Composite props and bird strikes

I was having a chat with a fellow builder about props, and he said something I have never thought of before;
If you strike a bird on takeoff with your composite prop ,you could loose part of a blade. This dis-balance could cause loss of control and so forth. Read crash.
I know this seems like a unlikely scenario, but could it happen? I'm no prop expert, but it does seem feasible after seeing pics of damage birds do to planes.

More than not, birds seem to pass through the prop arc without actually getting hit by the prop. And if they did...........it would be chop, chop....

Other than that, I don't have a real clue..

L.Adamson

A coupla years ago....

....a guy in a -4 hit a bird on takeoff at Sandersville, Ga, where big birds congregate on the runway for some strange reason. He was at about 5 feet and they jumped up and hit the wooden prop (not composite) and split it lengthwise. It shook badly but he managed a pattern and landing then noticed a pretty big dent in the right fuel tank as well.

I dodge big birds routinely while ferrying back 'n forth to fields and I've learned that if they're higher than 100' AGL, they'll dive when you come by and if they're closer than 5' to the ground, they'll go up.

My advice for you is that on takeoff, if you see birds on the runway, taxi past them to flush them, then go. In flight, steer clear of buzzards and such.


Regards,

Question

Why do you feel that a composite prop would be likely to break upon a strike? My experience with composites is that they are way more flexible and can take more of a beating before they break. Plus they are not suseptible to stress risers. My composite prop has a stainless leading edge to further keep the composite from suffering damage from rocks etc.

I think your fear may be unfounded, but some tests from the manufactures would be helpfull here.

Gary Specketer

Hey Pierre...

If anyone knows about birds, it should be you. Flying that Air Tractor around the farms puts you in their airspace most of the time. Thanks for the tips.
Regards,
Chris

Catto's props have a maple core with fiberglass on the outside. Here's what Catto says on their website:

We had one owner in a Long Eze that had an 8" piece of his exhaust come off and travel through his 3-bladed prop. He heard a horrific bang, but the blade stayed intact and was able to fly home.

I suspect his props could handle most birds.

It would seem your odds are better at winning the lottery.

Anyway, I think history shows the lighter mass of the composites props are less violent then loosing a metal blade. My neighbor lost a wood blade on his Lancair and was able to shutdown the engine and dead stick land without issue.

Although, Reno racers turning 4,000+ rpms are a whole different story.

Bird strike testing

Bird strike testing on composite props has been a "special condition" for certification of composite props. I believe it is now baked-into the new amendment of Part 35. The concern is based on a bird entering the propeller plane of rotation while at low speed and high power, which is more likely to occur during takeoff. The angle at which the bird strikes the blade at this condition is more of a "slap" than a "slice." Trust me, it can do real damage or snap-off portions of the blade. In fact, the bird strike condition can dictate the structural design of a composite blade, especially on longer turbine blades.

All of our composite props that make it to market have passed both bird strike testing and lightning strike tests. They are expensive tests to conduct and are not easy to pass.

Les Doud
Hartzell Propeller

Thanks Les, for the heads-up....

.....but in my line of work, it's a cr*p shoot whether the bird is sliced, diced or misses the prop....Ive had both, slaps and slices. Fortunately they were small birds, except for the occasional buzzard that puts a huge dent in the wing and sheared off my nav/strobe light assembly that costs an arm and a leg because you have to replace them with certified stuff whereas my RV, I can buy NAPA stuff if I want

Regards,