OV-10 Bronco

An OV-10 as displayed in Hurlburt Field Air Park.

The North American Rockwell OV-10 Bronco is a turboprop-driven light attack and cargo aircraft. It was developed in the 1960s as a special aircraft for COIN (counter insurgency) combat. Although it is a fixed-wing aircraft, its mission capabilities resemble a fast, long-range, inexpensive and reliable ultra-heavy attack helicopter. It flies at 350 mph (560 km/h), carries 3 tons of external munitions, and easily loiters for 3 or more hours. It is prized for its versatility, redundancy, load, wide field of view, short-field ability, low operational costs and ease of maintenance. In most cases, it flies acceptably on a single engine. In service, it was used primarily as a light attack and Forward Air Controller aircraft, and rarely if ever as a transport.

Although the United States military no longer flies the Bronco, other countries continue to operate it. It is in the active inventory of the Philippines, Colombia, Indonesia, Thailand and Venezuela, where it is used primarily for light attack counterinsurgent (COIN) missions, and utility missions such as border patrols, anti-piracy patrols, forward air control, surveillance, defense mapping and search-and-rescue.

A number of Broncos are in civilian use. The large cargo capacity makes the airframe well suited to dumping liquids. It is used for anti-drug crop-spraying aircraft (22, U.S. State Depts and BATF). The California Department of Forestry uses it for air tactical platforms (9 active, 7 spares). NASA has a few air-frames it uses for noise and stability research. By sheer accident, the Bronco's propellors revolve at a constant 2,000 rpm, simplifying noise research. It's also well-suited to some stability and vortex studies because either turboprop can be easily refitted to revolve either direction.

New air-frames are no longer produced, and spares are difficult to locate. Most operators keep several airframes to cannibalize.

Technical data

Visually, it has a central nacelle containing pilots and cargo, and twin booms containing twin turboprop engines. The visually-distinctive item of the aircraft is the combination of the twin booms, with the horizontal stabilizer that connects them. The North Vietnamese nickname for a Bronco was "pig sty," perhaps because it resembled a fenced enclosure.

It can perform short take-offs and landings on aircraft carriers without using catapults. The cockpit has extremely good visibility for a tandem pilot and co-pilot provided by a wrap-around 'greenhouse.' With the second seat removed, it can carry 1,452 kg (3,200 lb) of cargo, five paratroopers or two litter patients and an attendant. Empty weight was 3,161 kg (6,969 lb). Normal operating fueled weight, with two crew was 4,494 kg (9,908 lb). Maximum take-off weight was 6,563 kg (14,466 lb).

The bottom of the fuselage contains sponsons with four 7.62 mm M60C machine guns. The M-60Cs were 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.

Sponsons are "stub wings" underneath the fuselage. The sponsons were mounted horizontally on the prototype. Testing caused them to be redesigned for production aircraft. The downward angle assured that stores carried on the sponsons jettisoned cleanly. The sponsons are easy to remove, and this improves flight performance by decreasing aerodynamic drag. Most unarmed Broncos have now had their sponsons removed. Indonesia and Thailand have removed the light machine guns and retrofitted heavy .50 caliber (12.7 mm) machine guns (see .50 BMG).

Racked armament in the Vietnam War was usually seven-shot 2.75 inch (70 mm) rocket pods with marker or high-explosive rockets, or 5 inch (127 mm) four-shot Zuni rocket pods. Bombs, ADSIDS air-delivered seismic sensors, Mk-6 battlefield illumination flares, and other stores were carried as well.

Doctrine: Fire Support

In Vietnam, the U.S. Navy successfully operated fourteen OV-10A Broncos and a small support unit as a "Light Attack Squadron" designated VAL-4. The Broncos patrolled and scrambled in groups of two. After the first few weeks, most patrols carried a central fuel pod to extend their loitering time, a 4-missile Zuni pod outboard on each wing as their heavy weapons, the four light machine guns for suppressive fire, and a flare dispenser.

The efficient turboprops and wings gave the Bronco low operational expenses and a unique operational mode, not shared by either jets or helicopters: long loiter times from forward air bases. The result was that patrolling Broncos were often much more quickly available to the troops on the ground. Troops in fact, began asking for the Broncos, which were often available 40 minutes or more before conventional fast attack jets.

The Broncos' radio utilization was significant. Most use occurred on the radios used by ground troops: VHF-FM. The squadron officially wished for a direction finder for this type of radio, to locate ground troops needing help. The UHF radio was used for tower directions, and occasionally for finding downed airmen. The HF long-haul radio was rarely used.

In Vietnam there was a divided command in air support, so there was significant confusion between U.S. Air-Force forward air controllers (FAC), tactical aircraft deployments, and the Broncos. With their low speeds and great visibilitiy, the Broncos self-controlled very well, and often finished a requested fire-mission and left before the USAF TACAIR jets arrived. FACs said that the Broncos had a tighter turning radius than their little Cessna O-1s, and this caused difficulty for the FACs- they had to loiter near the outer edge of a target area to keep all aircraft in sight.

The Broncos were vulnerable to massed machine-gun fire, anti-aircraft artillery and light antiaircraft rockets. However, the aircraft's simplicity and redundancy rewarded careful flying. Over 7 months of combat by VAL-4, at 655 sorties per month (~4,550 sorties), only four aircraft were shot down.

In August 1969, VAL-4 reported availability at 85 hours per aircraft per month, with 1105 flight hours, 656 sorties and 12 aircraft. Doctrines required all flights to have two aircraft. An author of this article calculated average sortie times of about 3.2 hours, with about two sorties per day per aircraft.

The popular weapons were a GPU-2A/XN1 20 mm gun pod (always in short supply) and the Zuni 130 mm (5 in) rocket, single-fired at targets of opportunity. Ripple firing was possible, but rarely used. All communist insurgent targets could be destroyed with these weapons: sampans, light structures, bunkers and troop concentrations. The (4) 7.62 mm M-60 machine guns and 70 mm (2.75 in) rockets were used for antipersonnel and suppressive fire.

With the 130 mm Zuni rockets, the Navy pilots did not want heavy gravity bombs. The Zuni had good operational flexibility because it had forward fuzes (good for attacking material, and adequate for troops and vehicles), and proximity fuzes (exploding at 6 meters above ground, these were best for antipersonnel, and satisfactory for light structures and vehicles). The only problem with the Zuni was its 500 meter fragmentation radius, which, though usually an advantage, sometimes damaged aircraft and caused friendly fire casualties on the ground.

Flares were very useful for night attacks, and all patrols began to carry flare dispensers after the first few weeks.

CBU-55/B FAE cluster bombs were used in 1972 to good effect. These were the only 'bombs' used in combat (and possibly the first use of FAE against an armed enemy) This load consisted of 5 CBU's 4 MG's, and 4 Zuni loaded in LAU-33/A launchers mated to the LAU-7A launchers for AIM-9 Sidewinder missiles (originally developed for the F-8 aircraft) on the wing pylons (Station 1 and 7).

Doctrine: Forward Air Control

OV-10 Bronco aircraft firing a white phosphorus smoke rocket to mark a ground target.

The U.S. Marine Corps and U.S. Air Force operated the Bronco as an armed observation platform, usually manned by a forward-air controller and a pilot. Although more survivable and useful than a little O-1 or O-2, some authorities believe that this use was too limited, given the capabilities of the air-frame. A total of 81 0V-10 Broncos were ultimately lost during the course of the Vietnam War, to all causes: USAF 64, USN 7, and the USMC 10. [1]

Doctrine: Utility

The Bronco has 6,400 lb (2,900 kg) of cargo capacity, but its nacelle is not tall enough for easy cargo handling. A commercial version of the aircraft would have fixed this, possibly producing an excellent bush aircraft, given that the Bronco was designed for amphibious and short-runway operation. The Bronco exceeds 350 mph (560 km/h), has good fuel efficiency and range. Many air forces have adapted it to utility roles.

History

The Bronco began with a specification approved by the U.S. Navy, Air Force and Army, a "tri-service" specification called "LARA" (the Light Armed Reconnaissance Aircraft), issued at the end of 1963. Retired marine aviators K.P. Rice and William H. Beckett originated the LARA concept as an aircraft with very small wingspans of around 20 feet that could land in nearly any small clearing and use the same ammunition and fuel as ground troops used. His "L2 VMA" concept also would have the aircraft ground-mobile so it could be co-located with ground units and not be a pampered aircraft requiring runways and air bases.

Rice states:

"The military definition of STOL (500' to a 50' obstacle) allows takeoff and landing in most of the areas in which limited war might be fought. In addition, the airplane was designed to use roads so that operation would even be possible in jungle areas where clearings are few and far between. As a result the wingspan was limited to twenty feet and a heavy trailing arm type landing gear with a tread of 6.5ft was provided for operation from roads. Float operation is feasible...."[1]

"...it is quite feasible to design the various components so that it can be disassembled easily and stored in a box that would fit in a 6x6 truck bed together with the equipment needed for re-assembly in the field. It could thus be transported by amphibious shipping and either heli-lifted or driven ashore by a 6x6 truck."[2]

LARA was based on a perceived need for a new type of "jungle fighting" versatile light attack and observation aircraft. Existing aircraft (the O-1 Bird Dog and O-2 Skymaster) were perceived as obsolescent, with too small a cargo capacity for this flexible role.

The specification called for a twin-engined, two-man aircraft that could carry at least 2,400 lb (1,100 kg) of cargo, six paratroops or stretchers, and be stressed for +8 and -3 Gs (basic aerobatic ability). It also had to be launchable from an aircraft carrier, fly at least 350 mph (560 km/h), take off in 800 feet (240 m) and convert to an amphibian.

Various armament had to be carried, including four 7.62 mm machine guns with 2,000 rounds, and external weapons including a 20 mm gun pod and Sidewinder missiles.

Eleven proposals were submitted, nine of them were the Grumman Model 134R tandem-seat version of the already fielded OV-1 Mohawk observation/attack plane (marines dropped out of the program in 1958), Goodyear GA 39, the Beech PD-183, Douglas D-855, General Dynamics/Convair Model 48 Charger, the Helio 1320, the Lockheed CL-760, a Martin design and the North American/Rockwell NA-300.

In August 1964, the NA-300 was selected. A contract for seven prototype aircraft was issued in October 1964.

General Dynamics/Convair protested the decision and built a small-wing prototype of the Model 48 Charger anyway, which first flew on November 29, 1964. This was also a twin-boom aircraft that had a broadly similar layout to the Bronco. The Charger, while capable of outperforming the OV-10 in some respects, crashed on October 19, 1965 after 196 test flights. Convair dropped out of contention.

The Bronco started flying midway through the Charger's test program on July 16, 1965 and became one of the premiere COIN (COunter INsurgence) aircraft of the next thirty years but failed to live up to Rice's L2 VMA concept because DoD insisted on 40 foot long wings which made it yet another air base dependant aircraft. Rice concludes:

"The original concept of a small, simple aircraft that could operate close to the supported troops had been almost completely eviscerated by the 'system.' The ability to operate from roads (20ft span and 6.5 tread) had been ignored, and performance compromised by the short 30ft span, the extra 1000lbs for the rough field landing gear and another 1000lbs of electronics. The 'light, simple' airplane also had a full complement of instruments, ejection seats and seven external store stations. The concept of using ground ordnance and a bomb bay had been ignored, although it did have provisions for four M60 [medium] machine guns. In spite of this growth (almost double the size and weight of our home-built), the YOV-10 still had great potential. It would not achieve the advantages of integration with the ground scheme of maneuver, but it did have capabilities at the low end of the performance envelope that were still valuable and unique."[3]

The Bronco performed observation, forward air control, helicopter escort, armed reconnaissance, gunfire spotting, utility light air transport and limited ground attack. The Bronco has also performed aerial radiological reconnaissance, tactical air observation, artillery and naval gunfire spotting and airborne control of tactical air support operations, and front line, low-level aerial photography.

It was first acquired by the U.S. Marine Corps. Each of the Marine Corps' two observation squadrons had 18 aircraft, 9 OV-10As and 9 OV-10Ds night observation aircraft. There was also a Marine Air Reserve squadron. The OV-10 was phased out of the Marine Corps in 1995.

File:Ov-10-nog.jpg

The U.S. Marine Corps OV-10 Night Observation Gunship (NOGS) program modified four OV-10As to include a turreted forward-looking infrared (FLIR) sensor and turreted M197 20 mm 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. The US Marine Corps lost 10 OV-10's during the war, to all causes. [1]

Operation as forward air controllers in the U.S. Marines continued through July 1994, when the Broncos were decommissioned in large part to two Broncos being shot down during Operation Desert Storm due to a lack of effective infared countermeasures equipment. The doctrinal justification was that smart bombs would somehow enable faster fighter-bomber jets to drop ordnance without having to line up their aircraft because the bomb would "fly itself" to the target. Forward air control passed mostly to ground units with laser designators and digital radios (GFACs). The concept of using loitering Broncos or OV-1 Mohawks (AFACs) or airborne FACs to first acquire the targets from the air exploiting their low speeds and excellent pilot/observer visibility and then deliver munitions immediately while the fleeting targets were in sight instead of waiting for a fighter-bomber to take-off and arrive was not explored. Most operational U.S. Broncos were reassigned to civil governments in the U.S. Some were sold to other countries.

The USAF acquired the Bronco primarily as a forward air control (FAC) aircraft. The first USAF OV-10As for combat arrived in Vietnam on July 31, 1968. 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. [1]

In 1971, the 23d Tactical Air Support Squadron's Broncos at Nakhon Phanom Royal Thai Air Force Base received PAVE NAIL modifications. NAIL was the radio handle of this squadron. PAVE was Loral Aerospace's pod, mounted under the fuselage, containing a gyro stabilized optics system and in the back of the aircraft was a Loran-C navigational radio,and electronics to integrate them. PAVE NAIL illuminated targets for laser-guided precision bombs and used the laser/loran system to find downed aircrews. The program was very successful, but all this equipment was removed before the aircraft left South East Asia.

The Air-Force generally disliked the Bronco because it flew low and slow compared to a jet, and when acting as a forward air control, it was vulnerable to anti-aircraft artillery. It therefore did not fit any of the perceived U.S. Air Force missions of the 1980s, and was removed from service.

The U.S. Navy formed VAL-4, in January 3, 1969, and operated in Vietnam from April through April, 1972. The Navy used the Bronco OV-10A as a light ground attack aircraft, for interdiction of enemy logistics, and fire-support of Marines, SEALs and river boats. It succeeded in this role. The US Navy lost 7 OV-10's during the Vietnam War, to all causes. [1]

Indonesia and Thailand still fly COIN operations similar to the U.S. Navy's Vietnam missions with their Broncos, but have retrofitted .50-calibre (12.7 mm) Browning heavy machine guns in place of the light 7.62 mm (.30 calibre) machine guns. Reportedly Broncos won most Thai bombing competitions until heavily automated F-5s became available. At one time Thailand even flew Broncos as air-defense.

The Philippine Air Force flies Broncos on search-and-rescue and COIN operations in Mindanao. These are operated by the 15th Strike Wing based in Sangley Point, Cavite. Recent modifications by the PhAF included upgrades in the engine and propeller (now sporting a 4-bladed propeller), and flight controls and sensors.

Hazards

An engine failure on takeoff can cause the other engine to spin the whole aircraft around a couple of times. An immediate ejection is recommended when this happens. The Bronco is also said to be dangerous to ditch. In most reported incidents the aircraft came apart on contact with the ground or water. Ejections often failed, even with zero-altitude ejection seats.

Models

The original, or OV-10A model, was the definitive version.

The OV-10B model was produced for Germany to use as target tugs. A target towing pod was mounted underneath the fuselage. Some accounts claim that a turbojet was mounted above the nacelle. A clear dome replaced the rear cargo door. The rear seat was moved to the cargo bay to look backwards out the dome.

The OV-10B(Z) was a target tug version for Germany. 18 aircraft were supplied to the Germans.

The OV-10C, OV-10E, and OV-10F models were updated A models sold new to other countries, mostly with internal equipment modifications.

• OV-10C : Export version for Thailand.
• OV-10E : Export version for Venezuela.
• Ov-10F : Export version for Indonesia.

The OV-10D was the second-generation Bronco developed by the US Marine Corps. It was an extensively modified A model airframe. The D added a powerful Forward-Looking Infrared night-vision system with a camera mounted in a turret under an extended nose. It is easy to differentiate a D model from an A. The D has a long nose with a ball turret underneath, while the A has a short rounded nose. The D also has bigger engines, so it has larger fiberglass props that can be distinguished by their rounded tips. The A has squared-off aluminum props.

Other noticeable external differences are the square chaff dispensers midway down the booms on the D model (often covered with a plate when not in use) and infrared-suppressive exhaust stacks (they take air in the front and mix it with the exhaust before it exits, to reduce the heat given off and thus the ability of a heat-seeking missile to track the aircraft). The D model began life as the NOGS program.

The OV-10D+ was the next upgrade and consisted of A and D aircraft being extensively reworked at MCAS Cherry Point Naval Air Rework Facility with new wiring and strengthened wings. Engine instrumentation was changed from round dials to tape readouts. The easy way to distinguish the D form the D+ in photos is to look at the tail boom. The D has whip antennas and the D+ has blade antennas.

The YOV-10A was the original OV-10A prototype. The YOV-10D prototype was used to developed OV-10D Bronco.

Survivors

• Many OV-10's are currently on static display throughout the United States. The National Museum of the United States Air Force near Dayton, Ohio has had one on display in Air Force markings for many years.
• The original prototype YOV-10A was on display at the Yankee Air Museum at Willow Run Airport near Romulous, Michigan. It had been fully restored by a former OV-10 crew chief. Sadly, this aircraft was totally destroyed in the fire that burned the Museum to the ground in September 2004.
• There is currently an OV-10 at the Imperial War Museum Duxford in England, which whilst not on obvious display is clearly visible whilst passing along the M11

Operators

• Colombia, Germany ( 6 OV-10B and 18 OV-10B(Z) ), Indonesia (16 OV-10Fs), Philippines, Thailand (32 OV-10Cs), United States (US Air Force, US Marine Corps, US Navy), Venezuela (16 OV-10Es), Morroco

Civil Operators

California Department of Forestry and Fire protection.

Specifications (OV-10)

• Wing Span- 40 ft, O in (12.19 m)
• Length- 41 ft, 7 in (12.67 m)
• Height- 15 ft, 2 in (4.62 m)
• Wing Area 290.95 ft² (27.03 m²)
• Tailplane Span- 14 ft, 7 in (4.45 m)
• Weight Empty- 6,969 lb (3,161 kg)
• Normal Takeoff Weight- 9,908 lb (4,494 kg)
• Overload Takeoff Weight- 14,466 lb (6,563 kg)
• Powerplant- Two Garrett-AiResearch turboprop engines, T76-G-412 and T76-G-413, 715 shaft horsepower each

Performance

(A: OV-10A/C/E/F; B: OV-10B; C: OV-10B; D: OV-10D, with internal 20 mm ammnunition only):

• Max level speed at sea level, no weapons:
• A: 244 knots (452 km/h; 281 mph)
• D: 240 knots (444 km/h; 276 mph)
• Max level speed at 10,000 ft (3,050 m) at Normal T-O weight (10,000 lb/4,536 kg):
• B: 241 knots (447 km/h; 278 mph)
• C: 341 knots (632 km/h; 393 mph)
• Range (with max weapon load, no loiter): 228 miles (198 nm; 367 km)
• Ferry range (with aux. fuel): 1, 428 miles (1,240 nm; 2,298 km)
• Takeoff Run:
• A, at normal weight: 740 ft (226 m)
• B, at 12,000 lb (5,443 kg): 1,130 ft (344 m)
• C, at 12,000 lb (5,443 kg): 550 ft (168 m)
• D, at 13,284 lb (6,025 kg): 1,110 ft (338 m)
• Landing Run:
• A, at normal weight: 740 ft (226m)
• A, at overload weight: 1,250 ft (381 m)
• D, at landing weight: 800 ft (244 m)

External links

Wikimedia Commons has media related to:

OV-10 Bronco

• The OV-10 Bronco Association
• Historical documentation by the inventor, Col. K.P.Rice, USMC retired

Related content

Related development
REFERENCES;

1. Hobson, Chris. "Vietnam Air Losses, USAF, NAVY, AND MARINE CORPS Fixed-Wing Aircraft Losses In Southeast Asia 1961-1973." 2001. ISBN 1-857801-156 Comparable aircraft

• FMA IA 58 Pucará
• OV-1 Mohawk
• SOKO J-20 Kraguj

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