Prop overhaul time/calendar

DesertNomad

DesertNomad

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DesertNomad
I am looking to see what people's thoughts are on overhauling props based on a calendar date. Many props have an overhaul date of 2000 hours or 7 years (or similar), but most people are much more likely to run into the calendar date.

My prop was at 450 hours at engine overhaul and the prop was overhauled at the same time so they were then equal.

Now my prop (2 blade, constant speed) is about 1050 hours since new, 600 since overhaul (which is 11 years). It has been hangared the whole time and my A&P says there are no signs of corrosion anywhere on the plane.

My A&P said it would likely be about $4500 to overhaul or $8000 for a new 3-blade prop. He also said it was probable that it did not really need to be overhauled yet.

I am going in to discuss all this on Monday.

Thoughts?
 
under part 91 you NEVER want to "overhaul" your prop. Instead you send it in the an "inspection and reseal". The difference is that an "overhaul" requires the blades to be machined, and if they measure out ok you don't want thet.

A reseal is going to be more like $600-800. I'd suggest that's a good idea rather than waiting for the hub innards to start to develop corrosion.
 
Note that Hartzell won't do an IRAN (or other non-overhaul work) on a prop that exceeds the TBO limits. The blade limits have nothing to do with the need to grind the blades. The blade grinding is to stress relieve them. If your blades are already below limits, they're scrap anyhow. If grinding them takes them below limits, they're scrap. Hartzell scraps a lot of blades.

Note that while TBO itself is only advisory for part 91 small operators. THere are a few ADs out there that do impose either overhaul or service limits on props independent of just the TBO,
 
Repair stations are shying away from IRANs when the propeller has exceeded TBO times. It is purely a liability standpoint.

More propellers and components are scrapped because of corrosion than dimensionally being under limits. Corrosion never sleeps and the propeller has places that can't be checked unless it is disassembled and inspected. For example the bearings, and races can't been seen while it is assembled and are corrosion sensitive.


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DesertNomad said:
I am looking to see what people's thoughts are on overhauling props based on a calendar date. Many props have an overhaul date of 2000 hours or 7 years (or similar), but most people are much more likely to run into the calendar date.

My prop was at 450 hours at engine overhaul and the prop was overhauled at the same time so they were then equal.

Now my prop (2 blade, constant speed) is about 1050 hours since new, 600 since overhaul (which is 11 years). It has been hangared the whole time and my A&P says there are no signs of corrosion anywhere on the plane.

My A&P said it would likely be about $4500 to overhaul or $8000 for a new 3-blade prop. He also said it was probable that it did not really need to be overhauled yet.

I am going in to discuss all this on Monday.

Thoughts?
Click to expand...

If you are Pt 91 and don't have a prop with an AD or MSB on it requiring overhaul, you don't have to do it. Props are very simple things, if there is nothing during routine inspection that triggers an alert, I don't mess with them.
 
I favor overhauls at prescribed intervals. My own have turned up problems that would have become much more serious and expensive had they not been corrected. If you believe ignorance is bliss? Your choice will be different than if you believe in good maintenance of your equipment. Your call.
 
Stewartb said:
I favor overhauls at prescribed intervals. My own have turned up problems that would have become much more serious and expensive had they not been corrected. If you believe ignorance is bliss? Your choice will be different than if you believe in good maintenance of your equipment. Your call.
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True, but economically it kinda depends on exactly which prop you have. Some props are economically poor candidates for overhaul, mostly the Hartzels with the ADs, most people just replace them. Those props it's best to just run them until they indicate they have problems, and replace them then.
 
It is a Hartzell prop, but I'll have to ask my A&P about the Ads on it - he said all Ads on my plane have been done, but at this point putting $600 into a re-seal of the prop is more appealing than an $8K three-blade new one from McCauley or Hartzell. Any thoughts on which 3-blade is better?
 
DesertNomad said:
It is a Hartzell prop, but I'll have to ask my A&P about the Ads on it - he said all Ads on my plane have been done, but at this point putting $600 into a re-seal of the prop is more appealing than an $8K three-blade new one from McCauley or Hartzell. Any thoughts on which 3-blade is better?
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Arrow right? I would go with a 2 blade Scimitar. Yours likely does not have the ADs on it. A reseal is far short of an overhaul, if that's all you need, that is the best course of action. It's when it's time to spend $5k on the overhaul and still have the ADs to continue dealing with that the economics favor just replacing the prop.
 
Be carefull sending anything to Hartzell. The tend to grind up and ask later!

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tmyers said:
Be carefull sending anything to Hartzell. The tend to grind up and ask later!

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Exactly, that is the risk you take sending them in for overhaul while still serviceable.
 
after all the time I spent polishing the blades, that's the last thing I want is to turn them loose with a grinder!

bob
 
Just put it in writing that you don't want grinding done without consulting you first.
 
No, they don't grind on them, they grind them up as in condemn them, as in you don't get them back in a usable condition.
 
Anticept said:
Just put it in writing that you don't want grinding done without consulting you first.
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Do you realize that Prop Shops are Certified repair shops with rules they must comply to?
When you ask for an overhaul, they must comply with step by step instructions called for in the overhaul manuals.
 
What I mean is, ask them not to dispose of them. I would tell them I want the aluminium back. I would sell for scrap. Unless they want to credit me for it for about the same or more for a core charge.

It also means options for sending somewhere else if you think they might be full of it.
 
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Check the TCDS. Hartzell got language added to at least one TCDS that makes the Service Bulletin with the life limits mandatory as a ICAW. For props that have such language added, the Calendar TBO becomes mandatory even for Part 91.

That's not usual, but where it is the imposed the calendar TBO must be met, or you are violating the limits in the Type certificate.
 
Anticept said:
That's what I mean, ask them not to dispose of them. I would tell them I want the aluminium back. I would sell for scrap. Unless they want to credit me for it for about the same or more for a core charge.

It also means options for sending somewhere else if you think they might be full of it.
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:rofl::rofl::rofl: Not a chance. When they condemn it, you're done with it, they make it unrebuildable.
 
Henning said:
:rofl::rofl::rofl: Not a chance. When they condemn it, you're done with it, they make it unrebuildable.
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Not true, they can not destroy your property.
They will red tag it and record the S/N.

and they will make entries in your prop log as to the maintenance completed.
 
I'm not saying that I encourage it, but red tags can be turned into yellow tags once the discrepancies are fixed (or written off). I don't think anyone would ever try to override the manufacturer of a prop however. :p

Still, I don't trust manufacturers to always have our best interest in mind. They have to worry about liability, and they have to sell their parts. These are two huge motivations to scrap parts.

Hell, it's even becoming astronomically expensive just to have maintenance manuals on parts because they figured out they can make bank on them, or sell their own maintenance.
 
Lycoming, piper, and cessna want you to buy their manuals. If you want to be a repair station, you have to have the latest, and it sucks because it's tens of thousands just for a couple manufacturers' lineups.

I don't have any continentals that I work on.
 
Tom-D said:
Not true, they can not destroy your property.
They will red tag it and record the S/N.

and they will make entries in your prop log as to the maintenance completed.
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They took a chisel to the threads in my hubs before they sent them back.
 
OP, which of the advantages of a 3-blade is it that you desire? It it because they make you go slower, because they're heavier, or because it's more expensive ?
 
Tom-D said:
Not true, they can not destroy your property.
.
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You've obviously not dealt with Hartzell. When Hartzell determines a blade is not airworthy they deface them by stamping unserviceable into the metal. Perhaps they didn't destroy it, but if is effectively so when they get done.
 
Henning said:
No, they don't grind on them, they grind them up as in condemn them, as in you don't get them back in a usable condition.
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The overhaul process requires the props to be ground to relieve the stress. If there's not sufficient metal there (or Hartzell determines that the blades are otherwise unserviceable or profits are down that month), they "deface" the blades so they can't be reinstalled.

Hartzell won't IRAN or otherwise inspect (i.e. perform the eddy current/magnaflux AD inspection) on any prop that they determine needs an overhaul (that is, beyond the TBO time limits). Other prop shops have different rules.

Never send a prop to Hartzell.
 
Mine's a Mac. Overhaul includes profiling the blades and rebalancing. The big issue with my props is corrosion. CS hubs a susceptible to internal corrosion and Mac hubs, not being painted, are also vulnerable to external corrosion.
 
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