Cold Weather Engine Starts

Hello Sky Soaring Tow Pilot,

With the colder temperatures upon us it’s a good time to review cold engine starts and cold weather procedures for our tow plane. As you know the engine time on the Pawnee is approaching 2000 hours and it is imperative that we take care of it and prolong its life until the next overhaul.

Cold engine Starts;

The engine manufactures define cold as 20 degrees F and engine pre-heating is required.  While I don’t think that we will be operating at that temperature however it is possible that we will be near it. When the temperature is above 20 degrees F and below 40 degrees F, it does not require the use of preheat, but recommends that the post preheat engine starting procedures regarding RPM, oil pressure and oil temperature be followed.

Engine start is made at low engine RPM, not more than 1000, due to risk of cylinder damage from lack of lubrication and to assure that oil pressure comes into the acceptable range soon after start.

Pumping the throttle before or during start is not a good idea. It creates a high risk of engine fire on a cold start. Pumping the throttle more than once usually does nothing but flood the carburetor.

For a carbureted engine, the proper procedure is to use the primer to put fuel directly into the cylinders. Many operators recommend leaving the primer out and letting it fill with fuel after the last pre-start priming shot. Then, as the engine is cranking and fires, give another shot or two of prime.

Frequently checking oil pressure to assure that there is not congealed oil somewhere in the system that can cause engine damage—it will manifest itself by high or low oil pressure indications. Do NOT let the RPM exceed 1000 until some oil temperature is indicated. This is important—we’ve all seen the pilots who start the engine at 1500 or 1700 RPM; they’re damaging the engine, hot or cold. When the checklist says “throttle cracked,” it means a small fraction of an inch, not half-way to the firewall.

If the oil pressure cannot be maintained above 30 psi or below 100 psi, shut down.

Once oil temperature is indicating, the engine may be operated as high as 1700 RPM, however, it should be approached gradually to make sure oil pressure does not exceed 100 psi. The runup can be conducted.

Engine warm-up time will take longer in cold weather. Also, remember that we are running summertime oil which will take longer to warm up.

Let down after glider release;
Continue to use our procedure for let down after glider release. Keeping the engine warm and no shock cooling.

Fly Safe