View Full Version : Lycoming AEIO 540 Vibrating under G Load
Casting around for possible solutions for this one, have been down the usual paths. ie leads plugs mags mounts. vibration not airframe related. what would cause an engine to vibrate when subject to G force? as in a tight turn or agentle pull up??
mainwheel
7th Mar 2013, 16:50
When was engine fitted, same question with prop....
Its not newly fitted, it has over 1000 Hrs, However this issue is recently arisen
wrench1
8th Mar 2013, 01:45
What frequency vibration?...low <1000 rpm (like a mis-firing cylinder)...medium 1000-2500 rpm (prop speed)...high >3000 rpm (a buzz).
Where does the pilot feel it...in his seat?...controls?...feet on the floor?...airframe post?
Retractable gear or fixed?
In the mean time, if nothing has been changed or modified recently...and you think it is in engine area....
-engine mount rubbers separated...hardware loose or broken
-exhaust system cracked
-prop backplate cracked...spinner mount cracked
-depending type of prop...cones, seats, seals loose
Medium, the frequency changes with throttle movement so it is directly related to the rotation of engine, Remember it only occurs if there is a g loading present.
Have at this stage eliminated any airframe input, did an inflight inspection to see if any gear doors or panels were not flush or fluttering...nothing so at this stage I am firmly convinced it is engine related.
New Mags,leads,plugs,lord mounts in an effort to clear this problem with no joy
wrench1
8th Mar 2013, 10:23
I'd lean toward prop issue rather than "engine" issue. Best move, find someone with balance gear if possible and do a dynamic check on prop and a spectrum check on engine. If it really is a engine problem, i.e. no accessory mounting issues, prop, etc... then don't fly no more. Any true engine vib problem is normally crankshaft issue...weight slung off or worse a crack. Does it have a VAR crank?
In the meantime....
When g load applied...does vib get worse or better with increase in throttle?
What kind of prop and how many blades?
On ground...static (not running)...check prop blade track. Put reference item...tool box, chair, whatever next to one blade. Mark lead or trail edge position on ref item...then rotate to next blade and see if track is close...repeat with 3rd blade if necessary. For more info:
http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgAdvisoryCircular.nsf/list/AC%2020-37E/$FILE/AC%2020-37e.pdf
Exhaust, prop backplate, spinner, alternator, etc all serviceable?...no mount cracks?
Torque on prop bolts within limits?
w1
ericferret
8th Mar 2013, 20:34
Cracked engine mount?
I would not totally discount the airframe. If something is hanging loose it will vibrate in tune with the engine.
Maybe under G something is moving in to contact with the airframe.
mainwheel
9th Mar 2013, 19:27
You may have a crankshaft counterweight problem.
I wouldn't be flying it!:uhoh::uhoh:
Fleep
10th Mar 2013, 18:19
Thats what I have been thinking all along, Just waiting for someone to confirm,
Thanks for the input guys