This is aimed at those who already know, but for anyone not familiar: there are many moving parts in the engine and a lot of rotating mass. If the propeller strikes something that slows or stops it those moving parts will want to carry on moving. This can bend the crankshaft, the camshaft, pushrods and conrods. To make things worse, the propeller is a long lever so any for and aft force at its tip can and will bend the hub flange. Rules are rules and are often written in blood, there are many examples of superficial damage resulting in separation of the propeller or other serious damage some time later. Car engines stall all the time and they are not damaged by stalling but the cam be and clutches do include some shock protection, they also don't have big leavers putting huge forces on the cranchshaft.
Very interesting Jon. I had no idea the inspection was so detailed Note to insurance companies - challenge all claims for shock load testing of a high time engine. Classic opportunity for a scam turning wear and tear into "accident" damage that increases all our premiums! 25% to 30% of Norvic's work is doing shock load tests!! They almost advertised the benefits of having a prop strike when your engine needs an overhaul !! lol
Very interesting Jon. I have a background in Non Destructive Testing and am also rebuilding a light aircraft. Many engines offered for sale have, unfortunately, been involved in an incident. I have had the misfortune of buying and engine which subsequently proved to have a damaged crankshaft. A very expensive item to replace and, as a result, often ending in the breaking of an engine for spares. A prop strike should always be treated as serious. This is great content for the GA community. Carl
As always this is very similar to what we do with race car engines. When the bottom of a single seater race car hits a kerb or bottoms out the suspension the large flywheel can hit the track and crack the crankshaft. Some time later the crack grows and the crank snaps destroying the engine. I went through about 5 engines in 3 years once because of this as my chassis didn't have very good skid blocks :o( Similarly the only thing you can do when you bottom out the car heavily is dismantle the engine and spray the crack testing stuff all over the crank and block. It's really annoying but it's better than destroying your expensive engine.
When I was making the arrangements for my plane’s engine rebuild (fall 2020) the shop were dealing with an epidemic of prop strikes. They attributed it to rusty pilots flying again after you know what.
Good video thanks Jon. So here’s one for the insurance companies (and by implication our premiums) - do many prop strikes occur on engines approaching TBO, benefitting from an insurance company funded replacement engine? Or are the insurance companies wise to this and reducing payouts in-line with the hours flown on the engine?
Very interesting Jon,. One question, they didn’t mention damage to mags. I thought damage to the plastic gears inside a mag was one of the most common results of prop strikes? TonyS
Interesting video, thanks Jon.
This is aimed at those who already know, but for anyone not familiar: there are many moving parts in the engine and a lot of rotating mass. If the propeller strikes something that slows or stops it those moving parts will want to carry on moving. This can bend the crankshaft, the camshaft, pushrods and conrods. To make things worse, the propeller is a long lever so any for and aft force at its tip can and will bend the hub flange. Rules are rules and are often written in blood, there are many examples of superficial damage resulting in separation of the propeller or other serious damage some time later. Car engines stall all the time and they are not damaged by stalling but the cam be and clutches do include some shock protection, they also don't have big leavers putting huge forces on the cranchshaft.
Very interesting to see what actually happens after a prop strike, Jon. An excellent subject to cover 👌🏻 👍🏻
Do link up the videos when they have been released. I couldn't see them on the Norvic website, given your style, I'm sure they'll be interesting.
Very interesting Jon. I had no idea the inspection was so detailed
Note to insurance companies - challenge all claims for shock load testing of a high time engine. Classic opportunity for a scam turning wear and tear into "accident" damage that increases all our premiums! 25% to 30% of Norvic's work is doing shock load tests!! They almost advertised the benefits of having a prop strike when your engine needs an overhaul !! lol
Thank you Jon! ( And Norvic) Very interesting stuff😀Stu
Thanks Jon. Very educational.
Very interesting Jon
Great episode Jon
Thank you!
Very interesting Jon. I have a background in Non Destructive Testing and am also rebuilding a light aircraft. Many engines offered for sale have, unfortunately, been involved in an incident. I have had the misfortune of buying and engine which subsequently proved to have a damaged crankshaft. A very expensive item to replace and, as a result, often ending in the breaking of an engine for spares. A prop strike should always be treated as serious.
This is great content for the GA community.
Carl
Thanks Carl.
As always this is very similar to what we do with race car engines. When the bottom of a single seater race car hits a kerb or bottoms out the suspension the large flywheel can hit the track and crack the crankshaft. Some time later the crack grows and the crank snaps destroying the engine. I went through about 5 engines in 3 years once because of this as my chassis didn't have very good skid blocks :o(
Similarly the only thing you can do when you bottom out the car heavily is dismantle the engine and spray the crack testing stuff all over the crank and block. It's really annoying but it's better than destroying your expensive engine.
Good interview Q's really drilling down for understanding 👍 I used to do dye penetrant NDT and other methods.
Thanks.
When I was making the arrangements for my plane’s engine rebuild (fall 2020) the shop were dealing with an epidemic of prop strikes. They attributed it to rusty pilots flying again after you know what.
Sounds like it was a factor then...norvic said the same.
Good video thanks Jon. So here’s one for the insurance companies (and by implication our premiums) - do many prop strikes occur on engines approaching TBO, benefitting from an insurance company funded replacement engine? Or are the insurance companies wise to this and reducing payouts in-line with the hours flown on the engine?
Very interesting Jon,. One question, they didn’t mention damage to mags. I thought damage to the plastic gears inside a mag was one of the most common results of prop strikes?
TonyS
Not mentioned Tony.
Thats because the mags are replaced on every shock load