technical help for a helo pilot

[two0six]

Hi all,

Bit of a tricky one to deal with if you're not an engineer! (pilot only)

I was doing ground runs on a B206 after a 100 hour inspection the other day.

Igniter pulled, pushed starter to do the oil bleed. After 2 attempts only 1 teaspoon of oil (usually 1/2 a quart)

Pushed the machine into the hanger. The engineer remembered he had changed the oil check valve clamp. The clamp was of a smaller type. Problem solved with a new clamp as the next bleed showed a 1/2 quart of oil.

All set for a normal start, after 1 minute at idle the engine chip came on. The engineer cleaned the plug the the same thing happened twice after. He pulled the oil filter to find an alarming amount of fine shavings.

Pulled the engine and sent it to an Allison engine shop. The number 8 bearing was replaced. On the test bed all scavenge pumps were working fine, the only thing replaced was the bearing and the OIL CHECK VALVE!

Before the 100 hour the machine run as per normal with no chip lights.

As I am not in any way qualified to know whether it was the engineers fault I was wondering if any of you guys could give me a possible answer.

Its a difficult one and the last thing I want to do is blame somebody for no reason.

[ericferret]

You could hear a pin drop!!!!!!!!!!!!!!!!

[Cypherus]

Or the sound of said Alison engineers report on the probable cause of an errant #8 bearing failure landing on your desk maybe.????

[quichemech]

Hmmmmmmmmmmmmm.

[Fully Articulated]

TwoOsix, you said that the engineer had replaced the oil checkvalve clamp with a smaller type. This clamp is normally an un-cushioned clamp which is realitivly loose fitting. I am not certain if this is possible but if a smaller clamp was intalled on the checkvalve perhaps the pinching force would be great enough to cause the valve to stick. The subseqent oil starvation would then cause the #8 bearing to fail. You also mentioned that the O/H shop replaced the checkvalve, did they say why?

[Salusa]

Hmmm, its been a while but....

Check your maintenance schedule. There is a requirement to disassemble and clean the valve.

Now whilst it is Murphy proof in terms of installing it, it is possible to reassemble the 'internals' incorrectly so it will not operate as designed. It may be quite possible for it to pass no oil and then pass 'some' oil.

I cannot see how a 'smaller' clamp will cause any problems. You just won’t be able to fully close it around the valve when installing it.