Cessna A-37 Dragonfly
The Cessna A-37 Dragonfly, or Super Tweet, is a United States light attack aircraft developed from the T-37 Tweet basic trainer in the 1960s and 1970s. The A-37 served with distinction during the Vietnam War.
Design and development
The growing American military involvement in Vietnam in the early 1960s led to strong interest in counter-insurgency (COIN) aircraft. In late 1962, the U.S. Air Force's Special Air Warfare Center at Eglin Air Force Base in Florida evaluated two T-37Cs for the role.
The Air Force found the T-37 promising, but wanted an improved version of the aircraft that could carry a much larger warload, and had much greater endurance, as well as better short-field performance. This meant a heavier aircraft with more powerful engines. In 1963, the Air Force awarded a contract to Cessna for two prototype YAT-37D aircraft: T-37s with modifications that included:
- Stronger wings.
- Three stores pylons on each wing.
- Larger wingtip fuel tanks of 360 litre (95 US gallons) capacity.
- A General Electric GAU-2B/A 7.62 mm "Minigun" Gatling-style machine gun, with a rate of fire of 3,000 rounds/minute and 1,500 rounds of ammunition. The weapon was fitted in the right side of the aircraft's nose behind a large, convenient access panel. A gunsight and gun camera were also fitted.
- Better avionics for battlefield communications, navigation, and targeting.
- Tougher landing gear for rough-field operation.
These changes meant a drastic increase in aircraft weight, and the aircraft now had to carry a serious warload as well, so Cessna replaced the two Continental J-69 engines with General Electric J85-J2/5 turbojet engines with 10.7 kN (2,400 lbf) thrust each, twice as powerful as the old Continental J-69s.
The first YAT-37D flew in October 1964, followed a year later by the second prototype. The second prototype had four stores pylons under each wing, rather than three, and the first prototype was upgraded to this configuration as well.
Test results were good, but USAF interest in COIN aircraft had faded for the moment. The program went into limbo for a time, with the second prototype "put out to pasture" at the Air Force Museum at Wright-Patterson Air Force Base in Ohio.
However, the war in Southeast Asia continued to escalate. Losses of Douglas A-1 Skyraider close-support aircraft in US and South Vietnamese hands proved greater than anticipated, and so USAF interest in COIN aircraft revived. The YAT-37D seemed like a promising candidate for the job, but the Air Force felt the only way to be sure was to evaluate the aircraft in combat.
As a result, the USAF issued a contract to Cessna for a preproduction batch of 39 YAT-37Ds, with a few minor changes relative to the prototypes, to be rebuilt from existing T-37Bs. These aircraft were initially designated AT-37D, but the designation was quickly changed to A-37A. The second prototype YAT-37D was pulled out of the Air Force Museum and upgraded to A-37A standards as part of the test program.
The A-37A had a gross takeoff weight of 5,440 kg (12,000 lb), of which 1230 kg (2,700 lb) was warload. The A-37A retained the dual controls of its T-37B ancestor, allowing it to be used as an operational trainer.
In combat "forward air control (FAC)" operations, the second seat was occupied by an observer. Only one crewmember normally flew in the aircraft for close support missions, permitting a slight increase in warload.
Operational history
In August 1967, 25 of the A-37As were sent to Vietnam under the "Combat Dragon" evaluation program, and flew from Bien Hoa Air Force Base on USAF "air commando" missions, including close air support, helicopter escort, FAC, and night interdiction. Warloads included high-explosive bombs, cluster munition dispensers, unguided rocket packs, napalm tanks, and the SUU-11/A Minigun pod. For most missions, the aircraft also carried two additional external tanks on the inner stores pylons.
The A-37As flew thousands of sorties. None were lost to enemy fire, though two were wrecked in landing accidents. The A-37A was formally named the "Dragonfly", but most pilots called it the "Super Tweet." The Combat Dragon program was successful, but unsurprisingly the combat evaluation revealed some of the deficiencies of the A-37A. The most noticeable problem was that the aircraft lacked range and endurance. Other concerns were heavy control response during attack runs (the flight controls were not power-boosted) and the vulnerability of the aircraft's non-redundant flight control system.
The USAF signed a contract with Cessna in early 1967 for an improved Super Tweet, designated the "A-37B". The initial order was for 57 aircraft, but this was quickly increased to 127. The A-37Bs were primarily intended to be supplied to the VNAF South Vietnamese Air Force as replacements for their Skyraiders. The A-37B prototype was rolled out in September 1967, with deliveries to the South Vietnamese beginning in 1968.
The A-37Bs were all newly built airframes. These were stronger than those of the A-37A, capable of pulling 6 g instead of 5, and were built to have a longer fatigue life of 4,000 hours. Field experience would demonstrate that 7,000 hours between overhauls could be tolerated.
The A-37B weighed almost twice as much as the T-37C. A remarkable fraction of the loaded weight, 2.67 tonnes (5,880 lb), could be comprised of external stores. In practice, the A-37B usually operated with at least two and sometimes four underwing fuel tanks to improve combat endurance.
To get this increased weight off the ground, the A-37B was fitted with General Electric J85-GE-17A engines, providing 12.7 kN (2,850 lbf) thrust each. These engines were canted slightly outward and downward to improve single-engine handling. Air commando pilots in Vietnam operating the A-37A had found single-engine cruise an effective means of improving their flight endurance.
Modifications were made to control surfaces to improve handling. To improve aircraft and crew survivability, the A-37B was fitted with redundant elevator control runs that were placed as far apart as possible. The ejection seats were armored, the cockpit was lined with nylon flak curtains, and foam-filled self-sealing fuel tanks were installed.
The A-37B added a refueling probe to the nose, leading to pipes wrapped around the lower lip of the canopy, for probe-and-drogue aerial refueling. This was an unusual fit for USAF aircraft, which traditionally are configured for boom refueling. Other improvements included updated avionics, a redesigned instrument panel to make the aircraft easier to fly from either seat, an automatic engine inlet de-icing system, and revised landing gear. Like its predecessors, the A-37B was not pressurized.
The 20mm GPU-2/A and AMD 30mm cannon pods were tested with favorable results on the A-37B to give it more punch, [1] but reports indicate that such pods were rarely or never used in operation.
A total of 577 A-37Bs were built, with 254 delivered to the South Vietnamese Air Force. They reportedly performed well in actions against Communist forces. Before South Vietnam fell in early April 1975, a South Vietnamese Air Force officer, Captain Nguyen Thanh Trung, defected to the Communists in his F-5E and then led strikes against South Vietnamese government positions, with NVAF pilots flying in two squadron of A-37B based at Phuoc Long airbase.
There were about 187 A-37Bs in South Vietnamese hands when the country fell. Ninety-two were recovered by the Americans, while the other 95 were later used by the Communist Vietnamese in missions over Cambodia and during the China conflict in 1979. These "renegade" aircraft were phased out of service in the late 1970s or early 1980s, in all probability due to lack of spares. Some of the aircraft were shipped to Vietnam's allies like Poland, the Soviet Union, and East Germany. Others were sold to private foreign owners, 6 of A-37B became property of American Warbird fans, 4 of A-37Bs are now privately-owned in Australia and New Zealand.
After the war, the USAF passed their A-37Bs from the USAF Tactical Air Command to Air National Guard and Air Force Reserve units. In the early 1980s these aircraft were assigned the FAC role and given the designation OA-37B. The OA-37Bs were eventually phased out and replaced in the FAC mission by the much more formidable Fairchild OA-10A Warthog.
The A-37B was also exported to Latin America, mostly during the 1970s. It was well suited to their needs because of its simplicity, low cost, and effectiveness for insurgent warfare. Most of the A-37Bs exported south had the refueling probe shortened to act as a single-point ground refueling probe, or deleted completely.
Concept aircraft
Cessna also proposed enhanced strike variants of the T-37. The AT-37E/STOL (short takeoff & landing) concept incorporated more powerful engines, thrust reversers, and big flaps. Side-by-side and tandem seating versions were offered.
The A-37D also had more powerful engines, a centerline gun pod, and a single-seat configuration based on the TNT fuselage. As with the improved trainer concepts, the improved strike versions never flew.
Variants
- YAT-37D
- Two former T-37C trainer prototypes converted for counter-insurgency operations with two J-85-GE engines and six underwing pylons as prototypes for the A-37 series, redesignated YA-37A.
- YA-37A
- Two YAT-37D prototypes redesignated.
- A-37A
- (Cessna Model 318D) T-37B rebuilt with two J-85-GE-5 engines, a 7.62mm minigun in nose and eight underwing stores pylons, 39 conversions.
- A-37B
- (Cessna Model 318E) Production version with two J-85-GE-17A engines, provision for inflight refuelling, increased fuel capacity and strengthened airframe, 577 built.
- OA-37B
Operators
- Chilean Air Force received 44 aircraft - 14 are currently operational.
- Colombian Air Force received 32 aircraft - 13 are currently in service(to be withdraw by 2008)
- Dominican Air Force received 8 aircraft - all units had been written off or destroyed in accidents by March 2001.
- Ecuadorian Air Force received 28 aircraft - 20 are still operational.
- El Salvador Air Force received 15 aircraft - 9 are currently in service.
- Guatemalan Air Force received 13 aircraft - 2 remain in service.
- Honduran Air Force received 17 aircraft - 10 remain operational.
- Peruvian Air Force received 53 aircraft - only 10 remain operational.
- South Korean Air Force - all replaced by T-50 Golden Eagle. Also served with the ROKAF's aerial acrobatic team, the "Black Eagle", up until Seoul Air Show in 2007, the last show which the Black Eagle team used the A-37B.
- Vietnam Air Force received 254 aircraft.
- Royal Thai Air Force received 20 aircraft.
- Uruguayan Air Force received 14 aircraft - 10 currently in service.
- Vietnam People's Air Force captured 95 ex-South Vietnamese A-37B aircraft.
Super Tweets remain in service in some of these countries in slowly declining numbers.
Specifications (A-37B Dragonfly)
General characteristics
- Crew: 2
Performance
Armament
One GAU-2B/A 7.62mm Minigun mounted in the nose. Four pylons under each wing can carry a range of weapons including 30mm DEFA-553 cannon, 20mm GPU-2/A cannon, the SUU-11/A 7.62mm Minigun pod, 19 shot LAU-32A 2.75 in. rocket pods, Mk.82 bombs, napalm tanks, SUU-14 bomblet dispensers, multiple Ejection Racks with four 500 lb bombs, and AIM-9 Sidewinder missiles.
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
