what is prop strike and in relation to aircraft from a engineer's point?

Answer 1

Everybody so far has been fairly correct.

Typically propstrike is the prop hitting the ground, but it could be anything, reasonably from hitting a bird to another aircraft. Something as insubstantial as a bird usually isn't going to do much damage to the airplane, except in the event of a single engine, tractor aircraft meeting a large bird, in which case you'll have whatever damage results from trying to see through blood, internal organs, viscera and feathers as the pilot tries to land.

Prop strike, in the traditional sense of a prop meeting the ground, is usually v-e-r-y loud.

It transmits the force of the collision through the entirety of the engine, and unless you've got counter-rotating props, it's typically going to lift the engine on it's pylons up and to the right with the horsepower of the engine pushing and the weight of the aircraft pushing the other way. This isn't good for the bearings, the prop, or the pilot's nerves.

It's also not good for anything that's turning and connected to the shaft driving the prop.

In the case of the free turbine engines, such as the PT-6 and the Allison 250, the engine's N1 section may stay in operation leading to elevated EGT's and possible turbine damage.

In the Garrett's used by MU2's and T-Commanders, you have a compressor that spins at eight times the speed of the prop, directly linked to the prop. Obviously it's not good for the prop to go from spinning at nearly 2000 RPM to zero in the blink of an eye, so it can't be good for components behind it that are spinning upwards of 16,000 RPM.

In the case of piston engines that experience prop-stop, not only to the bearings take a beating, but the powercase can be cracked, piston rods bent or broken, valve pushrods can get bent, teeth knocked off the cam shaft timing gears, valves can get bent and stuck, pistons and valves can collide.

So, as well as being loud, it's also EXPENSIVE. Double check gear down and locked, three green.

Answer 2

Prop strike is something contacting the propeller from small a bird, to something major like a tree or the ground. The results from these strikes vary from just some damage to the prop to the very expensive damage to the engine and actual airframe. I have personally never seen these on a fixed wing aircraft as I work on rotory wing UH-60 Blackhawk helicopters but I have seen some pretty bad rotor strikes. There is a list of inspections for rotary wing aircraft that include sudden stoppage. This is when the prop hits something and from that it temporarily stops it from turning and yes everytime the prop hits anythng it does stop or slow. These inspection require engine teardown and airframe inspection. The engines are very expensive and all but airframe rebuilding is worse.

Answer 3

Not sure what you are looking for in an answer. A prop strike is not good news for nybody. It usually damages the propeller enough that it can't be repaired and heavy damage to the drive line and internal engine. from the engineers point of view, he wants to design the airplane is such a way that the prop won't hit the ground except in the absolute worst cases. Idealy, in a nose wheeled single engine airplane, the prop shouldn't come into contact with the ground if the nose tire and the nose oleo were flat. As a pilot, you definately do not want that prop to hit anything ecxept air and bugs.

Answer 4

The 2 previous answers are correct. But usually we would also check the Engine Mounts as well as a FULL visual inspection of the Airframe on the side of the strike to ensure that there was no further damage. When Prop Strikes happen they tend to make a mess.

Answer 5

A prop strike is when the prop hits anything besides air. From an engineering point of view, the shock transmitted from the prop to the engine is capable of breaking crankshafts and creating metal fatigue in the engine.

Answer 6

As above, but also note that the actual level of damage varies greatly depending on whether or not the engine was under significant power at the time of strike. The strip down etc. still has to be done regardless.

Answer 7

A prop strike means the engine has to be torn down and the crankshaft checked for any structural damage before it can be put back (legally) into service.