Time Expired Prop?

[BertP]

Hello,

I bought a homebuilt aircraft whose propeller (2 blade McCauley C/S) is damaged. I got a line recently on an equivalent 3 blade (also McCauley) that is in good shape but is time expired - which is why it was removed from its 206 and replaced. My question is: Is it a good idea to buy this prop for my aircraft and just install it in my aircraft or is it imperative that I get it overhauled first? It only has 600 hours on it since its last overhaul but it is 10 years old, which is the expiry point for it.

Thanks

Bert

[Marc Zeitlin]

I bought a homebuilt aircraft whose propeller (2 blade McCauley C/S) is damaged. I got a line recently on an equivalent 3 blade (also McCauley) that is in good shape but is time expired - which is why it was removed from its 206 and replaced. My question is: Is it a good idea to buy this prop for my aircraft and just install it in my aircraft or is it imperative that I get it overhauled first? It only has 600 hours on it since its last overhaul but it is 10 years old, which is the expiry point for it.What do you think McCauley would say if you asked them, and why would they say it?

[BertP]

What do you think McCauley would say if you asked them, and why would they say it?

Probably the same thing Lycoming or Continental would say about running one of their engines past TBO.

Bert

[Marc Zeitlin]

Probably the same thing Lycoming or Continental would say about running one of their engines past TBO.Maybe. But it would be good to know WHY there's a time limit as well as an hour limit. There are things in a C/S propeller that (especially if not used much) that can deteriorate with time (O-rings, etc.). Failures of these things might be relatively benign, or they might not. At least you should know what the consequences of ignoring the lifetime limit would be. Maybe you can just run the thing until it slowly starts to not work - maybe not... I'd at least ask McCauley so that you can make an informed decision one way or the other.

[BertP]

Maybe. But it would be good to know WHY there's a time limit as well as an hour limit. There are things in a C/S propeller that (especially if not used much) that can deteriorate with time (O-rings, etc.). Failures of these things might be relatively benign, or they might not. At least you should know what the consequences of ignoring the lifetime limit would be. Maybe you can just run the thing until it slowly starts to not work - maybe not... I'd at least ask McCauley so that you can make an informed decision one way or the other.

Hence my question. If I didn't think that there is an issue with it, I would have just bolted it to my aircraft and gone flying. Since I recognize the limit of my knowledge in this area, I decided to post the question to see if someone more learned than I on this topic could shed some light on what is and what is not a good idea and why.

Bert

[martymayes]

What do you think McCauley would say if you asked them, and why would they say it?

They would say "yes" to o'haul because we don't want to get sued "if" something happens. I mean the prop company is not going to publish recommended TBO then say it's okay to exceed that interval.

What did we ever do before manufacturers started including calendar times in recommending o'haul intervals? For that matter, how many components in 91 ops exceed the recommended TIS before overhaul? Lots?

Finally, what's to prevent someone from inspecting and repairing as necessary without complying with o'haul requirements? So you have new o-rings, etc, but no o'haul log entry....

Marty (playing devil advocate for the day)

[FlyingRon]

Which prop? Note there are some Mac props that have hard life limits at a certain time (or at any time if you can't compute time in service). An overhaul doesn't reset this clock.

[BertP]

They would say "yes" to o'haul because we don't want to get sued "if" something happens. I mean the prop company is not going to publish recommended TBO then say it's okay to exceed that interval.

What did we ever do before manufacturers started including calendar times in recommending o'haul intervals? For that matter, how many components in 91 ops exceed the recommended TIS before overhaul? Lots?

Finally, what's to prevent someone from inspecting and repairing as necessary without complying with o'haul requirements? So you have new o-rings, etc, but no o'haul log entry....

Marty (playing devil advocate for the day)

Good points, Marty. That's the kind of thing I was looking for. I would even go further and ask if *I* can overhaul a prop. Since this is an amateur built aircraft, technically, I can do anything I want to it. But, is it a good idea? Do I, an average shade tree mechanic, have the skillset and/or tools to safely overhaul a CS prop? Where would I get an overhaul kit?

Bert

[BertP]

Which prop? Note there are some Mac props that have hard life limits at a certain time (or at any time if you can't compute time in service). An overhaul doesn't reset this clock.

It's a D3A32C90-MN 3 blade C/S prop off a Cessna 206. It has about 600 hours since last overhaul but that overhaul was done 10 years ago so it is timed out. Not sure about TTSN.

Bert

[cub builder]

Good points, Marty. That's the kind of thing I was looking for. I would even go further and ask if *I* can overhaul a prop. Since this is an amateur built aircraft, technically, I can do anything I want to it. But, is it a good idea? Do I, an average shade tree mechanic, have the skillset and/or tools to safely overhaul a CS prop? Where would I get an overhaul kit?

Bert

McCauley is going to tell you the prop is not airworthy and that's the end of their conversation. Legalities come first with the manufacturer. I know if I had it here, I would stop in at my favorite propeller shop and have a chat with the owner of the shop. We have a good relationship and he would give me the straight dope on whether this is critical or not; and why. If he recommended a tear down inspection, I'd leave it with him to do it. But then, I also trust him to be straight with me about the need and not rape me on the service. If I were you, I'd go visit your closest prop shop and have a chat with them about why McCauley set a calendar time limit, then you can make a rational decision about whether or not you choose to comply. Until you can educate yourself, you should consider it to be non-airworthy until proven otherwise. Often times calendar time limits are set due to the potential for corrosion to initiate a stress riser at a critical place in the prop hub. So they recommend a tear down inspection on calendar time so any corrosion can be addressed, or the hub junked.

-Cub Builder

[WLIU]

If the 206 was used for Part 135 then they had to overhaul or replace it. Part 135 is different than Part 91. But the props do not magically start to disintegrate at 10 years or 11 years or whenever. If its not leaking oil you should get a bunch more hours out of it. The concern with age is corrosion. If the prop has 600 hours on it in 10 years, it was flying more each year than most of the posters here.

More importantly, the 3 blade prop is heavier than the 2 blade that came off your ship. What does the weight and balance calculation say about adding another 20lbs out on the pointy end of the airplane?

Best of luck,

Wes
N78PS

[BertP]

If the 206 was used for Part 135 then they had to overhaul or replace it. Part 135 is different than Part 91. But the props do not magically start to disintegrate at 10 years or 11 years or whenever. If its not leaking oil you should get a bunch more hours out of it. The concern with age is corrosion. If the prop has 600 hours on it in 10 years, it was flying more each year than most of the posters here.

More importantly, the 3 blade prop is heavier than the 2 blade that came off your ship. What does the weight and balance calculation say about adding another 20lbs out on the pointy end of the airplane?

Best of luck,

Wes
N78PS

Thanks, Wes.

And, you're right: A new W&B will have to be done if I go this route.

Bert

[Spezioman]

I suspect they put a conservative life limit on seals. Bendix does the same thing on fuel pumps, pressure carbs, and servos(20 years). I'm coming up on 20 on both my pump and servo and since both continue to work so well I would like to think:

If they say 20 years, maybe the "real" life is 40? and/or

If it's not broke, don't fix it.

But what if a seal does fail? How serious is it? I don't know?

Expert advice like from a trusted a prop shop as suggested would be nice. Same on my fuel system.

Engine failure is serious if my servo fails. I have a boost pump but engine driven pump failure is still not exactly benign. A propeller seal failure belching all your engine oil in 2 minutes isn't benign either but I don't know if that is a real issue?

Jack

[Eric Brown]

AD85-08-08 may have been the reasoning for removing the propeller. It specified a 1200 hr total time limit until the hubs were to be inspected and modified per a McCauley service bulletin. For hubs that showed red dye leakage even after modification, the propeller had to be removed from service. As already recommended, I'd check with a prop shop before just bolting it on.

[WLIU]

Red oil leakage is easy to spot. They have been putting red oil in the hubs for many years. If the prop came off in 2015 or 2016 the paperwork likely shows that the SB has been done. There is a plug that you can unscrew to check for red oil if you want.

Best of luck,

Wes
N78PS