Boeing YC-14
By the 1970s, the USAF was aware that the C-130 Hercules was getting older, and would need replacement sometime in the near future. In 1972, the USAF issued the Advanced Medium STOL Transport (AMST) requirement, calling for a jet-powered transport capable of landing 27,000 pounds of cargo on a 2000-foot landing field with a range of 1200 miles without refueling. Six companies put in designs, and the USAF chose Boeing's YC-14 and McDonnell Douglas' YC-15 for actual production of test aircraft.
Though the YC-15 was fairly conventional in its layout, Boeing's YC-14 was more radical. The company already had a great deal in experience with "blown" flaps with the 747, in which air is blown over the flaps to give them better low-speed handling. That was just the beginning: Boeing also wanted to use the new supercriticial wing design, which offered better low speed handling with the same drag coefficent as a swept wing, and engines mounted high on the wing to take advantage of the newly-discovered Coanda effect. The latter blows the engine exhaust over the flaps, not only giving the same benefit as blown flaps, but also forcing the exhaust towards the ground earlier than in conventional aircraft, allowing for a shorter takeoff run.
The YC-14 first flew in August 1976, and two were built. Some minor tweaks had to be made (such as moving the tail forward), but both it and the YC-15 exceeded the AMST requirement. Boeing had the inside track, however, as the YC-14 was able to carry a M60 tank, whereas the YC-15 was unable to, and fly as slow as 65 mph thanks to the various high-lift designs incorporated in the YC-14.
Neither aircraft's performance would matter, however: in 1979, the USAF decided that it wanted an aircraft that could fulfill the strategic role as well as the tactical, as a replacement for the C-141 Starlifter rather than the C-130. Both the YC-14 and YC-15 were too small for that, and the AMST program was cancelled. The research involved would be used a decade later in the C-17 Globemaster III, though it was based much more on the YC-15. The high-mounted engines taking advantage of the Coanda effect would be used in a production transport, however--but the transport was the Soviet An-72/An-74 Coaler.
Both YC-14s were put into storage in case they were needed for further research, and in 1981 the first prototype, 72-1873, was donated to the Pima Air and Space Museum. (The second prototype, 72-1874, is close by in "Celebrity Row" at AMARG, the legendary "Boneyard" storage area.) 72-1873 has looked better: its markings have badly faded in the Arizona sun, and it is missing some of the windscreen and both engines.
Boeing YC-14
By the 1970s, the USAF was aware that the C-130 Hercules was getting older, and would need replacement sometime in the near future. In 1972, the USAF issued the Advanced Medium STOL Transport (AMST) requirement, calling for a jet-powered transport capable of landing 27,000 pounds of cargo on a 2000-foot landing field with a range of 1200 miles without refueling. Six companies put in designs, and the USAF chose Boeing's YC-14 and McDonnell Douglas' YC-15 for actual production of test aircraft.
Though the YC-15 was fairly conventional in its layout, Boeing's YC-14 was more radical. The company already had a great deal in experience with "blown" flaps with the 747, in which air is blown over the flaps to give them better low-speed handling. That was just the beginning: Boeing also wanted to use the new supercriticial wing design, which offered better low speed handling with the same drag coefficent as a swept wing, and engines mounted high on the wing to take advantage of the newly-discovered Coanda effect. The latter blows the engine exhaust over the flaps, not only giving the same benefit as blown flaps, but also forcing the exhaust towards the ground earlier than in conventional aircraft, allowing for a shorter takeoff run.
The YC-14 first flew in August 1976, and two were built. Some minor tweaks had to be made (such as moving the tail forward), but both it and the YC-15 exceeded the AMST requirement. Boeing had the inside track, however, as the YC-14 was able to carry a M60 tank, whereas the YC-15 was unable to, and fly as slow as 65 mph thanks to the various high-lift designs incorporated in the YC-14.
Neither aircraft's performance would matter, however: in 1979, the USAF decided that it wanted an aircraft that could fulfill the strategic role as well as the tactical, as a replacement for the C-141 Starlifter rather than the C-130. Both the YC-14 and YC-15 were too small for that, and the AMST program was cancelled. The research involved would be used a decade later in the C-17 Globemaster III, though it was based much more on the YC-15. The high-mounted engines taking advantage of the Coanda effect would be used in a production transport, however--but the transport was the Soviet An-72/An-74 Coaler.
Both YC-14s were put into storage in case they were needed for further research, and in 1981 the first prototype, 72-1873, was donated to the Pima Air and Space Museum. (The second prototype, 72-1874, is close by in "Celebrity Row" at AMARG, the legendary "Boneyard" storage area.) 72-1873 has looked better: its markings have badly faded in the Arizona sun, and it is missing some of the windscreen and both engines.