Peter wrote:
Any grease leakage, any cracks or damage (other than nicks at or near the tips – there is a specification on permitted damage), any strikes on objects even if no visible damage (bird strikes are debatable, for small birds).
Nope.
Any grease leakage, any cracks or damage (other than nicks at or near the tips – there is a specification on permitted damage), any strikes on objects even if no visible damage (bird strikes are debatable, for small birds).
Fly310 wrote:
Is there anything other than calendar time telling you that it requires maintenance?
Well, no. My A&P told me he was willing to go up to 10 years, so extending TBO of 6 years to 10 years, but no more. Prop looks very good, working exactly as it should, very well balanced, always hangared, not flown in rain and so on. But then again, I would also like to have someone (with experience) have a look inside, to be able to tell me about the condition of the parts inside. I should be able to convince my A&P that repair can be done as good as an overhaul.
So maybe I should keep looking for a shop with more reasonable pricing. It’s a 2-blade prop and looks just as simple as it can get, no de-icing or whatsover. Will contact the british shop mentioned before.
Ultranomad wrote:
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.
I guess it depends on the type (bolted hub halves vs integral hub), but I would in general discourage such task as a field job. Both FAA and EASA require a shop environment or at least an FAA RS/Prop 145, for such tasks in most cases for good reason.
Also for inspection methods I would stick to the tried and proven and approved. NDT on blades is simple in most external areas and I would not hesitate to validate HFEC on them, even if not approved in a lot of cases, but it is complex to apply in some interface areas, which are indeed the most critical ones, as you rightly point out, hence sticking to the approved CMM procedures is best.
So I’m heading for a repair (reseal and check) and not for an overhaul.
As always a judgment call based on age of propeller, but if you and your engineer think the propeller and hub are/look in good condition, this would be the practical approach.
There seems to have been a fashion to use carbon fibre backing plates on some types, these tend to cause corrosion, so would revert to the standard metal ones when you remove the prop.
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.
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.
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.
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.
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.
