MT Prop overhaul

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CFIDave
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Re: MT Prop overhaul

Post by CFIDave »

Cary:
Assuming your plane is not in the shop for prop service or for the plane's required annual inspection (both of which require a sign-off in your plane's logbook), you don't currently need an IA to determine airworthiness.

Nonetheless I respect your conservative approach of not flying any more before prop overhaul. As is often said, what's legal isn't always safe.
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ihfanjv
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Re: MT Prop overhaul

Post by ihfanjv »

carym wrote:I have elected to take the conservative approach and have them overhauled.
I understand your frustration with this confusing issue. However, the "conservative approach" may not necessarily be the safest approach. You know the service history of your airplane because you are meticulous about maintenance. What happens during overhaul and reassembly is totally out of your control. You would be removing two 100% working and tested mechanical devices and would be replacing them with two mechanical devices with no service history that may or may not work. Most failures occur shortly after overhaul. Since your propellers are working 100% today - that is, they are 100% serviceable "on condition" right now - conservatively speaking you are probably better off leaving well enough alone and continuing to monitor them in the regular course, and later overhaul them "on condition" at some point in the future should they exhibit some sign of requiring an overhaul.

The theory of "minimalist maintenance" and the rationale therefor is the subject of Savvy Aviation's owner Mike Busch's new book "Manifesto: A Revolutionary Approach to General Aviation Maintenance." Busch's opinion is that “There’s a dirty little secret about aviation maintenance: it often breaks aircraft instead of fixing them.” Busch is big on the idea that servicing 100% working propellers based upon an arbitrary date limit or hours limit makes no sense whatsoever. Whether you agree with Busch's opinions on maintenance or not, the book is a great read.

Of course, this is just one person's opinion. But whether something is "conservative" or is "not conservative" with regard to safety is also not a matter of fact, rather a matter of personal opinion.
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Rich
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Re: MT Prop overhaul

Post by Rich »

Without going through the gory details of my experience yet again, the condition of the inner workings of your prop can not be determined by the fact that "it works". Because it will work until it doesn't, at which time you may no longer be looking at a moderate cost overhaul, but an expensive repair with extensive downtime. Mine had been about 6 years since overhaul when it started to "not work".

FWIW, next year it'll be 6 years since my last overhaul/100-day-AOG repair. I'll be overhauling mine.
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Re: MT Prop overhaul

Post by Antoine »

I have only one overhaul event in my experience:

At 5 years or so I took the plane to Straubing (MT's HQ) and had a grease leak on the hub fixed.
One of their senior mechanics checked my hub's wear at that time and he told me they had turned some part around (can't remember which) and that this would be Ok until next year until overhaul is due. His words were very similar to what Rich is referring to in the post above.

The prop was replaced (by an overhauled one, for faster turnaround) at about 600 hours.
This makes me wonder how the same prop would have survived 2400 service hours on a frequently flown AC.

I haven't read Mike Busch's book yet, but I will.
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