OPERATING INSTRUCTION MANUAL
for the
SIEMENS AERO-ENGINE
Sh 14A
SECTION ‘A’
PREPARATIONS FOR STARTING UP
1. Fill the oil tank with oil, but not right up to the edge. A space of 1 to 2 litres above the oil must be left for the recirculated oil [x]) which is returned to the tank from the oil sump by the recirculating pump when the engine is started. Before passing into the tank, the oil should be filtered through a close-meshed strainer. Keep all filling arrangements scrupulously clean.
2. Fill the petrol tank, placing a piece of clean wash-leather over the filling hole to act as a filter. After filling, carefully re-close both the oil and petrol tanks.
3. Oil the engine according to the instructions at Appendix ‘I’.
4. See that the following parts are secure, but without unduly loosening them:
a. The airscrew must be secured firmly to the hub and the latter securely to the shaft. The airscrew hub must be screwed tight and locked.
b. Oiling screws.
c. Connections of the ignition cables to the sparking plugs.
5. Test the carburettor gear to see that it works easily and properly.
6. Open both the petrol and oil cocks (if an oil cock is provided) and examine the connected feed pipes for leaks.
STARTING
A. Starting with Hand Magneto
1. Switch off the ignition.
2. Open the throttle, a little. The correct throttle opening facilities starting, but if the throttle is opened too far it cuts out the starting and idling arrangements on the carburettor.
3. Turn the engine through two or three complete revolutions and on each revolution pump in a charge of petrol using the petrol injection pump. When operating the pump, make the intake stroke slowly and the delivery stroke quickly. In cold or damp weather, two or three extra charges can be pumped in. Re-close the cock on the injection pump or cut off the flow of petrol through the pump.
4. On the report “airscrew released”, switch on the ignition (position M 1 + 2 on the switch, and in engines with double contact breaker also switch on the retarded ignition) and turn the magneto crank quickly until the engine starts. If the engine does not start, usually too much petrol has been injected. Cut off the ignition, turn the engine through several revolutions in the opposite direction to normal revolution, and again attempt to start up without injecting any more petrol.
If the engine again stops after a number of revolutions, the throttle is not open far enough or there is a shortage of petrol owing to choked jets, choked filters, or the idling jet is too small. In the latter cases the ignition must be cut off before attempting any adjustments.
B. Starting the Sh 14A engine with Compressed Air
1. Open the throttle to about a quarter.
2. Pump 3 or 4 (in cold weather 5 or 6) charges of petrol into the engine. Reclose the injection cock or cut off the petrol flow through the pump.
3. When the airscrew is released, switch on the ignition (retarded ignition with double contact breaker) and carefully open the cock on the compressed air cylinder. Then turn the magneto crank [x]) and slightly depress the check valve, when the engine will pick up.
4. Immediately the engine has started, re-close the compressed air cock.
If the same difficulties are experienced as already enumerated under a., then before any adjustments are made, close the compressed air cock and cut off the ignition.
Ground Test
After starting up the engine, allow it to run for about 4 minutes at a speed of 500 to 600 rpm. Note the oil pressure on the oil gauge. The speed of the engine may be gradually increased. In no circumstances must the oil pressure rise much above 4kgs per sq cm (60 psi), nor must it fall below 1.5 kg per sq.cm (20 psi), otherwise stop the engine immediately and determine the cause for this behaviour (“Engine Troubles” – Appendix ‘IV’).
Open the throttle quickly (but not too abruptly) to test the acceleration of the engine. A short spurt on full throttle will indicate if the engine touches top speed (2,200 rpm. A flight must not commence before the engine runs perfectly smoothly and satisfactorily on the ground. On the other hand, the engine should not be kept on full throttle for too long on the ground, the cooling action of the airscrew is insufficient for this.
To test the two ignition circuits, use the changeover switch to switch on each magneto separately. The resulting drop in speed should not be more than 30 rpm as compared with the speed on both magnetos. Should the drop be greater, this is due to sparking plug trouble, which is also indicated by the irregular noise of the exhaust.
In engines with electric ignition timers (with double breaks on the magnetos), test the running of the engine’s advanced ignition. Switch on the advanced ignition just before fully opening the throttle, but not later.
Flight Test
During flight, keep an eye on the revolution counter and the oil gauge. The maximum permissible speed of 2200 rpm must not be exceeded even in flying nose down or when diving.
The engine may suffer damage if the oil pressure drops below 1.5 kg per sq cm (20psi).
Feed petrol to the engine from time to time when gliding so as to keep it warm and to prevent the sparking plugs fouling or becoming moist.
Standard Running Data:
Maximum speed of engine 2200 rpm
Speed in continuous flight, about 2050 rpm
Fuel pressure, kg. Per sq cm 0.1 to 0.3 (1.5-5 psi)
Oil pressure, kg per sq cm 2 to 4 (30-60 psi)
Oil temperature Max 65oC (150oF)
Temperature of cylinders 250oC measured at the rear plug (482oF)
After a Flight
After landing it is advisable to keep the engine running freely for several minutes (at a speed of about 500 rpm) and then to stop it by cutting off the ignition. When the engine has stopped, immediately close the petrol and oil cocks. After long flights, overhaul the engine as laid down in Appendix ‘II’.
Care of Engine
1. Keep the outside of the engine clean. Never use benzole or petrol for cleaning as these attack the paint on the light-metal parts. Paraffin may be used, but the best medium is one of the various liquid cleaners for engines on the market, applying and removing it with compressed air.
2. Keep all paint in good condition especially on engines used for flights at sea. Make good all damaged paint with thin coats of fresh paint.
3. As regards the care of the airscrew, follow the instructions of the makers. Note that the paint on wood airscrews is nearly always attacked by benzole, petrol or paraffin.
4. When the aircraft is left out in the open, cover the engine with a canvas hood.
5. On seasonal changes in weather: Change all oil (see remarks on summer and winter oil at Appendix ‘I’).
Supervision of Engine
General Examination as regards Running Conditions
1. The valve clearance should only be tested with the engine cold.
Remove a sparking plug from each cylinder.
Start the cylinder 1 and move the piston into top dead centre between the compression and the working strokes. (Note that both valves must remain closed. If not, turn the crankshaft through a complete revolution.) The clearance between the valve and the valve lifting roller is measure with a steel gauge, 0.2 mm thick. In old engines, it is advisable before adjusting the clearance of the inlet and exhaust valves to first determine that position of the cam plate giving the smallest lift of the valves (Between its four cams, the cam drum has four segments of the same height; after each two revolutions of the crankshaft, the next segment comes under the pusher roller.) The clearance is adjusted if necessary by means of the screw on the valve lever. After adjustment, carefully retighten the locknut.
After cylinder 1 has been tested, pass on to the cylinders 2, 3, 4 etc., in succession, each time turning the crankshaft through one revolution.
2. Airscrew. The airscrew hub should be firmly attached to the shaft, and the airscrew itself securely attached to the hub. The airscrew hut nut should be tightened and properly locked. The airscrew should run smoothly and steadily, which should be tested from time to time by means of impact plates.
With flanged hubs, the security of all nuts on the hub should be tested periodically when a new wood airscrew has been mounted on the hub, and if necessary tightened.
Also note the instructions at Appendix ‘III’ for taking down airscrews.
5. External Examination. All nuts on the outside of the engine should be securely tightened, and the locknuts on the housing, the cylinders and the engine fixing nuts must be properly secured. Test the cap nuts of all oil and fuel pipes to ee that they are tight, but without unduly loosening them.
Pistons and Connecting Rods
Remove encrusted oil from the bottom of the piston and polish the surface. Also remove carbonised oil from the piston ring grooves, taking care not to damage the grooves. The rings should move easily in their grooves. It is not always necessary to remove the piston.
By moving the main and auxiliary connecting rods up and down, see whether the bearings are still secure. The gudgeon pins should also be firm.
Test the piston rings in the cylinder and measure the clearance at the sides with a steel gauge. The clearance should not exceed 0.8 mm., otherwise put in new piston rings.
On reassembling the cylinders, liberally oil the liners with oil of the brand used in service and give the engine a turn or two.
APPENDIX ‘I’
Lubricating Instructions
1. Before each flight : Examine the oil level. (Refer Preparations for Starting Up on page 2).
2. After 5 hours flying or in longer flights before each start : Oil the sockets on the pusher rods. To do this press the valve springs together and remove the pusher rods.
Lubricant : Graphite grease or vaseline with 10 percent graphite added or Shell valve rocker grease. See that the pusher rods are not interchanged on replacement.
Grease the needle bearings of the valve levers. As lubricant use hot-bearing grease or clear viscous mineral oil or Shell valve rocker grease, but not ordinary yellow Stauffer grease, which contains diluents such as lime, soap etc.
Lubricate each joint of the control gear with a drop of oil.
Screw off the oil drain plug from the oil sump and run off water condensate.
3. After 25 hours’ flying : Empty the oil in the tank and the oil sump. Clean the oil strainer in the oil sump and the oil filter in the oil feed pipe. After replenishing with clean oil, see that the oil feed pipe between the oil pump and the tank is filled throughout with oil and does not contain any air locks. To make this inspection, remove the pipe at the oil pump and see if the oil issues without bubbling. Refix the oil pipe.
Clean the petrol filter and strainer in the carburettor.
Rinse the strainers in the engine exhaust with petrol if choked with oil.
4. After several months’ idleness: Renew all oil (as per 3. above).
APPENDIX ‘II’
Examination of Engine after Long Flights
This examination should be made before the engine cools.
1. Temperature of cylinders. The cylinders should be at a uniform temperature overall. If there is a local overheating near the sparking plugs or the compressed air valves, examine these parts and see whether they are securely fixed. Over-heated cylinders must be replaced together with their pistons and the conditions of the liners carefully examined.
2. Examine the fuel, intake and oil pipes for leaks.
3. Compression. From each cylinder remove one sparking plug, except from the cylinder whose compression is to be tested.
4. Full-Throttle test on the ground (only for a short period). In this test the rated speed on full throttle on the ground must be obtained (See Page 2). If this speed is not obtained, locate the source of trouble as outlined in the instructions in Appendix ‘IV’ provided that the lack of power is not due to unusual weather conditions (very low barometric pressure, very high air temperature or very high atmosphere humidity).
c. Periodical Examination
1. After every 30 to 50 hours of flying, examine the following:
Packings on the intake pipes, for which purpose remove the flanges on the intake pipes at the intake ports.
Contact Breaker. Remove the contact breaker cover, separate the contacts, and, if necessary, clean with a fine flat file. If desired, special files for cleaning contacts can be supplied. Emery cloth or emery paper must not be used for cleaning the contacts as they are fibrous.
Revolve the engine until the contacts are completely apart. The contact gap should not exceed 0.3 to 0.4 mm and should be checked each time the contacts are cleaned; if necessary, readjust the clearance by means of the contact screws. Carefully retighten the locknut on each contact screw after adjustment.
If after long use the contacts become so worn that they can no longer be accurately adjusted, put in new contacts. This is best done by the firm supplying the magneto.
Take particular care that no oil gets on to the make and break contacts, as combustion of the oil causes the contacts to wear prematurely. The magneto is then also liable to work irregularly, as oil is a non-conductor.
Sparking Plugs. Test the gap between the electrodes, which should be 0.4mm. If a sparking plug tester is available the plugs should be tested under pressure (about 6 kg per sq cm).
Compressed Air Unit (in engines with a compressed air starter). Examine the check valve on the cylinder and if necessary regrind the valve cone. At the same time, check the tension of the valve spring.