During the fighting in Southeast Asia, it became clear that the supersonic fighter-bombers, created for the "big war", are poorly suited for destroying small targets in the jungle. Due to the high flight speed and poor visibility, the pilots of supersonic fighter-bombers could not confidently identify the target and provide the required bombing accuracy. On several occasions there have been cases when turbojet combat aircraft inflicted unintentional strikes on American or South Vietnamese units or, due to the proximity of the combat formations of the opposing sides, were unable to provide effective aviation support.
Soon the American command came to the conclusion that in order to destroy point targets in a jungle war, a relatively light combat aircraft is needed that meets the following requirements:
- maximum speed up to 800 km / h, and working speed no more than 300 km / h. Otherwise, the pilot will experience a lack of time to recognize the target and aim;
- special attention should be paid to providing forward-downward visibility. It was also desirable to have a second crew member on board to increase situational awareness;
- a light attack aircraft must have armor protection for the cockpit, fuel tanks and the most important parts from the rifle weapons;
- an anti-insurgency combat aircraft must carry a wide range of aviation weapons, operate day and night, which requires a set of optoelectronic and radar overhead and embedded systems;
- to perform typical patrol and reconnaissance missions, the minimum mass of the combat load must be in the range of 227-454 kg, and when departing for the provision of direct air support at the request of ground forces - at least 908 kg;
- provided for the ability to operate from poorly prepared unpaved airfields. For this, a light attack aircraft must have good take-off and landing characteristics, as well as be easy to maintain and repair.
The understanding of the value of light turboprop combat aircraft did not come immediately. Until the early 1970s, piston fighters and attack aircraft created during the Second World War or shortly after its end were widely used in local conflicts to strike ground targets. However, as the "Mustangs" and "Corsairs" were decommissioned, the combat squadrons received jet fighters that had a much higher rate of climb, altitude and flight speed, but at the same time they were not very suitable for dealing with moving point targets.
The first American reconnaissance and strike turboprop combat aircraft was the twin-engine OV-1 Mohawk, created by Grumman. This vehicle was adopted by the American army aviation in 1959 and was originally intended only for reconnaissance and artillery fire adjustment, and therefore there were no weapons suspension assemblies. The Mohawk was serially built from 1959 to 1970, a total of 380 aircraft were produced.
The appearance of this aircraft was influenced by three main criteria: ensuring good visibility, high protection of the crew and main systems, good takeoff and landing characteristics. The pilot and observer were located in ejection seats, which ensured leaving the aircraft at zero altitude and a speed of 185 km / h. The crew had a double control set, which greatly facilitated pilot training and increased the chances of a successful landing in the event of a pilot's death or injury. The Mohawk, which was a turboprop midwing with a two-seater cockpit and a three-keel tail, could carry a very diverse reconnaissance and search equipment: day and night cameras, side-looking radar, passive infrared stations and radio systems designed to detect working radio stations and radars.
Aircraft of the OV-1A modification were equipped with a Textron Lycoming T53-L-701 theater with a power of 1005 hp. each. The OV-1D modification was equipped with 1400 hp engines. The maximum takeoff weight was 8214 kg. The maximum flight speed was relatively low - 491 km / h. Cruising speed - 330 km / h. At the same time, the "Mohawk" had excellent maneuverability, and for takeoff it needed a runway no more than 400 m long. With outboard fuel tanks, the aircraft could stay in the air for 4,5 hours. Particular attention has been paid to providing excellent visibility from the cockpit.
From the very beginning, the Mohauk's security was good. The glazing of the cockpit was made with 25-mm bulletproof glasses, from below the pilots, sitting shoulder to shoulder, were protected by 6,4-mm armor made of light alloy, in addition to armored backs, the pilots were covered by sheets of aluminum armor in front and behind. Such armor protection protected the crew from being hit by small arms fire. The nacelles were located above the wing, due to which the elements of the wing structure partly protected the engines from fragments of anti-aircraft shells and bullets when fired from below. After the appearance of the Strela-2 MANPADS in Vietnam, it turned out that the wing shields the thermal radiation of the engines well, making it difficult to capture the thermal homing head. The fuel tanks were sealed and filled with neutral gas, which made it possible to confidently hold single shots with 12,7-14,5-mm bullets.
OV-1s made their first combat missions in Vietnam in 1962. A year later, the results of combat use were summed up, showing that the Mohawk is excellent for counterinsurgency operations. Sufficiently high speed, low noise level and modern reconnaissance equipment contributed to the successful implementation of search and reconnaissance flights. The maximum number of Mohaukes simultaneously deployed in Vietnam reached 80 units, and they were used mainly over the territory of South Vietnam. Unlike other types of aircraft, "Mohawks" were not transferred to the South Vietnamese allies, remaining in service only with US Army Air Squadrons.
It soon became clear that when carrying out reconnaissance missions there was a need to destroy the identified targets. To do this, six suspension nodes were installed on the initially unarmed aircraft, on which, in addition to suspended fuel tanks, 500-pound (227-kg) bombs, napalm tanks, blocks with 70 and 127-mm NAR, as well as SUU containers could be placed -12 with 7,62 mm M134 Minigun machine guns. After one Mohawk was shot down by a North Vietnamese MiG-1969 in 17, AIM-9 Sidewinder air-to-air missiles were suspended on planes flying on the Ho Chi Minh Trail for self-defense. Maximum payload mass - 1678 kg. However, taking into account the suspension of additional fuel tanks and reconnaissance equipment, the weight of bombs and missiles in most combat missions was half that.
However, the main threat to the "Mohauk" was not a small number of North Vietnamese fighters, but anti-aircraft artillery and large-caliber machine guns. Before US forces left Vietnam, 63 OV-1s were lost. According to American data, 25 aircraft were shot down by air defense systems, another one burned up on the ground after shelling an air base. The rest of the OV-1s were lost for "non-combat reasons". However, there is reason to believe that a significant part of the 36 cars that crashed in flight accidents were damaged by anti-aircraft fire.
Nevertheless, the effectiveness of the OV-1 Mohawk reconnaissance and strike aircraft turned out to be quite high. They operated successfully both day and night. Combat missions in pairs were carried out quite often. At the same time, the leading aircraft carried equipment that allowed detecting vehicles and crowded places in the jungle, and the wingman struck at the detected targets.
Interaction with combat helicopters was also very successful, which destroyed targets identified using a thermal imaging station or side-looking radar. Due to their ability to stay in the air for several hours, the Mohawks were on duty, patrolling in the vicinity of forward fortified bases, escorting transport convoys and acting on the call of ground units. OV-1 Mohawk participated in rescue operations for downed American pilots, corrected artillery fire, provided close air support, and hunted for sampans and trucks.
After the end of the Vietnam War, the Mohawks who remained in the ranks were oriented exclusively towards solving reconnaissance tasks and electronic warfare, for which they were equipped with new equipment. In the 1970s, the Philippine government considered the OV-1 as a possible candidate to replace the AT-28D piston attack aircraft. The Americans were ready to donate two dozen planes, but the Filipinos did not have the money to repair and re-equip them. Subsequently, several cars were transferred to Argentina and Israel. In the US armed forces, the operation of all modifications of the OV-1 Mohawk ended in the mid-1990s.
The modified version, known as the Model 134R with a tandem crew arrangement, was created to participate in the LARA competition (Light Armed Reconnaissance Aircraft) for a light anti-guerrilla aircraft. But the winner in 1964 was the North American NA-300 project. This aircraft was later designated OV-10 Bronco.
In addition to Mohawk and Bronco, several more prototypes participated in the competition. In parallel with the Bronco, North American offered the YAT-28E anti-insurgency attack aircraft based on the well-proven piston training T-28A Trojan. The armed version of the Troyan was often used to fight partisans.
The experienced YAT-28E turboprop attack aircraft was equipped with a Lycoming ЕТ-55L-9 engine with a capacity of 2445 hp. with a four-bladed propeller. In total, three T-28A, taken from storage, were converted into this version. The use of stored aircraft gliders made it possible to significantly reduce costs. The flight speed of an attack aircraft with a turboprop exceeded 600 km / h. However, the main focus was on increasing the combat load. Together with a pair of large-caliber machine guns, up to 12 kg of bombs, NAR blocks and incendiary tanks could be placed on 2730 underwing hardpoints. In general, the aircraft turned out to be not bad, but in the end the military preferred light attack aircraft of special construction with a better forward and downward view.
Due to poor visibility, the military also rejected the Turbo Mustang III proposed by Cavalier Aircraft Corp. This machine was a symbiosis of the P-51D piston fighter airframe with the Rolls-Royce RB.53 Dart turboprop engine with a capacity of 1760 hp.
Turbo mustang III
The aircraft had a maximum take-off weight of 6350 kg and could accelerate to 869 km / h without external hardpoints. In each plane there were three 12,7-mm machine guns, and on six external nodes it was possible to hang bombs, napalm tanks and missiles with a total mass of up to 2268 kg. The most vulnerable components and the cockpit were covered with ceramic armor. Although, compared to the original piston Mustang, flight data and combat load increased significantly, and operating costs, on the contrary, decreased, it was not possible to interest potential buyers.
Lockheed proposed a project for a multipurpose aircraft CL 760. The machine with a maximum takeoff weight of 3600 kg was to receive two turboprop engines with a capacity of 715 hp. A load weighing up to 1133 kg was placed on five suspension nodes. In this case, four of the five pylons were placed on the wing console. The bow provided for the installation of machine guns.
CL 760 layout
The CL 760 aircraft looked too futuristic, and things did not progress beyond the construction of a full-size model. In addition, the layout of the combat load raised many questions. To maintain controllability, the bombs from the console pylons had to be dropped in pairs, which was not always justified.
Intense competition for the Bronco was the Model 48 Charger from Convair. This machine was a double-girder monoplane, the nose of which was made of fiberglass, and the main part of the airframe was made of aluminum alloys. The aircraft was powered by two Pratt & Whitney Canada T74-CP-8/10 engines with a total power of 1300 hp. The two-seater cockpit was protected by polymer and aluminum armor. The maximum takeoff weight was 4800 kg.
Model 48 Charger
The prototype of the Convair light attack aircraft made its first flight on November 25, 1964. On tests, he demonstrated high flight data and fully met the requirements of the LARA competition. On a number of criteria, the aircraft was superior to competitors. The Model 48 Charger had very high maneuverability, handled well at low altitude and demonstrated excellent take-off and landing characteristics. For takeoff and landing, a runway no more than 200 m long was required.The maximum flight speed was 513 km / h. Combat load - 910 kg. Four rifle-caliber machine guns were installed in the bow of the cockpit.
Model 48 Charger prototype with aircraft weapons
However, during the 196 test flight, the only Model 48 Charger built by Convair crashed due to pilot error. Since the fighting in Vietnam revealed an urgent need for a light anti-guerrilla attack aircraft, the NA-300 aircraft from North American was declared the winner.
Externally, the NA-300 (the future Bronco) and the Model 48 Charger had a lot in common. Both machines were made on a double-girder scheme, with a short fuselage between the beams and two turboprop engines on planes. The flight test program involved seven NA-300 prototypes. One of them crashed while studying the behavior of an aircraft in flight at low speed on one engine and flaps and spoilers extended on one console.
In 1966, the NA-300 was declared the winner of the LARA competition, after which it received the "serial" designation OV-10A Bronco. The Air Force ordered 109 aircraft, with the Marine Corps ordering another 76. Serial production of OV-10A aircraft began in June 1967.
The Bronco was the first turboprop combat aircraft specially designed for counterinsurgency missions. Given that the attack aircraft was supposed to operate at low altitude under enemy fire, special attention was paid to increasing the resistance to combat damage. The hydraulics were used only to retract and extend the flaps, landing gear and steering the front wheel. Therefore, damage to the hydraulic system did not significantly affect the aircraft's ability to stay in the air. The observer pilot also had controls at his disposal, which made it possible to take control in the event of a pilot injury. Ejection seats were installed in the cockpit, which made it possible to rescue in the speed range from 0 to 370 km / h. Front, rear and bottom, the cockpit was covered with armor that could hold rifle bullets. The front and rear armored partitions, as well as the armor plate installed between the pilot and observer seats, were made of steel 9,5 mm thick. The crew was protected from fire from below by 12,7 mm aluminum armor. The front part of the cockpit canopy is made of bulletproof glass. The total mass of the armor is 159 kg. All fuel tanks are protected and can withstand single large-caliber bullets. The space between the walls of the tanks and the wing skin was filled with a fire-fighting agent. At the same time, due to limitations on the mass of armor, the side glazing of the cockpit did not provide protection against bullets and shrapnel. In this regard, about half of the losses of all aircraft occurred due to the defeat of the pilots through the unarmored glazing of the cockpit canopy.
The Bronco was equipped with two Garrett T76-G turbofan engines with a capacity of 715 hp, which ensured the maximum flight speed without external suspensions - 452 km / h. The minimum speed is about 100 km / h. Maximum takeoff weight - 6552 kg. Combat radius of action with a maximum combat load - 367 km. Takeoff / run length - 230 m. On seven suspension nodes, weapons with a total weight of up to 1633 kg could be placed. Built-in armament - 4 machine guns of 7,62 mm caliber with 500 rounds of ammunition per barrel.
Combat trials of the Bronco in Vietnam began in June 1968, when OV-10A of the USMC VMO-2 squadron arrived at Da Nang airbase. Pilots of naval aviation, air force and army aviation also flew on turboprop attack aircraft in Southeast Asia. The Air Force mainly used the OV-10A as air gunners and in search and rescue operations. The crews searched for targets, after which they "marked" their NAR, the warhead of which was equipped with white phosphorus. When bursting, such rockets produced a clearly visible white smoke, and also had a strong incendiary effect. The main blow to the target was delivered by F-100 Super Saber or F-105 Thunderchief fighter-bombers. The ability to fly at a relatively low speed made it possible to escort transport-combat helicopters and isolate the landing zone when rescuing downed American pilots. "Bronco" was used very intensively, which was facilitated by the ability to be based on poorly prepared airfields and a short preparation time for a second flight. For two and a half months since the beginning of the combat use of the OV-10A, 503 sorties were carried out, 107 of them were for ground attack.
Army aviation pilots initially performed reconnaissance flights and adjustments of artillery fire in unarmed vehicles, which replaced the piston O-1A Bird Dogs in this role. The observer pilots really liked the aircraft with a protected cockpit and the ability to fly with one engine running. Soon, NAR units and suspended containers with six-barrel 10-mm "miniguns" appeared on the army OV-7,62A. This was due to the fact that spotter aircraft crews often spotted small enemy groups, single vehicles and boats.
The actions of the VAL-4 "Black Ponies" squadron of the US Navy gained great popularity. The main arena for the Black Ponies was the Mekong Delta. Turboprop "Bronco" were used to search for Viet Cong detachments, and also covered American combat boats from the air.
During armed reconnaissance, OV-10A usually operated in pairs. If necessary, they were promptly supported by aircraft on duty at the airfield on high alert. The attack aircraft were able to appear over the target 15 minutes after receiving the application. Such a result was difficult to achieve with jet combat aircraft. In this case, the "Super Sabers" or "Thunderchiefs" were forced to conduct patrols in the air with outboard fuel tanks and a minimum combat load, which was very costly. Helicopters could compete with turboprop attack aircraft, but in any case, the Bronco, due to its higher flight speed, reached its target faster. The aircraft was inferior in maneuverability and accuracy of fire to a helicopter, but these shortcomings were fully compensated for by the greater mass of the combat load and less vulnerability to small arms fire.
During combat missions, the OV-10A demonstrated high efficiency and good combat survivability. There are cases when turboprop attack aircraft, due to their high maneuverability, successfully evaded attacks from North Vietnamese fighters. Based on the experience of combat use, combat survivability was found to be quite satisfactory. The design of the aircraft, with the exception of the side glazing of the cockpit, turned out to be resistant to fire from small arms. Fatal damage was usually inflicted by bullets from large-caliber machine guns and shells from rapid-fire small-caliber anti-aircraft guns. There is no reliable information about the defeat of the OV-10A by anti-aircraft missiles. The overall ratio in Indochina of downed aircraft to the number of combat damage requiring serious repair was 1 to 38, while about half of the losses were caused by the incapacitation of the crew, which was hit through the side unarmored fragments of the cockpit canopy. Taking into account the intensity of the use, the losses turned out to be quite sensitive: the Air Force lost 64 Bronco, the Navy - 7 and the KMP - 10.
Despite a number of shortcomings, the OV-10A Bronco has long become the standard of the anti-guerrilla attack aircraft. After the end of the Vietnam War, his combat biography continued and was very eventful. Subsequently, "Bronco" enjoyed some success in the foreign market, export modifications were created for foreign customers. But this will be discussed in the next part of the review, dedicated to turboprop combat aircraft.
Talking about the light combat turboprop aircraft used by the Americans in Southeast Asia, it would be wrong not to mention the "miniganships" created on the basis of the Pilatus PC-6 Porter and HST-550 Stallion general-purpose aircraft. These vehicles, with a relatively small size, had a good carrying capacity and could be based on unpaved airfields with short runways.
An armed aircraft based on the Pilatus PC-6 Porter, known as the AU-23A Peacemaker, was created by Fairchild as part of the South Vietnamese Air Force's rearmament program for modern aircraft adapted for warfare in the jungle. The Peacemaker was armed with a 20mm triple-barreled cannon mounted on the left in the doorway, with 500 rounds of ammunition. Machine-gun containers, 113- and 227-kg bombs, napalm tanks and NAR blocks could be suspended on five pylons. The crew consisted of three people: two pilots and a gunner. The aircraft is capable of carrying six passengers, five infantry with weapons, one wounded on a stretcher, or three seated wounded and one orderly.
The AU-23A was equipped with a Garrett TPE331-1-101F turbofan with a capacity of 650 hp. The maximum takeoff weight was 2767 kg, the maximum flight speed was 274 km / h. Cruising - 239 km / h. The plane could stay in the air for more than 4,5 hours.
The combat tests of the "Peacemaker" lasted from the beginning of January to the end of June 1971. Three aircraft took part in them. During the tests, the following tasks were practiced: escorting helicopters, direct air support, defending forward military bases and delivering supplies to them, evacuating the wounded, armed reconnaissance and surveillance, countering the penetration of guerrillas into protected areas. Crews from the 4400th US Air Force Special Operations Squadron flew 94 sorties. At the same time, 198 bombs were dropped and more than 3000 20-mm shells were used up.
Although there were no aircraft losses during the combat tests, based on their results, a conclusion was issued that the Peacemaker, due to its high vulnerability, was unsuitable for use as an attack aircraft. The almost complete absence of booking a combat aircraft, made on the basis of a purely civilian vehicle, without any protection of vital systems made the AU-23A very sensitive to fire from weapons of 7,62 mm caliber. In addition, in the course of combat use, cracks appeared in the rudder on all vehicles, and one vehicle crashed due to engine failure. After that, all delivered were returned to the Fairchild factory for revision.
Despite the negative feedback from combat pilots and recommendations not to use the aircraft in combat conditions without serious modernization, the Air Force command decided to continue the program. "Peacemaker" could be good as a night "gunship", but for this it was required to install special equipment on it, allowing it to fly and confidently search for targets in the dark. Although this was not done, a total of 35 AU-23A light attack aircraft were built for the US Air Force. But on June 30, 1972, the 4400th Special Operations Squadron delivered its Peacekeepers to the Davis Montan storage base in Arizona. The aircraft were not in storage for long. As part of military assistance, 13 vehicles were transferred to Thailand in the same year. In the Royal Thai Air Force, "Peacekeepers" were called for, they were mainly used to patrol the borders and did not often engage in armed clashes.
The AU-23A demonstrated high reliability, were cheap and easy to operate. In the absence of anti-aircraft countermeasures, the AU-23A was well suited for routine patrol flights, and, given the fact that this small aircraft carried quite powerful weapons, if necessary, it could provide fire support to ground forces. To make up for losses as a result of flight accidents and replace machines that were out of service due to resource depletion, until 1977, Thailand received another 21 aircraft of this type. It is not known whether Thai AU-23A are still taking off, but in March 2019, one Peacemaker made an emergency landing in the Khlong Hoi Hong area.
The light turboprop attack aircraft Helio AU-24A Stallion in its flight data and externally differed little from the AU-23A Peacemaker. Given that the Stallion appeared later than the Peacemaker, it was clear that it suffers from the same main drawback - the lack of armor and special technical solutions that increase resistance to combat damage, which made it very vulnerable above the battlefield in the daytime. time.
AU-24A on trial
United Aircraft PT6A-27 turboprop engine with 680 hp provided speed without external suspensions up to 348 km / h. The cruising flight speed was 260 km / h. Maximum takeoff weight - 2313 kg. The flight range without outboard tanks is 715 km. For the takeoff run, 200 meters were enough, the run length was 260 m.
AU-24A with 227 kg bombs suspended
Small arms consisted of a three-barreled XM-197 cannon mounted on the left side. There were also four underwing and one ventral suspension unit for weapons, on which NAR blocks and bombs weighing up to 227 kg could be placed.
The AU-24A was tested in combat conditions in April-May 1972. In June, all built aircraft went to the storage base. Between January and November 1972, 15 of the 18 Stallions were transferred to the Khmer Air Force. The aircraft were stationed at Pochentong airbase near Phnom Penh.
In the first phase, AU-24A in Cambodia was used to escort river convoys. In the final months of the civil war, turboprop Stallions attacked Khmer Rouge positions north of Phnom Penh. The attack aircraft mainly operated at night, which made it possible to avoid combat losses. The AU-24A crews have achieved good results. They managed to destroy up to 500 enemy soldiers, two dozen trucks and several launchers of Chinese-made Type 63 MLRS. However, the combat activities of the Stallions in Cambodia were constrained by a lack of aviation ammunition. Shortly before the fall of the Khmer Republic, in mid-April 1975, three AU-24A flew to Thailand. The Khmer Rouge got 9 "mini-gunships". By the time Vietnamese troops invaded the country, one turboprop attack aircraft was in good working order.
In the mid-1970s, research continued in the United States on the creation of turboprop combat aircraft. In 1979, the US Department of Defense allocated $ 11,9 million to Piper for a turboprop attack aircraft project that continued the Turbo Mustang III line.
Although the PA-48 Enforcer outwardly very much resembled the slightly enlarged Mustang, in fact it was a new aircraft. The design of the tail section of the fuselage underwent changes, new spars were used in the wing. The total vertical tail area increased by 9% and the stabilizer area by 35,8%. The aircraft was equipped with a booster aileron control system similar to that used on the Lockheed T-33 Shooting Star trainer. The Enfoncer was powered by a Lycoming YT55-L-9 turboprop engine with 2445 hp. Although the PA-48 had significant power reserves, the top speed was limited to 650 km / h. Cruising speed - 407 km / h. Combat radius of action - up to 700 km.
Six points of suspension could accommodate a load with a total weight of up to 2580 kg. Including containers with 30mm cannons, unguided rockets, napalm tanks and bombs. In the future, the attack aircraft was supposed to arm the AGM-114 Hellfire ATGM and the AIM-9 Sidewinder UR. In addition to destroying ground targets, the turboprop attack aircraft was supposed to be used to combat helicopters.
Two PA-48s in 1983 and 1984 were tested at the flight test center at Edwards AFB. Prototypes showed good results, but orders from the Air Force did not follow. Apparently, the fact was that there was no free space for this aircraft in the US Air Force. The A-10 Thunderbolt II jet attack aircraft was intended for the “big war,” and the OV-10A Bronco and A-37 Dragonfly firmly occupied the anti-guerrilla niche.
To be continued ...