72 Month Prop Inspection

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ahramin
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72 Month Prop Inspection

#1 Post by ahramin » Wed Jan 11, 2017 10:51 am

In the interest of not doing maintenance for nothing, we are considering not overhauling a Hartzell 2 blade constant speed propeller on an IO-540. Prop has 400 hours on it and the aircraft has always been stored in a heated hanger. Hartzell says:

All other 2 Bladed propellers manufactured after April 1997 as defined in Note 4* - See Figure 9 2400 hours / 72 months

Hartzell also says in their Service Letter that

(3) Experience has shown that special care, such as keeping an aircraft hangared, is not sufficient to allow extension of the calendar limit.

It doesn't seem reasonable to me that a propeller in a temperature and moisture controlled environment is at the same risk as one out in the rain. I inspect my engine every annual and wouldn't consider for a second sending it out for overhaul just because it's hit a magic calendar limit, but I realize propellers are different and don't have the same level of inspection at annual. Any thoughts?
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nbinont
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Re: 72 Month Prop Inspection

#2 Post by nbinont » Wed Jan 11, 2017 11:38 am

In Canada, the legal requirement for CS Prop Overhauls is 10 years: https://www.tc.gc.ca/eng/civilaviation/ ... c-2460.htm . You're welcome to do it more often, but not required.

One of the planes I flew was hangared (not heated), flown lightly for the years before I flew it. The CS prop went 7-8 years before it developed a small oil leak prompting a repair (which probably should have been an overhaul given the couple years till the overhaul anyways).

Personally, I'd monitor the prop closely and let the clock run to 10 years.
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Re: 72 Month Prop Inspection

#3 Post by C-GKNT » Wed Jan 11, 2017 1:01 pm

Each time a prop is overhauled, they ground off a small amount of the blades. They can generally do this 2 times before the blades become undersized and must be replaced. Personally, I wouldn't do it unless there are indications that it needs to be done or Transport Canada forces you to. If it makes you feel better, I would consider having it dissembled/inspected/seals replaced (IRAN) without overhauling the blades.

Glenn
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Re: 72 Month Prop Inspection

#4 Post by crazyaviator » Wed Jan 11, 2017 6:46 pm

EXCELLENT replies above :D
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Re: 72 Month Prop Inspection

#5 Post by PilotDAR » Wed Jan 11, 2017 7:17 pm

Piston engines on privately operated certified airplanes, by specific exemption (on condition maintenance) are permitted an alternative to the manufacturer's recommended service and overhaul periods. Is there a similar Transport Canada exemption/alternative maintenance practice approved for propellers?
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Re: 72 Month Prop Inspection

#6 Post by ahramin » Wed Jan 11, 2017 7:34 pm

PilotDAR my understanding is that "On Condition" no longer applies to private aircraft and has not for decades, if ever. There is no requirement to overhaul an engine when it gets to time or calendar TBO. In this case Hartzell does have a program to extend the hours between overhaul but not calendar time.

Thanks for that link nbinont, in this case the aircraft is a homebuilt so the 10 year requirement does not apply but we've decided to do it at that point anyway.
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Re: 72 Month Prop Inspection

#7 Post by photofly » Wed Jan 11, 2017 9:20 pm

I'm not sure that the homebuilt thing gets you an automatic pass.

CAR605.86 says that nobody can conduct a takeoff in an aircraft unless it is maintained in accordance with a maintenance schedule approved by the Minister. Private aircraft have the option of using CAR625 Appendix B and C as their schedule pre-approved by the minister without further reference to TC, as long as they declare it so, typically by inscribing it in the Journey log (the maintenance schedule is a mandatory entry as detailed in 605.94(1)). Nothing stops you creating your own maintenance schedule and having it approved (the fee is $180 for a small aircraft) but i doubt it's going to be more lenient than 625/B&C.

If you're not using CAR625 Appendix B and C you need to be using something else; I don't see that the basis of certification (homebuilt) grants you exemption from 605.86.

So if you're not maintaining your homebuilt in accordance with 625, what maintenance schedule are you using, has it been approved by TC, and what does it say about propeller overhaul intervals? Those are the rules you have to follow.
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ahramin
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Re: 72 Month Prop Inspection

#8 Post by ahramin » Wed Jan 11, 2017 10:10 pm

The aircraft in question is being maintained in accordance with 625 B and C. Appendix C exempts homebuilt aircraft from the variable pitch propeller requirements.
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Re: 72 Month Prop Inspection

#9 Post by photofly » Wed Jan 11, 2017 10:59 pm

In which case your propeller is exempt from any overhaul requirement, ever, as far as I can see. You can do as you wish :)
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Re: 72 Month Prop Inspection

#10 Post by cgzro » Thu Jan 12, 2017 5:25 am

Irrespective of the required overhaul periods, when you get grease / oil on the windscreen its probably an indication to look closely at the prop/hub and crank. An aircraft can suffer a lot of failures without killing people but a prop hub failure is not usually one of them.
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Re: 72 Month Prop Inspection

#11 Post by Heliian » Thu Jan 12, 2017 7:36 am

C-GKNT wrote:Each time a prop is overhauled, they ground off a small amount of the blades. They can generally do this 2 times before the blades become undersized and must be replaced. Personally, I wouldn't do it unless there are indications that it needs to be done or Transport Canada forces you to. If it makes you feel better, I would consider having it dissembled/inspected/seals replaced (IRAN) without overhauling the blades.

Glenn
You don't scrap the blades after 2 overhauls. When a shop determines that your blades have worn beyond limits then they are replaced.

Personally, I go with the manufacturers data. Just because you hangar your aircraft doesn't mean that there will never be corrosion or other issues that you can't see.

If you're so cheap as to not have your prop maintained then you need to sell your aircraft.
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Re: 72 Month Prop Inspection

#12 Post by photofly » Thu Jan 12, 2017 9:25 am

Spoken like a true AME!
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Last edited by photofly on Thu Jan 12, 2017 9:26 am, edited 1 time in total.
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ahramin
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Re: 72 Month Prop Inspection

#13 Post by ahramin » Thu Jan 12, 2017 9:26 am

Heliian wrote:Personally, I go with the manufacturers data. Just because you hangar your aircraft doesn't mean that there will never be corrosion or other issues that you can't see.
I assume you are referring to propellers only. What type of aircraft / engine / prop do you own?
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Re: 72 Month Prop Inspection

#14 Post by ahramin » Thu Jan 12, 2017 9:33 am

photofly wrote:In which case your propeller is exempt from any overhaul requirement, ever, as far as I can see. You can do as you wish :)
Thank you, as per the original question, we know the rules and are trying to figure out what is our wish.

In the case of the engine it's an easy decision. Completely ignore the manufacturers recommended calendar and time limits and overhaul when oil analysis / filter inspection / boroscope / anything else tells us we need to. I have little experience with constant speed prop maintenance and don't have any data on what is safe other than the manufacturers recommendations and TC rules for certified aircraft. In the absence of further info, we've decided to disregard the manufacturers recommendations and follow the TC ones since I can't see any evidence of aircraft falling out of the sky by doing that.
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Re: 72 Month Prop Inspection

#15 Post by Heliian » Thu Jan 12, 2017 12:47 pm

Props are for boats.

You have a 10 year requirement to o/h your prop under the appendix. It starts either from its initial date of installation following manufacture, from its last five year corrosion inspection or its last overhaul, whichever occurred last.
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Re: 72 Month Prop Inspection

#16 Post by C-GKNT » Thu Jan 12, 2017 12:56 pm

ahramin wrote: In the case of the engine it's an easy decision. Completely ignore the manufacturers recommended calendar and time limits and overhaul when oil analysis / filter inspection / boroscope / anything else tells us we need to. I have little experience with constant speed prop maintenance and don't have any data on what is safe other than the manufacturers recommendations and TC rules for certified aircraft. In the absence of further info, we've decided to disregard the manufacturers recommendations and follow the TC ones since I can't see any evidence of aircraft falling out of the sky by doing that.
If you want more data, look to the US where part 91 (non-commercial) operators have NO requirements to overhaul propellers. The US has a LARGE fleet of aircraft flying with constant speed propellers without an overhaul in the past 10 years.

In the US, it is common to do there is what I mentioned. IRAN (Inspect and repair/replace as necessary) - disassemble and inspect for corrosion, replace seals and what is needed and reassemble but NOT overhaul the blades unless otherwise indicated. Several AME/pilots that I know think that 7-8 years is good interval to IRAN a constant speed prop, less than the 10 years mandated by Transport Canada but of course that would depend on usage, environment etc.

I haven't checked but I don't believe that there is a proportionally larger number of aircraft in the US falling out of the sky due to failed propellers that have been maintained in this manner.

Glenn
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Re: 72 Month Prop Inspection

#17 Post by C-GKNT » Thu Jan 12, 2017 1:12 pm

***Just a cursory look*** but here is some data...

https://www.ntsb.gov/_layouts/ntsb.aviation/index.aspx

A quick search of "propeller failure" in the synopsis and full narrative returns 55 hits back to 1983. A quick look at the first 10, shows the majority unrelated to the propeller at all and no accidents related to failure of a constant speed propeller that would have been prevented if the US had a mandatory 10 year overhauls. Interestingly the one blade failure in that group was on a fixed pitch C-172.

Glenn
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Re: 72 Month Prop Inspection

#18 Post by ruddersup? » Mon Mar 13, 2017 12:09 pm

Looking for help before I get turned down with a dozen phone calls.
Got a question that I hope someone can answer. Just starting to do research.
I have an amateur built aircraft on floats with a Continental 0-470 K engine (Cessna 180)/ I would like to put a McCauley D2A34C58-0. It is 86" long and is common on Cessna 185. Anyone know if this can be done? Don't need an STC because it is amateur built but would like to know if it is compatible. (one 5th order, one 6th order crank). McCauley doesn't want to give advice on amateur built aircraft.
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Re: 72 Month Prop Inspection

#19 Post by AirFrame » Tue Mar 14, 2017 6:41 am

You don't need an STC but you do need to inform TC of the change and they may or may not want to inspect the installation.
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