Misplaced Pages

#639360

63-596: Prior to August 1945, the Vultee Division of Consolidated-Vultee looked at the possibility of a swept-wing aircraft powered by a ducted rocket. Years earlier, the company had performed designs which involved liquid-cooled radiator engines. With this design, fuel would be added to the heat produced by small rocket engines in the duct, creating a "pseudo- ramjet ". In August 1945, the United States Army Air Forces (USAAF), soon to be renamed

126-400: A convergent–divergent nozzle . Although ramjets have been run as slow as 45 metres per second (160 km/h; 100 mph), below about Mach 0.5 (170 m/s; 610 km/h; 380 mph) they give little thrust and are highly inefficient due to their low pressure ratios. Above this speed, given sufficient initial flight velocity, a ramjet is self-sustaining. Unless the vehicle drag

189-763: A long-range antipodal bomber , similar to the Sänger-Bredt bomber , but powered by ramjet instead of rocket. In 1954, NPO Lavochkin and the Keldysh Institute began development of a Mach 3 ramjet-powered cruise missile, Burya . This project competed with the R-7 ICBM developed by Sergei Korolev , but was cancelled in 1957. Several ram jets were designed, built, and ground-tested at the Kawasaki Aircraft Company's facility in Gifu during

252-434: A pitot -type opening for the inlet. This is followed by a widening internal passage (subsonic diffuser) to achieve a lower subsonic velocity that is required at the combustor. At low supersonic speeds a normal (planar) shock wave forms in front of the inlet. For higher supersonic speeds the pressure loss through the shock wave becomes prohibitive and a protruding spike or cone is used to produce oblique shock waves in front of

315-409: A turbine , which generates its own compressed air (i.e. ram air in a ramjet) in order to generate thrust. The diffuser converts the high velocity of the air approaching the intake into high (static) pressure required for combustion. High combustion pressures minimise entropy rise during heat addition, this minimising wasted thermal energy in the exhaust gases Subsonic and low-supersonic ramjets use

378-510: A combustor exit stagnation temperature of the order of 2,400 K (2,130 °C; 3,860 °F) for kerosene . Normally, the combustor must be capable of operating over a wide range of throttle settings, matching flight speeds and altitudes. Usually, a sheltered pilot region enables combustion to continue when the vehicle intake undergoes high yaw/pitch during turns. Other flame stabilization techniques make use of flame holders, which vary in design from combustor cans to flat plates, to shelter

441-429: A compact mechanism for high-speed, such as missiles . Weapons designers are investigating ramjet technology for use in artillery shells to increase range; a 120 mm ramjet-assisted mortar shell is thought to be able to travel 35 km (22 mi). They have been used, though not efficiently, as tip jets on the ends of helicopter rotors. L'Autre Monde: ou les États et Empires de la Lune ( Comical History of

504-403: A conventional layout would have stalled. The reason for this turned out to be the unexpected creation of a large vortex over the top of the wing, generated by the airflow between the fuselage and leading edge of the wing at high alpha. The vortex became "attached" to the upper surface of the wing, supplying it with air moving at speeds much greater than the aircraft's forward speed. By controlling

567-414: A final normal shock that occurs at the inlet entrance lip. The diffuser in this case consists of two parts, the supersonic diffuser, with shock waves external to the inlet, followed by the internal subsonic diffuser. At higher speeds still, part of the supersonic diffusion has to take place internally, requiring external and internal oblique shock waves. The final normal shock has to occur in the vicinity of

630-462: A hot fuel-rich gas which is burnt in the ramcombustor with the compressed air supplied by the intake(s). The flow of gas improves the mixing of the fuel and air and increases total pressure recovery. In a throttleable ducted rocket, also known as a variable flow ducted rocket, a valve allows the gas generator exhaust to be throttled allowing thrust control. Unlike an LFRJ, solid propellant ramjets cannot flame out . The ducted rocket sits somewhere between

693-533: A landing at 67 mph (108 km/h), 100 mph (160 km/h) slower than Convair had managed. In 1951, the XF-92A was refitted with an Allison J33-A-29 engine with an afterburner, offering a thrust of 7,500 lbf (33,000 N). The re-engined XF-92A was flown by Yeager for the first time on 20 July 1951. However, there was very little improvement in performance. In addition, there were maintenance problems with this engine and only 21 flights were made during

SECTION 10

#1732783706640

756-462: A minimum flow area known as the throat, which is followed by the subsonic diffuser. As with other jet engines, the combustor raises the air temperature by burning fuel. This takes place with a small pressure loss. The air velocity entering the combustor has to be low enough such that continuous combustion can take place in sheltered zones provided by flame holders . A ramjet combustor can safely operate at stoichiometric fuel:air ratios. This implies

819-529: A modified Polikarpov I-15 . Merkulov designed a ramjet fighter "Samolet D" in 1941, which was never completed. Two of his DM-4 engines were installed on the Yak-7 PVRD fighter during World War II. In 1940, the Kostikov-302 experimental plane was designed, powered by a liquid fuel rocket for take-off and ramjet engines for flight. That project was cancelled in 1944. In 1947, Mstislav Keldysh proposed

882-410: A nozzle to accelerate it to supersonic speeds and generate forward thrust . Ramjets are much less complex than turbojets or turbofans , requiring only an air intake, a combustor, and a nozzle to be built. Additionally, ramjets have little to no moving parts - liquid-fuel ramjets have only a fuel pump, whilst solid-fuel ramjets lack even this. By comparison, a turbojet uses a compressor driven by

945-487: A number of problems with this design. Convair found that by straightening the trailing edge and increasing the sweep of the leading edge, the characteristics of their new wing were greatly improved. Thus, contrary to suggestions that German designer Alexander Lippisch influenced it, Convair independently discovered the thin high-speed delta wing. Ralph Shick, chief of aerodynamic research, later met Lippisch at Wright-Patterson Air Force Base . This helped to convince him that

1008-572: A range of about 105 kilometres (65 miles). It was also used as a surface-to-surface weapon and was modified to destroy land-based radars. Using technology proven by the AQM-60, In the late 1950s and early 1960s the US produced a widespread defense system called the CIM-10 Bomarc , which was equipped with hundreds of nuclear armed ramjet missiles with a range of several hundred miles. It was powered by

1071-525: A solid fuel ramjet (SFRJ) vehicle test in August 2022. In 2023, General Electric demonstrated a ramjet with rotating detonation combustion. It is a turbine-based combined-cycle engine that incorporates a In the late 1950s, 1960s, and early 1970s, the UK developed several ramjet missiles. The Blue Envoy project was supposed to equip the country with a long range ramjet powered air defense against bombers, but

1134-593: A special test rig on a Dornier Do 17 Z at flight speeds of up to 200 metres per second (720 km/h). Later, as petrol became scarce in Germany, tests were carried out with blocks of pressed coal dust as a fuel (see e.g. Lippisch P.13a ), which were not successful due to slow combustion. Stovepipe (flying/flaming/supersonic) was a popular name for the ramjet during the 1950s in trade magazines such as Aviation Week & Space Technology and other publications such as The Cornell Engineer. The simplicity implied by

1197-488: A speed of Mach 3. It was used successfully in combat against multiple types of aircraft during the Falklands War . Eminent Swiss astrophysicist Fritz Zwicky was research director at Aerojet and holds many patents in jet propulsion. Patents US 5121670   and US 4722261   are for ram accelerators . The U.S. Navy would not allow Zwicky to publicly discuss his invention, US 2461797  

1260-439: A tandem arrangement. Integrated boosters provide a more efficient packaging option, since the booster propellant is cast inside the otherwise empty combustor. This approach has been used on solid-fuel ramjets (SFRJ), for example 2K12 Kub , liquid, for example ASMP , and ducted rocket, for example Meteor , designs. Integrated designs are complicated by the different nozzle requirements of the boost and ramjet flight phases. Due to

1323-452: A very large intake duct, which not only fed the jet engine but also passed air around the rocket exhaust to provide thrust augmentation . Located centrally, the large duct left nowhere to put a traditional cockpit; in its normal location it would have projected deep into the duct. To address this, the team modified the design in a fashion similar to both the Leduc 0.10 and Miles M.52 , placing

SECTION 20

#1732783706640

1386-543: Is extremely high, the engine/airframe combination tends to accelerate to higher and higher flight speeds, substantially increasing the air intake temperature. As this could damage the engine and/or airframe integrity, the fuel control system must reduce fuel flow to stabilize speed and, thereby, air intake temperature. Due to the stoichiometric combustion temperature, efficiency is usually good at high speeds (around Mach 2 – Mach 3, 680–1,000 m/s, 2,500–3,700 km/h, 1,500–2,300 mph), whereas at low speeds

1449-557: Is for the Underwater Jet, a ram jet that performs in a fluid medium. Time magazine reported on Zwicky's work. The first part of a ramjet is its diffuser (compressor) in which the forward motion of the ramjet is used to raise the pressure of its working fluid (air) as required for combustion. Air is compressed, heated by combustion and expanded in a thermodynamic cycle known as the Brayton cycle , before being passed through

1512-412: Is through ablation of the propellant by the hot compressed air from the intake(s). An aft mixer may be used to improve combustion efficiency . SFIRRs are preferred over LFRJs for some applications because of the simplicity of the fuel supply, but only when the throttling requirements are minimal, i.e. when variations in altitude or speed are limited. In a ducted rocket, a solid fuel gas generator produces

1575-485: The Austro-Hungarian Army , but the proposal was rejected. After World War I, Fonó returned to the subject. In May 1928 he described an "air-jet engine" which he described as suitable for high-altitude supersonic aircraft, in a German patent application. In an additional patent application, he adapted the engine for subsonic speed. The patent was granted in 1932 (German Patent No. 554,906, 1932-11-02). In

1638-511: The Leduc 0.10 was one of the first ramjet-powered aircraft to fly, in 1949. The Nord 1500 Griffon reached Mach 2.19 (745 m/s; 2,680 km/h) in 1958. In 1915, Hungarian inventor Albert Fonó devised a solution for increasing the range of artillery , comprising a gun-launched projectile united with a ramjet propulsion unit, thus giving a long range from relatively low muzzle velocities, allowing heavy shells to be fired from relatively lightweight guns. Fonó submitted his invention to

1701-640: The Lockheed D-21 spy drone. In the late 1950s the US Navy introduced a system called the RIM-8 Talos , which was a long range surface-to-air missile fired from ships. It successfully shot down enemy fighters during the Vietnam War , and was the first ship-launched missile to destroy an enemy aircraft in combat. On 23 May 1968, a Talos fired from USS Long Beach shot down a Vietnamese MiG at

1764-484: The United States Air Force , issued a proposal for a supersonic interceptor capable of 700 mph (1,100 km/h) speeds and reaching an altitude of 50,000 feet (15,000 m) in four minutes. Several companies responded, among which was Consolidated-Vultee, which submitted its design on 13 October 1945. This design featured swept wings and V-tails , as well as a powerful propulsion system. Besides

1827-574: The F-102 Delta Dagger. Related development Aircraft of comparable role, configuration, and era Related lists Ramjet A ramjet is a form of airbreathing jet engine that requires forward motion of the engine to provide air for combustion. Ramjets work most efficiently at supersonic speeds around Mach  3 (2,300 mph; 3,700 km/h) and can operate up to Mach 6 (4,600 mph; 7,400 km/h). Ramjets can be particularly appropriate in uses requiring

1890-595: The Second World War. Company officials claimed, in December 1945, that these domestic initiatives were uninfluenced by parallel German developments. One post-war U.S. intelligence assessment described the Kawasaki ram jet's centrifugal fuel disperser as the company's "most outstanding accomplishment ... eliminat[ing] a large amount of the fuel injection system normally employed." Because of excessive vibration,

1953-567: The Soviet Union, a theory of supersonic ramjet engines was presented in 1928 by Boris Stechkin . Yuri Pobedonostsev, chief of GIRD 's 3rd Brigade, carried out research. The first engine, the GIRD-04, was designed by I.A. Merkulov and tested in April 1933. To simulate supersonic flight, it was fed by air compressed to 200 bar , and was fueled with hydrogen. The GIRD-08 phosphorus-fueled ramjet

Convair XF-92 - Misplaced Pages Continue

2016-574: The States and Empires of the Moon ) (1657) was the first of three satirical novels written by Cyrano de Bergerac that are considered among the first science fiction stories. Arthur C Clarke credited this book with conceiving the ramjet, and as the first fictional example of rocket-powered space flight. The ramjet was designed in 1913 by French inventor René Lorin , who was granted a patent (FR290356) for his device. He could not test his invention due to

2079-510: The Vultee plants in summer 1947. The airframe was moved to Convair's plant in San Diego , and completed in the autumn. In December it was shipped without an engine to NACA 's Ames Aeronautical Laboratory for wind tunnel testing. After testing was completed, the airframe was returned to San Diego, where it was fitted with a 4,250 lbf (18,900 N) Allison J33 -A-21 engine. By the time

2142-468: The XF-92A by 14 October 1953. After the aircraft's last flight the nose gear collapsed as Crossfield taxied off the lake bed; the aircraft was retired. None of the pilots had much good to say about the design. Yeager commented "It was a tricky plane to fly, but ... I got it out to 1.05 Mach." Crossfield was more direct, saying "Nobody wanted to fly the XF-92. There was no lineup of pilots for that airplane. It

2205-568: The XF-92A was as a movie model, stepping into the role of the "MiG-23" in the Howard Hughes film, Jet Pilot , starring John Wayne and Janet Leigh . Due to the lengthy delay in releasing the film, by the time it appeared in 1957, the XF-92A's role had been left on the cutting room floor. It did appear in the film Toward the Unknown (1956) starring William Holden, again in the guise of another aircraft, this time as its descendant design

2268-472: The XF-92A. On his second flight he dove the aircraft in a 4 g split-S dive, reaching Mach 1.05 for a brief time. When approaching for landing on this flight he continued to pull the nose higher and higher in order to slow the forward speed to avoid the problems from his first attempt. Surprisingly, the aircraft simply wouldn't stall; he was able to continue raising the nose until he reached 45 degrees pitch , flying under control in that attitude to

2331-468: The aircraft was ready for testing, the concept of the point-defense interceptor seemed outdated and the (now redesignated) F-92 project was cancelled; the test aircraft was nevertheless completed as the XF-92A . In April 1948 the XF-92A was shipped to Muroc Dry Lake (later to become Edwards AFB ). Early tests were limited to taxiing, although a short hop was made on 9 June 1948. The XF-92A's first flight

2394-421: The booster is mounted immediately aft of the ramjet, e.g. Sea Dart , or wraparound where multiple boosters are attached around the outside of the ramjet, e.g. 2K11 Krug . The choice of booster arrangement is usually driven by the size of the launch platform. A tandem booster increases the length of the system, whereas wraparound boosters increase the diameter. Wraparound boosters typically generate higher drag than

2457-496: The booster's higher thrust levels, a differently shaped nozzle is required for optimum thrust compared to that required for the lower thrust ramjet sustainer. This is usually achieved via a separate nozzle, which is ejected after booster burnout. However, designs such as Meteor feature nozzleless boosters. This offers the advantages of elimination of the hazard to launch aircraft from the boost debris, simplicity, reliability, and reduced mass and cost, although this must be traded against

2520-648: The cockpit in a cylindrical body in the center of the intake. The design was presented to the U.S. Air Force in 1946 and was accepted for development as the XP-92. In order to gain inflight experience with the delta wing layout, Convair suggested building a smaller prototype, the Model 7002 , which the USAAF accepted in November 1946. In order to save development time and money, many components were taken from other aircraft;

2583-457: The compressed air bottle from which it is inflated, which is mounted lengthwise in the tank. This offers a lower-cost approach than a regulated LFRJ requiring a pump system to supply the fuel. A ramjet generates no static thrust and needs a booster to achieve a forward velocity high enough for efficient operation of the intake system. The first ramjet-powered missiles used external boosters, usually solid-propellant rockets, either in tandem, where

Convair XF-92 - Misplaced Pages Continue

2646-493: The ducted rocket, four 1,200 pounds-force (5.3 kN) rockets were positioned at the exhaust nozzle, along with the 1,560 pounds-force (6.9 kN) 19XB turbojet produced by Westinghouse. A proposal by Consolidated Vultee (later Convair) was accepted in May 1946, with a proposal for a ramjet-powered aircraft, with a 45° swept wing under USAAF Air Materiel Command Secret Project MX-813. However, wind tunnel testing demonstrated

2709-635: The engine was only intended for use in rocket, or catapult-launched pilotless aircraft. Preparations for flight testing ended with the Japanese surrender in August 1945. In 1936, Hellmuth Walter constructed a test engine powered by natural gas . Theoretical work was carried out at BMW , Junkers , and DFL . In 1941, Eugen Sänger of DFL proposed a ramjet engine with a high combustion chamber temperature. He constructed large ramjet pipes with 500 millimetres (20 in) and 1,000 millimetres (39 in) diameter and carried out combustion tests on lorries and on

2772-427: The flame and improve fuel mixing. Over-fuelling the combustor can cause the final (normal) shock in the diffuser to be pushed forward beyond the intake lip, resulting in a substantial drop in airflow and thrust. The propelling nozzle is a critical part of a ramjet design, since it accelerates exhaust flow to produce thrust. Subsonic ramjets accelerate exhaust flow with a nozzle . Supersonic flight typically requires

2835-557: The flow in this critical area, the performance envelope of the delta could be greatly expanded, which led to the introduction of canards on most delta-wing designs in the 1960s and 1970s. More recently leading edge extensions have become common on most fighter aircraft, creating the vortex over a more conventional wing planform. Data from Fighters of the United States Air Force General characteristics Performance An unusual application of

2898-418: The fuel to the ramcombustor is required, which can be complicated and expensive. This propulsion system was first perfected by Yvonne Brill during her work at Marquardt Corporation . Aérospatiale-Celerg designed an LFRJ where the fuel is forced into the injectors by an elastomer bladder that inflates progressively along the length of the fuel tank. Initially, the bladder forms a close-fitting sheath around

2961-425: The incoming air is slowed to subsonic velocities for combustion. In addition, the combustion chamber's inlet temperature increases to very high values, approaching the dissociation limit at some limiting Mach number. Ramjet diffusers slow the incoming air to a subsonic velocity before it enters the combustor. Scramjets are similar to ramjets, but the air flows through the combustor at supersonic speed. This increases

3024-483: The main gear was taken from a North American FJ-1 Fury , the nosewheel from a Bell P-63 Kingcobra , the engine and hydraulics were taken from a Lockheed P-80 Shooting Star , the ejection seat and cockpit canopy were taken from the cancelled Convair XP-81 , and the rudder pedals were taken from a BT-13 trainer. Construction was well underway at Vultee Field in Downey, California when North American Aviation took over

3087-479: The name came from a comparison with the turbojet engine which employs relatively complex and expensive spinning turbomachinery. The US Navy developed a series of air-to-air missiles under the name of " Gorgon " using different propulsion mechanisms, including ramjet propulsion on the Gorgon IV. The ramjet Gorgon IVs, made by Glenn Martin , were tested in 1948 and 1949 at Naval Air Station Point Mugu . The ramjet

3150-407: The next 19 months. A final engine change was made to the 5,400 lbf (24,000 N) J33-A-16. On 9 April 1953, Scott Crossfield began a series of flights on behalf of NACA. These tests revealed a violent pitch-up tendency during high-speed turns, often as much as 6 g, and on one occasion 8 g. The addition of wing fences partially alleviated this problem. Crossfield flew 25 flights in

3213-558: The pressure recovered from the streaming air and improves net thrust. Thermal choking of the exhaust is avoided by having a relatively high supersonic air velocity at combustor entry. Fuel injection is often into a sheltered region below a step in the combustor wall. The Boeing X-43 was a small experimental ramjet that achieved Mach 5 (1,700 m/s; 6,100 km/h) for 200 seconds on the X-51A Waverider . Point-defense Too Many Requests If you report this error to

SECTION 50

#1732783706640

3276-437: The reduction in performance of a dedicated booster nozzle. A slight variation on the ramjet uses the supersonic exhaust from a rocket combustion process to compress and react with the incoming air in the main combustion chamber. This has the advantage of giving thrust even at zero speed. In a solid fuel integrated rocket ramjet (SFIRR), the solid fuel is cast along the outer wall of the ramcombustor. In this case, fuel injection

3339-430: The relatively low pressure means the ramjets are outperformed by turbojets and rockets . Ramjets can be classified according to the type of fuel, either liquid or solid; and the booster. In a liquid fuel ramjet (LFRJ), hydrocarbon fuel (typically) is injected into the combustor ahead of a flameholder. The flameholder stabilises the flame with the compressed air from the intake(s). A means of pressurizing and supplying

3402-538: The resulting poor visibility. The combination of good high-speed and low-speed characteristics was very difficult to achieve for other planforms . Although the XF-92 itself was not liked, the design concept clearly had promise and the delta wing was used on several Convair designs through the 1950s and 1960s. Of particular interest to aircraft designers was the unexpectedly good low-speed behavior Yeager had noticed on his second flight. The aircraft continued to remain controllable at very high angles of attack (alpha), where

3465-539: The same engines as the AQM-60, but with improved materials to endure longer flight times. The system was withdrawn in the 1970s as the threat from bombers subsided. In April 2020, the U.S. Department of Defense and the Norwegian Ministry of Defense jointly announced their partnership to develop advanced technologies applicable to long range high-speed and hypersonic weapons. The Tactical High-speed Offensive Ramjet for Extended Range (THOR-ER) program completed

3528-1081: The simplicity of the SFRJ and LFRJ's unlimited speed control. Ramjets generally give little or no thrust below about half the speed of sound , and they are inefficient ( specific impulse of less than 600 seconds) until the airspeed exceeds 1,000 kilometres per hour (280 m/s; 620 mph) due to low compression ratios. Even above the minimum speed, a wide flight envelope (range of flight conditions), such as low to high speeds and low to high altitudes, can force significant design compromises, and they tend to work best optimised for one designed speed and altitude (point designs). However, ramjets generally outperform gas turbine-based jet engine designs and work best at supersonic speeds (Mach 2–4). Although inefficient at slower speeds, they are more fuel-efficient than rockets over their entire useful working range up to at least Mach 6 (2,000 m/s; 7,400 km/h). The performance of conventional ramjets falls off above Mach 6 due to dissociation and pressure loss caused by shock as

3591-613: The system was cancelled. It was replaced by a shorter range ramjet missile system called the Bloodhound . The system was designed as a second line of defense in case attackers were able to bypass the fleet of defending English Electric Lightning fighters. In the 1960s the Royal Navy developed and deployed a ramjet powered surface to air missile for ships called the Sea Dart . It had a range of 65–130 kilometres (40–80 mi) and

3654-571: The thin delta was the way forward, however the influence of Lippisch provided no more than "moral support" and Convair rejected many of his ideas, such as the thick wing of the Lippisch P.13a project and the DM-1 test glider which the US had tested. Thrust was to be provided by a 1,560 lbf (6,900 N) Westinghouse J30 jet engine assisted by a battery of six 2,000 lbf (8.9 kN) liquid-fueled rockets. This mixed-propulsion system required

3717-428: The unavailability of adequate equipment since there was no way at the time for an aircraft to go fast enough for a ramjet to function properly. His patent showed a piston internal combustion engine with added 'trumpets' as exhaust nozzles, expressing the idea that the exhaust from internal combustion engines could be directed into nozzles to create jet propulsion. The works of René Leduc were notable. Leduc's Model,

3780-428: Was a miserable flying beast. Everyone complained it was underpowered." The delta wing's thin airfoil cross section, low weight and structural strength made it a good candidate for a supersonic airplane. The large surface area of 425 ft (39 m) gave a low wing loading which in turn led to good low-speed performance. Very slow landing speeds could be achieved, at the cost of extremely nose-high landing angles and

3843-689: Was designed at the University of Southern California and manufactured by the Marquardt Aircraft Company . The engine was 2.1 metres (7 ft) long and 510 millimetres (20 in) in diameter and was positioned below the missile. In the early 1950s the US developed a Mach 4+ ramjet under the Lockheed X-7 program. This was developed into the Lockheed AQM-60 Kingfisher . Further development resulted in

SECTION 60

#1732783706640

3906-415: Was on 18 September 1948 with Convair test pilot Ellis D. "Sam" Shannon at the controls. On 21 December 1948 Bill Martin began testing the aircraft for the company. After 47 flights totaling 20 hours and 33 minutes, the aircraft was turned over to the USAAF on 26 August 1949, with the testing being assigned to Frank Everest and Chuck Yeager . On 13 October 1949 Yeager became the first Air Force pilot to fly

3969-520: Was tested by firing it from an artillery cannon. These shells may have been the first jet-powered projectiles to break the speed of sound . In 1939, Merkulov did further ramjet tests using a two-stage rocket , the R-3. He developed the first ramjet engine for use as an auxiliary motor of an aircraft, the DM-1. The world's first ramjet-powered airplane flight took place in December 1940, using two DM-2 engines on

#639360