Boeing YC-14

The Boeing YC -14 was built by the U.S. aircraft manufacturer Boeing experimental transport aircraft of the United States Air Force. The two built prototypes as well as the two competing McDonnell Douglas YC- 15 were tested from 1976 to 1977 as a possible replacement for the C -130 Hercules as part of the Advanced Medium STOL Transport ( AMST ) program. The test program of the shoulder Deckers was completed in the summer of 1977, a series production was no longer on the setting of the entire program.

  • 2.1 Hull
  • 2.2 drive, control and electronics



1971 put the U.S. Air Force set out the requirements for a new aircraft, which was to replace the then already nearly 20 years old C -130 Hercules transport. Nine manufacturers have been involved in the tender, Bell, Boeing, Fairchild, Lockheed, and McDonnell Douglas were until the end of the tender period on March 31, Activities. On November 10th, the orders were issued for the construction of two test patterns at McDonnell and Boeing. According to another study phase in which the requirements for the aircraft were slightly reduced, began on January 10, 1973 with the development of the aircraft under the internal model number 953 Boeing received to a budget of 96.2 million U.S. dollars. At the turn of 1973/74, however, the continuation of the AMST program was uncertain who work at Boeing and McDonnell were briefly almost silent, because you had to wait for new funds from the Department of Defense. The development budget of Boeing was increased after the confirmation of the program to 105.9 million dollars.

In order to achieve the required in the tender short take-off, put the Boeing designers at the " Upper Surface Blowing " concept, in which the exhaust jet of the two engines was led by the Coandă effect on the upper wing surface. In experiments in a wind tunnel at NASA Langley, this concept had proven to be promising. A similar approach in its Antonov transport plane An-72, which first flew in 1977.

In the summer of 1975 began with the assembly of the wings and fuselage. Marconi - Elliot Avionics System delivered in February 1976, the first electronic flight control system that was used in Seattle for laboratory tests. The systems for the first aircraft was followed in March. Also in February, was in Tulalip Bay, north of Seattle, began with the testing of a wing piece and the CF6 engine. In the tests, different flap positions and shear forces have been tried, the results were incorporated into the flight control with a. The mounting of the engines to the first prototypes were then made in March 1976, the rollout finally took place on June 11, 1976 on the Paine Field in Everett, near Seattle before 2000 invited guests.


After the rollout of the extensive test program began with the aircraft. After the first refueling tests and electronics reviews, the CF6 engines were started on June 21 for the first time. On July 7 began with the testing of the electronic flight control, after further testing for electromagnetic compatibility, which had been completed on 21 July, the machine with the USAF identifier 72-1873 1976 raised on the afternoon of August 9 from Boeing Field from the maiden flight. Was controlled the machine from a test pilot Raymond L. Mc Pherson of Boeing and Major David Please binder of the U.S. Air Force. During the one and a half hour flight, in which especially the electronic systems and the valves were tested, the aircraft reached a speed of 300 kilometers per hour and a maximum altitude of about 4500 meters. During the test flights in September, the buoyancy aids the YC- 14 were tested, and tested the flaps in flight.

The measurement data was recorded by a network of 1125 measuring points, the recording equipment were located in the cargo compartment of the aircraft. In later flight tests also test engineers were aboard, so that the measurement results could be directly evaluated.

The second aircraft ( 72-1874 ) was completed in September 1976; the maiden flight took place on October 21. After completion of the work trials, in which smaller defects in the machinery had been removed, the two prototypes were relocated to the Edwards Air Force Base in California after about 60 hours of flight on November 12, where further testing should take place. On 2 February 1977, the first successful short landing was carried out until April 1977 completed a total of 950 machines both short landings, 60 of them on unpaved runways. In the unloaded state, the machine needed only about 180 meters off run. Experiments with airdrops pallets and parachutists dummies from high and low altitude took place in time. After further loading experiments that took place in Yuma, the second prototype was on 21 May 1977, major demonstration tour to Europe. In the United Kingdom, Germany and France, a total of 177 short landings were carried out at 78 performances, including at the Paris Air Show. When loading demonstrations, a 50 -ton M-60 main battle tank was brought on board.

After the European tour of four pilots of NASA were then formed on the aircraft in August 1977, should the Quiet Short -Haul Research Aircraft ( soft short-range experimental aircraft ) fly later.

End of the project

After Jimmy Carter was elected president in 1977, the military budget was drastically reduced, which should lead to the end of the AMST program. Originally scheduled for the fall of 1977 provided for selecting a winner of the AMST program was initially postponed to spring 1978, then accounted for but complete with the termination of the project. The official end of the project came on 10 December 1979, the two aircraft were previously rented for a short time by Boeing for improvements and demonstrations.

Both aircraft still exist today, the first prototype is located in the Pima Air & Space Museum near Tucson, Arizona ( 32 ° 8 ' 16 "N, 110 ° 52 ' 3" W32.137861111111 - 110.86745833333 ); the second is placed in the vicinity of the 309th Aerospace Maintenance and Regeneration Group at Davis - Monthan Air Force Base ( 32 ° 10 ' 19 " N, 110 ° 50' 51" W32.171847222222 - 110.84744444444 ).



The 40.13 -meter-long hull with a circular, 5.44 meters measuring cross-section was constructed in conventional formers and. He is clad with aluminum panels at the rear are composite materials used. The recognized at the shoulder wings with a span of 39.32 meters possessed a continuous wing spar. The planking consisted of 30 -meter-long plates with integral stiffeners, making the number of parts was reduced by 50 percent. The wing area was 163.7 square meters. Under the high-set T-tail remained on the rear fuselage enough space for a large cargo hatch. The cargo hold was 18.66 meters long, 3.50 to 3.55 meters wide and a maximum of 3.66 meters high. The loading capacity was up to 36,740 kg, with short take-off 12,245 kg could still be loaded.

The chassis had a dirigible, zwillingsbereiftes nose wheel, the short main landing gear, each with two twin-wheel axles was attached to the side of the fuselage and was landing shocks up to 4.5 m / s intercept.

The first prototype remained unpainted, and the second was the then typical camouflage of the U.S. Air Force, which consisted of large patches in light brown, light green and olive gray.

Drive, control and electronics

The drive of the aircraft is carried out by two General Electric CF6- 50D turbofan engines with a thrust of 214.6 per kilo Newton. The engines were mounted rumpfnah very far in front of the wings, which gave the aircraft a very characteristic appearance. The thrust jet turbine was passed through a narrow, width adjustable by flaps nozzle directly to the wing surface. To reverse thrust the engines possessed a large deflector on the top, which diverted the thrust power very effectively.

Directly behind the engines to large double slotted flaps, which could be extended up to 70 degrees were. Through the Coandă effect of engine power remained on the flap surface "stick ", whereby very high lift coefficients were obtained. The flaps, which were also designed as a double slotted flaps, could be extended 36-58 degrees and supported the lift in slow flight or short take-off. This was supported by five fold-out spoilers and wings over the entire width reaching, extendable leading edge slats. At the same time the engine bleed air could be blown out of the wing leading edge in order to stabilize the boundary layer. Overall, as was an increase in the lift coefficient of about 20 percent can be achieved.

A large, three-part and double- hinged rudder increased maneuverability, especially since an engine failure would have caused a strong yaw and an asymmetric lift distribution. The tailplane was set to anhedral very high above the vertical stabilizer. Affixed to the outer end of the wing ailerons could also be easily lowered to increase lift.

The British manufacturer Marconi - Elliott Avionics System electronic flight control system was designed with triple-redundancy to ensure maximum safety. The cockpit had a head-up display that directly represented the pilot during the approach important aircraft data in the field of view. Addition, it was shown with superimposed flight control icons on a screen in the cockpit with poor visibility, a television image of a camera in the nose of the aircraft.

Due to the special lift devices, the aircraft reached the landing approach speeds of 160 kilometers per hour and came up with 360 meters landing roll out. The take-off run was laden ( 77,110 kg total mass ) at 305 meters. The maximum takeoff weight was 104,500 kg, the land mass was slightly lower 102,000 kilograms. The top speed of the Boeing YC -14 was 810 kilometers per hour (Mach 0.74 ), the normal cruising speed was 723 km / h The service ceiling was 13,716 feet, the maximum climb rate 32 m / s The aircraft had a maximum transfer distance of 4,815 kilometers and a combat radius of 740 kilometers.