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Vulcan

How to raise the engine on 'neutral gear'?

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I have noticed in real life the aircrafts while tuning up or just before take off as a part of the checking process raises the power but without any effect to the forward motion of the aircraft. If you were to compare to a motorcar, you can say

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Real life uses brakes. And in some cases there is plenty of power to drag locked wheels down the runway. In those cases, you limit to a specified RPM.When a Cessna or Piper does an engine runup at 1800,2000 rpm (or whatever), your feet are firmly on the brakes................. in addition to the parking brake if the plane has one & you're using it.The closest thing to neutral in a prop plane would be a reversable pitch prop (beta range), but your smaller singles or twins don't have them. L.Adamson

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Yes during the run up you have to use the brakes because if you throttle up to 1700rpm on a 172 you're going to movie. Actually neutral for a prop plane would be with a constant speed prop that is feathered, giving little to no thrust.

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>Actually neutral for a prop plane would be with a constant>speed prop that is feathered, giving little to no thrust.IMO ---- the greatest propeller drag on the engine while stationary would be in the "feather" position, where the blades are at 90 degrees to the engine rotation. No forward/backward thrust, but lots of drag. An example from a Piper Seminol information manual states that during the pre-takeoff runup; you set rpm at 1500 rpm and then pull the prop control all the way to feather position & then back. But don't allow an rpm drop of more than 500 rpms.For most "single engine" constant speed aircraft, the prop doesn't have a feathering position. Just a range of high to low rpm.L.Adamson

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Both of you are right. With respect to aircraft forward flight, the feathered position can be thought of as "neutral gear". With respect to the engine, the beta, flat position of the props can also be thought of as "neutral gear".The feathered prop is used as a "neutral gear" if the engine fails in flight since it aligns the propeller blade with the airflow to produce minimum drag. (On a single engine aircraft with constant speed prop, you can pull the prop lever back to the lowest rpm position when gliding in order to get as close to this condition as you can, since there is no actual feather position on most single engine aircraft.)During ground operations, the beta position can be used to eliminate engine thrust as "neutral gear" since it bites no air in the flat position, in order to control taxi speed.So both are "neutral gear", but only in their own respective situations.

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Others have answered in regard to props Shri, but just to complete the picture it is similar for airliners.If you look at the manuals that come with most of the payware aircarft you will see in the checklists that once lined up on the runway, brakes on, and run the engines up to about 40% N1 to check the engines are OK.That is make sure they are all running at a simialr speed, EGTs, fuel flow, and vibration are similar and all are within the specified range.No point in just blasting off on your take-off run only to find one engine malfunctions at V1 if a check at 40% N1 would have highlighted the problem.HTH

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