Thrust calculations?

Is there any way to calculate how much thrust an engine is putting out in pounds?

Here ya go, Len.

of course there are several dissenters, but this will get you close

Many thanks for the very swift replies. Confirms what I had hoped! The plane is a Flair Extra 300S/140 fitted with a Moki135 and an APC 16x8. All up weight is around 12 pounds so this combo should give the ability to prop hang? Engine isn't run in fully and according to the just-engines web site it ought to turn this prop at around 9000-9500 when it fully run-in.

cheers, Len

All up weight is around 12 pounds so this combo should give the ability to prop hang?

The ability to prop hang counts on just one thing. You msut have at least equal thrust to the weight of the plane. Keep in mind that the figures from these formulas are ballpark, and not entirely accurate. I'd install a little overkill.

Dr.1

Ok thanks. This engine isn't fully run in yet and should be able to swing the 16x8 at around 9200 so the web site says so that should give me that little extra I need.

cheers, Len

Also check out the site at

IF you have the ground clearance to do it, You might want to consider swinging 18 inch props the larger diameter will give you more thrust at lower RPM, and possibly higher ultimate thrust.

In spite of the fact that many people don't like them, a Zinger 18x6-10 or 18x8 square tip can be just about right. also don't overlook the Zinger Pro series less tip drag than the square tip blades, and I have had reasonable results with them.

YMMV bob