I've recently experimented with measuring the actual thrust of an engine/prop combination as it is mounted on the airplane. I would like to run this by all the engine gurus out there to see if this seems like a valid way to do so.

The way I've been doing this is to use a digital fish scale which is hooked to a 10' leather dog leash (it seemed to have less elasticity to it than some of the different types of rope I looked at...plus I know it will hold at least 40 lbs, the weight of my stupid mutt pulling her heart out). The other end of the leash is placed around the tail of the plane that I'm testing and the digital fish scale is attached to a metal spike driven deep into the ground. I start the engine and let it idle, take the slack out of the leash, and zero out the scale. I then throttle up and read the "weight" of the pull generated in lbs and oz.

It seems like it has been a fairly reliable test, especially when comparing different propeller sizes/pitches/brands to determine which one can generate more thrust. Does anyone see any flaws in this?

Thanks,

Dave