Grossly overspeed propeller

[Wolfala]

Let me preface the discussion: no it's not me. Had a guy who threw a rod from his engine while in cruise due to a rod bolt failure from manufacture. The engine data recorder recorded a 3500 RPM exceedance. The engine is trashed. The open sore question remains about the propeller and the accessories on the engine such as the governor alternators and various other pumps. There's little doubt that those accessories will go out for inspection if not out right scrapping: but the question is with the propeller. The maintenance manual only records exceedances up to 110% and this one was close to 150%. I'm inclined to recommend that the propeller be scrapped and have insurance replace it.

Am I going to bit overboard with that assumption?

[Mar]

Not that I know anything, but what is that prop made of?

[SIK1]

From your description. If I'm reading it correctly the prop has exceeded the acceptable limits.

[saggs]

Why on earth are you asking this kind of question on a video game forum?  Seriously... I don't think the Aces High BBS is FAA approved reference data.

If the answer is not clear in the maintenance manual, go to the component overhaul manual.  If the answer is still not crystal clear call the manufacturer of,  or an authorized repair station for said component.

[DaveBB]

If the prop is metal, just for fun, do a dimensional check on it. 

The stuff I deal with has built in safety factors of 3 to 8.  That means the allowable stress is the minimum specified tensile strength divided by 3. 

I would record that the prop has exceeded the speed tolerance (sometimes known as an "excursion") in the manual, and trash it.  It has become a legal liability issue now.  You could also perform all sorts of non-destructive testing on it, which would cost a fortune.  No method of NDE has a 100% detection rate either.

[icepac]

Does your manual state maximum prop rpm or just maximum engine rpm?

Is it possible that this prop. is rated for higher rpms than the engine is?

[Wolfala]

It'd asked because we have a lot of A&P and IAs on here. On the subject of exceeded estimates, max was 2700 rpm. Hartzel has published 110% limits but is pretty vague on what to do about them other then to call them. Agree on the legal liability, it would be best to scrap it.

The owner doesn't care 1 way or another, the engine he has to buy but the accessories are going to be a fight with insurance since they were along for the ride when the rod bolt went. But I think the best tact is get a written response saying the thing is toast from the accessory manufactures and handing it to the adjustor for a check.

[SFRT - Frenchy]

I'd call Hartzel customer service. 3500 RPM, does that means the tip blade went supersonic? 

[WWhiskey]

Why on earth are you asking this kind of question on a video game forum?  Seriously... I don't think the Aces High BBS is FAA approved reference data.

If the answer is not clear in the maintenance manual, go to the component overhaul manual.  If the answer is still not crystal clear call the manufacturer of,  or an authorized repair station for said component.

lots of guys here that do more than just play cartoon planes!  Some have been around aircraft a long long time and just might have an answer.

[saggs]

lots of guys here that do more than just play cartoon planes!  Some have been around aircraft a long long time and just might have an answer.

Yes, I'm one of those guys.  I'm an A&P who works on aircraft 45-50 hrs a week usually.  And yes, I do have a pretty good idea of what the answer is.  Odds are pretty dang high that that prop needs a complete NDI and overhaul, may even be scrap depending how long the overspeed condition lasted.  But not having a manual or other approved data for that specific propeller or component in front of me for reference, what I say means absolutely jack squat.

To the FAA and the lawyers it matters not if you did the right thing on the aircraft... what matters is if the paperwork and documentation are correct, it is a matter of CYA.  Years or even decades from now if that aircraft has an accident, and the NTSB looks through the logbooks, they will go after ANY questionable logbook entry whether it was a factor in the accident or not, and it you signed that entry, they will come after you.

So... how you going to sign off that powerplant logbook entry?    "Inspected (insert component here) I.A.W. what some guy on an internet forum told me.  Found to be serviceable, OK for service"  Yeah... the lawyers will love that, doesn't matter if the guy on the internet was right or not.


Wolfala said the guy has insurance, so this shouldn't even be a question.  Just send the whole prop off to the nearest Hartzell service station and let them deal with it.  That's why we have insurance right?

[saggs]

After my previous long-winded response, let me give the short answer.

Am I going to bit overboard with that assumption?

I don't think so.  But call Hartzell anyway.

[pembquist]

Saggs, is there any plus to being an aircraft mechanic? It seems like a lot of liability.

[Wolfala]

Saggs, is there any plus to being an aircraft mechanic? It seems like a lot of liability.

Very little.

[saggs]

Saggs, is there any plus to being an aircraft mechanic? It seems like a lot of liability.

I like aviation and working with my head and my hands, so it's a good fit for me.  I'll never be rich, but I enjoy the work.  Plus there are many, many avenues you can go with it.  My A&P career is still young (~ 5 years) but I've worked on everything from WWII bombers (a PV-2 called Attu Warrior), to light Cessnas and Pipers, to MD500 and Bell 206 helicopters (my last job) to old C-46 and DC-6 cargo birds (my current job).  Presently I'm thinking about getting my IA which would open up more opportunity in the general aviation world, but also bring me a WHOLE lot more liability, so I'm not sure it's worth it.... so yea, the liability issue can be a killjoy.

The simple rules are always have approved reference data to CYA for whatever you do, and never sign your name for any work that you're not comfortable with.  It can be scary, we had a plane lose a wheel on take off recently, and when I heard about it the next morning I had that gut check moment where I think "Gosh... I hope I wasn't the last guy to change that wheel."  Turns out it was a bearing failure so no one was to blame.

The worst example is the poor United Airlines mechanic whom the French blamed for the Concorde crash in 2000.  The French courts went after him for over a decade, basically ruined the guys life fighting it before he was finally exonerated.

[Bodhi]

Wolfala,
Any chance the data recorder misread the overspeed?  It's obvious to send the prop out for inspection, but in this day and age, they are expensive.  I'm not a prop guy, but I would not scrap it without a second, informed opinion.