TM 55-1930-203-10
portable air compressor and sufficient fuel for operation. LARC 's operating in a team of six or less will carry one air
compressor for the whole team.
2-30. Engine Warmup
Run engines at 600 r.p.m. 's until normal operating temperature is established. This warmup period offers an opportunity to check
the performance of the engines and to observe the action of various gages. Under no circumstances should the LARC be operated in
water if the engines are not operating efficiently.
a. Operating Temperatures. Operating temperature ranges (para 2-27) of engine coolant, engine lube oil, transmission oil, marine
gear oil, and gathering oil should be attained as the engines warm up. If the temperature increases rapidly during the warmup period
or during operation, the LARC should be stopped and condition reported to organizational maintenance.
b. Oil Pressure. When the engines are first started, the consistency of the oils in the engine crankcase, transmission, marine gear,
and gathering box may cause a sharp rise on the pressure gage. After the engines warm up, pressures should recede slowly to
normal reading.
c. Battery-Generator Indicator. The battery generator indicator (13, sheet 1, fig. 2-1) may indicate high charging rate for the first
few minutes after the engines have started and before the generators have restored the depleted current to the batteries. Normal
indicator reading is in the green zone.
CAUTION
If a warning light goes on during operation, shut down engine involved and investigate trouble.
d. Warning Lights. The master warning light (20, sheet 2, fig. 2-1) will illuminate when any of the port or starboard waning lights
(10, sheet 1, and 32, sheet 4) located on the cab bulkheads illuminate. Check that all warning lights go out after each engine has
been started.
2-31. Stopping the Engines
a. After parking or stopping the LARC, build up tire pressure to 60 p.s.i.
b. Run engines at idle for 3 to 5 rninutes before securing. This allows the lubricating oil and coolant to carry the heat away from
the engines.
c.
Push engine cutout valve (2, sheet 1, fig. 2-1) levers all the way forward to the off position.
d.
After the engines have stopped, return the engine cutout valve levers to the RUN (vertical) position.
e.
Isolate the air tanks by closing the main air supply valves (fig. 2-12) above each air tank.
f.
Close the tire air shutoff valve (2, fig. 2-2) to each wheel.
g.
Close airbrake shutoff valves (para 2-20).
NOTE
Brake pedal (29, sheet 3, fig. 2-1) must be depressed while closing the airbrake shutoff valves.
2-32. Steering
CAUTION
Since the effectiveness of the rudders is reduced when going astern, the engines must be used instead
of the rudders for steering. When backing to port, the port engines are idled and the starboard
propeller is run astern. This procedure is reversed when backing to starboard. Make the maneuvers
by using the propellers alone and holding rudders in the straight position.
The two steering levers (16, sheet 1, fig. 2-1) operate so that the direction of handle movement is in the direction of turn. Four
wheel steering refers to normal steering (1, fig. 2-14). Two wheel steering refers to truck steering (2). Oblique steering refers to crab
steering (3). For normal steering, locking pin (5) on the starboard lever is in up position and locking pin (6) on the port lever is in
down position. This ties both steering levers together; see figure 2-15. For truck steering, rear wheels are locked in straight ahead
position by placing locking pin on the starboard lever in down position (4, fig. 2-14) and locking pin on port lever in the up position
(8). Steering is then with port lever only. For crab steering, locking pins on both levers must be in up position (7). In this case, the
LARC will move to the right when the operator pushes both levers away from him or to the left when operator pulls both levers to him.
For marine steering, locking pins on steering levers are placed in same position as for truck steering. The rudders are steered with
the forward wheels by a wire rope connected between the starboard rudder quadrant and starboard wheel column steering arm.
2-26
