the rear seat. The pilot accessed the cockpit from the left side of the helicopter and the copilot from the right. The narrow, streamlined fuselage was only 3 ft 10 in (1.2 m) wide, which decreased the helicopter’s drag and increased its survivability by presenting a smaller target to enemy gunners. Behind the cockpit was a compartment that could be used for additional equipment or to transport personnel.

Sikorsky S-67 Blackhawk tail

This image shows the S-67’s original tail that did not have any rudders. Note the tail’s camber. Air brakes can be seen on the upper wing surfaces. The main gear had a 7 ft (2.1 m) track.

To cut expense and development time, the S-67 was designed to use the dynamic drive power system from a Sikorsky S-61/SH-3 Sea King. This included two 1,500 hp (1,119 kW) General Electric T58-GE-5 turboshaft engines and their drive, rotor, hydraulic, and electrical systems. The S-67’s five-blade rotors had 22 in (559 mm) of their tips swept back 20 degrees to delay compressibility effects, lower vibration, and reduce noise. The net effect was that the blades allowed the helicopter to achieve higher speeds. The main rotors also had a hub fairing, and their collective pitch control was modified to increase sensitivity and range.

The S-67’s main gear retracted into sponsons mounted on the fuselage sides. The helicopter’s thin wings extended from the sponsons. Each wing featured two hardpoints for weapons, auxiliary fuel tanks, or equipment. Each wing also had three air brakes: two that deployed along its upper surface and one that deployed along the lower surface. With the air brakes deployed, the helicopter slowed twice as fast as without the air brakes. In addition, the air brakes could be deployed during combat to offer unrivaled maneuverability. The S-67 was the first helicopter with air brakes.

A five-blade, 10 ft 7 in (3.2 m) diameter tail rotor was mounted to the left side of the S-67’s vertical fin. A lower fin with a non-retractable tailwheel extended below the helicopter’s tail. The large upper and lower fins were cambered to counteract the torque of the main rotor at speeds above 46 mph (74 km/h). This enabled controlled flight without the tail rotor as long as the S-67’s forward speed was in excess of 46 mph (74 km/h). If the tail rotor was lost, the helicopter could be flown back to base and landed like a conventional aircraft. The S-67 used an all-moving horizontal stabilizer that increased the helicopter’s maneuverability and decreased rotor stress.

Sikorsky S-67 Blackhawk landing

Note the angle of the all-moving horizontal stabilizer as the S-67 comes in for a landing. The landing gear was found to be insufficient for operating from unimproved locations. The helicopter’s double main wheels sunk into soft ground, and the gear doors only had 9.75 in (248 mm) of clearance.

With a 7,000 lb (3,175 kg) payload, the S-67 could accommodate a variety of armaments. A removable Emerson Electric Company TAT-140 turret mounted under the cockpit could carry a 7.62 mm minigun (M134), a 20 mm three-barrel rotary cannon (M197), a 30 mm single-barrel cannon (XM140), a 30 mm three-barrel rotary cannon (XM188), or a 40 mm grenade launcher (M129). The four underwing hardpoints could carry two drop tanks, up to 16 TOW missiles, or up to eight rocket pods. Each 2.75 in (70 mm) rocket pod contained 19 rockets, for a total of 152 rockets.

Sikorsky S-67 Blackhawk side

The S-67’s rudders can be seen in this image. One is on the upper fin below the tail rotor, and the other is on the lower fin. Pylons have been installed on the wings’ hardpoints, with drop tanks mounted to the inner stations. The turret is installed with a M197 three-barrel 20 mm cannon.

The S-67 had a wingspan of 27 ft 4 in (8.3 m) and a rotor diameter of 62 ft (18.9 m). The fuselage was 64 ft 2 in (19.6 m) long, and the helicopter’s total length including the rotor was 74 ft 1 in (22.6 m). The S-67’s mast height was 15 ft (4.6 m), and the top of the tail rotor was 16 ft 4 in (5.0 m). The helicopter’s top speed was 213 mph (343 km/h); maximum cruise speed was 201 mph (324 km/h), and normal cruise speed was 167 mph (269 km/h). The S-67 could climb at 2,000 fpm (10.2 m/s) and had a service ceiling of 20,000 ft (6,096 m). The helicopter could hover in ground effect up to 9,700 ft (2,957 m) and could hover without ground effect up to 6,500 ft (1,981 m). Maximum range on internal fuel was 325 miles (523 km), but its normal combat range was 220 miles (354 km). With external fuel tanks, range was extended to over 600 miles (966 km). The S-67 had an empty weight of 12,525 lb (5,681 kg), a normal weight of 18,500 lb (8,391 kg), and a maximum takeoff weight of 22,050 lb (10,002 kg).

Sikorsky S-67 Colonge Germany 1972

The S-67 seen in the same configuration as the previous image. The helicopter is over Cologne, Germany on its European and Middle Eastern tour in 1972.

Construction on the S-67 started on 15 February 1970 and proceeded rapidly. The helicopter made its first flight on 20 August 1970. Flight testing proved the S-67 to be very responsive, maneuverable, smooth, and quiet. The helicopter was able to perform rolls, loops, and split-S turns—although, only rolls to the right were made. On 14 December 1970, Sikorsky test pilots Kurt Cannon and Byron Graham in the S-67 established a new absolute speed record by averaging 216.841 mph (348.971 km/h) over a 3 km (1.86 mile) course. They then set a new record on 19 December 1970 by averaging 220.888 mph (355.485 km/h) on a 15–25 km (9.3–15.5 mile) course.

In 1971, the S-67 covered 3,500 miles (5,633 km) touring 12 US military bases. In addition to Sikorsky demonstration flights, the helicopter was flown on 147 demo flights with military personnel. The S-67 completed 155 rolls and 140 split-S turns during these flights.


A fan-in-fin anti-torque system was tested in the S-67. Note the rudders above and below the fan. No issues were encountered with the fan-in-fin, but the helicopter was converted back to a conventional tail rotor.

Between 25 May and 13 June 1972, the S-67 was flown 26 hours for a series of flight evaluations by the US Army. The helicopter was competing against the Bell 309/AH-1 KingCobra to replace the AH-56 Cheyenne, which had been cancelled. For the AAFSS role, the S-67 was designated AH-3, and Sikorsky’s proposal included adding an additional hardpoint to each wing, bringing the total number to six. This would enable the S-67 to carry up to 24 TOW missiles. While the S-67 was praised for its performance and most of its flight characteristics, the evaluation recorded a number of shortcomings. The Army did not award either Sikorsky or Bell a contract and decided to initiate a new Armed Attack Helicopter program, which eventually was won by the Hughes AH-64 Apache.

The S-67 underwent a number of modifications in late 1972. Rudders were added to the ventral and dorsal fins to increase yaw control. The compartment behind the cockpit was altered to enable the transport of six troops. Hardpoints were added to the wingtips for each to carry a Sidewinder missile. A hoist was added under the helicopter that allowed the S-67 to transport a 7,000 lb (3,175 kg) external load.

Sikorsky S-67 Blackhawk cockpit

After the fan-in-tail rotor tests, a small door was added on the left side of the fuselage to access the compartment behind the cockpit. Initially, access was gained (with some difficulty) via the door under the fuselage (seen above). The S-67 was then painted a light desert camouflage, and this was the helicopter’s final configuration.

With no interest from the US Armed Forces, Sikorsky offered the S-67 for export. In late 1972, the S-67 was taken on a two-month tour of Europe and the Middle East. More than 7,500 miles (12,070 km) were covered, and the helicopter was flown for 136 hours. Despite interest from Israel, no orders were placed. Sikorsky then modified the S-67 to test a fan-in-fin tail rotor installation. A 4 ft 8 in (2.6 m), seven-blade rotor was installed in the modified tail. The helicopter underwent flight tests, including a dive at 230 mph (370 km/h). After the tests in 1974, the S-67’s tail was converted back to its previous configuration (with rudders), and a door to access the rear compartment was installed in the helicopter’s left side. The S-67 was then painted a light desert camouflage. The data from the fan-in-fin test was used for the Sikorsky H-76 fantail demonstrator, which tested the tail configuration later used in the Boeing-Sikorsky RAH-66 Comanche.

Sikorsky S-67 Blackhawk inverted

The S-67 made hundreds of rolls in its lifetime, but they were always to the right. The square in the fuselage above the wing is the window in the new rear compartment access door. What appear to be two rectangular windows can be seen father aft. Note the helicopter’s rudders and deployed air brakes.

On 26 August 1974, the S-67 arrived in the United Kingdom to start another European tour. On 1 September 1974, the S-67 was destroyed after failing to recover from a second roll during a practice session for the upcoming Farnborough Air Show. The copilot, Stu Craig, was killed in the crash, and the pilot, Kurt Cannon, died from his injuries nine days later. The accident was caused by the second roll being initiated in a less than ideal configuration combined with low altitude. However, the accident investigators believed that the crash was survivable had the helicopter been fitted with five-point harnesses rather than four-point harnesses. The S-67 had accumulated 598.7 hours at the time of the crash.

With the prototype destroyed and no interest from the US military, Sikorsky decided to end the S-67 Blackhawk program. Its swept-tip rotor blades were developed into those used on the Sikorsky S-70/UH-60 Black Hawk (the name similarity is a coincidence) and other helicopters. The S-67’s speed record stood for eight years until it was broken on 21 September 1978 by the Soviet Mil A-10 (modified Mi-24B) at 228.9 mph (368.4 km/h).

Sikorsky S-67 Blackhawk crash

The S-67 tries to recover from a roll a split second before it impacts the ground. The helicopter’s low altitude left no room to recover from the roll, which was rushed and initiated in a flawed manner. The crash would ultimately kill the pilot and copilot and end the S-67 program.

– “Blackhawk’s Last Flight” Aeroplane Monthly (June 1976)
Attack Helicopter Evaluation, Blackhawk S-67 Helicopter by George M. Yamakawa, et al (July 1972)

CTA - ITA Heliconair Convertiplano drawing

CTA / ITA Heliconair HC-I Convertiplano

By William Pearce

In 1923, Henrich Focke partnered with Georg Wulf to create Focke-Wulf Flugzeugbau (Aircraft Company) in Bremen, Germany. Focke became fascinated with helicopters and other rotorcraft in the 1930s. This interest led to what is considered the first practical helicopter, the Focke-Wulf Fw 61, which first flew in 1936. That same year, Focke was ousted from Focke-Wulf due to internal disagreements about allocating company resources. In 1937, Focke partnered with Gerd Achgelis, the Fw 61’s lead designer, to create Focke-Achgelis & Co in Hoykenkamp, Germany. The new company would focus on helicopter and rotorcraft designs.

CTA - ITA Convertiplano side

The Heliconair HC-Ib Convertiplano sits nearly finished in a hangar. The slit behind the cockpit was the intake for air used to cool the fuselage-mounted R-3350 engine. The scoop on the upper fuselage brought air to the engine’s carburetor. Note the Spitfire wings and main gear.

In 1941, the RLM (Reichsluftfahrtministerium or Germany Air Ministry) requested that Focke-Achgelis design a fighter capable of vertical takeoff and landing (VTOL). Focke-Achgelis responded with the Fa 269 design, which was a tiltrotor convertiplane. The Fa 269 had two rotors—one placed near the tip of each wing in a pusher configuration. The rotors were powered by an engine housed in the aircraft’s fuselage via extension shafts and gearboxes. The rotors and extension shafts leading from the right-angle gearboxes mounted in the aircraft’s wings rotated down to “push” the Fa 269 into the air, achieving vertical flight. Once airborne, the rotors and shafts would slowly translate back into the wing to propel the aircraft forward, allowing the aircraft’s wings to provide lift. The project moved forward until 1944, when much of the developmental work, including models, a mock-up, and gearboxes, was destroyed in an Allied bombing raid.

CTA - ITA Heliconair Convertiplano

Drawings of how the completed HC-Ib was anticipated to look reveal a pretty compact aircraft, considering the engine installation and associated shafting. The R-3350 engine took up the space intended for a passenger compartment in the Double Mamba-powered HC-I. The Double Mamba would have been installed aft of the passenger compartment.

Immediately following World War II, Germany was prohibited from designing and manufacturing aircraft. Post war, Focke assisted with helicopter development in France and worked for a car company in Germany. He also spent some time in the Netherlands, where he began to design a VTOL aircraft that was capable of relatively high speeds. In 1952, Focke was recruited by the CTA (Centro Técnico de Aeronáutica or Technical Center of Aeronautics) to work in the recently established ITA (Instituto Técnico de Aeronáutica or Technical Institute of Aeronautics). The ITA was the first of four institutes formed by the CTA, all of which were located in São José dos Campos, Brazil. Brazil was working on building an aeronautics and aerospace industry and was actively recruiting German engineers. In addition to Focke, many of his associates and former co-workers were also recruited.

The CTA was impressed with Focke’s VTOL aircraft design and approved its construction. The CTA believed that the aircraft’s capabilities would allow it to reach remote parts of Brazil. Focke set to work on the aircraft—a tiltrotor convertiplane design that was partially inspired by the Fa 269. The aircraft was known as the Heliconair HC-I Convertiplano. Its fuselage and wings were fairly conventional for an aircraft, but it had of two sets of rotors. One pair of rotors was placed near the nose of the aircraft, and the other pair was placed between the wings and tail. All of the rotors were of a tractor configuration and rotated up for vertical flight. The HC-I accommodated two pilots in the cockpit and four passengers in the fuselage. The aircraft’s estimated performance included a top speed of 311 mph (500 km/h) and a range of 943 miles (1,517 km).

CTA - ITA Convertiplano engine test rig

The test rig for the engine, transmission, gearboxes, shafts, right-angle drives, and rotors illustrates the complexity of the HC-Ib’s power system. The R-3350 engine did not have any Power Recovery Turbines, which means it was not a Turbo Compound engine.

To save time and money, the decision was made to build the HC-I using the wings and the horizontal stabilizer from a Supermarine Spitfire. A Spitfire XIVe (RM874) was purchased without its Rolls-Royce Griffon 65 engine from Britain by the Brazilian Air Attaché on 19 December 1952. A new fuselage was built to house a 3,000 hp (2,237 kW) Armstrong Siddeley Double Mamba turboprop engine behind the passenger compartment. However, Armstrong Siddeley and the British did not want one of their new, advanced engines being used in such a radical project and declined selling a Double Mamba engine to Brazil.

Focke and the Convertiplano team changed the HC-I’s design to accommodate a 2,200 hp (1,641 kW) Wright R-3350 radial engine and redesignated the aircraft HC-Ib. The R-3350 was larger and heavier than the Double Mamba, and it produced less power. Some sources state a Turbo Compound R-3350-DA3 (3,250 hp / 2,424 kW) was used, but images show that there are no Power Recovery Turbines on the engine installed in a test rig. Extensive modifications to the aircraft’s fuselage were required to accommodate the air-cooled engine. The passenger compartment was omitted, and the R-3350 was installed in the middle of the fuselage. An annular slit behind the cockpit was added to bring in cooling air for the engine. After passing through the engine’s cylinders, the air exited via a jet-like duct at the rear of the aircraft. The Spitfire’s landing gear was strengthened to compensate for the R-3350’s weight.

CTA - ITA Convertiplano components

The HC-Ib sits in the background with the front and rear gearboxes and rotor drives in the foreground. The rotor blades, the only surviving component of the Convertiplano project, are not seen in the image. Note the opening at the rear of the fuselage, which was the exit for engine cooling air.

A gearbox transmission mounted to the front of the R-3350 split the engine’s power to two shafts. The front shaft extended from the engine to the front gearbox. The front gearbox had shafts that extended to the left and right. These shafts led to right-angle gearboxes that powered the front rotors. Power delivery for the rear rotors was more complex. A shaft extended vertically from the transmission on the front of the engine and met a right-angle gearbox positioned directly above the engine. From the right-angle gearbox, a shaft extended back to the rear gearbox. The rear gearbox had the same shafts and right-angle drives for the rear rotors as the front gearbox. The transmission and gearboxes were designed by Willi Bussmann and built by BMW in Germany. Bussmann was a former BMW employee and had worked with Focke on several Focke-Achgelis projects.

Each rotor consisted of three blades. The blades were built in Sweden and made of a steel frame that was covered with wood. The blades’ pitch automatically adjusted and had collective and cyclic control. The rotors were counter-rotating, with the right rotors turning counterclockwise and the left rotors turning clockwise. The HC-Ib had a 37 ft 6 in (11.42 m) wingspan and was 35 ft 3 in (10.74 m) long.

CTA - ITA Convertiplano engine hoist

Given the state of the aircraft and the surrounding unchecked growth of vegetation, it can be assumed this image is of the R-3350 engine being removed sometime after the HC-Ib project was cancelled. The image does give proof that the engine was installed in the airframe at one point.

A rig was built, and tests of the engine, gearboxes, shafts, right-angle drives, and rotors began in late 1953. However, vibrations from the radial engine caused some issues that took time to resolve. The HC-Ib airframe was almost completely constructed and had its engine installed when the project was cancelled in 1955. The aircraft was more expensive than anticipated, and interest in the HC-1b had steadily declined after the switch to the R-3350 engine. To make matters worse, many of the Germans returned to Europe or went to the United States as their contracts with the CTA expired. Some Germans did stay and ultimately became part of Embraer. After the project was cancelled, the HC-Ib Convertiplano was left to rot in outside storage for some time and was eventually scrapped in the 1970s. There are some reports that the rotor blades are the only part of the aircraft that survived.

A follow up Convertiplano project was considered. Designated HC-II, the aircraft would be powered by four 1,400 hp General Electric T58 turboshaft engines and reincorporate a four to six passenger cabin. The HC-II never progressed beyond the initial design phase.

CTA - ITA Convertiplano HC-II

The C-II Convertiplano had a GE T58 engine mounted directly to each of its four rotors. Otherwise, it retained the configuration of the original HC-I.

Axis Aircraft in Latin America by Amaru Tincopa and Santiago Rivas (2016)
– “Uma Breve História das Atividades do Prof. Focke no Brasil” by Joseph Kovacs, ABCM Engenharia Volume 9 Número 2 (April–September 2003)

Sud-Est SE 580 cowling

Sud-Est (SNCASE) SE 580 Fighter

By William Pearce

The state-owned French aircraft manufacturer SNCAM (Société nationale des constructions aéronautiques du Midi or National Society of Aircraft Constructors South) was formed in March 1937 when the Dewoitine firm was nationalized. Many Dewoitine personnel, including the company’s founder, Émile Dewoitine, continued to work for SNCAM. As a result, aircraft designed and built at SNCAM continued to bear the Dewoitine name.

Sud-Est SE 580 model

Wind tunnel model of the Sud-Est SE 580 complete with contra-rotating propellers.

In 1940, SNCAM began studies of a new fighter aircraft. The aircraft was based on a continuing design evolution that started with the Dewoitine D.520 production fighter and progressed through the D.551/552 pre-production fighters. SNCAM’s new fighter design was designated M 580.

The M 580 aircraft was a tractor design with conventional undercarriage. However, the power plant was unusual in that it utilized two Hispano-Suiza 12Z engines coupled in tandem and driving a coaxial contra-rotating propeller (similar to the Arsenal VB 10). The M 580 was designed by Robert Castello and Jacques Henrat, who had been very involved with previous Dewoitine fighter designs. Before much design work was completed, SNCAM was absorbed into SNCASE (Société nationale des constructions aéronautiques du Sud-Est or National Society of Aircraft Constructors Southeast) in late 1940.

With the SNCASE (often referred to as Sud-Est) takeover and the German occupation of France, the M 580 design languished during the war. Under Sud-Est, the aircraft was redesignated SE 580. Wind-tunnel tests were conducted in 1943, and the SE 580 design was changed to incorporate a new engine then under development. Gone was the tandem V-12 engine configuration, and in its place was a single 24-cylinder Hispano-Suiza 24Z engine. With much of France liberated in 1944, two SE 580 prototypes were ordered by the Ministère de l’Air (French Air Ministry). The Marine Nationale (French Navy) was interested in a navalized version designated SE 582 and ordered two prototypes in early 1945.

Sud-Est SE 580 HS 24Z

The SE 580 with open cowling revealing the 24-cylinder, 3,600 hp (2,685 kW) Hispano-Suiza 24Z engine.

Work on the SE 580 prototype was started first. The aircraft was of all-metal construction with fabric-covered control surfaces. The aircraft’s structure, especially the wings, followed basic Dewoitine design principals used in their earlier fighter aircraft. The SE 580 featured dive recovery flaps positioned under the wing and outside of the fully retractable main landing gear. Another unusual feature was that the incidence of the aircraft’s horizontal stabilizer was adjustable.

The smooth flow of the aircraft’s fuselage was interrupted by a large hump behind the cockpit. This structure housed the scoop that directed air through a radiator positioned horizontally in the aircraft’s rear fuselage. Cooling air entered a large opening just behind the cockpit, traveled down through the radiator, and exited the fuselage via a ventral flap. The intake also incorporated a slot for boundary layer air bleed. The radiator’s location in the center of the aircraft offered some inherent protection that was further enhanced by rear armor plating to protect against enemy fire.

Three fuselage fuel tanks and one fuel tank in each wing held a total of 660 gallons (2,500 L). A drop tank under the fuselage held an additional 79 gallons (300 L) of fuel. The SE 580’s Hispano-Suiza 24Z engine was an H-24 that was forecasted to produce 3,600 hp (2,685 kW). The 24Z would turn an 11.5 ft (3.50 m) diameter, six-blade, contra-rotating propeller.

Sud-Est SE 580 front

The supercharger intakes and numerous exhaust stacks interrupt the otherwise clean lines of the SE 580’s fuselage. The dorsal radiator scoop created a large blind spot for the pilot. One must wonder how cleanly air would flow into the scoop after being disrupted by the canopy.

The SE 580’s armament was quite substantial and consisted of a 30 mm cannon mounted between the engine’s upper cylinder banks and firing through the propeller hub. Each wing housed two 20 mm cannons and four 7.5 mm (or three 12.7 mm) machine guns. A hardpoint under each wing could accommodate a 1,102 lb (500 kg) bomb. A photo reconnaissance version would accommodate a vertical camera in the central fuselage.

The SE 580 had a 52.0 ft (15.86 m) wingspan and was 42.7 ft (13.0 m) long. The aircraft had an empty weight of 11,228 lb (5,093 kg) and a gross weight of 17,919 lb (8,128 kg). The SE 580 had a top speed of 373 mph (600 km/h) at sea level and 465 mph (749 km/h) at 30,512 ft (9,300 m). Its landing speed was 88 mph (141 km/h). The SE 580 could climb to 19,685 ft (6,000 m) in just over six minutes and had a theoretical ceiling of 44,619 ft (13,600 m). The aircraft’s maximum range was 1,709 miles (2,750 km).

By 1946, construction of the first SE 580 prototype was well underway, and a Hispano-Suiza 24Z engine was installed in the airframe. Unfortunately, problems with the 24Z engine resulted in its cancellation. The Arsenal 24H was selected as the replacement engine. The 4,000 hp (2,983 kW) 24H was also a 24-cylinder engine in an “H” configuration but had many differences when compared to the 24Z. The 24H was heavier and had a different propeller location; it used a single rotation, 12.1 ft (3.70 m) diameter, five-blade propeller. These differences required numerous, complex changes to the SE 580. The longer propeller was located 5.12 in (130 mm) lower on the engine and required changes to the aircraft’s landing gear and wings to maintain acceptable ground clearance. Wind-tunnel tests indicated further wing changes would be needed and that the engine had to be moved forward. In light of all the required changes, budgetary cutbacks, Sud-Est’s preoccupation with other projects, and the emergence of jet aircraft, the SE 580 was cancelled in 1947.

Sud-Est 580 rear

This rear view of the SE 580 shows the large radiator housing behind the cockpit. Note the cooling air exit flap under the fuselage.

SE 582 development trailed behind that of the SE 580; the French Navy was more interested in the Sud-Ost SO.8000, and Sud-Est was more focused on the SE 580. Changes needed to navalize the aircraft included incorporating an arrestor hook and folding wings. Construction of the SE 582 was limited to components that were shared with the SE 580, but it does not appear that any substantial part of the SE 582 was ever completed. The SE 582 had the same basic specification as the SE 582, except it was 712 lb (323 kg) heavier, at a gross weight of 18,631 lb (8,451 kg).

When Sud-Est abandoned the SE 580/582, the possibility of SNCAC (Société nationale des constructions aéronautiques du Centre or National Society of Aircraft Constructors Center) taking over the projects was discussed. However, the status of aviation could not be changed—the SE 580 and 582 were outdated, and existing aircraft already matched their performance. The first SE 580 prototype was never completed.

Sud-Est SE 580 cowling

SE 580 was a large aircraft, and its predicted performance equaled, but not bettered, existing aircraft then in service. Lack of available information about the aircraft, combined with its unique configuration and engine have made the SE 580 a curiosity for many aviation enthusiasts.

Les Avions de Combat Francais 1944-1960 I – Chasse-Assaut by Jean Cuny (1988)
Les Avions Dewoitine by Raymond Danel and Jean Cuny (1982),4110.0.html


Commonwealth Aircraft Corporation CA-15 ‘Kangaroo’

By William Pearce

In July 1942, Australia’s Commonwealth Aircraft Corporation (CAC) endeavored to improve the performance of their CA-12 (and CA-13) Boomerang fighter by installing a 1,700 hp (1,268 kW) Wright R-2600 engine in place of the 1,200 hp (895 kW) Pratt & Whitney (P&W) R-1830. However, the needed modifications to the Boomerang airframe proved to be too substantial. Since the need for an improved fighter was still pressing, CAC embarked to design an entirely new aircraft in November 1942. This new fighter aircraft was designated CA-15.

CAC CA-15 flight

The impressive Commonwealth Aircraft Corporation CA-15 on a test flight. Note the patches on the wings that replaced the gun ports for the .50 cal machine guns.

The preliminary design of the CAC CA-15 incorporated a Pratt & Whitney R-2800 engine, and the aircraft somewhat resembled a cross between a Boomerang and a Focke-Wulf Fw 190A. As the design was developed, the CA-15 changed to resemble a Hawker Tempest II with squared-off wings and tail, but with a General Electric (GE) C turbosupercharger installed in the rear fuselage, similar to the Republic P-47 Thunderbolt.

By mid-1943, a redesign was needed because the proposed power plant, the 2,000 hp (1,491 kW) R-2800-21, was not available. CAC selected the 2,200 hp (1,641 kW) R-2800-10W with a two-stage, two-speed supercharger as the new engine. With the engine change, the turbosupercharger was deleted, and a water-cooled intercooler was added in a large fairing under the engine. A geared cooling fan would help draw air in through the tight-fitting cowling. By December 1943, the R-2800-10W-powered CA-15 was estimated to have a maximum speed of 365 mph (587 km/h) at sea level, 436 mph (702 km/h) at 25,000 ft (7,620 m), and an initial climb rate of 4,200 fpm (21.3 m/s).

CAC CA-15 R-2800-21

The Pratt & Whitney R-2800-21-powered CA-15, with cutaway to show the fuselage fuel tank. The turbosupercharger installation in the rear fuselage is not visible. In this early 1943 drawing, the CA-15 has a passing resemblance to the Hawker Tempest II.

The switch to the R-2800-10W engine also shifted the CA-15’s area of maximum performance from high altitude to low/medium altitude. At the time, CAC had obtained a license to produce the North American P-51D Mustang as the CA-17 and CA-18; CA-17s would be assembled from parts, and CA-18s would be CAC-produced aircraft. Lawrence Wackett, CAC’s General Manager, envisioned the CA-17/CA-18 filling the high altitude fighter role and the CA-15 covering low and mid altitudes. From mid-1943, CAC was focused on CA-17 assembly and CA-18 production, and progress on the CA-15 slowed as a result.

With many components for the prototype CA-15 under construction, CAC was disappointed to learn in May 1944 that the R-2800-10W was no longer in production. CAC found a suitable replacement in the form of the 2,800 hp (2,088 kW) R-2800-57. With this engine change, the CA-15 was back to incorporating a turbosupercharger—now a GE CH-5 housed in a deeper fairing under the engine. The R-2800-57-powered CA-15 was estimated to have a maximum speed of 400 mph (644 km/h) at sea level, 480 mph (772 km/h) at 28,000 ft (8,534 m), and an initial climb rate of 5,700 fpm (29.0 m/s).

CAC CA-15 R-2800-57

A mid-1944 drawing of the CA-15 powered by a R-2800-57 engine. While the top view of the aircraft has not changed much, the bulky fairing under the engine has been added to house the intercooler and turbosupercharger.

By August 1944, the CA-15 prototype was around 50 percent complete. It was at this time that CAC was informed that supplies of the R-2800-57 could not be guaranteed. CAC again looked for an engine suitable for the CA-15 fighter. CAC found a new engine in the Griffon 125, then being developed by Rolls-Royce (R-R). The water-cooled Griffon 125 had a two-stage, three-speed supercharger and turned a single rotation propeller. The engine was capable of producing 2,440 hp (1,820 kW). A redesign of the CA-15 cowling was completed, and a scoop to house radiators for the engine coolant and oil was incorporated under the aircraft. With these changes, the CA-15 resembled a P-51D Mustang, but the resemblance was coincidental. The Griffon 125-powered CA-15 was estimated to have a maximum speed of 405 mph (652 km/h) at sea level, 467 mph (752 km/h) at 18,000 ft (5,487 m), and 495 mph (797 km/h) at 26,500 ft (8,077 m). The initial climb rate dropped slightly to 5,500 fpm (27.9 m/s).

Unfortunately, the Australian War Cabinet cancelled the CA-15 in September 1944. However, CAC continued work on the CA-15 at a reduced pace while it worked with the War Cabinet to reinstate the program. This was done in December, pending the approval of the Aircraft Advisory Committee, which followed in February 1945.

Work on the CA-15 now continued at a quicker pace, but engine issues surfaced again. R-R would not be able to provide a Griffon 125 until late 1945 at the earliest (but probably later). The CA-15 was ready for its engine, and CAC did not want to wait. As a substitute, two 2,035 hp (1,517 kW) Griffon 61s were loaned to CAC, the first being shipped in April 1945. The Griffon 61 had a two-stage, two-speed supercharger. As the CA-15 neared completion in December 1945, R-R informed CAC that the Griffon 125 would not be produced. The CA-15 used the Griffon 61 as its final engine, and the aircraft was completed in early 1946.


The completed CA-15 with its Griffon 61 engine bore a striking resemblance to the P-51D Mustang. However, the aircraft’s general layout changed little from the early 1943 drawing completed before CAC obtained a license for P-51 (CA-17/CA-18) production. Note the recessed engine exhaust stacks for improved aerodynamics.

The CA-15 was an all-metal aircraft of stressed-skin construction. The flaps and fully retractable gear were hydraulically operated. Various offensive armament combinations were considered, including four 20 mm cannons with 140 rpg, but six .50 cal machines guns were ultimately fitted with 250 rpg (various sources, including CAC documents, list 260, 280, or 290 rpg). The guns were not installed until a few months after the aircraft’s first flight. Underwing provisions existed for two 1,000 lb (454 kg) bombs or two 120 gal (100 imp gal / 454 L) drop tanks or 10 rockets.

In its final form, the CA-15 had a 36 ft (11 m) wingspan and was 36 ft 3 in (11 m) long. The aircraft’s internal fuel capacity was 312 gal (260 imp gal / 1,182 L), and it had a maximum range of 2,540 mi (4,088 km) with two drop tanks. The CA-15 weighed 7,540 lb (3,420 kg) empty, 10,764 lb (4,882 kg) with a normal load, and 12,340 lb (5,597 kg) at maximum overload. The Griffon 61-powered CA-15 had a maximum speed of 368 mph (592 km/h) at sea level, 448 mph (721 km/h) at 26,400 ft (8,047 m), and 432 mph (695 km/h) at 32,000 ft (9,754 m). The aircraft’s initial climb rate was 4,900 fpm (24.9 m/s), and it had a ceiling of 39,900 ft (12,162 m). The Griffon engine turned a 12 ft 6 in (3.81 m) diameter Rotol four-blade, wooden, constant-speed propeller. Initially, a 12 ft 1 in (3.68 m) propeller was used, the result of a damaged tip necessitating the blades being cut down. But a full-size propeller was fitted later during the flight test program.

CAC CA-15 side

This photo of the CA-15 illustrates the tailplane’s 10 degrees of dihedral and the relatively good view the pilot had over the nose of the aircraft.

Assigned serial number A62-1001, the CA-15 began taxi tests in February 1946. After a few modifications, the aircraft first flew on 4 March 1946 with Jim Schofield at the controls. The initial test flights went well, although the ailerons were noted as being heavy. Aileron control was improved, and numerous other refinements were made. Throughout the test flights, the CA-15 proved itself as an easy to fly aircraft with excellent performance and very good visibility.

After 16.5 hours of flying time, the CA-15 was handed over to the Royal Australian Air Force (RAAF) Aircraft Performance Unit (APU) No. 1 on 2 July 1946 for further flight testing. While at APU No. 1, the landing gear struts were over-pressurized, causing the CA-15 to bounce badly during taxi tests. The hopping action of the aircraft earned it the unofficial nickname “Kangaroo,” which has lasted over the years. Unfortunately, on 10 December 1946, a test gauge failed and resulted in the loss of all hydraulics. With no flaps and the unlocked gear partially extended, Flt. Lt. Lee Archer was forced to make an emergency landing that damaged the aircraft’s scoop and destroyed the wooden propeller. The failed gauge should have been removed before the aircraft was handed over to the RAAF. At the time, the CA-15 had 43.25 flying hours, and the damage was not too severe. However, with the war over and jets coming into service, there was no possibility of the CA-15 going into production. As a result, repairs to the one-off prototype were slow, after finally being approved in April 1947.

CAC CA-15 taxi

The CA-15 after a test flight. Note the scoop’s partially open cooling air exit flap. The aircraft in the background are most likely CAC-assembled CA-17s (P-51Ds), as the first CA-18 was not completed until 1947 (after the CA-15 was damaged).

CAC had repaired the CA-15’s airframe by October 1947, and the aircraft awaited a new propeller and radiator, which were the responsibility of the RAAF. The radiator was ready by February 1948, and the propeller followed in March. The CA-15 was returned to APU No. 1 on 19 May 1948. Later that month, the CA-15 grabbed headlines by achieving 502 mph (808 km/h) in a test flight over Melbourne, Victoria, Australia on 25 May 1948. This speed was recorded after Flt. Lt. Archer had leveled off at 5,000 ft (1,524 m) following a modest dive from 9,000 ft (2,743 m).

By February 1950, R-R wanted the two Griffon 61 engines back. In addition, there was no inventory of spare parts or any practical reason to continue flight testing of the CA-15. The engine was removed, and the CA-15 was scrapped, bringing an end to the highest performance aircraft ever designed and built in Australia.

CAC CA-15 rear

The CA-15 “Kangaroo” was a powerful fighter with performance rivaling that of the best piston-powered aircraft. Sadly, it was built too late for action in World War II and at a time when jet aircraft were the undeniable future.

Wirraway, Boomerang & CA-15 in Australian Service by Stewart Wilson (1991)
Wirraway to Hornet by Brian L Hill (1998)
– “Commonwealth CA-15: The ‘Kangaroo’ Fighter” by David Donald Wings of Fame Volume 4 (1996)
R-2800: Pratt & Whitney’s Dependable Masterpiece by Graham White (2001)