912 engine inspection after oil supply disruption

[Dusty]

I had a suboptimal day yesterday.
I had done an oil change followed by a 1hr test flight all good,followed by a trip out to a satellite field when things went bad.
My engine sounded off? Gauges showed nothing abnormal so I headed back to base.

My engine was sounding like it had split an exhaust,then the oil pressure and revs began to drop.30 psi rather than 55psi,4800 at 27inches where I would expect to see 5500rpm.
on reaching my home base after 10 min? Shutdown saw a lot of smoke pour out the cowling:eek:

The problem was traced to a braided hose on the tank to pump circuit had failed internally and was sucking air which I believe let the lifters bleed down?

On shutdown a small amount of oil flowed out and onto the exhaust causing the smoke,the pipe was replaced an extended ground run was done with all appearing normal,another flight of approximately 1 hour failed to show anything different to normal operation.

I plan to get to the hanger to investigate further tomorrow.
I will remove the rocker covers and inspect the retainers and valve stem to head length in case the valves have stretched.I can't find online an acceptable length to use as a baseline,the engine is an early ul with dual valve springs.

Is there a published valve length,and procedure for checkling after this sort of problem?
Cheers
Dusty

[Av8r3400]

Your best bet is to reference the Heavy Maintenance Manual available on line from Rotax. They have step-by-step procedures for inspection after this this contingency.

[efwd]

I understand that Ops are normal after replacing the hose. How come you believe valves may be stretched? Would it not being running differently if that were the case?

[kmach]

How much oil in the tank after this occurred?

[Dusty]

I'll have another look online but I could only find reference to air entering via the oil pump seals.
No oil was lost other than the tee spoon amount dropped on shutdown.
I was worried about valve stretch after an aircraft from our field flew for a while with an air leak,the valves stretched to the point of low compression making starting difficult.
I used the rocker cover face as a reference on mine and another engine ,they were the same,the collets and springs visually liked ok.
I flew or a couple of hours today with pressure and performance as before,
Maybe i've dodged a bullet.
Time will tell.

[Av8r3400]

Oil starvation will first impact the camshaft and lifters with extreme wear. I've seen lifters destroyed by starting an engine after an oil change without bringing up oil pressure first. I don't know how the valves would be "stretched".


I also believe you have most likely dodged a bullet, but careful inspection of the valve train and an oil change with a thorough filter inspection for metal is defiantly warranted.

[kmach]

www.rotax-owner.com has all the engine manuals for free, click support and your engine and you will be able to download all the manuals, operators, line maintenance, Heavy maintenance.