Advanced Pilot Training: Ground Operation of Engines

Starting of Aircraft Engines

First

Make sure ignition is off, then turn engine over four or five revolutions if engine has been idle for over two hours, or if excessive priming has been used during starting attempts.

Second

Open cowl flaps,

Third

Move carburetor air heat control to "COLD" position.

Fourth

Make sure fuel valve is turned on to a tank that contains fuel. On multi-engined airplanes, set fuel cock to supply fuel to all engines.

Fifth

Be certain that the cross-feed fuel shut-off cock is in "OFF" position on twin-engined airplanes. This cross-feed fuel cock permits the fuel pump on one engine to supply fuel to both engines in case of a fuel pump failure on the other engine.

Sixth

Move throttle almost to closed position - 600 to 800 rpm. With low-pressure carburetor, put Fuel Mixture control in "RICH." With high-injection carburetor keep in "IDLE CUT-OFF" until engine fires.

Seventh

Make sure that the propeller controls of two position and Hamilton Standard propellers are set in the "LOW" rpm position, where they should be upon stopping the engine. About one minute after starting shift into "HIGH" rpm as this reduces the load on the engine and improves cooling.

Other constant speed propellers should be in the "HIGH" rpm position when stopped, so they will be properly set for starting and warm-up.

Eighth

Prime engine while energizing starter by using either hand type priming pump or electric type priming pump. Three or four strokes are usually adequate but up to 10 strokes may be used on large radial engines when cold. (One second on electric primer is equal to one stroke of the hand primer.) Avoid excessive priming as it washes the oil off of the cylinder walls causing scoring of the barrels and seizing of the pistons. Throttle priming is not authorized for any engine except where special instructions issued in Technical Orders pertaining to a particular engine advise this method.

Ninth

Turn ignition to "BOTH" position. Energize the starter, then hold meshing switch "ON" until engine fires. Open the throttle slowly to the desired warm-up speed.

Supercharger Control

Engines equipped with turbo-driven superchargers should be started with the waste gate open and supercharger regulator in "OFF" position.

Engines equipped with two-speed superchargers should in all cases be started and take-off made with supercharger in low blower.

Engines equipped with two-stage superchargers should be started in accordance with the flight operating instructions for the specific engine involved.

Warm-Up Procedure and Oil Pressure Check

Aircraft engines will always be warmed up on the ground until proper lubrication and engine operation for the take-off and flight are assured. Excepting in an emergency, engines will not be run on the ground for warm-up or test unless chocks are placed in front of the wheels of the airplane regardless of whether or not the airplants is equipped with brakes.

Be sure to watch the oil pressure gage. If it does not indicate pressure within 30 seconds, shut off the engine and have an investigation made.

After the oil gage indicates pressure, shift propeller to take-off setting and run engine at 600-800 rpm until oil pressure is normal (30-65 lb sq in.) for this speed.

Do not permit engine rpm to exceed 1/2 of the maximum permissible ground rpm during the warm-up period. When the engine maintains at least 2/3 of the minimum full power oil pressure specified for the particular engine, and the oil temperature gage shows a definite increase in oil temperature, the engine rpm may be increased to check for proper functioning of the engine and engine instruments, except that the maximum permissible ground rpm will not be maintained for periods in excess of 20 to 30 seconds on the ground.

Ignition System

Switch from one magneto to the other and note the loss of revolutions or manifold pressure. The normal loss in rpm on one magneto should not exceed 100 rpm.

NOTE: Whenever an engine is operating on only one magneto, the manifold pressure must not exceed maximum cruising manifold pressure to avoid detonation when firing on only one set of plugs.

If the airplane is not equipped with a manifold pressure gage, the magneto check will be made with not more than 85 per cent of the rpm developed when the throttle is opened to the throttle stop.

If the engine is equipped with an "Idle Cut-Off" carburetor, it is necessary to check the "OFF" position of the ignition switch to assure the proper connection of the ground wires. This check, made at idling speeds, need only be made at the start of the day's flying.

On installations using the combination inertia direct cranking starters engage both the meshing switch and energizing switch at the same time after the starter has been energized.

Controllable Propellers

Check the operation of the controllable propeller. During ground operation, the manifold pressure must not exceed the specified maximum cruising manifold pressure, to prevent overheating of the engine while operating in the low rpm (high pitch) position.

Fuel Supply

Check the functioning of all fuel tanks during the warm-up by switching the fuel valve to each tank long enough to insure that the fuel from that tank has a chance to flow to the engine.

Superchargers

Check the operation of the two-speed supercharger by shifting the clutches immediately following each engine warm-up.

1. Set propeller governor in low pitch (high rpm).

2. Set engine speed at 1,500 rpm.

3. Move supercharger control lever to the "HIGH" position and lock.

4. Open throttle to obtain not more than 30 in. Hg.

5. Check manifold pressure.

6. Immediately shift to "LOW" position. A sudden decrease in manifold pressure shows the two-speed supercharger drive is operating properly.

Check flight operating instructions for specific engines for check on two-speed and two-stage superchargers.

Taxiing

Taxi from the line for take-off or to the line after landing with propeller controls in "HIGH" rpm (low pitch) position.

Set engine and cowl flaps "FULL OPEN" to prevent overheating the engine.

Changing Power Condition

To avoid excessive pressures within cylinders with resultant detonation and possibility of failure, use the following procedure when changing condition of power:

Increasing Engine Power

1. Adjust mixture control to obtain fuel-air ratio specified for power condition desired.

2. Adjust propeller control to obtain desired rpm.

3. Adjust throttle control to obtain desired manifold pressure.

4. Readjust mixture control, if necessary.

Decreasing Engine Power

1. Adjust throttle control to obtain desired manifold pressure.

2. Adjust propeller control to obtain desired rpm.

3. Readjust throttle controls, if necessary.

4. Adjust mixture controls to obtain desired fuelair ratio.

Stopping Aircraft Engines

This preliminary procedure applies to all engines regardless of the type of carburetor or fuel system installation:

1. Mixture control in "FULL RICH."

2. Throttle in normal idling position.

3. Propeller controls of two position and Hamilton Standard will be in "LOW" rpm; other constant speed propellers in "HIGH" rpm.

4. Nose cowl or radiator shutters (if installed) fully opened at normal idling speed until engine temperature has cooled below cruising temperature.

The following procedure applies to engines equipped with float type carburetor WITHOUT idle cut-off.

1. Turn the fuel valve to "OFF" position.

2. Idle engine at 800-1,000 rpm until fuel I drops to zero.

3. As engine dies, move throttle slowly forward. When engine stops, cut ignition.

4. Turn fuel valve "ON" after engine has stopped, and operate wobble pump until fuel pressure gage indicates pressure showing that carburetor and fuel lines are filled with fuel.

The following procedure applies to engines equipped with float type carburetor WITH idle cutoff.

1. Leave fuel valve "ON."

2. Idle engine at 800-1,000 rpm.

3. Set mixture control at "IDLE CUT-OFF."

4. Set throttle at "FULL OPEN."

5. Cut ignition after engine stops.

The following procedure applies to engines equipped WITH fuel injectors (no carburetor).

1. Leave fuel valve "ON."

NOTE: Fuel cock will never be shut off except in emergency.

2. Idle engine at 600-800 rpm.

3. Set mixture control to maximum lean without moving the throttle.

4. Cut ignition after engine stops.

CAUTION

On high output engines it may be necessary to idle at a higher speed than normal to prevent overheating and fouling of plugs.

Oil Dilution

To operate oil dilution system before stopping the engine:

1. Turn oil dilution control "ON," when a cold weather start is anticipated, for four minutes at 1,000 rpm, then stop the engine.

2. Repeat the oil dilution after approximately 15 minutes.

NOTE: Dilution is ineffective while oil temperatures are above 70'C (158'F).

If oil temperatures are too high, stop engine and wait for it to cool to 40'C to 50'C (1040F to 1220F), then restart it and proceed with the oil dilution.

A normal start should be made without regard to the oil dilution system. If a heavy viscous oil is indicated by oil pressure too high, or by fluctuating oil pressure when engine rpm is increased, push dilution control "ON." This method should be used only if time and extreme temperature conditions do not permit engine warm-up in the usual manner. Over-dilution is likely to occur under these conditions because of low oil flow and a cold engine which

Oil dilution switches.

results in little evaporation until engine warms up. If dilution is used, close observation of oil pressure is necessary to determine whether or not the oil has been over-diluted, resulting in low oil pressure.

NOTE: If necessary, immediate take-off may be made after oil dilution without the normal warm-up, provided there has been a rise in oil temperature and the oil pressure is steady.

Over-dilution will not occur usually if the diluting operation is done immediately after flight, while the engine and oil are warm. Over-dilution has no serious effect on engine bearings if the oil pressure remains normal.

To Eliminate Engine Failure

Excessive ground running time of airplanes is one of the main reasons for early failure of the engines. Reduce the ground running time by the following procedures:

1. Hold ground tests and warm-up periods to a minimum.

2. Do not taxi away from the line for take-off until the control tower operator gives the necessary instructions.

3. Shut off the engine when it appears that takeoff will be delayed due to other planes landing or other causes.

4. Use proper judgment in taxiing to position to prevent long periods of ground running of engines.

REFERENCE: Technical Order 02-1-29, dated Nov. 23, 1942