When is it required for reciprocating engines to be tested on a dynamometer test cell?
I don't know of any recip overhaul manual that requires a dyno for testing. Most of them even allow post overhaul tests to be done on the aircraft rather than a test cell.
Remember, for a recip without a geared supercharger, direct driver or geared with a simple spur gear, overhaul is a MINOR repair and can be done by an A&P. He has to have the proper tools and tech pubs, but it is still only a minor repair.
Thanks for the information.
Dyno and test cell are not the same thing. Consult your engine manufacturer's requirements. For instance, Lycoming suggests a test cell (no dyno) be used for post overhaul run. They do allow run in on the airplane with certain requirements, 1 being that a test club be used and 2 being that the engine gauges have been calibrated. When was the last time you've seen that done? Yes, this is a mandatory requirement if you are overhauling the engine IAW with the Lyc Overhaul manual.