Our Light Aircraft Association, who handle the certification of nearly all homebuilts and non-EASA types in the UK have recently published a new procedure for the continued airworthiness of Hartzell and MT propellers which don’t get to the hours limitation before the manufacturers’ recommended calender time periods for overhaul.
This is an inspired bit of cost-saving airworthiness engineering and is well worth reading at www.lightaircraftassociation.co.uk/engineering/Airworthiness%20Alerts/LPIP%20Basics.pdf
“Until recently the only approach to maintaining a constant speed or variable pitch propeller involved a complete overhaul, irrespective of the number of hours flown”
LAA is apparently in denial about how most aircraft propellers have been maintained for decades. Propellers being maintained on condition is the standard practice on FAA Part 91 aircraft, with no special program or name. My MT prop was built in 1999, lightly used but overhauled anyway while chasing a problem in 2013. There was nothing wrong with it at that time, and based on that experience there is no chance it’ll be overhauled again any time soon. I’d guess another 10-15 years from now or perhaps a little more. Mine is stored carefully, corrosion is not likely in my service and MT has now got their seals working.
“So far, most propellers surveyed have required little more than a re-seal, re-grease, adjustment and re-assembly, though some have required a major rework before they can be safely released back for service; in these cases a full manufacturer’s overhaul may be required”
For propellers operating under Part 91, this is most often the approach taken by owners and their FAA repair stations. Overhaul adds cost and given the frequent overhaul manual requirement for blade work that can only be done so many times, it often subtracts long term value.
Mine didn’t require any of that in actuality, it needed nothing. MT did update the seals while they had it… which required an overhaul paperwork process (and bill) to be legal since the seal update was covered by their repair station overhaul procedure.
Indeed; the FAA scene is way bigger than probably the rest of the world’s GA and it works ok there. The UK’s 6 year overhaul regime (£4000 for mine, if I was G-reg) is just a pointless industry support measure. I have done mine at 8 years most recently, but to take out the nicks in the blades.
I love the LAA but some things they do irk me a bit: the insistence of CS prop overhauls one of them. They don’t have to try and re-invent the wheel, nor are they going into some uncharted territory – they merely have to look west and see how CS props do on FAA part 91 for evidence. I don’t understand why they don’t just do that.
I’ve just been reading up on this as I have a couple of years left on my McCauley. I’ve been quoted £800 for an LPIP, but no idea if this is reasonable or not. A couple more articles from the LAA: safety_spot_may_2020 & safety_spot_oct_2018
Is there damage on the prop?
It’s no better for fixed pitch props Less than 4 years since new, 2000 hours all operated off grass. Yet it needs an overhaul.
Now I know nothing about engineering but it looked in pretty good nick to me. Far better than a prop that’s done half as many hours off tarmac.
And then what annoyed me most was 50 hours after ithe overhauled prop was refitted the back plate was found to be cracked. Which is 800 quid for a 5 dollar piece of metal.
I wonder if that would of happened if the prop hadn’t been removed?
I think all this prop overhauling is destructive rather than constructive maintenance. It’s expensive too.
Peter wrote:
Is there damage on the prop?
A couple of nicks on one blade, but I think they could be dressed out easily
I use them too. Good company.
