SI VIS PACEM, PARA BELLUM: Il Cessna A-37 Dragonfly era un aereo da attacco al suolo leggero biposto, bimotore a getto, prodotto dall'azienda statunitense Cessna Aircraft Company negli anni sessanta

Il Cessna A-37 Dragonfly era un aereo da attacco al suolo leggero biposto, bimotore a getto, prodotto dall'azienda statunitense Cessna Aircraft Company negli anni sessanta.

Sviluppato dall'addestratore T-37 Tweet, venne utilizzato in combattimento durante la guerra del Vietnam dall'United States Air Force e dalla sudvietnamita Không Quân Việt Nam e rimane ancora in servizio operativo in alcune forze aeree mondiali.

Storia del progetto

Il crescente coinvolgimento statunitense nelle vicende belliche del Vietnam nei primi anni sessanta produsse un forte interesse verso una particolare tipologia di velivolo, un aereo da attacco al suolo specializzato in controguerriglia (COIN dall'inglese COunter-INsurgency). Verso la fine del 1962, lo Special Air Warfare Center della United States Air Force basato presso la Eglin Air Force Base, Hurlburt Field in Florida, decise di valutare due esemplari di T-37C per questo ruolo.

Nelle prove che ne derivarono la commissione esaminatrice USAF giudicò il T-37 promettente, richiedendo tuttavia alla Cessna lo sviluppo di un modello derivato che fosse in grado di trasportare un carico bellico nettamente superiore, dotato di un'autonomia considerevolmente aumentata e migliori prestazioni nel volo a bassa quota. Un modello con queste caratteristiche sarebbe stato necessariamente più pesante e, di conseguenza, era necessario dotarlo di una coppia di motori a reazione dalla maggior spinta.

Visionato i progetti preliminari, nel 1963 l'USAF stipulò con l'azienda un contratto per la fornitura di due prototipi, identificati come YAT-37D, che rispetto ai T-37 di serie presentavano le seguenti modifiche:

struttura alare rinforzata.
tre piloni subalari per ciascuna semiala.
grandi serbatoi di combustibile della capacità di 360 L (95 US gal) posizionati alle estremità alari.
una mitragliatrice a canne rotanti General Electric GAU-2B/A "Minigun" calibro 7,62 mm con una cadenza di tiro di 3 000 colpi al minuto e 1 500 giri/min per il riarmo. L'arma era posizionata nel lato destro nel naso dietro un opportunamente largo pannello d'accesso ed era equipaggiata da un mirino e dotato di fotomitragliatrice.
avionica migliorata per le comunicazioni sul campo di battaglia, la navigazione e l'acquisizione di bersagli.
un carrello d'atterraggio irrobustito per operare da terreni non preparati.

Tutte queste modifiche andarono ad aumentare drasticamente il peso del modello il quale era destinato a trasportare un altrettanto significativo carico utile, per cui la Cessna ritenne necessario raddoppiare la spinta disponibile sostituendo gli originali Continental J-69 con due turbogetto General Electric J85-J2/5 in grado di fornire 10,7 kN (2 400 lbf) ciascuno.

Il primo YAT-37D venne portato in volo per la prima volta nell'ottobre 1964, seguito un anno più tardi dal secondo prototipo. Quest'ultimo introduceva un quarto pilone subalare per lato, soluzione ritenuta più soddisfacente ed adottata in seguito anche dal primo esemplare.

I test risultarono pienamente soddisfacenti, tuttavia l'iniziale interesse USAF per un velivolo COIN era venuto per il momento a mancare. Il programma subì quindi un arresto ed il secondo prototipo venne destinato ad essere esposto al National Museum of the United States Air Force presso la Wright-Patterson Air Force Base in Ohio.

la guerra nel teatro del sudest asiatico, tuttavia, continuava ad evolversi. La perdite di Douglas A-1 Skyraider nelle forze aeree statunitense e sudvietamita si rivelarono più pesanti del previsto e la necessità di trovare un adeguato rimpiazzo riaccesero l'interesse USAF per un aereo COIN. Lo YAT-37D sembrava il candidato più idoneo per questo compito, tuttavia l'Air Force ritenne che l'unico modo per esserne certi fosse quello di valutare l'aereo in combattimento.

Come risultato l'USAF sottoscrisse un contratto con la Cessna per un primo lotto consistente in 39 YAT-37D di pre-produzione, che introducendo alcune piccole modifiche rispetto ai prototipi, era possibile ricavare dalla conversione di T-37B già prodotti. Questi esemplari vennero inizialmente identificati come AT-37D, ma la designazione venne velocemente cambiata in A-37A. Il secondo prototipo YAT-37D venne quindi reintegrato e inviato dall'Air Force Museum alla Cessna per essere aggiornato allo standard A-37A come parte di un programma di prove.

L'A-37A era caratterizzato da un peso a pieno carico al decollo di 5 440 kg (12 000 lb) dei quali 1 230 kg (2 700 lb) consistevano in armamenti, e manteneva il doppio comando del precedente T-37B così da poterlo impiegare anche come addestratore avanzato.

Nelle missioni di "forward air control (FAC)" l'equipaggio era composto da due persone, con il secondo posto occupato da un osservatore, mentre nelle missioni di supporto aereo ravvicinato era normalmente condotto dal solo pilota, cosa che permetteva anche un lieve incremento del carico bellico.

Versioni:

YAT-37D - due prototipi di T-37C da addestramento convertiti per operazioni COIN con due motori J-85-GE e sei piloni subalari come prototipi per la serie A-37, ridesignata YA-37A.
YA-37A - redisegnazione dei due prototipi YAT-37D.
A-37A - (Cessna Model 318D) sviluppo del T-37B equipaggiato con due motori J-85-GE-5, una mitragliatrice multicanna calibro 7,62 mm nel naso e otto piloni subalari, 39 conversioni.
A-37B - (Cessna Model 318E) versione di produzione in serie equipaggiata con una coppia di motori J-85-GE-17A, caratterizzato dall'impianto per il rifornimento in volo, una maggiore capacità di combustibile e cellula rafforzata, realizzata in 577 esemplari.
OA-37B - versione da osservazione armata, sviluppata durante la guerra del Vietnam e che sostituì gli anziani O-2A Skymaster nei primi anni ottanta. Rimase in servizio con l'Air National Guard e le unità dell'Air Force Reserve come velivolo da osservazione fino alla fine degli anni ottanta.

Utilizzatori:

Cile - Fuerza Aérea de Chile - acquisì 44 esemplari, 14 dei quali attualmente in servizio. 10 esemplari sono stati ceduti alla Fuerza Aérea Salvadoreña.
Armada de Chile
Colombia
Fuerza Aérea Colombiana - Dei 72 acquistati, al luglio 2018 restano in servizio 7 A-37B (integrati nell'armamento dalla bomba a guida laser Paveway II da 500lb), 14 T-37B e 3 T-37C.
Corea del Sud - Daehan Minguk Gonggun
Rep. Dominicana - Fuerza Aérea Dominicana - operò con 8 esemplari, tutti fuori servizio dal marzo 2001 per raggiunti limiti di vita operativa o per incidenti.
Ecuador - Fuerza Aérea Ecuatoriana
El Salvador - Fuerza Aérea Salvadoreña - 40 tra A-37B e OA-37B consegnati (10 sono esemplari ex Fuerza Aérea de Chile), 15 in servizio al settembre 2019.
Guatemala - Fuerza Aérea Guatemalteca
Honduras - Fuerza Aérea Hondureña
Pakistan - Fi'saia Pakistana - 40 T-37 consegnati nuovi negli anni 1962-1977, seguiti nel 1980 da altri 22 di seconda mano. Questa flotta è stata poi incrementata con 74 T-37 (in parte modernizzati, in parti da cannibalizzare) ceduti da Stati uniti e Turchia tra il 2009 ed il 2015.
Perù - Fuerza Aérea del Perú - 36 consegnati nel 1975-1977, ai quali si sono aggiunti altri 17 esemplari ex USAF tra il 1992 e il 2002. Di queste macchine 10 sono state ammodernate nel 2002 e le altre ritirate, mentre altre 8 sono state cedute dalla Corea del Sud, quindi al dicembre 2016 ne risultano in servizio 18.
Rhodesia - Rhodesian Air Force
Sri Lanka - Sri Lanka Air Force
Stati Uniti - United States Air Force
Thailandia - Kongthap Akat Thai
Uruguay - Fuerza Aérea Uruguaya - 6 A-37B in servizio al dicembre 2018.
Vietnam del Sud - Không lực Việt Nam Cộng hòa.

ENGLISH

The Cessna A-37 Dragonfly, or Super Tweet, is an American light attack aircraft developed from the T-37 Tweet basic trainer in the 1960s and 1970s by Cessna of Wichita, Kansas. The A-37 was introduced during the Vietnam War and remained in peacetime service afterward.

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's Hurlburt Field 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 payload, and had much greater endurance and 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 litres (95 US gal) capacity.
A General Electric GAU-2B/A 7.62 mm (0.300 in) "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 significant payload as well. Cessna, therefore, doubled the engine power by replacing the two Continental J-69 engines with General Electric J85-J2/5 turbojet engines with 2,400 lbf (11 kN) thrust each.

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 counter-insurgency (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 National Museum of the United States Air Force at Wright-Patterson Air Force Base in Ohio.

The war in Southeast Asia, however, continued to escalate. Losses of Douglas A-1 Skyraider close-support aircraft in USAF, United States Navy, and Republic of Vietnam Air Force service proved greater than anticipated and USAF interest in COIN aircraft was revived. The YAT-37D seemed like a promising candidate for the job, but the Air Force felt that 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 pre-production 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 12,000 lb (5,400 kg), of which 2,700 lb (1,200 kg) was ordnance. 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 crewman normally flew in the aircraft for close support missions, permitting a slight increase in ordnance.

Operational history

Vietnam War

In August 1967, 25 A-37As were sent to Vietnam under the "Combat Dragon" evaluation program, and flew from Bien Hoa Air Base on USAF "air commando" missions, including close air support, helicopter escort, FAC, and night interdiction. Combat loads 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 fuel tanks on the inner stores pylons.

During this period, the A-37As flew thousands of sorties. None were lost to enemy fire, although 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 Republic of Vietnam Air Force (RVNAF) as replacements for their A-1 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, 5,800 lb (2,600 kg), could be external stores. In practice, the A-37B usually operated with at least two and sometimes four underwing fuel tanks to improve combat endurance.

In order to accommodate the increased weight, the A-37B was fitted with General Electric J85-GE-17A engines, providing 2,850 lbf (12.7 kN) 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-37 excelled at close air support. It could engage targets at speeds 100 miles per hour slower than swept-wing fighters. The slower speed improved bombing accuracy, enabling pilots to achieve an average accuracy of 45 feet (14 m).

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 A-37 required a relatively low amount of maintenance compared to contemporary fighters—only two hours of maintenance for each hour of flight time. This was partially due to multiple access panels in strategic locations.

The 20 mm (0.787 in) GPU-2/A and AMD 30 mm (1.18 in) cannon pods were tested with favorable results on the A-37B, but reports indicate that such pods were either seldom or never used in operation.

Post-Vietnam era

A total of 577 A-37Bs were built, with 254 delivered to the RVNAF. At war's end, the A-37 had flown over 160,000 combat sorties with only 22 USAF losses.

When North Vietnamese forces captured Da Nang Air Base, at the end of March 1975, they captured large amounts of stores and equipment, including 33 intact A-37s. On 28 April 1975, several captured A-37s were used by the North Vietnamese to attack Tan Son Nhut Air Base, still held by the South Vietnamese. Approximately 187 A-37Bs were in RVNAF service at the Fall of Saigon in April 1975. Ninety-two were recovered by the US, while the other 95 were later used by the Vietnam People's Air Force 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, likely due to the lack of spares. Some of the aircraft were shipped to Vietnam's then-Communist allies such as Czechoslovakia, Poland, the Soviet Union and East Germany. Others were sold to private foreign owners. Six examples of the A-37B became property of American warbird fans, while four 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 (TAC) to TAC-gained units in the Air National Guard and Air Force Reserve. In the early 1980s these aircraft were assigned to the FAC (Forward Air Control) role and given the designation OA-37B. The OA-37Bs were eventually phased out in the 1980s and 1990s and replaced in the FAC mission by the much more formidable Fairchild Republic A-10 Thunderbolt II in Air Force, Air National Guard and Air Force Reserve service.

OA-37s from the 24th Composite Wing's (later 24th Wing's) 24th Tactical Air Support Squadron (24 TASS) also saw service during Operation Just Cause.

Salvadoran Civil War

A-37Bs were used extensively by the Salvadoran Air Force during the Salvadoran Civil War, supplied by the United States in 1983 as a replacement for the Salvadoran Air Force's Dassault Ouragans, several of which had been destroyed on the ground by the FMLN. A-37Bs were used to bomb rebel bases, columns, towns, provided close air support, and flew interdiction missions. A total of 21 A-37Bs and 9 OA-37Bs were supplied during the war, one of which was lost on November 18, 1989 when sniper fire killed the co-pilot, causing the pilot to eject, and another that was shot down by an SA-7 missile on November 23, 1990.

Nine A-37s remained in operational condition by the end of the war.

Other Latin American countries

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.

The Guatemalan Air Force flew the A-37 in extensive counter-insurgency operations throughout the 1970s-1990s, losing one aircraft in action in 1985. It has also been widely used for counter-narcotics operations.

On 20 April 2001, a Peruvian Air Force A-37B Dragonfly shot down a civilian Cessna A185E floatplane with a minigun under surveillance by CIA controllers who advised against engaging. The Peruvian controller had the final authority in this situation, and he believed that the flight was carrying drugs out of the country, and so ordered the A-37 pilot to open fire. As a result a US missionary and her daughter were killed. The Cessna A185E crash landed in a river where locals in their boats helped the passengers.

Specifications (A-37B Dragonfly)

General characteristics:

Crew: Two

Length: 28 ft 3  1⁄4 in (8.617 m)

Wingspan: 35 ft 10  1⁄2 in (10.935 m) (over tip tanks)

Height: 8 ft 10  1⁄2 in (2.705 m)

Wing area: 183.9 sq ft (17.08 m2)

Aspect ratio: 6.2:1

Airfoil: NACA 2418 (modified) at root, NACA 2412 (modified) at tip

Empty weight: 6,211 lb (2,817 kg)

Max takeoff weight: 14,000 lb (6,350 kg)

Fuel capacity: 507 US gal (422 imp gal; 1,920 L) usable internal fuel (including tip tanks)