Category Archives: Aircraft

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.

Sources:
Soviet and Russian Ekranoplans by Sergy Komissarov and Yefim Gordon (2010)
WIG Craft and Ekranoplan by Liang Lu, Alan Bliault, and Johnny Doo (2010)
https://en.wikipedia.org/wiki/Rostislav_Alexeyev
https://en.wikipedia.org/wiki/Caspian_Sea_Monster
https://rtd.rt.com/stories/caspian-monster-ekranoplan-vessel/
https://www.theregister.co.uk/2006/09/22/caspian_sea_monster/

Supermarine Spiteful RB518

Supermarine Spiteful and Seafang Fighters

By William Pearce

In 1942, the British Royal Aircraft Establishment at Farnborough and Supermarine Aviation were working on ways to improve the Spitfire fighter. One of the main limiting factors of the aircraft was with its wing encountering compressibility at high speed. The investigation led to interest in designing a laminar flow airfoil and adapting it to an existing Spitfire airframe. In late 1942, the British National Physics Laboratory joined the effort, and Supermarine issued Specification No 470 for the new Spitfire wing in November. As designed, the new wing was 200 lb (91 kg) lighter, would increase the aircraft’s roll rate, and was expected to increase the aircraft’s speed.

Supermarine Spiteful NN660 1st prototype

The first Supermarine Spiteful prototype (NN660) consisted of new laminar flow wings mounted to a Spitfire XIV fuselage. Note the wide and shallow radiator housings under the wings and the standard canopy

A proposal was submitted to the British Air Ministry and gathered enough interest for Specification F.1/43 to be issued in February 1943, calling for a single-seat fighter with a laminar flow wing for Air Force service and provisions for a folding wing to meet Fleet Air Arm (FAA) requirements. Supermarine proceeded with the design under the designation Type 371. Originally, the aircraft was to be named Victor or Valiant, names that were previously (but temporarily) applied to advanced Spitfire models. However, the Type 371 eventually had its name changed to Spiteful. Three prototypes were ordered, and a fourth was added later.

The design of the Supermarine Spiteful was overseen by Joseph Smith. The laminar flow wing was much thinner than the wing used on the Spitfire and necessitated a complete redesign. The all-metal wing had two spars and a straight taper on the leading and trailing edges, which simplified its manufacture. The skin used was relatively thick to add rigidity and improve aileron control. Unlike with the Spitfire, the landing gear retracted inward with the main wheels being housed in the comparatively thick wing roots. The landing gear struts compressed as the gear retracted to minimize the space needed within the wing. Wide and shallow radiators for engine cooling were housed behind the main gear wells. The oil cooler was positioned behind the coolant radiator in the left wing, and the intercooler radiator was positioned in front of the coolant radiator in the right wing. The radiator housings had adjustable inlets and exit flaps. Each wing had two 20 mm cannons with 167 rounds for each inner gun and 145 rounds for each outer gun. The underside of each wing could accommodate two 300 lb (136 kg) rockets or a hardpoint for a drop tank or a bomb up to 1,000 lb (454 kg).

The all-metal, monocoque fuselage of the Spiteful was similar to that of the Spitfire. The cockpit was raised to improve the pilot’s view over the aircraft’s nose. A new, sliding bubble canopy covered the cockpit. Four fuel tanks in the fuselage, forward of the cockpit, held a total of 120 gal (100 Imp gal / 455 L), and a tank in each wing root held 10 gal (8 Imp gal / 36 L). Starting with the third prototype, a 74 gal (62 Imp gal / 282 L) fuel tank was added behind the cockpit, bringing the total internal capacity to 214 gal (178 Imp gal / 809 L). Two 108 gal (90 Imp gal / 409 L) drop tanks could be carried under the wings, or a single 204 gal (170 Imp gal / 773 L) drop tank could be mounted to the aircraft’s centerline.

Supermarine Spiteful NN664 2nd prototype

The Spiteful prototype (NN664) is considered the first true Spiteful because it incorporated the new fuselage. The aircraft was never painted. Note the standard, Spitfire F.21 tail.

The Spiteful’s Mark numbers were a continuation of those used on the Spitfire. The Spiteful F.XIV (F.14) was powered by a 2,375 hp (1,771 kW) Rolls-Royce Griffon 69 with a five-blade, single-rotation propeller. The Spiteful F.XV (F.15) was powered by the 2,350 hp (1,752 kW) Griffon 89 or 90 with a six-blade, contra-rotating propeller. Both Griffon engines had a two-stage, two-speed supercharger, and both the five- and six-blade propellers were 11 ft (3.35 m) in diameter and built by Rotol. Originally, a Rolls-Royce Merlin engine could be substituted for the Griffon if Griffon engine production was found to be lacking, but the Merlin option was dropped in mid-1944.

The Spiteful had a 35 ft (10.67 m) wingspan, was 32 ft 11 in (9.76 m) long, and was 13 ft 5 in (4.10 m) tall. The aircraft had a maximum speed of 409 mph (658 km/h) at sea level, 437 mph (703 km/h) at 5,500 ft (1,676 m), and 483 mph (777 km/h) at 21,000 ft (6,401 m). Cruising speed for maximum range was 250 mph (402 km/h) at 20,000 ft (6,096 m). The Spiteful’s stalling speed was 95 mph (153 km/h). The aircraft’s range was 564 mi (908 km) on internal fuel and 1,315 mi (2,116 km) with drop tanks. The Spiteful had an empty weight of 7,350 lb (3,334 kg), a normal weight of 9,950 lb (4,513 kg), and a maximum weight of 11,400 lb (5,171 kg). The aircraft had an initial rate of climb of 4,890 fpm (24.8 m/s) and a ceiling of 42,000 ft (12,802 m).

Supermarine Spiteful NN667 and RB523 long scoop

A comparison of the third Spiteful prototype (NN667) and the ninth F.XIV production aircraft (RB523). Both have the elongated intake scoop mounted under the engine and just behind the spinner. Note the larger tail compared to the first two Spiteful prototypes.

With other war work taking priority, it was some time before Supermarine had anything related to the Spiteful to test. A mockup was inspected in March 1944, and the aircraft’s name was changed to Spiteful around this time. A set of wings was fitted to a Spitfire XIV (serial number NN660), which became the first Spiteful prototype. The aircraft was first flown on 30 June 1944, with Jeffrey Quill as the pilot. The aircraft used the same 2,035 hp (1,518 kW) Griffon 61 engine as installed in a standard Spitfire XIV, but its performance was superior to that of a standard Spitfire XIV. However, the Spiteful also exhibited rather violent stalling characteristics compared to the fairly docile stall of the Spitfire. This was attributed to the outer wing with the aileron stalling first, which was the opposite of how the Spitfire’s elliptical wing stalled. With the Spitfire, the outer wing stalled last and enabled the ailerons to remain effective deep into the stall. On 13 September 1944, NN660 crashed while engaged in a dog-fight test with a standard Spitfire XIV. The pilot, Frank Furlong, was killed in the crash. A definitive cause was never determined, but it was believed that the aileron control rods became jammed during moderate G maneuvers.

On 8 January 1945, the second Spiteful prototype (NN664) took to the air, piloted by Quill. The aircraft incorporated updated aileron controls and the new Spiteful fuselage. However, NN664 had a tail similar to that used on the Spitfire F.21. Extensive handling tests were undertaken on NN664 that resulted in a few changes. The most significant change was a redesigned tail with its vertical stabilizer and rudder area increased by 28 percent and its horizontal stabilizer and elevator area increased by 27 percent. NN664 first flew with the new tail on 24 June 1945, and the aircraft was sent to the Aeroplane and Armament Experimental Establishment (A&AEE) at RAF Boscombe Down for flight trials.

Supermarine Spiteful RB515 underside

The underside of Spiteful RB515, the first production aircraft, illustrates the wings’ straight leading and trailing edges. Note the standard, short intake scoop. Outlines of the radiator housing doors are visible.

Shortly after NN664’s first flight, the Air Ministry ordered 650 Spiteful aircraft. The order went through a number of reductions, including the cancellation of 150 Spitefuls around 5 May 1945 so that a comparable number of Seafangs (see below) could be ordered. The fourth prototype was included in these cancellations.

The third Spiteful prototype (NN667) was sent to the A&AEE for service evaluations on 1 February 1946. It was found that the aircraft exhibited several areas of poor build quality, and there were numerous concerns with its ease of serviceability. A multitude of fasteners needed to be undone in order to remove the engine cowling, and rearming the aircraft was a time-consuming process that involved disconnecting the controls to the ailerons. A number of modifications and improvements were suggested, but it is not clear just how many were implemented. For at least part of its existence, NN667 had an elongated air intake that would be featured on the Seafang (see below). Other Spitefuls also had the longer scoop (at least RB517, RB518, RB522 and RB523).

The first production Spiteful F.XIV (RB515) made its first flight on 2 April 1945, with Quill in the pilot’s seat. The aircraft originally had an F.21 tail, but a larger Spiteful tail was installed after RB515’s third flight, which ended in a forced landing. The aircraft’s first flight with the new tail was on 21 May 1945. On 27 September 1945, RB515 suffered an engine failure and made another forced landing at Farnborough. The damaged aircraft was subsequently written off.

Supermarine Spiteful RB515 in flight

Another view of RB515 illustrates the larger Spiteful tail that was later applied to the Spitfire F.22 and F.24. The tail improved the Spiteful’s handling, but the aircraft’s stall was still violent compared to the Spitfire’s.

Spiteful RB518 was fitted with a rounded Seafang (see below) windscreen and a 2,420 hp (1,805 kW) Griffon 101 engine to become the sole Spiteful F.XVI (F.16). The Griffon 101 had a two-stage, three-speed supercharger and turned a five-blade, single rotation propeller. In 1947, RB518 achieved 494 mph (795 km/h) at 27,800 ft (8,473 m), the highest level-flight speed recorded by a British piston-powered aircraft. Testing of this aircraft with not-fully-developed engines resulted in seven forced landings—the last was at Chilbolton in March 1949 and resulted in the landing gear being pushed through the wings. The aircraft was then dropped by the recovery crane, ending any hope of repair.

By February 1946, the Spiteful order had been reduced to 80 aircraft. This was again reduced on 22 May 1946 to 22 aircraft, and the Spiteful order finally dropped to 16 aircraft on 16 December 1946. The production order basically covered the aircraft that had been built, although some of the last aircraft may not have flown. A 17th Spiteful, RB520 (the sixth production aircraft), was handed over to the FAA for Seafang (see below) development on 22 September 1945. The aircraft was modified for carrier feasibility trials with a “stinger” arrestor hook incorporated into a special housing below the rudder. RB520 retained the standard, non-folding Spiteful wings.

Supermarine Spiteful RB518

Powered with a two-stage, three-speed Griffon 101 engine, Spiteful RB518 achieved a level-flight speed of 494 mph (795 km/h), the highest recorded by a British piston-powered aircraft. RB518 was the only F.XVI Spiteful and was subsequently written off after its seventh forced landing.

The production aircraft were serialed RB515 to RB525, RB527 to RB531, and RB535. The final Spiteful was delivered on 17 January 1947. Of the three Spiteful prototypes and 17 production aircraft, most were sold for scrap in July 1948. It appears RB518 was the last Spiteful to fly, and no examples of the type survive. The larger “Spiteful tail” was incorporated into the last Spitfires, the F.22 and F.24.

The Spiteful’s cancellation was based on a number of realities including the more impressive performance of jet aircraft, the end of World War II, and serviceability questions about the Spiteful. While the Spiteful’s speed was impressive, it was below the 504 mph (811 km/h) that was originally estimated. Furthermore, the performance of the aircraft’s laminar wing decreased substantially if there were imperfections, including smashed bugs, on the leading edge. It was unlikely that an in-service warplane would be free of all imperfections.

Supermarine Spiteful RB520

Spiteful RB520 was loaned out for Seafang development and is considered by some as a Seafang prototype. Note the tail hook housed below the rudder and the “Royal Navy” stenciling on the fuselage.

Back in October 1943, Supermarine designed the Type 382, which was basically a navalized Spiteful. The design had started with mounting a Spiteful-type, laminar flow wing on a Seafire XV. Little official interest was given to the project until 21 April 1945, when the Air Ministry issued Specification N.5/45 for a single-seat fighter for the FAA. Subsequently, Supermarine was awarded a contract for two prototype Type 382 fighters, which became the Seafang. An order for 150 Seafang aircraft was placed on 7 May 1945; this order was essentially a reallocation of Spiteful aircraft that had been cancelled around two days prior.

The production Seafang closely matched the Spiteful but incorporated wings designed so that the last four feet folded vertically. The folding mechanism was hydraulically-powered. The Seafang had an elongated carburetor intake scoop, with the opening just behind the propeller. The aircraft also had a rounded front windscreen rather than the flat plate used on the Spiteful. Under the rudder was a stinger tail hook for catching the arresting cables on the carrier deck. The Seafang’s landing gear was re-enforced to handle carrier operations. The fuel tank behind the cockpit was reduced to 54 gal (45 imp gal / 205 L), resulting in a total internal capacity of 193 gal (161 Imp gal / 732 L).

Supermarine Seafang VG471 front

The first production Supermarine Seafang F.31 (VG471) was essentially a Spiteful with arrestor gear. All F.31 aircraft had standard, non-folding wings. Note what appears to be a wide-cord propeller.

Like the Spiteful, two Seafang variants were planned. The F.31 used the 2,375 hp (1,771 kW) Griffon 69 engine with a five-blade, single-rotation propeller, while the F.32 used the 2,350 hp (1,752 kW) Griffon 89 with a six-blade, contra-rotating propeller. The F.31 was basically a Spiteful with an arrestor hook and did not incorporate folding wings. The F.31s would serve as a test aircraft while the F.32 was being developed.

The Supermarine Seafang had a 35 ft (10.67 m) wingspan, was 34 ft 1 in (10.39 m) long, and was 12 ft 7 in (3.84 m) tall. With wings folded, the span was reduced to 27 ft (8.23 m). The aircraft had a maximum speed of 397 mph (639 km/h) at sea level, 428 mph (689 km/h) at 5,500 ft (1,676 m), and 475 mph (764 km/h) at 21,000 ft (6,401 m). Cruising speed for maximum range was 250 mph (402 km/h) at 20,000 ft (6,096 m). The aircraft’s range was 393 mi (632 km) on internal fuel. The Seafang weighed 8,000 lb (3,629 kg) empty, 10,450 lb (4,740 kg) with a normal load, and 11,900 lb (53,98 kg) maximum. The aircraft had an initial rate of climb of 4,630 fpm (23.5 m/s) and a ceiling of 42,000 ft (12,802 m).

Supermarine Seafang VG471

The side view of Seafang VG471 illustrates many of the aircraft’s features: long intake scoop, straight wing edges, radiator scoop doors, rounded windscreen, bubble canopy, large tail, and arrestor hook.

As previously mentioned, some Spitefuls had the long intake carburetor scoop; RB518 had a Seafang windscreen; and RB520 was fitted with an arrestor hook (resulting in some sources classifying it as a Seafang prototype). This was all done to lead up to Seafang F.31 production aircraft, which were basically Spitefuls with arrestor hooks. The first Seafang F.31 was VG471, which followed the fifth Spiteful off the production line. All of the F.31s had the five-blade propeller, lacked folding wings, and would end up the only production Seafangs that were completed. VG471 was first flown in early January 1946 and used in arrestor hook trials. The original hook installation proved to be weak, and a redesigned system was installed in March 1946. The aircraft passed the trials on 1 May.

The prototype Seafang F.32s were serial numbers VB893 and VB895, and both had contra-rotating propellers and folding wings. VB895 was first flown in early 1946 and was delivered to the A&AEE on 30 June. In August 1946, VB895 was demonstrated separately to the Royal Netherlands Navy, French representatives, and United States representatives in an attempt to sell the Seafang to allies. However, no orders were placed. In May 1947, test pilot Mike Lithgow successfully performed deck trials in VB895 on the HMS Illustrious. The aircraft’s wide track landing gear drastically increased its stability while on the ground, and the contra-rotating propeller eliminated the torque effect. VB895 was also tested with a single, fuselage-mounted 204 gal (170 Imp gal / 773 L) drop tank, and the aircraft was used for armament trials. During a static test firing of the cannons on 18 May 1948, a build-up of gases in the left wing resulted in an explosion that damaged the wing. Extra vents were added, and no further issues occurred.

Supermarine Seafang VB895

The Seafang F.32 prototype VB895 was the first fully-navalized aircraft of the series. The contra-rotating propellers eliminated the torque effect that led to the downfall of many aviators, especially when operating from the short deck of an aircraft carrier.

While praised for its handling and responsiveness, the Seafang did not offer any real advantage over the Seafire 47, and the Seafang’s stall was certainly a disadvantage. An order was subsequently placed for the Seafire. The original interest in the Seafang was based on doubts regarding the suitability of jet aircraft for carrier operations. As those doubts faded, so did interest in the Seafang, and the aircraft was cancelled. A few Seafangs were kept active for a brief time to continue evaluating the laminar flow wing, which was used on the Supermarine Type 392 Attacker. The Attacker was often referred to as a “Jet Spiteful,” although it had Seafang folding wings with the radiators removed and additional fuel tanks installed. The Attacker first flew on 27 July 1946, and it was the first jet fighter to enter operational service with the FAA.

Eighteen production Seafangs were built, carrying serial numbers VG471 to VG490. The first 10 aircraft were F.31s, and the remaining eight were F.32s. However, only the first eight or so aircraft were completed, with the remaining units delivered disassembled. Sadly, like the Spiteful, all of the Seafang examples were scrapped.

Note: The Royal Air Force and Fleet Air Arm used Roman numerals for mark numbers up thorough 1942. From 1943 through 1948, the Roman numerals were phased out for new aircraft, and Arabic numerals were applied. From 1948 onward, Arabic numerals were used exclusively. The Spitefuls were typically referred to using Roman numerals, but the slightly later Seafang used Arabic numerals. The use of both Roman and Arabic numerals in this article refers to the most common use applied for the particular aircraft type.

Supermarine Seafang VB895 wings folded

The folding wings on Seafang VB895 were hydraulically operated and decreased the aircraft’s wingspan by 8 ft (2.4 m). Although, the wide tack landing gear contributed to snaking at low speeds, it enhanced the stability at higher speeds and as the aircraft slammed down on a carrier deck.

Sources:
Spitfire: The History by Eric B. Morgan and Edward Shacklady (2000)
British Experimental Combat Aircraft of World War II by Tony Buttler (2012)
Supermarine Aircraft since 1914 by C.F. Andrews and E.B. Morgan (1981)
Ultimate Spitfires by Peter Caygill (2006)
Supermarine Fighter Aircraft by Victor F. Bingham (2004)
Griffon-Powered Spitfires by Kev Darling (2001)
Fighters: Volume Two by William Green (1961)
Interceptor Fighters for the Royal Air Force 1935–45 by Michael J.F. Bowyer (1984)
Spitfire: A Complete Fighting History by Alfred Price (1992)
Wings of the Weird & Wonderful by Captain Eric Brown (2012)

Fisher P-75A top

Fisher (General Motors) P-75 Eagle Fighter

By William Pearce

Donovan (Don) Reese Berlin had worked as the Chief Engineer for the Curtiss-Wright Corporation. He had designed the company’s successful P-36 Hawk and P-40 Warhawk fighters. Berlin also designed a number of unsuccessful fighters. He left Curtiss-Wright in December 1941 in frustration because he felt the company was not sufficiently supporting his efforts to develop a new fighter. At the request of the US government, Berlin was quickly hired by General Motors (GM) in January 1942 as the Director of Aircraft Development at the Fisher Body Division (Fisher).

Fisher XP-75 43-46950

The Fisher P-75 Eagle was supposed to be quickly and inexpensively developed by utilizing many existing components. However, many resources were expended on the aircraft. The first XP-75 (43-46950) had a uniquely pointed rear canopy. It was also the only example that used a relatively unaltered Douglas A-24 empennage. Note the fixed tailwheel and the fairings that covered the machine gun barrels in the aircraft’s nose.

Fisher was already engaged by the government to build large assembles for the North American B-25 Mitchell bomber, and plans for the manufacture of other aircraft components were in the works. It made sense to have a prominent aeronautical engineer as part of Fisher’s staff. In March 1942, Fisher was tasked to build various components (engine cowlings, outer wing panels, ailerons, flaps, horizontal stabilizers, elevators, vertical stabilizers, rudders) of the Boeing B-29 Superfortress and 200 complete aircraft. A new plant in Cleveland, Ohio would be built to support this order. Beyond Fisher, a number of other GM divisions were involved in building aircraft and aircraft engines under license from other manufacturers. However, GM wanted to design and manufacture its own products to support the war effort. Berlin was a believer in applying automotive methods to produce aircraft, which was a good match for the automotive giant GM.

On 10 September 1942, GM, through Fisher, submitted a proposal to the Army Air Force (AAF) for a new interceptor fighter. The proposal was based on an AAF request from February 1942 for such an aircraft with exceptional performance. The aircraft from Fisher was designed by Berlin, powered by an Allison V-3420 24-cylinder engine, and constructed mainly of components from other aircraft. The aircraft offered impressive performance with a top speed of 440 mph (708 km/h) at 20,000 ft (6,096 m), a 5,600 fpm (28.5 m/s) initial climb rate, a service ceiling of 38,000 ft (11,582 m), and a range of 2,240 miles (3,605 km) with only internal fuel. All of this came with a promise to deliver the first aircraft within six months of the contract being issued.

Fisher XP-75 line

The top image shows at least five XP-75A aircraft under construction. The middle image, from right to left, shows the first two XP-75 aircraft (43-46950 and 43-46951) and the first two XP-75A aircraft (44-32161 and 44-32162). The second XP-75 (second from the right) has the wide H-blade propellers installed, while the other aircraft have the narrow A-blade propellers. The bottom image is a P-75A under construction. Note the V-3420 engine. (Veselenak Photograph Collection / National Museum of the US Air Force images)

Back in February 1941, the Army Air Corps (name changed to AAF in June 1941) had considered the Allison V-3420 as a possible replacement for the Wright R-3350 engine intended for the B-29. The Allison Engineering Company was a division of GM, and at the time, development of the V-3420 was focused on creating the basic engine and not much more. However, the priority of the V-3420 program was scaled-back after the Japanese attacked Pearl Harbor on 7 December 1941.

GM had been searching for an application for its Allison V-3420 engine, and the AAF had tried to entice other manufactures to incorporate the engine in a fighter design. Fisher’s fighter project offered a solution for both entities. The AAF was sufficiently impressed with Fisher’s proposal, and they approved the construction of two prototypes (serials 43-46950 and 43-46951) on 10 October 1942. The aircraft was given the designation P-75 Eagle, with the prototypes labeled XP-75. Some believe the pursuit number “75” was issued specifically at Berlin’s request, as his “Model 75” at Curtiss-Wright became the successful P-36 and led to the P-40. Although there were some reservations with the aircraft’s design, it was believed that a team working under the experienced Berlin would resolve any issues encountered along the way.

Fisher XP-75A long-range side

Aircraft 44-32162 was the fourth of the XP-75-series and the second XP-75A with additional wing fuel tanks. Note the revised canopy and tail compared to the first prototype. The aircraft has narrow A-blade propellers, and the 10-gun armament appears to be installed.

The XP-75 was of all metal construction with fabric-covered control surfaces. The cockpit was positioned near the front of the aircraft and provided the pilot with good forward and downward visibility. The pilot was protected by 177 lb (80 kg) of armor. The cockpit canopy consisted of front and side panels from a P-40. The aircraft’s empennage, with a fixed tailwheel, was from a Douglas A-24 Banshee (AAF version of the Navy SBD Dauntless). Initially, North American P-51 Mustang outer wing panels would attach to the inverted gull wing center section that was integral with the fuselage. However, the P-51 wings were soon replaced by wings from a P-40 attached to a normal center section. The main landing gear was from a Vought F4U Corsair, and it had a wide track of nearly 20 ft (6.10 m). Four .50-cal machine guns were mounted in the aircraft’s nose and supplied with 300 rpg. Each wing carried three additional .50-cal guns with 235 rpg. Under each wing, inside of the main gear, was a hardpoint for mounting up to 500 lb (227 kg) of ordinance or a 110-US gal (416-L) drop tank.

The 2,600 hp (1,939 kW) Allison V-3420-19 engine with a two-stage supercharger was positioned in the fuselage behind the pilot. Each of the engine’s four cylinder banks had an air-cooled exhaust manifold with two exhaust stacks protruding out of the fuselage. Two extension shafts passed under the cockpit and connected the engine to the remote gear reduction box for the Aeroproducts six-blade contra-rotating propeller. Two different types of propellers were used. Initially, a 13 ft (3.96 m) diameter, narrow, A-blade design was used. Many sources state that this propeller was used on the first 12 aircraft. However, some of these aircraft flew with the second design, a 12 ft 7 in (3.84 m) diameter, wide, H-blade. The gear reduction turned the propeller at .407 crankshaft speed.

Fisher XP-75A 44-32161 crash

The empennage (left) and inverted wings and fuselage (right) of XP-75A 44-32161 after its crash on 5 August 1944. An engine explosion and inflight fire led to the empennage separating from the rest of the aircraft. Russell Weeks, the pilot, was able to bail out of the stricken aircraft. (Veselenak Photograph Collection / National Museum of the US Air Force images)

A two-section scoop was located under the fuselage, just behind the wings. The left section held an oil radiator, and coolant radiators were positioned in both the left and right sections. The aircraft’s oil capacity and coolant capacity were 28.5 US gal (108 L) and 31.5 US gal (119 L) respectively. A 485-US gal (1,836-L) fuel tank was positioned in the fuselage between the cockpit and engine. The tank was made of two sections with the extension shafts passing between the sections.

An XP-75 mockup was inspected by the AAF on 8 March 1943. On 6 July, six additional prototypes (serials 44-32161 to 44-32166) were ordered with some design modifications, including changes to the cockpit canopy, the use of a 2,885 hp (2,151 kW) V-3240-23 engine, and additional fuel tanks in each wing with a capacity of 101 US gal (382 L). The extra fuel enabled the P-75 to cover the long-range escort role, something that the AAF was desperately seeking. The long-range fighter prototypes are often referred to as XP-75As, although this does not appear to be an official designation.

Fisher XP-75A assembly

This image shows either 44-32165 or 44-32166 being completed in the Cleveland plant. These two aircraft, the last of the XP-75As, had a bubble canopy, retractable tailwheel, and a new, tall rudder and vertical stabilizer. Note the P-40-style rounded wings. (Veselenak Photograph Collection / National Museum of the US Air Force image)

Since the need for interceptors had faded, many in the AAF were optimistic that the long-range P-75 would be able to escort bombers all the way into Germany and that the aircraft would be able to outperform all German fighters for the foreseeable future. The P-75 also served as insurance if the P-51 and Republic P-47 Thunderbolt could not be developed into long-range escort fighters.

On 8 July 1943, a letter of intent was issued for the purchase of 2,500 P-75A aircraft (serials 44-44549 to 44-47048), but a stipulation allowed for the cancellation of production if the aircraft failed to meet its guaranteed performance. A definitive contract for all of the XP-75 work was signed on 1 October 1943 and stipulated that the first XP-75 prototype would fly by 30 September 1943, and the first long-range XP-75A prototype would fly by December 1943. The first production aircraft was expected in May 1944, and production was forecasted to eventually hit 250 aircraft per month. The production costs for the 2,500 P-75A aircraft was estimated at $325 million.

Fisher XP-75A 44-32165 side

XP-75A 44-32165 with the new (and final) large, angular tail and horizontal stabilizer. However, the aircraft retained the rounded wings. Note the ventral strake behind the belly scoop, and the wide H-blade propellers. The same modifications were applied to 44-32166. The stenciling under the canopy says “Aeroproducts Flight Test Ship No 4.”

The Fisher XP-75A had a wingspan of 49 ft 1 in (14.96 m), a length of 41 ft 4 in (12.60 m), and a height of 14 ft 11 in (4.55 m). The aircraft’s performance estimates were revised to a top speed of 434 mph (698 km/h) at 20,000 ft (6,096 m) and 389 mph (626 km/h) at sea level. Its initial rate of climb was 4,200 fpm (21.3 m/s), with 20,000 ft (6,096 m) being reached in 5.5 minutes, and a service ceiling of 39,000 ft (11,887 m). The aircraft had an empty weight of 11,441 lb (5,190 kg) and a fully loaded weight of 18,665 lb (8,466 kg). With the fuselage tank, a total of 203 US gal (768 L) of fuel in the wings, and a 110-US gal (416-L) drop tank under each wing, the XP-75A had a maximum range of 3,850 miles (6,196 km).

The AAF gave the XP-75 priority over most of Fisher’s other work, particularly that of constructing 200 B-29 bombers. Construction of the first two prototypes was started at Fisher’s plant in Detroit, Michigan. The other six XP-75 aircraft were built at the new plant in Cleveland, Ohio, which opened in 1943. Production of the aircraft would occur at the Cleveland plant.

Fisher P-75A assembly line

The production line with P-75A numbers two through four (44-44550 through 44-44553) under construction. While the aircraft have square wingtips, at least the first one still has the rounded horizontal stabilizer. Note the V-3420 engine by the first aircraft. The wing of an XP-75A is visible on the far right.

Flown by Russell Thaw, the XP-75 prototype (43-46950) made its first flight on 17 November 1943, and it was the first aircraft to fly with the V-3420 engine. Almost immediately the aircraft ran into issues: the center of gravity was off; the ailerons were heavy; the controls were sluggish; the aircraft exhibited poor spin characteristics; and the V-3420 engine was down on power and overheating. The trouble is not very surprising considering the aircraft consisted of parts from other aircraft and was powered by an experimental engine installed in an unconventional manner. The V-3420’s firing order was revised for smoother operation. Modifications to the second prototype (43-46951) included changes to the ailerons and a new rear canopy. The size of the rudder was decreased, but the surface area of the vertical stabilizer was increased by extending its leading edge. The second XP-75 prototype first flew in December 1943.

The first of the six XP-75A long-range aircraft (44-32161) flew in February 1944. The last two of these aircraft, 44-32165 and 44-32166, were finished with a bubble canopy and a new empennage. The new empennage had a retractable tailwheel and a taller vertical stabilizer and rudder. Lateral control was still an issue, and these two aircraft were later modified with larger and more angular vertical and horizonal stabilizers. These changes were also incorporated into most of the P-75A production aircraft.

Fisher P-75A 44-44549

The first production P-75A (44-44549) with its square wingtips and original rounded tail. Note the ventral strake and the fins attached to the horizontal stabilizer. It is not known when the picture was taken (possibly 22 September 1944), but the aircraft and pilot were lost on 10 October 1944.

The third long-range XP-75A aircraft (44-32163) crashed on 8 April 1944, killing the pilot, Hamilton Wagner. The crashed may have been caused by the pilot performing unauthorized aerobatics. On 7 June 1944, the AAF issued the contract for 2,500 P-75A aircraft. Official trials were conducted in June 1944 and indicated that the XP-75A aircraft was well short of its expected performance. A top speed of only 418 mph (673 km/h) was achieved at 21,600 ft (6,584 m), and initial climb rate was only 2,990 fpm (15.2 m/s). However, the engine was reportedly not producing its rated output. On 5 August 1944, XP-75A 44-32161 was lost after an inflight explosion, which separated the empennage from the rest of the aircraft. The pilot, Russell Weeks, successfully bailed out.

In addition to other changes made throughout flight testing of the prototypes, the P-75As incorporated extended square wingtips with enlarged ailerons, the controls were boosted to eliminate the heavy stick forces, and a ventral strake was added that extended between the scoop exit doors and the tailwheel. The P-75A had a wingspan of 49 ft 4 in (15.04 m), a length of 41 ft 5 in (12.62 m), and a height of 15 ft 6 in (4.72 m). The aircraft’s performance estimates were revised down, with a top speed of 404 mph (650 km/h) at 22,000 ft (6,706 m). Its initial rate of climb dropped to 3,450 fpm (17.5 m/s), and the service ceiling decreased to 36,400 ft (11,095 m). The aircraft had an empty weight of 11,255 lb (5,105 kg) and a fully loaded weight of 19,420 lb (8,809 kg).

Fisher P-75A runup

P-75A 44-44550 with the new (and final) square tail and horizontal stabilizer. Note the two-section belly scoop and the F4U main landing gear.

The first two P-75As (44-44549 and 44-44550) were not originally finished with the latest (angular) empennage. Rather, they used the tall, round version that was originally fitted to the last two XP-75A prototypes. A dorsal fillet was later added to the vertical stabilizer. The first Fisher P-75A (44-44549) took flight on 15 September 1944, with the second aircraft (44-44550) following close behind. Aircraft 44-44550 was later altered with the enlarged, square-tipped vertical and horizontal stabilizers, but it is not clear if 44-44549 was also changed. At some point (possibly late September 1944), aircraft 44-44549 had stabilizing fins added to the ends of its horizontal stabilizer. Both aircraft were sent to Eglin Field, Florida for trials. On 10 October 1944, aircraft 44-44549 was lost with its pilot, Harry Bolster. The crash was caused by the propellers becoming fouled by either a nose-gun tube failure or by part of the spinner breaking free. The damaged propellers quickly destroyed the gear reduction, and once depleted of oil, the propeller blades went into a flat pitch. Bolster attempted a forced landing but was not successful.

By the time of the last crash, the AAF had realized it would not need the P-75A aircraft. The P-51B/D and P-47D/N had proven that they were up to the task of being long-range escort fighters, and the war’s end was in sight. The P-75A was larger, heavier, slower, and sluggish compared to fighters already in service. The production contract for the 2,500 P-75As was cancelled on 6 October 1944, and further experimental work was stopped on 8 November. Five P-75A aircraft were completed, with an additional, nearly-complete airframe delivered for spare parts. Construction of approximately 20 other P-75A production aircraft had started, with some assemblies being completed.

Fisher P-75A top

A top view of 44-44550 provides a good illustration of the square wingtips and horizontal stabilizer. The wings were only slightly extended, but the area of the ailerons was increased by a good amount. The square extensions to the horizontal stabilizer increased its area significantly. Note that the machine gun armament is installed.

P-75A 44-44550 was later transferred to Moffett Field, California where it underwent tests on the contra-rotating propellers. The aircraft was scrapped after the tests. In an attempt to produce more power, a new intercooler was installed in 44-44551, and the aircraft was lent to Allison on 28 June 1945. Later, a 3,150 hp V-3420 was installed. Aircraft 44-44552 and 44-44553 were sent to Patterson Field, Ohio and stored for further V-3420 development work. None of the aircraft were extensively flown. The last completed P-75A, 44-44553, was preserved and is currently on display in the National Museum of the US Air Force in Dayton, Ohio. The aircraft went through an extensive restoration in 2008. All other P-75 aircraft were eventually scrapped.

The eight prototype aircraft had cost $9.37 million, and the manufacturing contract, including the six production aircraft, construction of the Cleveland plant, and tooling for production, had cost $40.75 million. This gave a total expenditure of $50.21 million for the 14 P-75 aircraft. In the end, the expeditious and cost-saving measure of combining existing components led to delays and additional costs beyond that of a new design. It turned out that the existing assemblies needed to be redesigned to work together, essentially making the P-75A a new aircraft with new components.

Fisher P-75A side

The pilot under 44-44550’s bubble canopy helps illustrate the aircraft’s rather large size. The P-75’s sluggish handling and lateral instability did not endear the aircraft to test pilots. Note the nearly-wide-open rear shutter of the belly scoop.

An often-cited story states that then Col. Mark E. Bradley, Chief of Aircraft Projects at Wright Field, was so dissatisfied with the XP-75 after making a test flight, that he requested North American add a large fuel tank in the fuselage of the P-51 Mustang. This act led to the ultimate demise of the XP-75 and the ultimate success of the P-51. However, that sequence of events is not entirely accurate.

Bradley initiated North American’s development of the P-51 fuselage tank in July 1943, after evaluating the XP-75’s design. Experiments with the P-51’s 85-gallon (322-L) fuselage tank were successfully conducted in August 1943. In early September 1943, kits to add the tank to existing P-51s were ordered, and about 250 kits arrived in England in November. At the same time, the fuselage tank was incorporated into the P-51 production line. These events preceded the XP-75 prototype’s first flight on 17 November 1943. Bradley’s later flight in the XP-75 solidified his view that the P-51 with the fuselage tank was the best and quickest option for a long-range escort, and that the XP-75, regardless of its progression through development, would not be superior in that role.

Fisher P-75A USAFM

Fisher P-75A 44-44553 has been preserved and is on display in the National Museum of the US Air Force. (US Air Force image)

Sources:
U.S. Experimental & Prototype Aircraft Projects Fighters 1939–1945 by Bill Norton (2008)
Vees For Victory!: The Story of the Allison V-1710 Aircraft Engine 1929-1948 by Dan Whitney (1998)
P-75 Series Airplanes Advance Descriptive Data (20 May 1944)
P-51 Mustang: Development of the Long-Range Escort Fighter by Paul A. Ludwig (2003)
Development of the Long-Range Escort Fighter by USAF Historical Division (1955)
– “Le Fisher XP-75 Eagle” by Alain Pelletier, Le Fana de l’Aviation (August 1996)
– “A Detroit Dream of Mass-Produced Fighter Aircraft: The XP-75 Fiasco” by I. B. Holley, Jr. Technology and Culture Vol. 28, No. 3 (July 1987)
http://usautoindustryworldwartwo.com/Fisher%20Body/fisherbodyaircraft.htm
http://www.alexstoll.com/AircraftOfTheMonth/3-00.html
https://en.wikipedia.org/wiki/List_of_accidents_and_incidents_involving_military_aircraft_(1943%E2%80%931944)

Caproni Ca90 side

Caproni Ca.90 Heavy Bomber

By William Pearce

Giovanni (Gianni) Caproni founded his first aircraft company in 1908. From the start, Caproni and his company leaned toward the production of large aircraft, typically bombers. By 1929, Caproni and engineer Dino Giuliani had designed the world’s largest landplane, the Caproni Ca.90.

Caproni Ca90 side

The Caproni Ca.90 was a huge aircraft. The aircraft’s tires are taller than the bystanders. Note the servo tab trailing behind the aileron used to balance the aircraft’s controls. Note the radiators for the front engines immediately behind the propellers.

The Ca.90 was conceived as a heavy bomber and was often referred to as the Ca.90 PB or 90 PB. The “PB” stood for Pesante Bombardiere (Heavy Bomber). The aircraft was a large biplane taildragger powered by three pairs of tandem engines. The Ca.90 was built upon lessons learned from the smaller (but still large) Ca.79. The wings, fuselage, and tail were constructed with steel tubes connected by joints machined from billets of chrome-nickel steel. The steel frame was then covered with fabric and doped, except for the fuselage by the cockpit and the aircraft’s extreme nose, which were covered with sheets of corrugated aluminum.

The biplane arrangement of the Ca.90 was an inverted sesquiplane with the span of the upper wing 38 ft 4 in (11.68 m) shorter than the lower wing. The lower wing was mounted to the top of the fuselage so that its center section was integral with the airframe. The upper wing was supported by struts and braced by wires about 18 ft 8 in (5.7 m) above the lower wing. The ailerons were on the lower wing only. All control surfaces were balanced, and the ailerons and rudder featured servo tabs to assist their movement. The design of the control surfaces and the cockpit layout enabled the aircraft be flown by just one pilot. The open, side-by-side cockpit was located just before the leading edge of the lower wing. Access to the fuselage interior was gained by a large door on either side of the aircraft below the cockpit.

Caproni Ca90 frame

The partially finished airframe of the Ca.90. The cylindrical tanks are for fuel, with 11 in the nose, one visible in wing center section, and four vertically mounted between the rear engines. The open space in the middle of the fuselage is the bomb bay. An oil tank can be seen between the engines. The radiator for the rear engine is in place. Note the radiator under the struts for the center engines.

The Ca.90 was powered by six Isotta Fraschini Asso 1000 direct-drive engines. The Asso 1000 was a water-cooled W-18 engine that produced 1,000 hp (746 kW). The six engines were mounted in three push-pull pairs. A pair of engines was mounted on each wing just above the main landing gear. Another pair of engines was mounted on struts midway between the upper and lower wings. The front engines all had radiators mounted behind their propellers. The rear, wing-mounted engines had radiators attached to wing-support struts. The rear-facing center engine had its radiator positioned under the suspended engine gondola. All radiators had controllable shutters to regulate engine temperature. Engine oil tanks were positioned between each engine pair. The front engines turned two-blade propellers, and the rear engines turned four-blade propellers. All propellers had a fixed pitch and were made of wood.

The bomber was protected by seven gunner stations: one in the nose, one atop the upper wing, two in the upper fuselage, one on each side of the fuselage, and one in a ventral gondola that was lowered from the fuselage. However, it appears only the nose, upper wing, and upper fuselage stations were initially completed, with the side stations completed later. It is doubtful that machine guns were ever installed. The Ca.90 was designed to carry up to 17,637 lb (8,000 kg) of bombs in an internal bomb bay that was located behind the cockpit.

Caproni Ca90 close

Close-up view of the Ca.90’s nose illustrates the corrugated aluminum sheets covering the nose, fuselage under the cockpit, and top of the fuselage between the nose and cockpit. Note the large access door. The three holes under each engine are carburetor intakes.

The aircraft’s fuel was carried in 23 cylindrical tanks—11 tanks were positioned between the nose gunner station and the cockpit; eight tanks were located in the lower wing center-section just behind the cockpit; and four tanks were immediately aft of the bomb bay. The aircraft was supported by two sets of fixed double main wheels. The strut-mounted main gear was positioned below the wing-mounted engines. The main landing gear was given a wide track of about 16 ft 3 in (8 m) to enable operating from rough ground. The main wheels were 6 ft 7 in (2.0 m) in diameter and 16 in (.4 m) wide. The tailwheel was positioned below the rudder.

The Caproni Ca.90 had a lower wingspan of 152 ft 10 in (46.58 m) and an upper wingspan of 114 ft 6 in (34.90 m). The aircraft was 88 ft 5 in (26.94 m) long and stood 35 ft 5 in (10.80 m) tall. The Ca.90 had a top speed of 127 mph (205 km/h) and a landing speed of 56 mph (90 km/h). The aircraft had a ceiling of 14,764 ft (4,500 m) and a maximum range of 1,243 miles (2,000 km), or a range of approximately 870 miles (1,400 km) with a 17,637 lb (8,000 kg) bomb load. Empty, the Ca.90 weighed 33,069 lb (15,000 kg). Its useful load was 33,069–44,092 lb (15,000–20,000 kg) depending on which safety factor was used, giving the aircraft a maximum weight of 66,137–77,162 lb (30,000–35,000 kg).

Caproni Ca90 side paint

The Ca.90 in its final form with a (blue) painted nose, side gunner positions, and aerodynamic fairings for the main wheels. Note the dorsal gunner positions in the upper fuselage, and the new servo tab on the rudder. Another Caproni aircraft (Ca.79?) can be seen flying in the background.

The Ca.90 was first flown on 13 October 1929. Domenico Antonini was the pilot for that flight, and he conducted all test flying, which demonstrated that the massive aircraft had light controls and did not have any major issues. On 22 February 1930, Antonini took off in the Ca.90 with a 22,046 lb (10,000 kg) payload and set six world records:
1) 2) Altitude with 7,500 and 10,000 kg (16,535 and 22,046 lb) of unusable load at 3,231 m (10,600 ft);
3) 4) 5) Duration with 5,000; 7,500; and 10,000 kg (11,023; 16,535; and 22,046 lb) of unusable load at 1 hour and 31 minutes;
6) Maximum unusable load at 2,000 m (6,562 ft) of altitude at 10,000 kg (22,046 lb).

The aircraft was passed to the 62ª Squadriglia Sperimentale Bombardamento Pesante (62nd Heavy Bombardment Experimental Squadron) for further testing. Around this time, the aircraft was repainted, side (waist) gunner positions were completed, and aerodynamic fairings were added to the main wheels.

Italo Balbo, head of the Ministero dell’Aeronautica (Italian Air Ministry), was not a supporter of large-scale bombing using heavy bombers and did not pursue the Ca.90. Caproni had proposed that the aircraft could be reconfigured to cover long-distance international routes as a transport with up to 100 seats or as a mail plane, but no conversion took place. An attempt to market the Ca.90 in the United States was made under a joint venture with the Curtiss Airplane and Motor Company, but the Great Depression had curtailed military spending, and there was little interest in the aircraft. A flying boat version was designed and designated Ca.91, but this aircraft was never built. Only one Ca.90 prototype was built, and it remains the largest biplane ever flown.

Caproni Ca90 takeoff

A rare image of the Ca.90 airborne shortly after takeoff. A slight trail of dark smoke is visible from the engines, perhaps from a rich mixture.

Sources:
The Caproni “90 P.B.” Military Airplane, NACA Aircraft Circular No. 121 (July 1930)
Gli Aeroplani Caproni by Gianni Caproni (1937)
– Jane’s All the World’s Aircraft 1931 by C. G. Grey (1931)
Italian Civil and Military Aircraft 1930-1945 by Jonathan W. Thompson (1963)
Aeroplani Caproni by Rosario Abate, Gregory Alegi, and Giorgio Apostolo (1992)
– “The Caproni 90 PB” Flight (9 January 1931)
https://it.wikipedia.org/wiki/Caproni_Ca.90

LWF H Owl nose 1923

LWF Model H Owl Mail Plane / Bomber

By William Pearce

In 1915, the Lowe, Willard & Fowler Engineering Company was formed in College Point, Long Island, New Work. Of the founders, Edward Lowe, provided the financing; Charles Willard was the engineer and designer; and Robert Fowler served as the shop foreman, head pilot, and salesman. Willard was previously employed by the Curtiss Aeroplane and Motor Company and had developed a technique for molding laminated wood to form a monocoque fuselage. Willard was eventually granted U.S. patent 1,394,459 for his fuselage construction process. Previously in 1912, Fowler became the first person to fly west-to-east across the United States.

LWF H Owl nose

The LWF Model H Owl in its original configuration with six main wheels. The engine on the central nacelle has a spinner, a single service platform, and a separate radiator. Note the numerous drag inducing struts and braces for the wings, nacelle, and booms.

The business partnership was short-lived. In 1916, Fowler and Willard left the company, and Lowe assumed control, renaming the company LWF Engineering. By this time, LWF had become well-known for its molded wood construction process. However, management changed again as other financiers forced Lowe out. In 1917, the firm was reorganized as the LWF Engineering Company, with “Laminated Wood Fuselage” taking over the LWF initials.

By 1919, LWF began design work on a large trimotor aircraft intended for overnight mail service between New York City and Chicago, Illinois. Other uses for the aircraft were as a transport or bomber. Designated the Model H (some sources say H-1), construction began before an interested party came forward to finance the project. Because of its intended use for overnight mail service, the aircraft was given the nickname “Owl.” As construction continued, the United States Post Office Department declined to support the Model H. However, LWF was able to interest the United States Army Air Service, which purchased the aircraft on 16 April 1920. The Model H was assigned the serial number A.S.64012.

LWF H Owl rear

In the original configuration, the Owl’s cockpit was just behind the trailing edge of the wing, and visibility was rather poor. Note the aircraft’s two horizontal stabilizers and three rudders. The smooth surface finish of the booms is well illustrated.

The LWF Model H Owl was designed by Raoul Hoffman and Joseph Cato. Although the Owl’s design bore some resemblance to contemporary large aircraft from Caproni, there is nothing that suggests the similarities were anything more than superficial. The Model H had a central nacelle pod that was 27 ft (8.23 m) long and contained a 400 hp (298 kW) Liberty V-12 positioned in the nose of the pod. The cockpit was positioned in the rear half of the pod, just behind the wing’s trailing edge. The cockpit’s location did not result in very good forward visibility. Accommodations were provided for two pilots, a radio operator, and a mechanic. Mounted 10 ft (3.05 m) to the left and right of the central pod were booms measuring approximately 51 ft (15.54 m) long. The booms were staggered 24 in (.61 m) behind and 16 in (.41 m) below the central pod and extended back to support the tail of the aircraft. At the front of each boom was a 400 hp (298 kW) Liberty V-12 engine. Each boom housed fuel tanks and small compartments for cargo. The main load was carried in the central nacelle.

The monocoque central nacelle and booms were made using LWF’s laminated wood process. The construction method consisted of a mold covered with muslin cloth. Strips of thin spruce were then laid down and spiral wrapped with tape. Another layer of spruce was laid in the opposite direction and spiral wrapped with tape. The final, outer layer of spruce was laid straight. The assembly was then soaked in hot glue and covered with fabric and doped. The resulting structure was about .25 in (6.4 mm) thick, was very strong, and had a smooth exterior. Where reinforcement was needed, formers were attached to the inside of the structure.

LWF H Owl in flight

The Owl was a somewhat sluggish flier and reportedly underpowered. However, its flight characteristics were manageable. It was the largest aircraft in the United States at the time.

The nacelle and booms were mounted on struts and suspended in the 11 ft (3.35 m) gap between the Model H’s biplane wings. The wings were made of a birch and spruce frame that was then covered in fabric, except for the leading edge, which was covered with plywood. The upper and lower wing were the same length and were installed with no stagger. The wings were braced by numerous struts and wires. Large ailerons were positioned at the trailing edge of each wing. The wings were 100 ft 8 in (30.68 m) long with an additional 26 in (.66 m) of the 17 ft 8 in (5.38 m) ailerons extending out on each side. The incidence of the upper and lower wings was 4.5 and 3.5 degrees respectively. A bomb of up to 2,000 lb (907 kg) could be carried under the center of the lower wing.

A horizontal stabilizer spanned the gap between the rear of the booms. A large, 24 ft (7.32 m) long elevator was mounted to the trailing edge of the stabilizer. Mounted at the rear of each boom was a vertical stabilizer with a large 6 ft 9.75 in (2.08 m) tall rudder. A second horizontal stabilizer 28 ft (8.53 m) long was mounted atop the two vertical stabilizers. A third (middle) rudder was positioned at the midpoint of the upper horizontal stabilizer. Attached to the upper horizontal stabilizer and mounted between the rudders were two elevators directly connected to the single, lower elevator. The lower stabilizer had an incidence of 1.5 degrees, while the upper stabilizer had an incidence of 4 degrees.

LWF H Owl crash 1920

The Model H was heavily damaged following the loss of aileron control and subsequent hard landing on 30 May 1920. However, the booms, central nacelle, and tail suffered little damage.

The Owl’s ailerons and rudders were interchangeable. Each engine was installed in an interchangeable power egg and turned a 9 ft 6 in (2.90 m) propeller. Engine service platforms were located on the inner sides of the booms and the left side of the central nacelle. The Owl was equipped with a pyrene fire suppression system. The aircraft was supported by a pair of main wheels under each boom and two main wheels under the central nacelle. At the rear of each boom were tailskids.

The LWF Owl had a wingspan of 105 ft (32 m), a length of 53 ft 9 in (16.38 m), and a height of 17 ft 6 in (5.33 m). The aircraft had a top speed of 110 mph (117 km/h) and a landing speed of 55 mph (89 km/h). The Model H had an empty weight of 13,386 lb (6,072 kg) and a maximum weight of 21,186 lb (9,610 kg). The aircraft had a 750 fpm (3.81 m/s) initial rate of climb and a ceiling of 17,500 ft (5,334 m). The Owl had a range of approximately 1,100 miles (1,770 km).

LWF H Owl crash 1921

The Owl on its nose in the marshlands just short of the runway at Langley Field on 3 June 1921. The nose-over kept the tail out of the water and probably prevented more damage than if the tail had been submerged.

Although not complete, the Model H was displayed at the New York Aero Show in December 1919. On 15 May 1920, the completed Owl was trucked from the LWF factory to Mitchel Field. Second Lt Ernest Harmon made the aircraft’s first flight on 22 May. The aircraft controls were found to be a bit sluggish, but everything was manageable. An altitude of 1,300 ft (396 m) was attained, but one engine began to overheat, and the aircraft returned for landing. The second and third flights occurred on 24 May, with a maximum altitude of 2,600 ft (792 m) reached. The fourth flight was conducted on 25 May. Water in the fuel system caused the center engine to lose power, and an uneventful, unplanned landing was made at Roosevelt Field. Modifications were made, and flight testing continued.

On the aircraft’s sixth flight, it had a gross weight of 16,400 lb (7,439 kg). The Owl took off and climbed to 6,000 ft (1,829 m) in 15 minutes. The engines were allowed to cool before another climb was initiated, and 11,000 ft (3,353 m) was reached in seven minutes. No issues were encountered, and the aircraft returned to base after the successful flight.

LWF H Owl nose 1923

The Owl in its final configuration with four main wheels. On the central nacelle, note the new radiator, lack of a spinner, service platforms on both sides of the engine, and the opening for the bombsight under the nacelle. A bomb shackle is installed under the wing on the aircraft’s centerline.

On 30 May, a turnbuckle failed and resulted in loss of aileron control while the Owl was on a short flight. A good semblance of control was maintained until touchdown, when the right wing caught the ground and caused the aircraft to pivot sideways. The right wheels soon collapsed, followed by the left. The owl then smashed down on the right engine, rotated, and then settled down on the left engine, tearing it free from its mounts. The cockpit located near the center of the isolated central nacelle kept the crew safe, allowing them to escape unharmed.

The Model H was repaired, and flight testing resumed on 11 October 1920. Tests continued until 3 June 1921, when Lt Charles Cummings encountered engine cooling issues followed by engine failure. The Owl crashed into marshland just short of the runway at Langley Field, Virginia. The aircraft ended up on its nose, but the crew was uninjured. The Owl was recovered and returned to the LWF factory for repairs.

LWF H Owl rear 1923

The new cockpit position just behind the engine can be seen in this rear view of the updated Owl. In addition, the gunner’s position is visible at the rear of the central nacelle.

While being repaired, various modifications were undertaken to better suit the aircraft’s use in a bomber role. The cockpit was revised and moved forward to directly behind the center Liberty engine. The middle engine had a new radiator incorporated into the nose of the central pod. An engine service platform was added to the right side of the central pod so that both sides had platforms. A gunner’s position, including a Scraff ring for twin machine guns, was added to the rear of the nacelle pod. A bombing sight opening was added in the central nacelle. The ailerons were each extended 10 in (.25 m), increasing their total length to 18 ft 6 in and increasing the wingspan to 106 ft 8 in (32.51 m). The landing gear was modified, and a single wheel replaced the double wheels for the outer main gear. A bomb shackle was added between the center main wheels.

The Owl flew in this configuration in 1922. To improve the aircraft’s performance, some consideration was given to installing 500 hp (373 kW) Packard 1A-1500 engines in place of the Libertys, but this proposal was not implemented. In September 1923, the Owl was displayed at Bolling Air Field in Washington, DC. The aircraft had been expensive, and it was not exactly a success. Quietly, in 1924, the LWF Model H Owl was burned as scrap along with other discarded Air Service aircraft.

LWF H Owl Bolling 1923

The Owl on display at Bolling Field in September 1923. Note the windscreen protruding in front of the cockpit. The large aircraft dwarfed all others at the display.

Sources:
– “The Great Owl” by Walt Boyne, Airpower (November 1997)
– “The 1,200 H.P. L.W.F. Owl” Flight (14 April 1921)
– “The L.W.F. Owl Freight Plane” Aviation (1 March 1920)
Aircraft Year Book 1920 by Manufacturers Aircraft Association (1920)
Aircraft Year Book 1921 by Manufacturers Aircraft Association (1921)
American Combat Planes of the 20th Century by Ray Wagner (2004)