Category Archives: Post World War II

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)

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://s1rus.livejournal.com/154716.html
https://www.thedrive.com/the-war-zone/15542/russia-supposedly-bringing-back-giant-ekranoplans-for-arctic-missions
http://iiaat.guap.ru/?n=main&p=pres_spasatel
https://en.wikipedia.org/wiki/Spasatel
https://igor113.livejournal.com/51213.html
https://igor113.livejournal.com/52174.html
https://igor113.livejournal.com/52878.html

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)

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://aviationhumor.net/the-last-flight-of-the-soviet-beach-assault-ekranoplan-a-90-orlyonok/#
http://www.volga-shipyard.com/index.php?section=history&lang=eng

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/

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.

Sources:
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)
https://www.secretprojects.co.uk/forum/index.php?topic=15792.0;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.

Sikorsky S-67 Blackhawk fan-in-tail

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.

Sources:
http://www.sikorskyarchives.com/S-67%20BLACKHAWK.php
https://en.wikipedia.org/wiki/Sikorsky_S-67_Blackhawk
http://www.aviastar.org/helicopters_eng/sik_s-67.php
http://1000aircraftphotos.com/Contributions/Visschedijk/6269.htm
– “Blackhawk’s Last Flight” Aeroplane Monthly (June 1976)
Attack Helicopter Evaluation, Blackhawk S-67 Helicopter by George M. Yamakawa, et al (July 1972)