The Mohawk is a completely integrated battlefield surveillance system that supplies the army field commander with information on the strength, disposition, and activity of enemy forces. This two-place twin turboprop aircraft is equipped with the latest cameras and electronic sensory equipment and can perform its mission day or night or in inclement weather. Directly responsive to the field commander (and directly under his control), the Mohawk is designed to live in the field with the troops: It is extremely rugged, readily maintained without extensive support equipment, and capable of operating from small unimproved fields and roads. Trucks and trailers carry all ground-based system components. the aircraft is powered by tow Lycomng T53-L-7 engines and has a speed range of 60 to 390 knots and excellent low-speed flight characteristics.Three versions of the Mohawk have been produced: OV-1A, basic visual, photographic; OV-1B, visual, photographic, side-looking radar; and OV-1C, visual, photographic, infrared. (The OV-IA is, essentially, an OV-1B or OV-1C without electronic sensors.) All three versions are actively engaged in Vietnam and with Army units throughout the world.
The radar imagery incorporates data annotation: Aircraft position, date, time, and other data are imprinted directly on the film edge to assist the radar operator or intelligence personnel in quickly orienting the imagery. The APS-94 also has a data transfer system, which enables the radar pictures and data-annotation information to be transmitted from the Mohawk to a ground station many miles away. The complete system is designated AN/UPD-2.
AN/AAS-14 INFRARED
Like the SLAR, the IR has a near-real-time cockpit display. The display uses CRT's; however, a permanent film record is also made by a printer, which is located in the sensor equipment bay beneath the wing.
The IR imagery incorporates data annotation: Aircraft position, date, time, altitude, and other data are imprinted directly on the film to assist intelligence personnel in orienting the imagery. A data transfer system transmits the IR picture and data annotation information from the Mohawk to a ground station many miles away. The complete system is designated AN/UAS-4.
PHOTOGRAPHIC
The camera, located in the fuselage mid-section, is operated by the console operate switch, the manual switch on the pilot's control column, or a manual button on the observer's instrument panel. These switches pulse the cameras for extra pictures for day photography and pulse individual flashes for night photography.
A mount selector switch on the photographic control panel is used to rotate the camera mount remotely to left or right 15- or 30-degree oblique and vertical positions. The left, right, and vertical camera window protective doors open only when the corresponding mount position is selected. For the KA-30 camera, 3-, 6- or 12-inch lens cones may be installed. No adapters are needed.
A limited number of aircraft have been configured with the KA-60 camera system for forward oblique panoramic photography--primarily during low-altitude missions. This system comprises the camera, electronic controls, and a cockpit control panel. The camera is rigidly mounted in the nose of the aircraft at a depression angle of 20 degrees from the horizontal. The mount rotates to a vertical position for fast, easy access to the camera for installation and removal of the film magazine. The film capacity is sized to permit 60 percent overlap photographic coverage of a flight line 60 miles long from an altitude of approximately 1000 feet.
AN/ARC-55 RECEIVER-TRANSMITTER
AN/ARC-54 RECEIVER-TRANSMITTER
AN/ARC-134 TRANSCEIVER
AN/ARC-102 TRANSCEIVER
AN/AIC-12 INTERCOMMUNICATION SYSTEM
MA-1 OR AN/ASN-76 GYROCOMPASS
ARN-30E VOR NAVIGATION RECEIVER
R-844/ARN-58 RECEIVER
AN/ASN-33 INTEGRATED FLIGHT SYSTEM
AN/APN-22 RADAR ALTIMETER
AN/ASW-12 UNIVERSAL AUTOMATIC FLIGHT CONTROL SYSTEM
AN/ASN-64 NAVIGATION AND FLIGHT CONTROL SYSTEM
AN/ARN-52 TACAN
AN/APX-72
In the cockpit the pilot sits on the left, the observer on the right. All instrumentation and controls are convenient to the pilot and visible to the observer. The low-profile instrument panel is sloped 15 degrees forward of the vertical for good pilot instrument visibility. A central pedestal provides one set of control levers equally accessible to both pilot and observer. The observer's position is equipped with either SLAR or infrared control and display equipment. If desired, this sensory equipment can be removed and replaced with flight controls for training or other purposes.
Major communications, navigation, and photographic panels are housed in a double-width console located between the pilot and observer. Store release, IFF, HF communication, ventilation, and lighting panels are housed in a single-width overhead console, also between the pilot and observer. "Eye-brow" panels, above the windshield, accommodate engine, fuel, and electrical master panels on the left and weather controls and OAT on the right.
Regulators for the gaseous oxygen system are located on the lower outboard edge of both pilot's and observer's panels. This system comprises two 514-cubic-inch oxygen bottles and two panel-mounted regulators with associated piping. A circuit-breaker panel, first-aid kit, binoculars, and a fire extinguisher are located on the sloping bulkhead aft of the crew.
ESCAPE
For ejection, the occupant pulls either the face curtain or the secondary firing handle on the leading edge of the seat bucket. Primary ejection is through the over-head hatch (if time permits, the hatch may first be jettisoned). After ejection, the main parachute, stowed on the seat behind the occupant's shoulders, is automatically deployed and separates him from his seat. A barostat delays deployment of the parachute if ejection is initiated at high altitude; a "g" limiter delays it if ejection is at very high speeds. A seat mounted bail-out oxygen system is automatically actuated upon ejection.
The seat bucket is designed to accept an energy-absobing-type seat cushion and a survival equipment container. An electrical actuator provides 5 inches of vertical seat adjustment.
PROTECTION
PROPULSION
At take-off power each engine develops 1100 shaft horsepower at a gas producer speed of 25,000 rpm and a propeller shaft speed of 1700 rpm. The gear ratio between the power turbine and propeller drive is 12.40:1.
Anti-icing of the power plant is accomplished by electrically heating the propeller blades, spinner, and engine inlet cowling and by air heating the engine inlet struts.
The engine nacelle allows easy access to the engine, controls, and accessories. The two side panels are hinged at the top and swing upward; the lower panel is hinged at the forward end and swings down to provide 360 degrees of accessibility. The lower panel contains the oil cooler, oil cooler ducts, and the oil cooler flap.
All fuel control adjustments are easily accessible for servicing. The entire power plant package including propeller, engine accessories, and engine mount with vibration isolators may be removed as one assembly and is interchangeable with the package on the opposite side.
A combination starter-generator is employed for all starting requirements, both air and ground.
ELECTRICAL
The ac system consists of dc-powered 750- and 2500-volt-ampere inverters. The 2500-volt-ampere inverter furnishes power to all ac equipment except instruments and the deicing system. It is also capable of assuming the full system load should the 750-volt-ampere generator become inoperative.
FUEL
All tanks may be fueled through 3-inch gravity filler units, one at each tank, or by single-point pressure fueling. Float switches in the drop tanks and a pilot valve in the main tank control automatic tank shut-off.
Fuel is fed to the engines by two centrifugal pumps in the main tank. These fore and aft pumps provide positive fuel flow for all conditions of aircraft attitude and fuel quantity. A secondary ejector-type pump backs up the forward pump. Two electric motor-driven vane-type pumps in the wings transfer fuel from the drop tanks to the main tank.
The fuel system is controlled from the cockpit: left and right engine master switches control the fuel gate valves; a fuel master switch arms the main tank fuel pump switch and energizes the drop tank transfer system.
Fuel quantity is measured by a capacitance-type system that indicates total fuel or fuel in each tank. Flowmeters indicate the rate of fuel flow to each engine. Lights warn the crew of such system conditions as fuel transfer and low pressure.
HYDRAULICS
ENVIRONMENTAL CONTROL
The cockpit is heated by engine bleed air, which is first cooled in a heat exchanger located in the nose-wheel equipment compartment. Ventilation is by diverting ram air to the cockpit air distribution system. This system also includes defogging nozzles for transparent areas and foot air diffusers and face nozzles for each crewman. A control panel in the overhead console permits selection of various heating, venting, and defogging combinations and automatic control of the heating and defogging air temperature.
The camera compartment has a separate automatic temperature sensing control system. The system regulates the flow of bleed air to the camera window defogging nozzles. A 6-quart-capacity windshield anti-icing and washing system is also provided; its tank filler is located in the nose of the airplane.
A built-in gust lock system is controlled by a lever in the cockpit. With the gust lock lever engaged, the handle blocks the throttle levers to prevent take-off. Locking is effected at the rudder torque tube by a latch that engages a pin on the torque tube arm. Duplicate safety springs disengage the latch if any system component fails.
LATERAL - Control sticks at the pilot's and observer's stations are mechanically connected to aileron spring tabs. A pushrod system provides direct mechanical connection between both ailerons.
Separate auxiliary surfaces (inboard ailerons) on each wing are used when additional lateral control is required for slow-speed flight conditions. Irreversible power systems drive these surfaces; they are linked to the basic control system only when the flaps are extended. When the flaps are retracted, flap motion mechanically shifts them out of this control system. Failure of the power actuators does not limit aileron motion.
Trim is controlled by a manual cable and drum system operating a tab on the right aileron. A built-in gust lock is similar to the one for directional controls.
LONGITUDINAL - Conventional control sticks actuate the elevators through a simple mechanical system consisting mainly of cables used as tension members between cranks. Pulleys and sectors have been avoided to minimize friction. Two independent systems run the full length of the fuselage.
Trim control is accomplished through a manual cable and drum system controlling the neutral position of the geared tab.
A built-in gust lock, similar to that for the directional system, locks the longitudinal control system at the aft end of the fuselage.
AUXILIARY FLIGHT CONTROLS
SPEED BRAKE ACTUATING MECHANISM (OV-1C only) - Two speed brakes are located on the sides of the fuselage in the aft section. They swing about vertical hinge lines. Each is extended and retracted by its own hydraulic cylinder mounted between the brake and fuselage structure. The two brakes are synchronized aerodynamically with a 5 percent maximum error in synchronization.
ALIGHTING GEAR
Both nose and main landing gear can mount skis for operation from snow.
In addition to ease of accessibility, all major assemblies are interchangeable: The power plant assemblies will fit either wing; the left and right members of major landing gear components, stabilizers, elevators, outboard fins, and rudders are interchangeable. The wing tips, horizontal and vertical tails, and fuselage nose and tail sections are all readily replaceable as units.
Mohawk electronics are maintained in the field by the replacement of faulty black boxes. In many instances, electronic test equipment is available as an aid in determining the precise location of a malfunction. All U.S. Army divisions include a third-echelon repair capability that can perform limited repair of electronic components in the field.
The various components of the TKQ-2 system are housed in a standard shelter, which is mounted on a 3/4-ton truck. The system power supply is mounted on a trailer that is towed by the truck.
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(1)The airborne portion of the UPD-2 system comprises the AN/APS-94
Side-looking Radar System and the AN/AKT-18 Data Transfer System
AN/TAQ-1 GROUND SENSOR TERMINAL
The various components of the TAQ-l system are housed in a shelter that is carried by a 3/4-ton truck.
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(2)The airborne pottion of the UAS-4 system comprises the AN/AAS-14 Infrared
Detecting Set and the AN/ART-41 Data Transfer System
AN/TSQ-43 ( ) TACTICAL IMAGE INTERPRETATION FACILITY
ES-38 LABORATORY DARKROOM
MISSIONS
The Mohawk has shown its flexibility as a surveillance system in CONUS, Europe, Alaska, Korea, and South-East Asia under diverse conditions and has proved its effectiveness in guerilla, defined-front, and cold-war operations in these areas. In all its operations, the Mohawk is flown to optimize the effectiveness of the particular sensor being employed while providing the greatest survivability for both aircraft and crew.
In guerilla-type operations, the Mohawk negates the one advantage the guerilla has: Mao Tse Tung has declared that the guerilla will always use darkness and weather to cloak his activities to defeat a superior enemy. The Mohawk surveillance system denies the guerilla the protection once afforded by these conditions: the radar, by detecting a wide variety of vehicular movement, land or water borne; the infrared, by detecting heat emissions, such as cooking fires or boat engines, associated with guerilla activities. These sensors are not dependent upon ambient light, but are equally effective at night -- when the guerilla is most active.
In a European-type air-defense environment where the front is more clearly defined, the SLAR-equipped Mohawk is deployed in a stand-off mode to monitor vehicular traffic in the enemy-held sector beyond the forward edge of the battle area (FEBA). Because of the long-range capabilities of the SLAR, the OV-lB can operate safely some distance behind the FEBA, beyond the range of enemy tactical air-defenses, and still see a considerable distance into the enemy-held area. If a regular patrol is maintained, the enemy activity can be kept under continuous surveillance to preclude surprise build-up and attack. Once the activity is localized, an OV-1A (photographic) or OV-1C (infrared) aircraft may be dispatched on a penetration mission to pinpoint and further define the activity.
In the penetration mission, the OV-1A or OV-1C Mohawk is flown into enemy-held territory at minimum altitude using terrain features to mask its passage. (Tests and combat experience have proven that an aircraft operating at lower speeds and minimum altitudes is exposed to fire no more than high-speed aircraft, which must fly at higher altitudes to preclude literally flying into the ground.) Once in the target area, the penetration aircraft climbs rapidly (pops up) to a somewhat higher sensor altitude, makes its run, and then returns to the protection of the terrain where its quiet operation (owing to its free turbine engine and low propeller speed) further reduces exposure to ground fire.
In cold-war operations, the OV-1B Mohawk offers the capability of monitoring the activities of a potential aggressor without committing border violations. Most important this capability can be used at will regardless of time of day, weather, or political situation.
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Surveillance Airplane Company (SAC) - Home Page
No restricted and/or classified information is contained herein. This home page and web site have been constructed and will be maintained entirely by the author, and the author is responsible for the contents and accuracy of this site. The contents of this page have not been reviewed, approved, or monitored by the United States Army, nor is this page and/or it's contents a representation of such. All comments, questions, and concerns should be directed to the author - John E. Akers
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