02 Engine Runup - Power and Temprature

by: Jan Zumwalt

About the author - Jan Zumwalt, earned his Aeronautical engineer degree from the University of Alaska - Anchorage. Jan has over 2000hrs as pilot in command and has been employed as maintenance supervisor for several small commuter flight services. He also served as shift maintenance supervisor for Continental Airlines. He has designed and assisted many successful kit aircraft.

Engine runup

Pre-start Check

Check the power-plant throughly. (i.e., engine, mount, carburetor, wiring, intake and exhaust manifold, oil level, reduction unit if applicable and propeller)

Add 1 gallon of fuel to each tank and check for leaks.

The recomemndation given here should be modified as neccesary to comply with the manufacturer's recommendations. (This is especially important with the two-cycle engines that have become more and more popular recently.)

Remember, the engine cooling system is not designed for indefinite full throttle on the ground. Usually the cowling must be installed because the baffling is needed to cool the engine evenly. You can burn out the aircraft engine in less than 30 seconds at full throttle without a cowl.

FAA laws require a qualified pilot at the controls during the start and run of any aircraft. So, the engine runup requires at least two people to safly perofrm all operations and checks. It may be wise to tie the aircraft down for extra precaution.

[ ] static RPM (30 seconds)

To check THRUST, park the airplane on a hard surface with "hard" inflated tires. Measure thrust with large fish scale at the aircraft's tail end. Thrust in pounds should be approximately four times the horsepower for a cruise prop, five times the horsepower for a climb prop. You may want to do it several times for better accuracy. (See Figure 1 and 2)

[ ] Cool down at 150% idle - 3min

[ ] Viberation check - 1min
From full throttle, check that no part of the aircraft is shaking and/or vibrating heavily - check every 250 rpm from full throttle to idle. Pay close attention to motor mount, tail, control surfaces, and the bottom of the fuselage.
[ ] Leaks
Shut engine off and immeditly look for oil or fuel leaks. Then look for abnormal chafing or wear on the entire aircraft. Pay particular attention to the engine compartment.
[ ] Fuel qty and fuel lines
At the same time it is important to check the fuel quantity gauge (empty equals when engine stops running in above critical attitude) at 1/4, 1/2, 3/4 and full. This is not only important for fuel consumption and range check but also to detect quickly if sudden unusually high fuel consumption develops (i.e. leak).
Post Runup Check

Check the power-plant throughly again. (i.e., engine, mount, carburetor, wiring, intake and exhaust manifold, oil level, reduction unit if applicable and propeller). The aircraft should also be given a good inspection, looking for any parts that may have shifted or viberated loose.