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Propeller overhaul (merged)

For Permit Fixed Blade metal props, an NDT check for cracks has been suggested ( not by the LAA) as an occasional safety check, instead of the Macaulay recommended overhaul.

Is that with prop removal?

You have to strip the metal to NDT it, and one “could” respray a prop in situ.

Administrator
Shoreham EGKA, United Kingdom

It takes about 15 minutes to remove a FP propeller…

Can anybody add some update on actual EASA maintenance requirements for privately owned aircraft regarding recommended or required prop overhaul?I receive quite different input on that topic.

As far as I understand there is no such requirement to overhaul a prop in the time specified from the manufacturer, in fact it seems all to be up to the owner. An A&P I’ve asked just replied why the heck I even want to dismount the prop if all is good. (for what may be seen from outside my Prop is in perfect condition)

However, the guy running the CAMO I’m in convinced me, that according to his (long-term) experience the repair bill of the props tends to get more and more costly if the prop is not redone every now and then, preventing rust and so on. So I’m heading for a repair (reseal and check) and not for an overhaul.

Now I’ve got a reasonable quote from a prop repair shop. Estimated 1.5k for a repair and close to 7k for an overhaul, € of course. As I’m not yet into it, I called another prop repair shop to get another quote to get an idea whether the quotes are good. And this guy seriously wanted to convince me that it’s totally impossible to do any repair on the prop if it is outside the recommended TBO. And that the outcome with any shop will be, in the end, that an overhaul is necessary, the only difference that he was honest about that right from the beginning. He told me that as a shop they are only allowed to do what is recommended by the manufacturer.

Said that, it sounds weird. Anything in it?

Germany

That’s completely normal unfortunately. If you ask 3 people, you get 4 anwers on how you should or must go about with props repairs/IRANS or overhauls. As with almost everything, you must use your own judgement and decide what to do.

Mainz (EDFZ) & Egelsbach (EDFE), Germany

One has to do this objectively, getting away from those who are going to make money out of it, and those who don’t actually know anything.

I think my post above is a good start.

I would send it to the shop I suggested (if you can) for an IRAN and they will advise if this is uneconomical.

Administrator
Shoreham EGKA, United Kingdom

Peter wrote:

One has to do this objectively

Yah, according to the above posting all would be fine. But then again the guy running the CAMO does not get any money if I do anything on my prop, so I tend to take his advice. And he has lots of experience. And I can understand, that after some time risk of internal damages can increase, and if you do a repair and visual inspection (no overhaul) after some time, that it may increase blade life and decrease overall cost over a certain period of time.

This is what I was heading for. So I think the “overhaul is a requirement” is Bulls**t.

Germany

Well, ideally you want to get the prop opened and inspected by an OH shop and, depending on findings, decide on OH or repair.

There are four main matters of interest in the shop inspection on a CS prop:

1- Internal corrosion
2- Seals
3-Hub/Blade cracks
4-Mechanical function and clearances

Deicers , if any, can be inspected and replaced in service.

The first two only require dissasembly , inspection and reseal . They are affected mainly by calendar.
The third one requires the closest to a full OH as it needs stripping the blades and hub..once you are there it makes sense to dress the blades, check dimensions etc and complete the full OH…Other than incidents, this is mostly affected by flying time.
The effect on the last one is combined calendar and flying time.

So if you dont fly a lot, ideally you want to do 1, 2 and 4 (IRAN) every 4-10 years depending on environment, and only decide on 3 and hence OH depending on findings. That way you extend blade life and minimze cost while remaining safe.

Unfortunately it is rare to find a shop in Europe willing to do 1, 2 and 4 : the SOP is thus full OH. Should you do it eveyr 6 years? If you fly only 100 hrs a year, it seems a bit overkill, but if your CAMO and ARC inspector and authority allow, and the environment is known (oftentimes you do not have historic details) and not too harsh, (hangared, dry) then I would do 10 years , otherwise I would stick to 6.

Even more important is to keep it balanced, protected and dry while in service, and to be exhaustive about removal when it hits hard objects other than minor allowed nicks. Blend those out soon!

IN my last prop OH, after two decades in dry climate and hangared, light corrosion was found on the blade bearing races requiring expensive replacement. Had I gone for IRAN it would have ended up being and OH anyway. Better that than finding it starts making metal or worse still…those bearings are subjected to very high stress.

Antonio
LESB, Spain

Antonio wrote:

There are four main matters of interest in the shop inspection on a CS prop:

1- Internal corrosion
2- Seals
3-Hub/Blade cracks
4-Mechanical function and clearances

On most CS props, by far the most corrosion-prone area is the hub-blade interface. Blades can usually be removed in the field, so this area can be inspected and blade seals can be replaced without visiting a specialist shop. I assisted in such an inspection, and on a 2-blade prop it took the two of us about an hour.

The third one requires the closest to a full OH as it needs stripping the blades and hub..once you are there it makes sense to dress the blades, check dimensions etc and complete the full OH…

Again, blades are usually more likely to suffer cracking than the hub, but you don’t have to strip the paint on them to check for cracks – eddy current or phased-array ultrasonic NDT are actually more sensitive than liquid penetrant testing.

LKBU (near Prague), Czech Republic

7k sounds a lot. I paid about 4.5 for a Hartzell three blade. That was including the hub AD …If the prop is running fine has no leaks and less then 12 years or so Why remove it ? You will have to rebalance… I would be weary of maintenance induced issues during an Iran…What’s the trigger to do it? Did it sit outside? Hub corrosion? ..Blade life is decreased after each overhaul.

Last Edited by Vref at 24 May 23:02
EBST

Is there anything other than calendar time telling you that it requires maintenance? If not, keep it on for a couple of more years and see what happens to the cost of overhaul once you get there. If you have 5-6 years TBO today, I would try 10-12 years and send it in after that if you wish to try your CAMOs thesis.

Obviously, if you find during an annual inspection that the propeller needs maintenance due to its actual condition, you will send it anyway.

ESSZ, Sweden
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