German guy
Cleared for Takeoff
In our former flying club we had two Piper Archers. Same model, same engine, same prop, similarly equipped, almost identical empty weight. One of them accelerated and climbed however so sluggish that I was close to aborting my first take off with it, because it did not feel right. Others also claimed that particularly the take off was extremely slow. The engine was checked multiple times, but nothing was found to be wrong with it. The other Archer was a great performer, despite of its much higher time engine.
I heard from other pilots that they easily do better than the POH numbers. Others claim that planes, particularly older ones, 'of course' never make the numbers mentioned in the POHs, because they were created by the marketing department, the plane was flown by a god-like test pilot and the airframe, as well as the engine were new.
As I've seem people with unmodified Cessna 170s, 172s and engines past TBO do shorter take offs than stated in the POH (OK, owner's manual back then), as well as others who came nowhere close to the POH numbers, for the given weight and density altitude, despite of a low time engine, I don't think that the common explanations make much sense.
So - what causes these deviations, to the better or worse, at a given aircraft's take off weight, assuming the maintenance is done right? Frankly, I don't see too many parameters which could vary: Static compression seems to have a negligible effect on the engine's power, the ignitions is either set correctly or not, the aerodynamic qualities of a plane won't change much and I can hardly imagine that props vary greatly in their efficiency, if model and pitch are identical.
I heard from other pilots that they easily do better than the POH numbers. Others claim that planes, particularly older ones, 'of course' never make the numbers mentioned in the POHs, because they were created by the marketing department, the plane was flown by a god-like test pilot and the airframe, as well as the engine were new.
As I've seem people with unmodified Cessna 170s, 172s and engines past TBO do shorter take offs than stated in the POH (OK, owner's manual back then), as well as others who came nowhere close to the POH numbers, for the given weight and density altitude, despite of a low time engine, I don't think that the common explanations make much sense.
So - what causes these deviations, to the better or worse, at a given aircraft's take off weight, assuming the maintenance is done right? Frankly, I don't see too many parameters which could vary: Static compression seems to have a negligible effect on the engine's power, the ignitions is either set correctly or not, the aerodynamic qualities of a plane won't change much and I can hardly imagine that props vary greatly in their efficiency, if model and pitch are identical.