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Flying Tigers P-40 Tomahawk manual (part 4)

NOTES ON THE ALLISON V-1710-C15 ENGINE
(Using 100 Octane Fuel)

27. The following should be carefully noted:

(i) Limited operational conditions

Take-off * Maximum r.p.m. 3000
Maximum boost at S.L. 41.0 in.Hg.
Maximum boost above 2600 ft. 38.9 in.Hg.
Mixture control below 3500 ft. "Full-rich"
Mixture control above 3500 ft. "Auto-rich"
Climb* Maximum r.p.m. 2600
Maximum boost 35.0 in.Hg.

* Note: - For take-off and climbs of short duration (not exceeding 5 min.) from sea level, the throttle should be adjusted to give 41 in.Hg. and left in this position until the boost falls to 38.9 in.Hg. This boost should then be maintained by adjustment of the throttle. For climbs of longer duration the boost should be adjusted to 35 in.Hg.

Maximum cruising
(mixture control
"Auto-rich")
Maximum r.p.m.
Maximum boost
2600
35 in.Hg.
Maximum cruising
(mixture control
"Auto-rich" or
weakened.)
Maximum r.p.m.
Maximum boost
2280
29.2. in.Hg.
Maximum level
(5 minute limit)
Maximum r.p.m.
Maximum boost
3000
38.9 in.Hg.
Maximum dive Maximum r.p.m.
Maximum boost
3120
38.9 in.Hg.

(ii) Oil Pressure

Normal 60-65 lb./sq.in
Minimum 50 lb./sq.in

(iii) Oil inlet temperatures

Minimum for take-off 40°C
Normal 70-80°C
Maximum 85°C

(iv) Coolant temperature

Maximum 125°C
Minimum for take-off or flight 85°C

FUEL CAPACITY AND CONSUMPTIONS

28. Note the following:

(i) Fuel capacity (in Imperial gallons)

Main tank 50 gallons [62.5 gal U.S]
Fuselage tank 47 gallons [58.75 U.S.]
Reserve tank 33 gallons [41.25 U.S.]
Total 130 gallons [162.5 U.S.]

(ii) Fuel consumptions (in Imperial gallons per hour):

Approximate consumptions at 12,000 feet are as follows:

Climbing: at 2600 r.p.m. and 35 in.Hg. boost 84 [105 U.S.]
Cruising: at 2600 r.p.m. and 35 in.Hg. boost 84 [105 U.S.]
-- (mixture at 2280 r.p.m. and 29.2 in.Hg. boost 52 [65 U.S.]
-- (control at 2280 r.p.m. and 27.9 in.Hg. boost 50 [62.5 U.S.]
-- ("Auto-rich") at 2190 r.p.m. and 25.2 in.Hg. boost 42 [52.5 U.S.]

Note: It is possible to improve on the last cruising consumption by weakening the mixture as described in para. 12.

Tye Lett's additional notes on the Allison

[Like the Tomahawk manual, the following notes came from the copies of the Pistole Collection at the NASM Archives. The repetition between part 1 and part 2 is in the original. "sic" indicates a typo in the original.]

ALLISON ENGINE
FIELD SERVICE MEMORANDUM
FAR EAST NO.2

RANGOON, BURMA
September 26, 1941

To: Col. C. T. Chien.
From: Tye. M. Lett, Jr.
SUBJECT; STARTING PROCEDURE, ALLISON MODEL V 1710 C 15 ENGINES

1. The Starting procedure described below is the latest as recommended by Allison for the V 1710 C 15 Engine.

2. It is observed that several methods of starting subject engine are in use at various points.

3. To provide specific instructions regarding procedure it is suggested that this information be relayed to all pilots and ground personnel concerned with the operation of Allison Engines.

1. PROPER STARTING PROCEDURE

The priming system on all Allison engines is independent of the carburetor, and pumping the carburetor throttle will not discharge fuel into the engine, as all fuel is injected by the fuel discharge nozzle to the supercharger inlet, where it is mixed with the air passed through the carburetor throttle openings.

(a) Set propellor [sic] to manual low pitch.

(b) Carburetor Heat Control should be in the OFF position.

(c) Set throttle at position corresponding to 1000-1200 R.P.M.

(d) Set carburetor manual mixture control in IDLE-CUT-OFF POSITION, and operate the wobble pump to maintain a fuel pressure of 4 lbs./sq in.

(e) Energize starter.

(f) Prime a COLD engine with not over two strokes for a large size primer, or four for a small size primer. For a WARM engine, one stroke with large primer; or two with a small size primer is sufficient.

(g) Turn on ignition switch and engage starter. When propellor turns, maintain fuel pressure by wobbling; and as engine starts firing, move the carburetor manual mixture control to Automatic-Rich position.

Should engine stop, return the manual mixture control to IDLE-CUT-OFF position to avoid flooding the engine with fuel, as the fuel pressure will build up to normal operating pressure (12-14 lbs./sq in.) when engine starts firing. Another start can be made using the same procedure, and using priming charge only if necessary, and the engine is not over-primed.

(h) IF OIL PRESSURE is not established within 15 seconds after starting, stop engine by setting manual mixture control in IDLE-CUT-OFF and investigate oil pressure failure. If oil pressure is established at start, continue to warm engine up at 900-1000 R.P.M. as too low idling and warm-up speeds will result in oil and fuel load fouling of the spark plugs.

Warm-up speed can be increased up to 1400 R.P.M. as oil and coolant temperatures rise, and oil pressure is stabilized.

2. STARTING

(a) With Ignition Switch "OFF" pull engine through several revolutions, turning propellor by hand, with throttle open.

(b) Carburetor Heat in "OFF" or "COLD" position.

(c) Radiator flap position as required.

(d) Throttle 1/10 open, or 1000-1200 R.P.M.

(e) Mixture control in "IDLE-CUT-OFF".

(f) Electric and Propellor switches "ON".

(g) Propellor in Manual "Low Pitch".

(h) Fuel tank selector on "Reserve".

(i) Pump up, and maintain 4 lb fuel pressure.

(j) Start energizing starter.

(k) Prime "COLD" engine 3 strokes - "WARM", 1 stroke--close and lock primer.

(l) Turn ignition switch to "BOTH ON" position.

(m) Engage starter, and when engine starts firing, move mixture control to Automatic-Rich position.

(n) After engine starts, IDLE at 600 R.P.M. and if oil pressure is not established within 15 seconds, stop engine and investigate oil pressure failure.

(o) Start warming-up by operating the engine at 900-1000 R.P.M. gradually increasing to 1400 R.P.M. as the temperatures rise, and oil pressure stabilizes.

With throttle closed the Klaxon horn will be silent, if landing gear is locked down.

2. UNDERPRIMING AND OVERPRIMING

(a) Underpriming is sometimes caused by leaking primer lines and connections, or defective primer pump packing. The fuel supply to the primer, wobble or electric fuel supply pump, if so equipped, should be checked.

(b) Overpriming is first indicated by very weak combustion, followed by black smoke discharge from the exhaust. Excessive priming is evidence by wet spark plugs and fuel appearing at the exhaust stacks.

(c) As the prime fuel is injected directly into the intake manifolds of each cylinder, excess fuel will not be carried off by the supercharge scroll drain which relieves the scroll housing of excess fuel delivered only by the discharge nozzle which has opened, either by too high fuel pressure being wobbled with carburetor manual mixture control out of IDLE-CUT-OFF position, or by leakage of the discharge nozzle. Check nozzle for leakage, or holding open due to dirt or foreign material.

(d) Overprining [sic] constitutes a dangerous fire hazard, as well as a detriment to the oil film lubrication of the pistons, rings, and cylinder walls of the engine.

(e) Extreme CAUTION should be taken to aboid [sic] overpriming on either a HOT or COLD engine.

(f) To relieve overpriming, crank engine several revolutions, with switch in OFF position, throttle wide-open, and carburetor manual mixture control in IDLE-CUT-OFF position. This can also be accomplished by turning propellor by hand in direction of rotation.

(g) Loss of compression (check by rotating propellor by hand in direction of rotation) due to over priming may require lubrication of pistons, rings, and cylinder walls with oil through the valve ports or spark plug holes.

NOTE: IT IS RECOMMENDED THAT ALL PERSONNEL BECOME FAMILIAR WITH THE SUGGESTIONS ON "GROUND TEST" AND "GROUND CHECK" AS DESCRIBED IN ALLISON TROUBLE SHOOTING AND MAINTENANCE MANUAL RECENTLY RELEASED.

/s/ TYE. M. LETT, JR.
Far Eastern Representative
ALLISON DIVISION