Lycoming AEIO 540 RPM Fluctation

[Fleep]

Have a 540 in my stable, thats causing me to scratch my head, Newly overhauled out of the box, new everything, runs great on the ground, above approx 2000ft its rpm fluctuates by about 100 RPM

Changed
Prop Governor
Fuel Injector

Symptoms still remain.

Very open to advice, suggestions at this stage, Thanks in advance

[stevef]

That's odd. What aircraft?
A few questions to build up a picture:
1) Do the the revs fluctuate all through the range?
2) What happens if you adjust the mixture?
3) Is the manifold pressure steady?
4) Is the alternate air flap sealing OK?

[wrench1]

Fleep

If Bendix RSA could be automatic mixture control unit at altitude or induction leak at speed. May want to put gauges on fuel servo and check outputs. But since new install may consider contacting overhaul shop for input and possible warranty to offset your additional costs.

Good luck!
W1

[stevef]

Unlikely that there would be much effect (flashover) at 2000 feet but it's worth checking that you have a vented magneto timing window plug. There should be 3 or 4 holes in it.

[Fleep]

Thanks very much for the feed back, alternate air door was not something i had thought of, how ever its shut tight, excellent suggestion though,

Only happens at cruise setting, 2300 rpm or there about and only above 2000 ft , rpm fluctuates up and down 80-100 rpm. pilot feels like its the prop changing pitch, however surly this would happen on ground run if this was the case.

Mag flash over?
these are un-pressurized mags, but will check for venting. its a possibility as this engine is being operated in 35 deg plus ambient temps,
Thanks again
Fleep

[Fark'n'ell]

Fleep

Did you find what the fault was. (just curious)