TROUBLE-FREE STARTING AND OPERATION OF LYCOMING ENGINES IN LOW TEMPERATURES

Let’s start with the overall condition of the engine.

When attempting to start an engine in adverse conditions, it is essential that the engine is well-maintained and in perfect working order.

The spark plug gaps and magnetos should be properly set and ready to operate efficiently. In addition to the ignition system, other systems can also affect the proper operation of the engine.

Regular maintenance should include checking the heating system for leaks. It is worth taking this opportunity to remind you that you cannot smell carbon monoxide in the cabin!

In cold weather, another factor to consider before starting the engine is preheating.

The Lycoming service manuals provide specific guidelines as to when preheating should be used, but the timing or method of preheating is generally left to the good judgment of the pilot or the person performing the preheating.

Lycoming does not recommend the use of a heated oil dipstick, although most other methods are considered satisfactory.
In cold countries, pilots can be observed using home remedies before a cold start, such as an electric heater that blows warm air directed at, for example, the filter housing 10 minutes before takeoff. Of course, remember not to place such devices directly under a component from which, for example, fuel could leak!!

For most Lycoming models, preheating should be used whenever the temperature is -12 ° C or below. The exception to this rule are the 76 series models, which include the O-320-H and O/LO-360-E. These engines should be preheated when the temperature drops below -6 ° C.

It is recommended that these guidelines be followed even when using oil of different viscosities. In addition to difficult starting, failure to properly preheat the entire engine and oil system as recommended can cause small amounts of abnormal wear to internal engine parts, and ultimately reduce engine performance and shorten the time to overhaul.

Water is one of the most likely contaminants in aviation gasoline.

The engine will not run on water and although we can get away with a little moisture in the fuel in warm weather, flying in freezing temperatures makes any moisture in the fuel system very critical. Even a small bubble of moisture can freeze in the fuel line and completely cut off the fuel supply.

If the helicopter/aircraft is parked outside in rain or snow, first, keep the fuel tanks full to prevent condensation and make sure the fuel caps are tight. Second, check the fuel for contaminants before each flight by draining fuel samples from the tanks.

If flying in cold weather is planned, the pre-flight inspection should also include an inspection of the engine breather pipe opening to eliminate any moisture freezing at the end of the breather, which could result in a loss of engine oil.

Oil is another factor to consider in the cold weather starting process. All oils are affected by temperature, as they tend to thicken as temperatures drop. The engine may be reluctant to crank when the oil is thick.

Summer oil is not suitable for use in cold weather, so using multi-viscosity oil and warming up the engine before starting is a good argument here. Because multi-viscosity oils are thinner (lower viscosity), they allow the engine to crank more easily. The easier and faster oil flow also helps to lubricate the internal engine parts more quickly after starting. Proper oil viscosity is very important in all aspects of engine starting and operation. The recommendations for oil grade and temperature range in Lycoming Service Manual 1014 should be followed.

Probably the most important factor in starting an engine is obtaining a satisfactory fuel/air mixture for combustion. Because the engine usually starts very easily, many pilots are unaware of the change in starting procedure required for a successful start under varying temperature conditions.

Warm weather is thinner, so less fuel needs to be mixed with it than cold weather. Also, warm weather fuel will evaporate more easily, making starting easier. Simply put, as temperatures drop, it becomes increasingly important to have a fuel priming plan that will provide the proper fuel/air mixture.

When priming a carbureted engine, the pilot's plan must take into account the temperature, the number of cylinders with priming lines installed, and the number of primer pump strokes needed to create the proper fuel/air mixture. Fuel priming lines and pumps are ordered or installed by the airframe manufacturer, so not all airplanes/helicopters are configured the same.

For example, on Robinson helicopters, the optional fuel priming system has a fuel line to each cylinder, while some airplanes were manufactured with only one cylinder priming. Engines with single-cylinder priming are notoriously difficult to start in cold weather. The number of primed cylinders must be taken into account, since all the fuel supplied by the pump will be distributed to all the cylinders to which the primer pipe is connected. As the air becomes colder and denser, the amount of fuel pumped must be increased. The number of pumpings must be planned by some experimentation, which we will achieve by trial and error for each aircraft individually.
Once the correct number of primer pump strokes for each temperature range is established, the engine will usually start very quickly.
It may be found that the engine starts easily when one stroke of the primer is used in the range of 15˚C, two in the range of 10˚C, three in the range of 5˚C, etc.
This is just an example, which we must determine ourselves by trial and error.