Hard to turn prop when engine is hot (O-235)

[Ericson]

Hello !

Recently we borrowed C152 from another club . After few flights one pilot reported that it takes effort of both hands and some weight to turn prop after the flight. When engine is cool the is no problem with turning the prop by hand.

Engine is 800 hrs after overhaul that was done in 2007, TT for engine is 6000 hrs. Overhaul shop owner says that there was a series of Lycoming O-235 with limited clearance on crankshaft and there is Service Letter or something to cover that topic. When asked "please give me the number of this letter" he could not remember but he says that engine is airworthy.

We made oil analysis and compression check - no problems.

Anyone of you heard something about such series of O-235 ?

thanks

[glug]

Try this

If there is a SB it should be on this: Service Bulletins - Lycoming

Rgds

[Capot]

I was taught to give a hot prop a very wide berth. Getting both hands on it to turn one sounds dangerous to me. It might get caught in my gray beard if a cylinder fires, is how I see it.

I was grounded for a week for trying to move a nosewheel aircraft by heaving on its prop when hot.

Does that piece of ancient wisdom no longer apply?

[Aviator1512]

This engine is about to fail - do not fly it & take all steps necessary to prevent it from flying - it could hurt someone.

Tightness when hot is caused by a fretted crankcase. ie the two halfes of the case have been wearing (usually at the centre main bearing), have lost material and is starting to squeeze the main bearings and crankshaft. This repidly gets worse, and what happens next? The main bearings start to rotate, oil supply to the crank is interupted - engine gets very hot - engine seizes. Game over. This will happen, and I have known this to happen from first signs to engine stoppage in less than 2hours in service.
It is fairly common and very dangerous. If your engineer says its OK - then sack him - he is wrong and being negligent.

Get the engine to an overhaul shop & tell them - fretted crankcase!
(This effects all Lycomings, but is more common on the O-235 as the design of the through studs is different to the bigger engines & is more prone to severe fretting).

[Agaricus bisporus]

Clearly something severely wrong, isn't there? It indicates that something inside is binding (could be any number of things), and friction like that can only produce vast amounts of localised excess heat when the engine is running. A siezure or major failure is clearly imminent.

Agree entirely with the view "don't fly it" under any circumstances. Don't even let the club you borrowed it from fly it home. Ground it.
Get it stripped down and examined!

[ericferret]

Had a similar problem with an O-320, ended up in the overhaul shop.

What you don't do is ground it!!!!!

You will lay yourself open to a damages claim for loss of revenue e.t.c. It is the operators responsibility to deal with the problem and yours to advise them of it.

Depends on their response and attitude as to how far you go. If necessary report it to the local airworthiness authority.

[Agaricus bisporus]

Eric, are you suggesting that you lay yourself open to a claim if you write an aircraft unserviceable? I've never heard such cobblers. It is your duty to declare unserviceabilities as YOU are the operator, and the scenario described above is very definately in that category. If we're going down the road of imagining unlikely legal actions what about the dependants' claims against you when you allowed them to take away an aircraft that you believed was not airworthy? That one would be far more likely to succeed.

They'd have to prove negligence, incompetence or malicious intent in your scenario which is all but impossible, and the case would cost far, far more to bring than the loss incurred. Ain't gonna happen outside the movies or an overactive imagination.

[camlobe]

"Anyone of you heard something about such series of O-235 ?"

For what ir is worth, yes I have. Came across this a number of years ago on a 235 in a Traumahawk. Aviator1512 has given you the cause far more clearly and lucidly than I could have.

If the aircraft was your own, I would support Aviator1512's statement in its entirety.

However, as you have 'borrowed' it, I would recommend in the strongest terms possible you do as Aviator 1512 says and DO NOT FLY IT. Do your very best to ensure the owner(s) actually understands this point and why. Make your point in writing to ensure your back is covered if the engine should fail when someone else is flying it (a sad reflection of our present-day litigious society).

As to the overhaul shop, could you please PM me who it is.

camlobe

[Ericson]

Thank you all for replies.

Plane is on the ground since dicovery of the problem and will be utill we know what's going on. Problem was discovered by pilot after ladning and shutdown because starter could not crank the engine due to internal friction.

Overhaul shop owner that made OH says that this engine showed such behavior before and after overhaul and it's 800 hrs past overhaul

[Desk Jockey]

When newer engineers than me asked me about a defect found on inspection and what should they do about it my answer would be to write it up and then we would work out if it it servicable or not and give the answer in the paperwork.