By 1950, the United States Air Force was unsure as to whether to introduce a new turbine engine powered trainer or to continue with the cheaper option of a piston engine powered aircraft, in the end they took the conservative approach and went with the piston engine option. Two years later the situation arose again and after considerable discussion it was decided that a primary trainer powered by a jet engine should be ordered. The decision was far from unanimous as opponents to the idea not only raised the issue of higher costs but were also concerned about increases in the accident rate. They reasoned that students using a high performance aircraft would be more prone coming to grief in the early stages of their training, especially due to engine failures caused by mishandling what (in the early fifties) was still a new and sometimes temperamental power plant. Supporters of the idea pointed out that the different handling techniques between piston and turbine engine aircraft meant that after initially learning to fly on the former, transferring to the latter involved having to learn a whole new set of skills, thus lengthening student's training period. If students were to start from scratch on a jet trainer it would simplify training no end and as the USAF was introducing more and more jet aircraft it seemed logical to introduce all through jet training.
In the end, those for outweighed those against and in 1952 a specification for a primary jet trainer was issued. After various prototypes were evaluated, the contract was awarded to the Cessna Aircraft Company for its proposed Model 318. Two prototypes, designated XT-37, were ordered with the first making its maiden flight on October 12, 1954. The aircraft was of all metal construction powered by two 920 lb thrust Continental YJ69-T-9 turbojets (an Americanised version of the French Turboméca Maboré) mounted in the wing roots. The tailplane was mounted about a third of the way up the tail so that the jet efflux would not disturb the airflow over it. Contrary to the normal American practice of tandem seating used in most trainers, the student and instructor were seated side by side in what was long considered an ideal arrangement. An initial order for 11 production aircraft, the T-37A, was placed during 1954. The first of these flew on September 27, 1955 and entered service in 1957 with a total of 534 eventually being built. The T-37B, with more powerful 1,025 lb thrust Continental J69-T-25 turbojet engines, entered service in November 1959 and as a result, all remaining T-37As were converted to this standard. The T-37B was followed by the final version, the T-37C, which had provision for wingtip fuel tanks and armament on underwing hardpoints. By the time production ended in 1977, a total of 1,268 T-37s had been built.
At the start of the 1960s there was an increase of interest in light Counter Insurgency (COIN) aircraft for so-called "brushfire wars". A Special Air Warfare centre was set up by the USAF and evaluation of suitable aircraft began, one of these being a T-37B. The T-37B seemed to hold promise for use as an attack aircraft so a further 2 were evaluated during 1962. Using their original powerplants, they had increasing external stores added until their take off weight reached 8,700 lbs, almost 33% more than the maximum take off weight of a standard T-37. The airframes were then modified to accept a pair of 2,400 lb thrust General Electric J-85-GE5 turbojets. With the new engines installed it was found that the maximum take off weight could be safely increased to 14,000 lbs, thus allowing for the carriage of a considerable amount of weaponry. The re-powered aircraft were given the experimental designation of YAT-37D.
United States involvement in the Vietnam war changed what had been a purely academic exercise into a more practical one when it was realised that a new light strike aircraft would be needed. Consequently, a contract to convert 39 T-37B trainers to a light strike configuration was awarded to Cessna in 1966. The contract stated that the aircraft were to be taken new from the production line and modified to a standard similar to the YAT-37D. This redesigned aircraft was designated the A-37A Dragonfly and, like the YAT-37D, was powered by 2 J-85-GE5 turbojets. The structure was strengthened considerably, 8 underwing hardpoints were added allowing a wide variety of stores to be carried and fixed wingtip fuel tanks were fitted to increase the internal fuel capacity. Deliveries of the Dragonfly to the USAF began on May 2, 1967 and in the latter half of the same year a squadron of 25 aircraft were sent to South Vietnam for a 4 month operational evaluation. At the end of their evaluation, they were assigned to the 604th Air Commando Squadron based at Bien Hoa before ending up with the South Vietnamese Air Force in 1970.
Meanwhile, Cessna had been working on an improved version of the Dragonfly. Although still based on the T-37 airframe, this new model was a purpose built light strike aircraft rather than an adaptation of a jet trainer. The prototype first flew in September 1967 with production deliveries starting in May 1968. Given the designation A-37B, this was to become the definitive Dragonfly with a total of 577 being built by the time production ended in 1977. Compared to the A model, the airframe of the A-37B was stressed for loads of up to 6g. Slotted flaps, a ventral airbrake and hydraulically operated landing gear were fitted as well as comprehensive bad weather and night flying instrumentation. The side by side seating arrangement was retained in the unpressurised cockpit and, as a weight saving measure, a layered nylon flak curtain provided crew protection in lieu of armour plating. An inflight refuelling probe was installed in the nose and the maximum internal fuel capacity was increased to 507 US gallons. The ability to carry up to 4 drop tanks added a further 400 US gallons to this total. Offensively, a GAU 2B/A 7.62 mm Mini-gun was installed in the nose and over 5,000 lbs of mixed stores such as bombs, napalm tanks, air to air missiles, rocket pods and gun pods could be carried on the 8 underwing hardpoints.
Although a number of Dragonflies served with the USAF, most were supplied to various "friendly" nations. The South Vietnamese Air Force received the majority (254), 95 of which were later captured and flown by the Vietnamese Peoples Air Force after the fall of South Vietnam in 1975. Other than Vietnam, the other major recipients of the Dragonfly were Latin American countries and the US Air National Guard who operated them as the OA-37B in the forward air control role. The A-37B has no military connection to New Zealand there are reported to be three privately owned aircraft in the country. The aircraft pictured here (71-845 c/n 43392) is the only airworthy example. It was built in August 1972 and sent to the 604th Squadron in Bien Hoa where it was operated by the Squadron Commander. In October 1972 it was passed to the VNAF and was used in a FAC role in both South and North Vietnam as well as Cambodia. In October 1991 the aircraft was imported into New Zealand and, on July 2 1992, was registered as ZK-JTL. A rebuild lasting two years was undertaken by AeroTech at Ardmore which included replacing five fuel bladders, anti-corrosion work and the installation of reconditioned engines. The aircraft is now painted in a VNAF scheme as A-37B '854' and is based at Tauranga.
Text © 2002 Stuart Russell.
Power plant: Two 12.68kN (2,400lb st) General Electric J85-GE-5 turbojets
Wingspan: 10.93m (35ft 10 1/2in) over tip tanks
Length: 8.62m (28ft 3 1/4in)
Max T-O weight: 6,350kg (14,000lb)
Max level speed: 816km/h (507mph)
Range: 740km (460miles)