The Mohawk in Vietnam

Introduction

In limited warfare, the initial advantage usually lies with the enemy. His knowledge and use of the terrain, especially when clouded by bad weather or darkness, make extremely difficult the task of detecting his activities.

In 1962, the Army OV-1 Mohawk Surveillance system was deployed in South Vietnam to accomplish this detection task. Initially, the Mohawk performed its mission through photographic and visual observation, later adding infrared and radar surveillance. The intelligence thus supplied by the Mohawk system has proven to be a major tactical advantage for both U.S. and RVN (Republic of Vietnam) ground forces and air strike teams.

This report presents a brief description of the Mohawk Surveillance System and its trial-by-combat in Vietnam.

 

THE MOHAWK SURVEILLANCE SYSTEM

The Mohawk is a small, two-place, twin-turboprop aircraft capable of STOL operations from unimproved fields. It was produced in three versions:

The Mohawk's bubbled canopy and side hatches, and the short, steep slope of its nose, permitted excellent downward visibility to the side, rear, and front. On all versions, protection from ground fire was provided by armor on the cockpit floor, a bullet-resistant windshield, flak curtains on the forward and aft cockpit bulkheads, and a self-sealing fuel cell. Additional personnel armor kits were also provided for the pilot and observer. Martin-Baker ejection seats permitted emergency egress from the aircraft, at low speeds and minimum altitudes.

 

MOHAWK MISSIONS

The Mohawk's primary role was to detect and monitor the movement of insurgent forces and materiel into South Vietnam, and to perform aerial surveillance and target acquisition within the country itself. The enemy's elusiveness coupled with the region's difficult terrain required the Mohawk to utilize its full range of sensors, and to operate in close coordination with U.S. and RVN forces. Indeed, a number of specialized air-strike operations were developed in Vietnam to take advantage of the rather unique capabilities of the Mohawk Surveillance System.

Visual/Photographic

Photographic surveillance was one of the primary means of daylight reconnaissance in Vietnam, and was performed for both U.S. and RVN tactical elements. Photographic target surveillance missions were normally flown by the OV-1A on a preplanned, priority basis. Typically, a team of two aircraft approached the target area, flying in loose formation to allow freedom for quick maneuvers and provide mutual support. When defensive firepower was required during visual/photo missions, the planes deliver mutually supporting fire, in accordance with the rules of engagement. (Those rules allowed the Mohawk pilot to fire only if fired upon.)

Photographic surveillance, using the KS-61 and KA-60 camera systems, was usually performed by means of the single-pass technique, at altitudes between 500 and 1500 feet. Visual surveillance was normally accomplished using the multiple-random-pass technique. The SLAR and IR Mohawks, being fully equipped for the visual/photographic surveillance mission, were used by the U.S. 1st Infantry and 1st Cavalry Divisions, where OV-1As weren't available.

SLAR

The OV-1B Mohawk, equipped with side-looking airborne radar (SLAR), was one of the primary means for night detection of vehicular traffic in Southeaset Asia. The OV-1B detected fixed and moving targets on land and along coastal and inland waterways. With this surveillance system, the locations of moving targets were determined, as well as the long-term pattern of land and waterborne traffic in critical areas. The multiple-parallel-pass technique was used to obtain target speed and direction. In other cases, a single pass was flown.

SLAR equipped Mohawks performed surveillance in all but the most severe weather, and were frequently called on to fly missions under completely IFR weather conditions. The altitudes (7000 to 14,000 feet) flown during SLAR missions normally allowed radio line-of-sight between the OV-1B and ground based electronic navigation aids. Operation at these altitudes also minimized the need for evasive tactics due to the threat of enemy ground fire, particularly when operating in the southern regions.

During a mission, the RO-166 Recorder-Processor-Viewer enabled target radar images to be recorded and reported to appropriate agencies by the crew. This inflight spot reporting frequently initiated immediate actions against Vietcong or North Vietnamese activities.

Based on the validity of the targets plotted, the SLAR missions were considered highly successful. Due to the high rate of confirmed hits recorded by strike aircraft, coordinates plotted by the OV-1B were often hit even when there was no visible evidence of enemy activity. On an early SLAR mission, the strike team looked over a flare-illuminated area and reported negative findings. They were, nevertheless, directed to hit the coordinates. The subsequent attack on the area resulted in a secondary explosion, confirming the find and adding to the confidence in the OV-1B system.

The OV-1B also proved its ability to acquire moving targets in the inland areas. The SLAR's recorder-processor-viewer, by providing a permanent image, permitted continuing tracking of a particular target. Vehicles kept under surveillance in this manner were followed to their ultimate destination. When numerous vehicles were tracked to the same location, the area was assumed to be a VC staging area. Such information, coordinated with other collection efforts, then formed the basis for raids by B-52s or other strike aircraft.

Infrared

As the Vietcong increased their nighttime operations, the need became urgent for airborne surveillance equipment capable of reliably detecting their activities. The OV-1C and its infrared sensor fulfilled this need by detecting heat emissions in areas suspected of being occupied by the VC. The major sources of such emissions were cooking fires and the hot engines of land or waterborne vehicles.

The number and pattern of IR emissions aided in determining the location, strength, and disposition of enemy forces. Such information, supplied in real time by the Mohawk's sensors, often led to immediate action to stem the VC's activities. However, IR data was normally used in conjunction with information from other sources to develop overall Vietcong activity trends. After analysis, these trends were forwarded to operational elements for appropriate action.

To provide the best combination of target detection and image reference, OV-1C missions were flown at altitudes between 1000 and 2000 feet, using the multiple-parallel-pass technique. At these altitudes, the IR sensor was capable of detecting high background contrast emissions, even through the jungle growth. If the mission objective was verification of target information developed by other means, the Mohawk was flown at its best IR imaging altitude....generally, between 500 and 1000 feet.

The OV-1C Mohawk and its IR system proved quite effective and reliable in acquiring targets for air strike teams. A good example was the support given Marine forces in the Chu Lai area. The Mohawk flew five missions for the Marines; during four of them the aircraft acquired and made inflight reports on 23 targets. At the start of the Mohawk's operations, the Marines, being relatively unfamiliar with the aircraft's capabilities, had no strike aircraft ready for immediate response. However, they soon came to rely on the Mohawk's reports, releasing strike aircraft soon after a target was acquired. On another flight, the OV-1C located Vietcong units in two positions. These targets were reported to the ground control unit, which then requested naval gunfire on the VC positions.

An unexpected benefit resulting from Mohawk IR operations was a lowering of Vietcong morale. The best IR returns were being received by OV-1Cs operating in the southern delta regions of South Vietnam, where the jungle canopy was less dense than in the central highlands. The subsequent decrease in IR returns, coupled with the fact that IR operations were conducted at night, led to the belief, later confirmed, that the VC had been forced to substantially curtail their cooking and, therefore, were eating less hot food. Prisoner interrogation indicated that the one daily hot meal was being eaten during the day, in an attempt to escape IR detection.

 

MOHAWK OPERATIONS

Firefly

In this operation, the OV-1B Mohawk was used as the sensor aircraft. Flying at an altitude suitable for SLAR surveillance (typically, around 7500 feet), the aircraft patrolled along known or suspected enemy traffic arteries in the Mekong Delta region. Any moving target acquired by the radar was displayed to the observer in the Mohawk by the inflight processor-viewer. Because of the curfew in effect during the hours of darkness, any movement detected was considered to be enemy.

In Operation Firefly, the observer fixed the target's position and transmitted it to an alerted helicopter unit. Armed UH-1Bs were then directed to the area, where they conducted the strike, with a spotlight-equipped UH-1B providing target illumination.

The ability of the OV-1B to "see without being seen" and to operate quietly during these operations was a big advantage, because of the enemy's well-known ability to disperse rapidly under cover of darkness and terrain.

Market Time

The purpose of this operation was to destroy infiltration shipping along the South Vietnamese coast. On a typical mission, the OV-1B Mohawk acquired targets by flying parallel to the coastline. Once a target was acquired by the SLAR, its position was reported to the Navy's Coastal Surveillance Center. At the Center, the decision was made regarding the proper course of action...interception by Swift-type boats, destruction by naval gunfire, or destruction by attack aircraft.

Game Warden

OV-1B surveillance of the many waterways of the Mekong Delta was the object of this operation. Targets acquired by the Mohawk were attacked by Swift-type boats.

Tiger Hound

The objective of this operation was to interdict the movement of enemy troops, equipment, and supplies from neighboring countries into South Vietnam. The Mohawk's full range of sensors were utilized in Tiger Hound, with great effect. The prime sensor employed was the OV-1B's SLAR, owing to its capability to detect and plot moving targets at night along the various infiltration routes.

On one occasion, after initial detection by an OV-1B, three targets were located by a "C" model. The next day, after intensively searching for the most likely parking areas, an excellently camouflaged convoy of "a few" trucks were located by an OV-1A. Air Force strike aircraft were called in. On their first pass, the near miss of their bombs blasted off enough camouflage to expose several trucks. Upon completion of the strike, forty trucks were left burning or destroyed.

Tally Ho

This operations was similar to Tiger Hound, except that only the OV-1B and its side-looking radar were utilized.

Traffic Cop/Sea Dragon

This operation...the detection of waterborne vehicles moving along the coast...was companion to Tally Ho. It differed only in that detected targets were reported to the Navy, which then attacked with surface vessels.

Hight Hawk

A part of the major operation Rolling Thunder, which encompassed air strikes against reported targets, Night Hawk is a tactic that made use of the SLAR equipped OV-1B, a command and control aircraft, and strike aircraft to seek out and destroy enemy cargo vehicles. In this operation, near-real-time target acquisition information from the OV-1B was relayed to the C&C aircraft, which, in turn, vectored the strike aircraft to the target. This team effort accounted for numerous vehicles, including trucks and motorized barges.

 

OV-1 CHRONOLOGY IN SOUTHEAST ASIA

Sept '62 Initial deployment of JOV-1Cs (armed OV-1Cs, without IR sensors); assigned to 23rd SWAD (Special Warfare Aviation Detachment), Nha Trang, Vietnam.

July '63 ACTIV (Army Concept Team in Vietnam) evaluation found the Mohawk especially well suited for the COIN role, citing its speed, range, speed-noise, maneuverability, endurance, survivability, etc.

Dec '64 New Mohawk unit, 4th ASTA (Aerial Surveillance and Target Acquisition) Platoon formed at Ft. Bragg, N.C., and deployed to Vietnam, with OV-1Bs and Cs.

Jan '65 23 SWAD and 4th ASTA combined, resulting in formation of 73rd Aviation Company, Vung Tau.

Sept-Nov '65 Three additional Mohawk units deployed to Vietnam:

June '66 20th ASTA expanded into new 131st Aviation Company, Hue Phu Bai.

 

What we have learned

The fact that effective, routine operations, such as those just described, could be built around the OV-1 surveillance system testified to the soundness of the Mohawk concept...to combine in a modern, fieldworthy airframe an unprecedented electronic/photographic surveillance capability. The operational know-how gained with this system in Vietnam was being used to improve the capabilities of future Mohawk versions for performing a wider range of limited warfare roles.