COOLING SYSTEM AND OIL SYSTEM P-51D MUSTANG

Oil System

            The oil system includes a tank, located just forward of the firewall, and a radiator in the air scoop under the fuselage. The tank is hooper type-that is, it is designed with hooper or compartments which facilitate quick warm-up and alsu make it possible to fly the airplane in abnormal positions, with little oil in the system. With this tank you can fly the P-51 in any attitude when the tank is full. Or you can put it into a vertical climb or dive when the tank is only ¼ full and still get proper lubrication.

However, when the plane is in inverted flight, the oil pressure falls off because no oil reaches the scavenger pump. For that reason you must limit inverted flying to 10 seconds-which is plenty of time for any normal or combat manuvers.

An outlet door on the bottom of the air scoop controls the oil temperature. Under ordinary circumstances this door operates automatically. However, if you want to operate it manually when you’re running your engine on the ground, for example, or in case the automatic regulator fails in the air-you can do so by means of an electrical switch on the left side of the cockpit.

            This switch has three positions: AUTO-MATIC, OPEN, and CLOSE. You can stop the door at any position by holding the toggle switch in the OPEN or CLOSE position for the necessary length of time, then returning the switch to neutral. The oil system has standard AAF oil dilution equipment. This allows you to thin the oil with gasoline to make the engine easier to start in temperatures below 40° F.

Operation of the oil dilution equipment is simple. Allow the engine to idle, coolant flaps open, until the oil temperature drops to 50°C or less. Then, before stopping the engine, use dilution switch on the pilot’s switch panel. This dilutes the oil until you are ready to start the engine again. Once the engine warms up, the gasoline in the oil is quickly evaporated. If the engine temperature is it high, stop the engine and allow it to cool to an oil temperature of about 40°C. Then start it again, and immediately dilute the oil as explained above.

            Two minutes of oil dilution is sufficient for any temperature down to 10°F. When starting in temperatures lower than that, heat is sometimes applied to the engine and oil system. Therefore, no fixed oil dilution time can be given this manual; you’ll be specially instructured in accordance with local operating conditions. Total capacity of the oil system is 21 gallons.

Coolant System

            With the radiators located in the big aor scoop aft of the cockpit under the fuselage, the cooling of the P-51 engine is quite different from that of any other airplane. The engine is cooled by liquid in two separate cooling systems. The first system cools the engine proper, the second (called the after-cooling system) cools the supercharger fuel-air mixture. Each performs a separate function and the systems are not connected in any way. They both pass trough a single large radiator, but in different compartments. 

The engine coolant system is a high-pressure system (30psi) and its capacity is 16½ gallons. Operating pressure of the after-cooling system is lower (20psi), and its capacity is 5 gallons. The coolant used is a mixture of ethylene glycol and water, treated with “NaMBT” (a corrosion preventive). There are two types-type D for normal use, which consists of 30% glycol and 70% water, and type C for winter use (below 10°F), which consists of 70% glycol and 30% water.

An air outlet door at the rear of the air scoop controls the temperature of the coolant. This door operates similarly to that of the oil cooler. Normally, it works automatically, but you can control it manually by means of a switch on the left side of the cockpit, next to the oil cooler door control switch. Both switches are on the radiator air control panel.

Before take-off (Run-Up)

1. At 2000 RPM, check the following:

Suction	3.75 to 4.25 inches HG.
Hydraulic pressure	800-1100 lbs/sq. inch.
Ammeter	not to exceed 50 amps.

2. Check the instruments for the following limitations:

	Desired	Maximum
Oil Pressure	70-80 lbs/sq. in.	90 lbs/sq. in.
Oil Temperature	70 deg C - 80 deg C	90 deg C
Coolant Temperature	100 deg C - 110 deg C	121 deg C
Fuel Pressure	12-16 lbs/sq. in.	19 lbs/sq. in.

3. Check mags at 2300 RPM. Maximum drop 100 RPM.
4. At 2300 check propeller - 300 RPM maximum drop - and return to full INCREASE RPM.
5. Oil and coolant shutters AUTOMATIC.
6. Wing flaps 20 ° if desired.
7. Mixture AUTO RICH.
8. Propeller in full INCREASE RPM.
9. Fuel booster pump on EMERGENCY, check for 14-19 lbs/sq. in.
10. Generator switch ON.

Before landing

1. Mixture AUTO RICH.
2. Oil and coolant shutters AUTOMATIC.
3. Fuel selector to fullest tank. NOTE: Never land on droppable wing tanks.
4. Booster pump switch to NORMAL position.
5. RPM increased to 2600.
6. Normal gear procedure:
1. Retard throttle to check landing gear warning light (17"-22" M.P.).
2. IAS 170 or below. Put landing gear handle in DOWN position.
3. Allow time for gear to extend.
4. Retard throttle to check warning lights. If light does NOT come ON at previously noted position of throttle, gear is DOWN and LOCKED.
7. Lower flaps as desired. Full flap speed 165 or below.

After landing

1. Raise flaps.
2. Booster pump OFF.
3. Oil and coolant shutters OPEN.
4. Run engine to 1500 RPM, set mixture control to IDLE CUT-OFF and move throttle fully open.
5. Turn ignition switch OFF after propeller stops turning.
6. Fuel shut-off valve OFF.
7. Turn all switches OFF.
8. Lock controls.

Source : https://www.digitalcombatsimulator.com/de/products/mustang/?PAGEN_1=2

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