IS MY ENGINE POWERFUL ENOUGH?

Quite a reasonable amount of our customers ask the above question about various types & sizes of engines that they have sitting on shelves just waiting for the correct aircraft to come along.

We decided that it may be beneficial to our customers (and anyone else that cares to view our site) to set out a fairly simple test to determine the answer to that question. While we avoid attempting to answer questions on specific engines (mainly because we don't know about them) we do realize that such simple information as offered on this page can be a deciding factor as to which way to go.

This simple diagram below shows an engine mounted on a suitable trolley with prop ground clearance, anchored back to a suitable securing point via a spring balance. A good rule of thumb to go by, is to have a fair idea of the expected finished all up weight of the proposed aircraft to hopefully be flown with this engine. Use the test bed arrangement below (or the aircraft) to run the engine in order to ascertain its static pull.

Other F A Qs.
Is my aircraft over propped & how can I tell?

Will my prop selection from this test fly my plane at a suitable speed?

The most desirable amount of static pull to fly the aircraft is approximately 25% of the expected all up weight of the plane to be flown. If you intend flying from a very good smooth surface where long shallow take off runs can be performed, the static pull need only be 20%. It is a known fact that quite a bit less pull than this can fly the plane, but unless you really know what you are doing it is best not to go below these guidelines.

It is worth remembering that the prop becomes much more efficient when traveling through the air due to it gaining full purchase on the air and therefore escaping from its stall condition. When this point is achieved, the pull on the firewall can exceed 50% in flight which is more than ample power to weight ratio for average flying with average aerobatics.