Yes, certainly. It just so happens that the engine is rarely stopped without prop damage. What happens a lot more often is that the blade tips hit, the engine continues to run, and often the pilot doesn’t notice until the next flight. And the prop is repaired or replaced, and then, in the past, say 2002 when I had my pothole prop strike, nothing had to be done to the engine, but nowadays one has to do a shock load inspection.
Another thing which has changed is if there is say a nose wheel collapse while stationary. In the past, a crankshaft (prop flange) runout test was considered adequate. Nowadays it is a shock load inspection too – the crankcases can be cracked, etc.
This is on a certified aircraft. On a homebuilt, especially non UK LAA, the rules aren’t the same.
huv wrote:
I was told (sorry, no reference) that anytime the engine, even if idling, is stopped by a force applied to the propeller, a shock load inspection is required. Even if the prop has no damage. It could well be an OWT.
The relevant Lycomming SB spells it out very clearly : If the prop strike results in a sudden loss of RPM OR is stopped, then a tear down inspection is considered required.
Peter wrote:
Another thing which has changed is if there is say a nose wheel collapse while stationary. In the past, a crankshaft (prop flange) runout test was considered adequate. Nowadays it is a shock load inspection too – the crankcases can be cracked, etc.
Not if the prop blade is not damaged to the extent that it needs to be replaced.
If, for example your nose wheel suffered a leak and you found it parked in the hangar with the prop hitting the tow- bar and the damage to the prop blade has just a nick that is within tolerances for being dressed out, then no engine R&R is mandated.
This is a mandatory shock load inspection. This is the aircraft from the “going around after a gear up landing is a bad idea” thread that survived to tell the tale.
It clearly shows that the props hit the tarmac at at low power setting, i.e. before power was added for the go-around.
aren’t these the newly invented wing tips for props ?
You need a shock load inspection even if the engine was not under power, because the sudden change in rotational velocity translates into extra stresses on anything that has inertia, which is just about everything that moves and has mass (so an engine made out of neutrinos would be ok – however that is disputed). You can also get cracked gears in the accessory gearbox. Rare but I am told in about 1% of shock loads they find cracks. And there will be more which are not found because standard dye penetration NDT doesn’t find subsurface cracks.
Peter wrote:
Rare but I am told in about 1% of shock loads they find cracks
Does that mean that 99% of the inspections find nothing ?
So where does that data point come from ?
Various engine shops I have spoken to over the years.
I think the 1% comment would refer to parts probably damaged by the shock load. It is obviously not the case that mostly they find nothing to do at all, because when you open up a random engine you cannot put it back together if any part is outside service limits. It is the classic “can of worms” case, which is why most people don’t want their engine opened up… I was once told that any corrosion for example is outside “service limits”; no idea if that is the case currently.
One has to remember that not sooo long ago there was NO REQUIREMENT to perform and engine R&R following a prop strike and guess what ? Planes were not falling out of the sky …
Yes, there were a couple of high profile fatal accidents and that is what prompted the Manufactures to issue multiple SB on the subject but not so much so that the FAA never wrote a “blanket” AD mandating engine R&Rs on every prop strike incident.
I think we have a classic case of CYA more than anything else.
ps: I have NO data on the amount of serious damage that has been un-covered on shock load inspections, but I personally know of none, although I suspect that a crankshaft failure that occurred on a plane I but COULD have been due to a previously un-reported prop strike, but have no proof.
