Prop "TBO" - Opinions?

denverpilot

denverpilot

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DenverPilot
Ahh what the heck... Let's start the debate...

Prop times and calendar dates...

(In my case, 2400 hours or 72 calendar months whichever comes first.)

Since most of us never get anywhere close to the hour limits before the calendar dates roll by...

Thoughts on the calendar dates?

Realistic? Silly?

Alternatives?

Things to watch for if you choose to go over them?

Inspections to pay for if going beyond the date?

Cost/Benefit analysis on options?

Interested in your thoughts.
 
I agree to the 'silly' part...

If it is a fixed pitched metal prop, passing annuals every year, does not exibit dings and is kept painted and there is no sign of corrosion then why 72 months ?????? I mean, a plane could sit in a hangar for 30 years and what does the FAA think... The aluminum in the prop is gonna degrade???:dunno::dunno::dunno:

Ben.

Edit............. In hindsite,, seeing how this is Nate asking the question and he owns a 182 then it is a constant speed prop,, not a fixed pitch one so... Disregard my earlier comments and IRAN the prop.....

Ben.
 
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We had a constant-speed prop that needed repacked bearings close to 'calendar' rebuild time even though it wasn't anywhere near 'hour' rebuild time.
 
denverpilot said:
Ahh what the heck... Let's start the debate...

Prop times and calendar dates...

(In my case, 2400 hours or 72 calendar months whichever comes first.)

Since most of us never get anywhere close to the hour limits before the calendar dates roll by...

Thoughts on the calendar dates?

Realistic? Silly?

Alternatives?

Things to watch for if you choose to go over them?

Inspections to pay for if going beyond the date?

Cost/Benefit analysis on options?

Interested in your thoughts.
Click to expand...


What kind of prop?

Is there really a calendar TBO for the fixed-pitch prop commonly found on warriors and 172's?

btw - back in 2002 when I did an extensive overhaul of my cherokee, we pulled the prop to have it inspected and re-pitched. Turns out the prop serial number didn't match the serial number in logs. I wonder how many other old aircraft have discrepancies in actual serial numbers and the logs.
 
I'm no mechanic, but my guy has my props "resealed" vs overhauled. From what I understand overhauling means the cut the blades, regardless of their condition and resealing is a teardown, inspection and replace or repair as necessary. I had my 421 props resealed this spring, one was leaking, figured the other one would sooner or later, I think it was $2-3K each, not cheap but less than an overhaul.;)
Back to your question, I wouldn't overhaul strictly on a calendar basis, but for a constant speed prop it isn't a bad idea to get it resealed every 5-10 years.;)
I did have a shop refuse to sign off an annual on our 182 unless I had the prop overhauled, it was barely 15 years old, with only 400 hours on it.;)
 
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N747JB said:
I'm no mechanic, but my guy has my props "resealed" vs overhauled. From what I understand overhauling means the cut the blades, regardless of their condition and resealing is a teardown, inspection and replace or repair as necessary. I had my 421 props resealed this spring, one was leaking, figured the other one would sooner or later, I think it was $2-3K each, not cheap but less than an overhaul.;)
Back to your question, I wouldn't overhaul strictly on a calendar basis, but for a constant speed prop it isn't a bad idea to get it resealed every 5-10 years.;)
I did have a shop refuse to sign off an annual on our 182 unless I had the prop overhauled, it was barely 15 years old, with only 400 hours on it.;)
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The overhaul on my prop zero timed it. New log book so essentially new prop. Yup, they can only be overhauled once or twice so the reseal does allow the prop to stay in service longer from a practical point of view. I don't know if they still make new blades for my prop so next time (300 more hours) may require replacement. With only one engine, I figure a conservative approach to engine and prop maintenance is a good thing.

On another note, dynamic balance followed the prop overhaul. The aircraft has been smooth ever since. Before the overhaul and balance the engine could only be run at a few specific rpm settings or the vibration was terrible.
 
Disassemble, clean, inspect and repair as required to continue in service.
 
For those that asked...

McCauley 2-bladed constant speed. Bog-standard Cessna 182 type.

Questions for the group:

When they start to leak, what and where do you usually see that? Not sure if I've seen that.

I also *assume* that if you're doing engine oil analysis that if you've got something severely wrong in the hub, you might get warning of that via metal in the oil, or would the forces involved mean it comes apart badly long before that? Just curious.

Any screens there or something that would attempt to keep that out of the engine, just as an afterthought question. I think not, but don't know.

Just learning a little Prop Maintenance 101 here.

Not something you usually get trained on during PP-ASEL bookwork, ya know? ;)

(There's a lot of stuff like that, actually. The CPA systems course fills in a lot of holes... Highly recommend it as a "primer" on MX issues. It's not worth much for pilot technique however. I always joke they're really the Cessna Mechanics Assn. Nothing wrong with that... Mechanics run the place. The "Legacy" 182 course was well-worth the price.)

We're coming due on the calendar months with around 400 hours on it. It was overhauled to zero time by Rocky Mountain Propeller roughly six years ago. (Prior to us owning the aircraft.)

Right now it has some roughness on the leading edge (yeah, I've read the FAA guidance for A&Ps on how they dress them, remove dings, etc... fascinating stuff actually, the distances from a major ding that has to be removed and shaped and the forces involved), and it was repainted and dressed at last year's Annual. We fly off of grass/dirt a few times a year so once in a while it gets tiny pits.

I flew in some rain this summer and I'm pretty sure that's what took the leading edge paint off it again. Cleans the airplane itself up pretty well, but trashes the paint on the prop. ;)

Much of the reading I've done indicates that some of the reason for the calendar month limitation is to check for corrosion. We don't see much in the way of corrosion here on anything really, too dry. There's plenty of well maintained 1970s cars running around here as collector's items that have never had any major body panels replaced or bondo'd or anything like that.

Our government decided to start putting magnesium chloride on roads in winter some time ago (apparently they get the stuff from Utah) and it's good at eating otherwise fine vehicles and sticks to everything bad, but not used at airports. Stuff is awful to get off a car.

Our rubber and plastic parts suffer in the dry air though... especially mixed with the higher UV sun here at altitude if the bird is outdoors... Trade-offs... ;) We're hangared so those UV rays haven't done much destruction.

Any other thoughts on constant speed props appreciated.
 
For us, we started noticing a somewhat heavy film on the windscreen after longer flights. We followed the trail along the cowl and discovered it was coming from the prop. Talked to an MT guy at OSH one year and he said it was probably just over-greased to begin with and it's probably not a big deal. Well, it kept happening until eventually the blades would sometimes 'stick' at cruise 'pitch' when descending to land. Called the MT guys up and they asked how old it was. We told them and they said "Send it to us for overhaul." We said "But we only have a couple hundred hours on it." They said "Doesn't matter, it's at the calendar rebuild and we need to repack with fresh grease."

Sent it off to them and they repainted the blades, repacked with fresh grease, and sent it back to us. Been good ever since.
 
denverpilot said:
When they start to leak, what and where do you usually see that? Not sure if I've seen that.
Click to expand...
I've seen it as a pink fluid all over the windshield. This happened a long time ago so I don't remember the details but I know the prop oil was dyed red so you could tell when the hub started to leak. This one started to leak all at once so we returned to the airport ASAP.
 
Part of it depends on your plans with the plane/prop.

If you are happy with your propeller and don't intend on doing an upgrade for whatever reason (example: the 310 has props that are required for the 550 conversion, which were done when the old ones needed replacement), then it probably makes sense to have it inspected at the year mark. Propellers seem to be more sensitive to this than engines, and I have been told by propeller overhaul shops they can tell when a prop is past its calendar time. They also might just be looking for more sales.

Personally, I'd run the prop out if it's not giving you any signs of problems and then look at an upgrade if it's the stock prop. Most of the originals have some STCs that provide improvements as far as appearance, ADs, noise, etc. are concerned.
 
CJones said:
For us, we started noticing a somewhat heavy film on the windscreen after longer flights. We followed the trail along the cowl and discovered it was coming from the prop. Talked to an MT guy at OSH one year and he said it was probably just over-greased to begin with and it's probably not a big deal. Well, it kept happening until eventually the blades would sometimes 'stick' at cruise 'pitch' when descending to land. Called the MT guys up and they asked how old it was. We told them and they said "Send it to us for overhaul." We said "But we only have a couple hundred hours on it." They said "Doesn't matter, it's at the calendar rebuild and we need to repack with fresh grease."

Sent it off to them and they repainted the blades, repacked with fresh grease, and sent it back to us. Been good ever since.
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When the grease gets old, it breaks down and is more viscous. This is a good sign to have the prop resealed with new grease, as the old grease is no longer performing its function. Often a prop will go ten years without needing a reseal, but if you notice the grease leaking out in a very fine spray, the prop is talking to you that it is time to have the reseal.
 
Everskyward said:
I've seen it as a pink fluid all over the windshield. This happened a long time ago so I don't remember the details but I know the prop oil was dyed red so you could tell when the hub started to leak. This one started to leak all at once so we returned to the airport ASAP.
Click to expand...

The reason that the prop hub was filled with red dye was to make a mess that the pilot would not ignore and have the prop looked at. Originally, the prop hub was not filled with oil. The retention system for the blades consisted of a threaded blade and matching hub. If the retention system corroded or had a crack, it was possible to result in slinging a blade, not a good thing. By filling the hub with oil that has a red dye in it, if there was a crack in the threads, the oil would leak out and make a horrible mess. This intended to get the pilot to have the prop checked before it failed. It had one unintended good consequence, since there was oil in the hub, it inhibited corrosion in the hub and they tend to last longer as a result.
 
I think the prop overhaul date limit is very conservative. I have ignored it and gone to ten years before I perform prophylactic maintenance on the prop and even then I have a reseal performed rather than an overhaul as it is half the cost and if the prop needs an overhaul, the shop will notify me anyway. If grease starts to seep out, I will have a reseal done anyway. It is not uncommon for props not to get any attention between engine overhauls, but I personally would not go past 10 years without some attention.
 
On condition for me, but I'm tempted to do it with my engine.


FWIW McCaulley has an instruction for dealing with oil leaks. It involves deep cycling the prop to seat the seals at the blades. Works well.
 
Skylane81E said:
FWIW McCaulley has an instruction for dealing with oil leaks. It involves deep cycling the prop to seat the seals at the blades. Works well.
Click to expand...

That's kinda interesting... got an online link, or just a paper doc?
 
John Collins said:
The reason that the prop hub was filled with red dye was to make a mess that the pilot would not ignore and have the prop looked at.
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I guess it works because it also makes it difficult to see out the windshield. :rofl:
 
This has turned out to be a highly informative thread. Thanks everyone.

How much grease is typically packed in the bearings in a hub? I have never seen one disassembled.

Is it just a bit, or does it take a tub of the stuff?
 
The McCauley fixed-pitch props on 172s is a six-year/2000 hour overhaul item. In Canada the government wants that adhered to for commercial airplanes but will permit a five-year corrosion inspection on private airplanes. Corrosion can happen easily; the aluminum propeller is bolted to a steel crankshaft flange with steel bolts, and any moisture will cause galvanic corrosion. Corrosion can result in failure if it's bad enough.

Constant-speed props suffer corrosion INSIDE the propeller. They are actuated by engine oil, and a cold engine gets water vapor insides its crankcase as a result of combustion gas blowby. That water mixes with the oil and gets into the propeller hub. If the prop isn't cycled much, that oil/water mix stays in the hub and forms acids that eat the metal bits inside the hub. The 182's McCauley prop is also a six-year/2000 hour item, and the Canadian government allows a ten-year corrosion inspection for private aircraft.

Look for oil or grease leakage at the blade roots where they rotate in the hub, and at the propeller/crank flange interface. The latter can be hard to see; might have to feel for oil or sludge with your fingers in behind the prop.

Dan
 
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When I bought my plane, there was no record of a prop OH in 30 years, so I pulled my prop at the first annual after purchase and took it to Byam at FTW (I lived five miles away). I asked for an IRAN (Inspect, repair as necessary).

They said the innards looked great, resealed and repainted the blades.

I plan on doing this about every five years or so.
 
In the FWIW category, Hartzell has added TBO as mandatory gor certain props. Hours of use or calendar time, whichever comes first.

via Tapatalk
 
wsuffa said:
In the FWIW category, Hartzell has added TBO as mandatory gor certain props. Hours of use or calendar time, whichever comes first.

via Tapatalk
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The mandatory requirement issued by a manufacturer is not binding on a part 91 operator unless it is part of a AD or it is included in the type certificate limitations section and that requires FAA prior approval. This is well established law.
 
True, there are some hartzell props that do require AD inspections at impracticly frequent intervals. They are the exception and not the rule however.
 
Prop shops are getting even more scarce, and the liability risks of a request for an iran go up. It might be a better business decision for the mnufacturer to red tag a hub or blades or make the price of replacement close to the cost of repairs, which would decrease their liability risk. This is especially true if the prop is sent to the factory.

Plus, there is the cost of freight, although some prop shops will pick up and deliver.

But, even with low hours but many years, it might be worth having the prop disassembled and inspected, even if it appeared to be working well.
 
Skylane81E said:
True, there are some hartzell props that do require AD inspections at impracticly frequent intervals. They are the exception and not the rule however.
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I think that Hartzell has certain propellers that they don't like for various reasons, probably especially older models that have been out for long times and, over 50 years or so, may have shown to have some problems.

As the GA fleet continues to age, it wouldn't surprise me if this trend continues.
 
John Collins said:
The mandatory requirement issued by a manufacturer is not binding on a part 91 operator unless it is part of a AD or it is included in the type certificate limitations section and that requires FAA prior approval. This is well established law.
Click to expand...

For the props I am thinking of, the requirement is included in the TC limitations section. The appropriate FAA certification office confirms the requirement.

via Tapatalk
 
McCauley's have the red dye in them, and as another already mentioned, if you see red, the thing needs work. I don't think anybody else is doing the dye, but I could be wrong.

Hartzells are supposed to be lubed at 100/hr annuals I think. I don't remember the actual frequency off the top of my head. Purge lube, pull the fitting on the other side of the blade where grease goes in, fresh grease in until new is coming out. McCauleys are sealed. Prop shop does all the work.
 
When the seals started leaking on my Hartzell 2-blade, I noticed a streak of thick grease on the back side of the prop and had it resealed instead of an overhaul. If I had vibration issues or any operational problems, I might have considered the overhaul.
 
Since you asked for opinions...

For no good reason, I live in fear of chucking a blade out of a prop while I am flying somewhere. I often study the blue knob and calculate the milliseconds' response required to respond to a chucked blade and prevent the remaining prop pieces jerking my engine out of its mounts and sending me ass-first into an NTSB report.

I'm a riot at parties and pre-flight briefings. :D

I always IRAN any CS prop immediately upon acquisition. I have found some odd things over the years like this (phenolic blocks worn to within mm of failure, incorrect blade shank retaining hardware, hub cracks) -- and I have no idea if they would've failed spectacularly, but I fly a little easier with a known set of eyes having been on the inside of that whirlimajig. :)

I have no such superstitions about FP props.

I personally think Hartzell AD issuances are as much a business development decision as a safety one, and I find the company irksome.

$0.02

- Mike
 
Appreciate all the thoughts from everyone.

As far as chucking a whole blade goes, there's a photo floating around somewhere where the engine of a very low horsepower aircraft was spinning around inside the cowl. It lost a tip.

It won't matter your reaction time pulling anything, and the prop control won't be the right one to pull. It'd be the mixture.

Lose a small but significant chunk of mass rotating at that speed and you're going to have engine mount and likely engine damage, and if you didn't, it would be a miracle.

Lose the whole blade and you're definitely going to have significant damage.

Hopefully that makes you feel better about it. No need to be on pins and needles over it.

It'll be so catastrophic you won't have any time to make any significant decisions about it other than when to kill the fuel to the whirling dervish under the cowl. ;)

Look up the videos of the racers losing props at Reno. Less than one second from chucking the prop, the engine blows. Yeah, they're monster engines but, same idea on smaller ones.
 
Yup. It is the blue knob that reminds me of the giant "jesus nut" out there, not that I study it with intent to pull it. I had always planned on pulling throttle, though.. but as you point out, there is no time to pull anything. I think I figured at one point that I'd have 40ms to respond to that particular failure mode. Maybe that's why I'm so fascinated with it.

I don't get to choose my irrational fears, unfortunately. Given all of the stupid things I do and have done with airplanes, this one is infinitesimal in the "probability of killing Mikes" list. "Mike" is still the overwhelming favorite. :D
 
schmookeeg said:
For no good reason, I live in fear of chucking a blade out of a prop while I am flying somewhere. I often study the blue knob and calculate the milliseconds' response required to respond to a chucked blade and prevent the remaining prop pieces jerking my engine out of its mounts and sending me ass-first into an NTSB report.
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You can't. If you actually do chuck a blade on an aluminum prop, you will be lucky if all the engine does is come dislodged from its mounts. If you're unlucky, you'll be minus an engine and prop, and you're dead. Worst part there is it won't be instantaneous.

If you chuck just a piece of prop at the end, that's another matter. But even then you have to diagnose the problem and try to shut off the correct engine (if you have two). If you have one, then you have to slow the plane down enough to allow the prop to stop spinning.

FWIW, I've been happy with Hartzell as a company in my dealings with them, both for personal aircraft and professional purposes. What I'd also point out is that it only takes one lawsuit to make a company very wary of whatever product or line caused the lawsuit.
 
One of our Fairchild club lost a complete blade from a Beach Roby prop, and flew the aircraft to a safe landing.

That old Ranger was a shaking, but it stayed in its mountings.
 
Tom-D said:
One of our Fairchild club lost a complete blade from a Beach Roby prop, and flew the aircraft to a safe landing.

That old Ranger was a shaking, but it stayed in its mountings.
Click to expand...


Wooden blade, though, right? A lot lighter than an aluminum blade.

Dan
 
So, a number of people have mentioned having a prop "sealed" or "re-sealed" as needed.

I'm clueless about that process, so fill me in... Is it disassembled for this "sealing" or is it somehow done externally?

In other words, can any inspecting be done or is there nothing visible?
 
N747JB said:
I did have a shop refuse to sign off an annual on our 182 unless I had the prop overhauled, it was barely 15 years old, with only 400 hours on it.;)
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Getting the prop overhauled is the owner's choice unless an AD requires it. Signing off the annual is not a shop or IA choice if they performed the annual. They are required by regulation to sign off the annual. However, they may sign off the annual as unairworthy with a written list of discrepancies provided to the owner. If the only discrepancy that they list is that the prop not being overhauled and is over TBO by date, all you have to do is to get an A&P sign the logbooks indicating the aircraft is airworthy and returned to service with all discrepancies have been corrected as required. The discrepancy list doesn't go into the logbook and doesn't need to be kept after it has been dealt with. Even if the IA put an entry in the logbook stating that the prop was past TBO and therefore the aircraft was unairworthy, an A&P could put a following logbook entry that stated something such as Prop past TBO, overhaul not required for part 91 operator, aircraft returned to service.
 
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