Cessna T-37 Tweet
- For the Soviet light tank, see T-37 tank
The Cessna T-37 Tweet[1] is one of the most prominent of the trainer-attack type aircraft. This small, economical twin-engine jet aircraft flew for decades as a primary trainer for the United States Air Force, and in the air forces of several other nations. The A-37 Dragonfly variant served with distinction in the light attack role during the Vietnam War.
Fifty-two years after its first flight, the T-37 is still serving the U.S. military, giving the Air Force's primary pilot training students the experience needed before moving on to the Northrop T-38 Talon, Beechcraft T-1A Jayhawk, Bell UH-1 Huey, United States Navy Beechcraft T-44 Pegasus, or other advanced Navy, Marine Corps or Allied trainers. Over 1,000 Cessna T-37s were built, with more than 100 still serving in the United States Air Force. In 2001, the United States Air Force began replacing the T-37 with the T-6 Texan II.
Development
Origins
The Cessna Aircraft Company of Wichita, Kansas earned a good reputation with the United States Army during World War II and the Korean War with the company's highly-regarded utility, light transport, and observation aircraft, particularly the "O-1 Bird Dog" series.
In the spring of 1952, the United States Air Force (USAF) issued a request for proposals for a "Trainer Experimental (TX)" program, specifying a lightweight two-seat basic trainer for introducing USAF cadets to jet aircraft.
Cessna responded to the TX request with a twin-jet design that featured side-by-side seating. The USAF liked the Cessna design, which was given the company designation of "Model 318", and particularly liked the side-by-side seating since it let the student and instructor interact more closely than with tandem seating. In the spring of 1954, the USAF awarded Cessna a contract for three prototypes of the Model 318, and a contract for a single static test aircraft. The Air Force designated the type as XT-37.
The first XT-37 first flew in October 1954. It had a low straight wing, with the engines buried in the wing roots; a clamshell-type canopy, hinged to open vertically to the rear; a control layout similar to that of contemporary operational USAF aircraft; ejection seats; and tricycle landing gear with a wide track of 4.3 m (14 ft).
The wide track and a steerable nosewheel made the aircraft easy to handle on the ground, and the short landing gear avoided need for access ladders and service stands. The aircraft was designed to be simple to maintain, with more than a hundred access panels and doors. An experienced ground crew could change an engine in about a half hour.
The XT-37 was aerodynamically clean, and so an air brake was fitted behind the nosewheel door to reduce landing speed. Since the short landing gear placed the engine air intakes close to the ground, screens pivoted over the intakes from underneath when the landing gear was extended, to prevent foreign object damage.
The XT-37 was fitted with two Continental-Teledyne J69-T-9 turbojet engines with 920 lbf (4.1 kN) thrust each. These were French Turbomeca Marboré engines built under license. The engines had thrust deflectors to allow the engines to remain spooled up (i.e. rotating at speeds above idle) during landing approach, permitting shorter landings while still allowing the aircraft to easily make another "go-round" in case something went wrong. Empty weight of the XT-37 was 2.27 tonnes (5,000 lb).
Tests showed the XT-37 had a maximum speed of 628 km/h (390 mph) at altitude, with a range of 1,505 km (935 mi). The aircraft was unpressurized, and so limited to a ceiling of 7.6 km (25,000 ft) by USAF regulations.
The initial prototype crashed during spin tests. The later prototypes had new features to improve handling, including long strakes along the nose, and an extensively redesigned and enlarged tail. After these modifications, the USAF found the aircraft acceptable to their needs, and ordered it into production as the T-37A. Even so, the aircraft remained tricky in recovering from a spin; the recovery procedure was complex compared with most aircraft.
Production
The production T-37A was similar to the XT-37 prototypes, except for minor changes to fix problems revealed by the flight test program. The first T-37A was completed in September 1955, executing its maiden flight that year, and was delivered to the Air Force in June 1956. The USAF began cadet training in the T-37A during 1957.
Instructors and students considered the T-37A a pleasant aircraft to fly. It handled well and was agile and responsive, though it was definitely not overpowered. It was capable of all traditional aerobatic maneuvers.
The T-37A had one noticeable drawback: it was very noisy, even by the standards of a jet aircraft. The intake of air into its small turbojets emitted a high-pitched shriek that led some to describe the trainer as a "Screaming Mimi", and it was referred to as the "6,000 pound dog whistle" or "Converter" (converts fuel and air into noise and smoke). The piercing whistle quickly gave the T-37 its name: "Tweety Bird", or just "Tweet". The Air Force spent a lot of time and money sound-proofing buildings at bases where the T-37 was stationed, and ear protection remains mandatory for all personnel when near an operating aircraft.
The Air Force ordered 444 T-37As, with the last produced in 1959. During 1957, the US Army evaluated three T-37As for battlefield observation and other combat support roles, but eventually procured the Grumman OV-1 Mohawk for the mission instead.
The Air Force liked the T-37A, but felt it was underpowered. As a result, the service ordered an improved version, the T-37B, with uprated J-69-T-25 engines. The new engines provided about ten percent more thrust and better reliability. Improved avionics were also specified for the new variant.
The first T-37B was delivered in 1959. A total of 552 newly-built T-37Bs were constructed through 1973. All surviving T-37As were eventually upgraded to the T-37B standard as well.
Due to a series of accidents caused by bird strikes between 1965 and 1970, all T-37s were later retrofitted with a new windscreen made of Lexan polycarbonate plastic 12.5 mm (½in) thick, which could tolerate the impact of a 1.8 kg (4 lb) bird at a relative speed of 460 km/h (288 mph).
In 1962, Cessna suggested the T-37B as a replacement for the North American F-100 Super Sabre as the primary aircraft for the USAF aerobatic demonstration team, the Thunderbirds. The T-37B was proven as an aerobatic aircraft, was economical to operate and support, and could be flown from small airports. However, the USAF was satisfied with the F-100 and were not interested in trading it in for the Tweet. Its later decision to switch to the F-105 Thunderchief caused several problems, though the supersonic T-38 trainer would later be selected as an economical alternative to front-line fighters.
The T-37A and T-37B had no built-in armament and no stores pylons for external armament. In 1961, Cessna began developing a modest enhancement of the T-37 for use as a weapons trainer. The new variant, the T-37C, was intended for export and could be used for light attack duties in a pinch.
The prototype T-37C was a modified T-37B. The primary changes included stronger wings, with a stores pylon under each wing outboard of the main landing gear well. The T-37C could also be fitted with wingtip fuel tanks, each with a capacity of 245 l (65 US gallons), that could be dropped in an emergency.
A computing gunsight and gun camera were added. The T-37C could also be fitted with a reconnaissance camera mounted inside the fuselage.
The primary armament of the T-37C was the General Electric "multi-purpose pod", which carried a 12.7 mm (0.50 caliber) machine gun with 200 rounds; two 70 mm (2.75 in) folding-fin rockets; and four practice bombs. Other stores, such as folding-fin rocket pods or even Sidewinder air-to-air missiles, could be carried as well.
The changes increased the weight of the T-37C by 650 kg (1,430 lb). As the engines were not upgraded, this reduced top speed to 595 km/h (370 mph), though the wingtip tanks increased maximum range to 1,770 km (1,100 mi).
T-37 production ended in 1975. The list of exports above amounts to 273 T-37Cs. Adding this to the 444 T-37As and 552 T-37Bs gives a total of 1,269 aircraft built.
The type remained in service with the USAF into the 21st century, having survived various attempts to find a replacement. However, the Tweet is now being phased out in favor of the turboprop-powered Beechcraft T-6A Texan II (a turboprop aircraft with more power and modern avionics), going into retirement after over four decades of reliable service.
Variants
- XT-37A
- T-37A
- T-37B
- T-37C
- XAT-37D
Concept aircraft
Cessna proposed a number of innovative variants of the Tweet that never went into production. In 1959, Cessna built a prototype of a light jet transport version of the T-37, designated the Cessna Model 407, which was stretched 61 cm (2 ft) to accommodate a four-place pressurized cockpit with an automobile-type configuration. Only a wooden mockup of the "Model 407" was constructed. The project was cancelled due to insufficient customer interest. The company also proposed a similar four-place military light transport, the "Model 405", with a big clamshell canopy, but it was never built either.
In response to a United States Navy "Tandem Navy Trainer" (TNT) requirement, Cessna proposed a T-37 with a modified fuselage featuring a tandem cockpit. The Navy selected the North American T-2 Buckeye instead, and the Cessna concept never got off the drawing board.
Cessna proposed various other trainer derivatives for the US Navy and Air Force, including a vertical takeoff version based on the TNT configuration and incorporating lift-jet pods in the wings, but none of them got to the prototype stage.
Operators
T-37s, including both new-build and ex-USAF aircraft, were supplied to a number of foreign operators, including:
Bangladesh- 30 aircraft, including 12 Cessna T-37 Tweet in active service.
Brazil- 65 T-37Cs, later passing 30 on to South Korea and 12 on to Paraguay.
Burma- 12 T-37Cs.
Cambodia- 4 T-37Bs.
Chile- 32 aircraft, including 20 T-37Bs and 12 T-37Cs.
Colombia- 14 aircraft, including 4 T-37Bs and 10 T-37Cs.
Ecuador- 20 aircraft including 10 A-37's and 10 T-37B's.
Germany- 47 T-37Bs, all operated in the US with USAF markings.
Greece- 32 aircraft, including 8 T-37Bs and 24 T-37Cs.
Jordan- 15 aircraft, apparently ex-USAF T-37Bs.
Morocco- 14 aircraft, received in 1995
Pakistan- 63 aircraft, including 24 T-37Bs and 39 T-37Cs.
Peru- 32 T-37Bs.
Portugal
- Portuguese Air Force - 30 T-37Cs. Some T-37Cs were used as the primary aircraft for the aerobatic demonstration team, the Asas de Portugal (Wings of Portugal) starting in 1977.
South Korea- originally 25 T-37Cs, plus 30 later bought from Brazil.
South Vietnam- 24 T-37Bs.
Thailand- 16 aircraft, including 10 T-37Bs and 6 T-37Cs.
Turkey- 50 T-37Cs.
United States
Vietnam- captured ex-South Vietnamese T-37s
Specifications (A-37B Dragonfly)
General characteristics
- Crew: 2
Performance
Armament
- Guns: 1× 7.62 mm (0.30 in) GAU-2B/A machine gun, 618 rounds
- Bombs: 6,000 lb (2,720 kg) on 8 underwing hardpoints
See also
Related development
Aircraft of comparable role, configuration, and era
Related lists
References
The initial version of this article was based on a public domain article from Greg Goebel's Vectorsite.
External links
