@AdamFrisch, wow, really a badass airplane :)
As I remember with fixed pitch metal props that have suffered a prop strike, you have to remove material from the tips until the angle of the remaining bent blade is below some number of degrees (maybe 10 degrees?) Then the remaining blade can be straightened and if when finished the diameter complies with the aircraft TCDS, its legally good to go. Beware of this when buying used fixed pitch props because you never know what dark and evil history they may have.
The methods used by prop shops do appear a bit medieval. Its similar to truing up a built up crankshaft in that regard. I imagine its best to keep the customer away while his precision equipment is being made more precise!
It’s not all bad news from Hartzell. The composite bladed propellers on the King Air 250 are 65 pounds lighter per set than the metal blades, and are a major contributor to the 18% reduction in TOD required. The blades are quieter and have an unlimited fatigue life.
I think developments in propeller technology has a lot of potential to improve the performance even at SEP level.
Good story, eal! Though perhaps some people will have stressed stomachs, at least, after reading it.
I recently came to appreciate my Hartzell metal prop, and it’s very generous tolerances.
I had a “minor” by P&W definition prop strike due to a lazy runway inspection at the grass airfield on my part…. the one day I was lax, was the day it bit me, but the end result was that three blades had tip damage, one in particular had a nasty dent at the end.
Bearing in mind the prop was about 9 hours out of overhaul, and as the tears began welling up on my part, to my layman’s eyes, the damage looked considerable.
Lady luck smiled on me, when after several frantic emails and photos to the overhaul shop I discovered that the owner, the very man who had just finished overhauling the prop in Australia was on holiday in Phuket round the corner at a resort not far from the airfield.
I managed to coerce him to come have a look, (amazing incentive a cold beer can have on an Ozzie).
He took one look at the damage, grunted, declared it a non event, grabbed a nearby lump hammer, and beat the crap out of the blades, whilst I held a bucking bar cringing at every blow.
After some additional filling, the end result is perfect, the only visible damage left was to my nerves, you would never know the prop had hit anything, and I have recently repainted over the bare metal so the whole episode, other than religious runway inspections, is thankfully fading into the past.
Over another cold beer, the prop guy told me they can work the metal out to some pretty large tolerances, and often do. He said they only scrap blades in extreme circumstances, and that in a commercial operation my level of damage would be defferred until the next overhaul, dent and all.
I am not sure a compostite propeller would have fared as well in this situation.
Cheers. E
I don’t know what the implications are in the US and for N-Reg airplanes. What I was told is, that Hartzell no longer RECOMMEND but MANDATE the calendar limit. The change in wording in the service letter has obviously led to it becoming obligatory here.
Its a cultural disconnect. The word ‘mandatory’ when written in a Service Bulletin means nothing in the US, particularly for private operations, except that the manufacturer wants you to do it. It is not a legal mandate under FAA rules, because in the US it is clearly understood by all parties that a manufacturer cannot write law. Manufacturers use the word ‘mandatory’ anyway as a defense against law suits etc. I suspect that in Germanic culture that may be an unfamiliar situation, but in the US it is not customary in business to acquiesce to self-proclaimed authority with no legal basis. That’s true even when the self-proclaimed authority uses the word ‘mandatory’.
I have run into this before, in reverse. A friend of mine is a US tech rep for a French aerospace company. He’s also (as tech reps are apt to be) a bit of a character with a long term GA background, university education, A&P IA, multi-engined IR commercial flight instructor and so on. He seems to enjoy explaining this situation to the French guys when they’ve told him that something on some aircraft is ‘mandatory’ and the response back from the very experienced customer/operator is “tell them to pound sand” Link. The French get the same response when they try to ‘audit’ the US customer’s maintenance records – which the customer considers proprietary data. An amusing situation, and my friends job is to help the French company make money on service without totally pissing off customers who know their business very well 
For example a prop shop is clearly not allowed to hack the last 100mm off the end of each blade ( following a prop strike) and decide using their own A&P authority that that is OK….
The minimum diameter is typically in the type certificate data sheet.
check with your maintenance organisation
I did, also around 2013 timeframe. If your maintenance organisation told you this, I’d seriously start asking questions there.
If this goes any further I will start a Hartzell thread
If this is not an AD it is not binding on a Part 91 N-reg.
What happens in Europe is a separate thing. The CAAs can do what they like and the prop shops can do what they like. For example I am very familiar with a fairly big maintenance company which does turboprops and they absolutely refuse to implement Part 91. They always do the full MM, cover to cover (and unlike many they do actually do it all) and their reason is that they are in business to make money.
What I have come across, on my 3B prop, is that if two or more blades have to be removed for repair, the hub has to be scrapped. That is in the MM which I guess is FAA approved. NDT of the hub is not good enough. It costs £2.5k (10 years ago, so more now). I don’t know whether a maintenance shop has discretion on this. I know a guy in the US who runs a forum for a certain aircraft type and he says the CMM (component maintenance manual) has to be followed, with no exceptions. I do know he makes up a lot these interpretations but there may be some truth in it. For example a prop shop is clearly not allowed to hack the last 100mm off the end of each blade ( following a prop strike) and decide using their own A&P authority that that is OK….
Silvaire,
With the explanation that there was no FAA or other government AD, the details of what the prop shop and Hartzell wanted to do after they received the prop appear irrelevant in relation to the original quote from Mooney Driver. Hartzell has no legal authority over private property, so they can’t validate or invalidate operation of anything.
I don’t know what the implications are in the US and for N-Reg airplanes. What I was told is, that Hartzell no longer RECOMMEND but MANDATE the calendar limit. The change in wording in the service letter has obviously led to it becoming obligatory here. The person I talked to from MT told me that this service letter and it’s implications have caused quite a frustration and anger not only in Europe but elsewhere as well. Whether in the US, like Adam said, Hartzell now uses other strategies to pull this one through or whether it is simply ignored there, I don’t know. According to the specialists here, the instruction leaves no room for interpretation whatsoever. So the question would be, what would the legal implications be, if a thus overtime prop would fail in the US and cause damage of any kind. Would your insurance cover claim you violated an instruction by the manufacturer which makes you grossly negligent? I also don’t know if Hartzell seeks to turn this into an official AD in the US, as they have done with the hubs Adam mentions. I have one of those affected and the check costs about 300$ each year.
Urs, welcome to a European reg.
