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Check Idle

Slight variations in rpm with the throttle closed can cause trouble.

Most before takeoff checklists in piston-powered airplanes include the item “Throttle – idle.” And while you may pull the throttle lever all the way back to the stop, you may not have a clear idea of what to look for. You may think the action is simply done to ensure that the engine keeps running smoothly when you close the throttle. But there are other things that you as a pilot should take into consideration as you complete this step of the runup.

An excessively low throttle setting will likely have you bring the airplane to a mechanic as the engine will run rough and even quit while on the ground. It is, however, not very likely that the engine will stall during flight since the airflow keeps the propeller spinning. However, certain maneuvers with the throttle closed may shut the engine off in flight if the idle setting is too low.

A throttle setting that is too high is also bad. While the engine will likely run very smoothly on the ground, your trouble will come when you are coming in for a landing. With a throttle setting that is too high at idle, you will have trouble getting the airplane to descend on final. If you are planning to land on a short runway or practice short field landing, you will definitely have a difficult time.

The next time you check the idle throttle setting before takeoff, pay attention to the RPMs. You should check the engine manufacturer’s recommendations, but a good setting for most piston-powered airplanes is 600-700 RPM. If it is below 600 or up near 800 or 900 RPM, you should have a mechanic make an adjustment to make sure that your airplane does what you want it to do when you close the throttle.

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