Flightline: 121 - Cessna A-37 Dragonfly
Developed from the T-37 Tweet trainer, the A-37 served as an observer and COIN aircraft for the USAF and RSVAF during the War in Vietnam.
Beginning in the early 1960s, the USAF started taking more of an interest in acquiring specialized counter insurgency (COIN) aircraft, spurred on by the growing war in Vietnam. Evaluations at the USAF Special Air Warfare center at Eglin AFB pointed to the existing T-37 Tweet (so named because of the high pitch of its engines), a two engine jet trainer from Cessna, as having potential. In 1963, a contract was awarded to Cessna to modify two T-37s as prototypes for the new aircraft. The changes to these YAT-37D would include:
*Three stores pylons on each wing.
*Larger wingtip fuel tanks of 95 US gal capacity.
*A General Electric GAU-2B/A 7.62mm machine gun, with a rate of fire of 3,000 rounds/minute and 1,500 rounds of ammunition. A gunsight and gun camera were also fitted.
*Better avionics for battlefield communications, navigation, and targeting.
*Tougher landing gear for rough-field operation.
*Replacement of the Continental J69 engines with higher power GE J85-J2/5 jets.
Orthograph of the A-37 Dragonfly. | Illustration: Cessna/USAF
YAT-37A-1 first flew in October 1964, with #2 flying the following year. The second prototype differed from the first in having four pylons per wing rather than three. The first prototype was later modified to the same configuration, and the eventual production aircraft also featured a total of eight pylons. Interest in COIN aircraft cooled for a time, but losses of the Douglas Skyraider reignited the USAF's push for a dedicated plane. A contract was awarded to Cessna to convert 39 T-37Bs, creating AT-37Ds. The second YAT-37D, which had been turned over to the USAF Museum, was pulled out of storage and returned to flying condition. Recognizing that the Dragonfly was quite different from the Tweet, the designation was later changed to A-37A.
The second YAT-37D after being retired to the USAF Museum. | Photo: NMUSAF
Under Operation COMBAT DRAGON, 25 A-37As were shipped to Vietnam for combat evaluation in 1967. Based at Bien Hoa Air Base, Dragonflies participated in USAF "air commando" missions: close air support (CAS), helicopter escort, forward air control (FAC) and night interdiction. An A-37A could carry 2,700lbs of bombs, rockets, napalm or gun pods, in addition to its own gun. To extend the aircraft's range or loiter time, two drops tanks could be carried on the innermost pylons. During FAC missions, the A-37 would have a crew of two, pilot and observer, while other missions would only have a pilot, allowing an increased fuel and/or weapons load. Although officially named Dragonfly, many pilots, familiar with the aircraft's older brother from their training days, called it the Super Tweet. Over thousands of Combat Dragon sorties, no A-37s were lost to enemy fire, though two were destroyed in landing accidents.
A Cessna A-37A (s/n 67-14504) in a revetment at Bien Hoa Air Base, South Vietnam in 1968. | Photo: USAF
Son of Super Tweet
Though successful, Combat Dragon did highlight some flaws with the A-37A, chiefly a lack of power, limited range and endurance, the vulnerability of its flight controls and the effort required to move them during combat maneuvers. Cessna had already been awarded a contract for 57 improved A-37Bs, and these complaints were being addressed in the new plane. The A-37Bs were all new-build aircraft, with reinforced airframes now capable of pulling 6 Gs in combat as opposed to the 5 G limit of the A-37A. Crew survivability had been addressed by adding armored ejection seats and flak curtains in the cabin, as well as self-sealing fuel tanks in the wings. Redundant flight controls were also added, as well as being power-boosted to reduce the effort needed. The aircraft were fitted with uprated J85-GE-17A engine, allowing for higher speeds as well as more fuel or weapons to be carried. Since pilots during Combat Dragon had found that shutting down one engine improved endurance, the engines on the A-37B were angled slightly downward and outward to improve handling when cruising on a single jet. The B model also added aerial refueling capacity, though unusually for an Air Force plane it was fitted with a Navy-style probe-and-drogue rather than the USAF-style flying boom and receptacle. The new model also had upgraded avionics, a redesigned instrument panel, revised landing gear, and automatic deicing equipment. The Dragonfly was relatively low-maintenance, requiring only 2 hours of work per flight hour. This was partially due to the aircraft's low stance, as well as though-out access panels for major systems. Payload for the A-37B was increased to 5,800lbs. The 7.62mm gun was retained from the A, but external pods for 20mm and 30mm cannon were tested, but not adopted for combat.
The GAU-25B/A minigun installation in the nose of an A-37B. Also notable is the aerial refueling probe. | Photo: USAF
An A-37B on display at Nha Trang AB in 1969, showing the many types of weapons that could be carried. | Photo: USAF
In addition to the USAF, the A-37B was also acquired by the RVNAF, who purchased 254. The Dragonfly was found to excel at CAS, its slow speed allowing more accurate delivery of weapons compared to faster fighter-bombers like the F-105 and F-4. By the end of the Vietnam War, A-37s had flown more than 150,000 combat sorties, with only 22 losses. Nearly 120 RVNAF Dragonflies were captured by the North Vietnamese during 1975, and were pressed into service against the South. After the Fall of Saigon, they were used by the Vietnam People's Air Force in missions against Cambodia and China, as well as being shipped to allied nations like Poland and the USSR. In the USAF, the A-37Bs were passed from TAC to Air Force Reserve and ANG units. In the 1980s, they were replaced in the CAS role by the A-10 Thunderbolt II, and were redesignated OA-37B and assigned to FAC roles. The last combat service for the USAF's OA-37B was during the 1989 Operation JUST CAUSE in Panama.
An A-37 on display at the USAF Museum in Dayton, OH. | Photo: NMUSAF
Caballito del Diablo
Ex-USAF A-37Bs saw wide export to Central and South America in the '70s and '80s, seeing service in the air forces of Chile, Colombia, Dominican Republic, El Salvador, Ecuador, Guatemala, Honduras, Peru and Uruguay. Surplus Dragonflies were also supplied to South Korea and Thailand. Export customers liked the Dragonfly for its low cost and ease of operation compared to more complex aircraft like the F-16 or other 4th generation strike fighters. In Colombian service, the A-37 was modified to carry GBU-12 500lb laser guided bombs.
A-37 Dragonfly on display at the Military Museum, Bogota. | Photo: Acad Ronin