A friend flew into Helgoland with a Piper Archer 3 and after turning off the engine he rolled out a little and the propellor just barely hit something. He could hear tik-tik. The propellor did not abruptly stop, but the blades where damaged a little with some splinters off so probably has to be replaced. The question is related to the shock load testing of the engine. One maintenance shop insists that the engine has to be taken out and tested. Another maintenance shop says that this is not a requirement from the engine manufacturer and that it is up to the judgement of the maintenance shop to decide. He would suggest that if if a pole in the ground just touched the blades hearing tik-tik without the propellor being powered or abruptly stopped, a shock load testing of the engine is not necessary, so suggests to replace the propellor (was due to be replaced) and to keep on flying with the engine.
Is there anyone that can be of help here as I am no expert in these matters and would like to give him a good (inofficial and off the record) advise on what to do.
Here is the Lycoming Mandatory Service Bulletin.
As I read it, the first mentioned company is right, if the propeller needs to be fixed and you follow Lycomings instructions. However, the person / organisation who releases the aircraft into service after inspection would be responsible.
[link fixed, moved to local storage]
The link doesn’t work for me.
I would say that if your friend has a self-declared AMP he can do as he pleases since this is a Service Bulletin, then he should also write it into his AMP. If not, then I would suggest that he deals with the maintenance shop that is least restrictive if he really does not want to do a shock load. But in the end, it is a matter of his own personal safety and he is the only who knows the true circumstances when the propeller hit the ground.
If it is covered by insurance I would get the tear-down done…otherwise it opens up a whole debate and raises doubt with a potential buyer when it comes time to sell…
The engine must be shock load inspected.
There is a long history on this and eg 15 years ago an engineer could countermand a SL inspection if the engine never actually stopped,
The resale value might be impacted, if the buyer is fairly savvy.
A lot of this stuff is done off the books……
The probability of something being actually broken is about 1%, assuming that the crankshaft flange has been runout checked.
Peter wrote:
The engine must be shock load inspected.
Well, it does say “recommended”, doesn’t it? The one thing that is clear from the Service Bulletin is that this does definitely classify as a Propeller Strike.
Let’s hope it gets mentioned in the books!
after turning off the engine he rolled out a little and the propellor just barely hit something
I appreciate that you’ve nothing to go on other than the pilot’s report, but the circumstances sounds little strange. The engine stopped before the aircraft stopped, but the prop continuing to run for long enough to strike something, but not stop it.
Most occasions the engine is stopped well after the aircraft comes to a stop.
Most occasions the prop stops very quickly after fuel supply is cutoff.
If power is removed from the prop, it’s not going to run for very long, so if it hits something it’s going to be hard to say if that stopped it or not.
If the inspection is only recommended, it might be a case of the engineers being somewhat suspisious of the explination and therefore taking a more cautious approach.
Well, I was not there, but you are right @dublinpilot as it sounds strange. Reading the docs that were posted I would say that the aircraft engine/shaft has to be checked.
