North American Rockwell OV-10 Bronco
The North American Rockwell OV-10 Bronco is an American twin-turboprop light attack and observation aircraft. It was developed in the 1960s as a special aircraft for counter-insurgency combat, and one of its primary missions was as a forward air control aircraft. It can carry up to 3,200 lb of external munitions and internal loads such as paratroopers or stretchers, and can loiter for three or more hours.
Development
Background
The aircraft was initially conceived in the early 1960s through an informal collaboration between W.H. Beckett and Colonel K.P. Rice, U.S. Marine Corps, who met at Naval Air Weapons Station China Lake, California, and who also happened to live near each other. The original concept was for a rugged, simple, close-air-support aircraft integrated with forward ground operations. At the time, the U.S. Army was still experimenting with armed helicopters, and the U.S. Air Force was not interested in close air support.The concept aircraft was to operate from expedient forward air bases using roads as runways. Speed was to be from very slow to medium subsonic, with much longer loiter times than a pure jet. Efficient turboprop engines would give better performance than piston engines. Weapons were to be mounted on the centerline to get efficient unranged aiming. The inventors favored strafing weapons such as self-loading recoilless rifles, which could deliver aimed explosive shells with less recoil than cannons, and a lower per-round weight than rockets. The airframe was to be designed to avoid the back blast.
Beckett and Rice developed a basic platform meeting these requirements, then attempted to build a fiberglass prototype in a garage. The effort produced enthusiastic supporters and an informal pamphlet describing the concept. W.H. Beckett, who had retired from the Marine Corps, went to work at North American Aviation to sell the aircraft.
Rice states:
Light Armed Reconnaissance Aircraft
A "tri-service" specification for the Light Armed Reconnaissance Aircraft was approved by the U.S. Navy, Air Force, and Army, and was issued in late 1963. The LARA requirement was based on a perceived need for a new type of "jungle fighting", versatile, light attack and observation aircraft. Existing military aircraft in the observation role, such as the Cessna O-1 Bird Dog and Cessna O-2 Skymaster, were perceived as obsolescent, with too slow a speed and too small a load capacity for this flexible role.The specification called for a twin-engined, two-man aircraft that could carry at least of cargo or six paratroopers or stretchers, and be stressed for +8 and −3 g. It also had to be able to operate from an aircraft carrier, fly at least, take off in, and convert to an amphibious version. Various armaments had to be carried, including four machine guns with 2,000 rounds, and external weapons including a gun pod with M197 electric cannon, and AIM-9 Sidewinder air-to-air missiles.
Eleven proposals were submitted, including the Grumman Model 134R tandem-seat version of the already-fielded U.S. Army's OV-1 Mohawk, Goodyear GA 39, Beechcraft PD-183, Douglas D-855, Convair Model 48 Charger, Helio 1320, Lockheed CL-760, a Martin design, and the North American Aviation/Rockwell NA-300.
In August 1964, the NA-300 was selected. A contract for seven prototype aircraft was issued in October 1964. Convair protested the decision and built a small-wing prototype of the Model 48 Charger anyway, which first flew on 29 November 1964. This was also a twin-boom aircraft that had a broadly similar layout to the OV-10. The Charger, while capable of outperforming the OV-10 in some respects, crashed on 19 October 1965 after 196 test flights. Convair subsequently dropped out of contention.
The Bronco started flying midway through the Charger's test program on 16 July 1965, and became one of the premier COIN aircraft of the next 30 years. It did not achieve Rice's L2 VMA concept, because the DoD insisted on 40-ft-long wings, which made it depend on airbases. Rice concludes:
The Bronco performed observation, forward air control, helicopter escort, armed reconnaissance, utility light air transport, and limited ground attack. The Bronco has also performed aerial radiological reconnaissance, tactical air observation, artillery and naval gunfire spotting, airborne control of tactical air support operations, and front-line, low-level aerial photography. A prototype in Vietnam designed to lay smoke was extremely successful, kept in service by evaluators for several months, and only reluctantly released, but was not purchased due to a perceived lack of mission.
Design
The OV-10 has a central nacelle containing pilots and cargo, and twin booms containing twin turboprop engines. The visually distinctive feature of the aircraft is the combination of the twin booms, with the horizontal stabilizer that connects them.The aircraft's design supported effective operations from forward bases. The OV-10 can perform short takeoffs and landings, including on aircraft carriers and large-deck amphibious assault ships without using catapults or arresting wires. Further, the OV-10 was designed to take off and land on unimproved sites. Repairs could be made with ordinary tools. No ground equipment was required to start the engines. If necessary, the engines could operate on high-octane automobile fuel with only a slight loss of power.
The aircraft had responsive handling and could fly for 5 1/2 hours with external fuel tanks. The cockpit had extremely good visibility for a tandem pilot and co-pilot, provided by a wrap-around "greenhouse" that was wider than the fuselage. North American Rockwell custom ejection seats were standard, with many successful ejections during service. With the second seat removed, it can carry of cargo, five paratroopers, or two litter patients and an attendant. Empty weight was. Normal operating fueled weight with two crew was. Maximum takeoff weight was.
The bottom of the fuselage bore sponsons or "stub wings" that improved flight performance by decreasing aerodynamic drag underneath the fuselage. The sponsons were mounted horizontally on the prototype. Testing caused them to be redesigned for production aircraft; the downward angle of the sponsons on production models ensured that stores carried on the sponsons jettisoned cleanly. Normally, four 7.62 mm M60C machine guns were carried on the sponsons with the M60Cs accessed through a large forward-opening hatch on the top of each sponson. The sponsons also had four racks to carry bombs, pods, or fuel. The wings outboard of the engines contain two additional racks, one per side.
Racked armament in the Vietnam War was usually seven-shot rocket pods with white phosphorus marker rounds or high-explosive rockets, or 5 in four-shot Zuni rocket pods. Bombs, ADSIDS air-delivered/para-dropped unattended seismic sensors, Mk-6 battlefield illumination flares, and other stores were also carried.
Operational experience showed some weaknesses in the OV-10's design. It was significantly underpowered, which contributed to crashes in Vietnam in sloping terrain because the pilots could not climb fast enough. While specifications state that the aircraft could reach, in Vietnam the aircraft could reach only. Also, no OV-10 pilot survived ditching the aircraft.
Operational history
The OV-10 served in the U.S. Air Force, U.S. Marine Corps, and U.S. Navy, as well as in the service of a number of other countries. In total, 81 OV-10 Broncos were ultimately lost to all causes during the course of the Vietnam War, with the Air Force losing 64, the Navy 7, and the Marines 10.U.S. Marine Corps
The OV-10 was first acquired by the U.S. Marine Corps. Each of the Marine Corps's two observation squadrons had 18 aircraft – nine OV-10As and nine OV-10Ds night observation aircraft. A Marine Air Reserve observation squadron was also established. The OV-10 operated as a forward air controller and was finally phased out of the Marine Corps in 1995 following its employment during Operation Desert Storm, which also saw the final combat losses of OV-10s by U.S. forces. Among these losses were two USMC OV-10s being shot down due to a lack of effective infrared countermeasures. Its slow speed was thought to make it more vulnerable to antiaircraft weapons. Forward air control passed mostly to ground units with laser designators and digital radios and the twin-seat F/A-18D Hornet. Most operational Broncos were reassigned to civilian government agencies in the U.S., while some were sold to other countries.The U.S. Marine Corps YOV-10D night observation gunship system program modified two OV-10As to include a turreted forward-looking infrared sensor, laser target designator and turreted 20 mm XM197 gun slaved to the FLIR aimpoint. NOGS succeeded in Vietnam, but funds to convert more aircraft were not approved. NOGS evolved into the NOS OV-10D, which included a laser designator, but no gun.
U.S. Air Force
The USAF acquired the Bronco primarily as an FAC aircraft. The first combat USAF OV-10As arrived in Vietnam on 31 July 1968 as part of "Operation Combat Bronco", an operational testing and evaluation of the aircraft. These test aircraft were attached to the 19th Tactical Air Support Squadron, 504th Tactical Air Support Group at Bien Hoa Air Base in South Vietnam. The test roles included the full range of missions then assigned to FAC aircraft, including day- and night-strike direction, gunship direction, bomb damage assessment, visual reconnaissance, aerial artillery direction, and as escorts for aircraft engaged in Operation Ranch Hand. The aircraft's ability to generate smoke internally was used for strike direction and "in four specific instances under conditions of reduced visibility, the smoke was seen by strike aircrews before the detected." Operation Combat Bronco ended on 30 October 1968.After the end of Combat Bronco, the USAF began to deploy larger numbers to the 19th TASS, 20th TASS, and for out-of-country missions to the 23d TASS. The 23d TASS conducted Operation Igloo White, Operation Prairie Fire/Daniel Boone, and other special operations missions.
Between 1968 and 1971, 26 pilots from the Royal Australian Air Force and Royal New Zealand Air Force flew the OV-10A on FAC sorties, while attached to USAF squadrons. The 19th TASS hosted 13 RAAF pilots and three from the RNZAF; another seven RAAF pilots and three from the RNZAF were assigned to the 20th TASS.
From April to June 1969, the USAF conducted an operational exercise called "Misty Bronco" in South Vietnam's III Corps tactical zone to evaluate the OV-10A's performance as a light strike aircraft. The results were positive, and as of October 1969, all USAF OV-10As were to be armed with their internal.308 in M60C machine guns, which had generally been left out during the Combat Bronco evaluations and subsequent deployment. High-explosive 2.75 in rockets were also authorized for use against ground targets.
In 1971, the 23d TASS's OV-10A Broncos received modifications under project Pave Nail. Carried out by LTV Electrosystems during 1970, these modifications primarily included the addition of the Pave Spot target laser designator pod, and a specialized night periscope and LORAN equipment. The call sign Nail was the radio handle of this squadron. These aircraft supported interdiction of troops and supplies on the Ho Chi Minh Trail by illuminating targets for laser-guided bombs dropped by McDonnell F-4 Phantom IIs. After 1974, these aircraft were converted back to an unmodified OV-10A standard.
At least 157 OV-10As were delivered to the USAF before production ended in April 1969. The USAF lost 64 OV-10 Broncos during the war, to all causes. In the late 1980s, the USAF started to replace their OV-10s with OA-37B and OA-10A aircraft. Unlike the Marine Corps, the USAF did not deploy the Bronco to the Middle East in response to the Iraqi invasion of Kuwait, as it believed that the OV-10 was too vulnerable. The final two USAF squadrons equipped with the Bronco, the 19th and 21st Tactical Air Support Squadron retired the OV-10 on 1 September 1991.
In 2012, $20 million were allocated to activate an experimental unit of two OV-10s, acquired from NASA and the State Department. Starting in May 2015, these aircraft were deployed to support Operation Inherent Resolve flying combat missions over Iraq and Syria, flying more than 120 combat sorties over 82 days. They reportedly provided close air support for Special Forces missions. The experiment ended satisfactorily, but an Air Force spokesman stated they are unlikely to invest in reactivating the OV-10 on a regular basis because of the overhead cost of operating an additional aircraft type.