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I could approximate the thrust by knowing the weight of my aircraft and timing the acceleration to takeoff speed, but I think that would be a little dangerous of me as well as only an approximation due to rolling and wind resistance as well as inaccuracies of the airspeed indicator. I also realize the thrust would vary as airspeed increases due to changes in propeller and engine efficiency.

Nevertheless, was there every an actual rated or measured thrust for the C172? You can use whatever year model you want, although I usually fly the C172N at 160Hp using a stock propeller. I would also assume if there was a measurement, it would be at standard atmospheric conditions (sea level, 15C, standard 29.92 pressure).

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A fixed pitch prop will develop maximum thrust somewhere between static and maximum air speed depending on its pitch. Finer pitch will give better acceleration from a standing start, more coarse will give more thrust at cruise. People generally do not quote thrust numbers with props, charts calculating weight and weather effects on performance are far more important than "thrust".

However, if you want to know, do it the same way James Watt did, either by lifting a weight, moving a weight, or lifting AND moving a weight. Watt knew just to take the first meter, where air drag was negligible. For a Cessna, I would take the first 100 feet, release the brake, and hold a stop watch. As John K said, it should be 500-600 lbs. F=ma.

Just keep in mind, the key to those performance charts is that weather conditions have MAJOR effects on power and prop efficiency (prop thrust), this is what you MUST be aware of before takeoff.

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