Bird Strike!

Jay Honeck said:
How did it get through that whirling prop? We never saw, felt, or heard a thing:
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That is a very good question and I did the math some time ago.
Brief explanation: after seeing a story on TV about a birdstrike in a Baron which injured the single pilot, I wondered about whether a prop in front of a windscreen spins fast enough to chop up the bird into smaller chunks, thus reducing the risk of the plexi breaking. (which would be a big advantage to twins)

The calculations yielded a surprising (to me) result that a small enough bird can pass through the prop arc unscathed and hit the windshield/cowling/whatever whole. The slower the prop turns, the bigger the bird that can pass through. So on final approach with the engine RPM very low, is the highest chance for a bigger bird to pass through the prop arc. In a climb, with maximum engine RPM and at low speed, the chances are much smaller for bigger birds but small birds can still pass.

Example math for cruise (using made-up numbers since I do not know your RV's performance):
aircraft speed: 150 kt
engine RPM: 2400
bird speed: negligible
number of prop blades: 2

To get a common denominator (not literally), you can calculate everything per second.
aircraft travels 150 nm in an hour and that translates to ~ 250 fps
prop spins at 2400 rpm which translates to 40 rps or 80 blades per second
So while your aircraft travels 250 feet, a blade passes in front of your cowling 80 times, once per 3 feet (approx) of travel.
A small bird can pass by the spinner while a bigger bird could pass in the tip arc.

Anyway, enough math. Glad it was a non-event.
 
BigBadLou said:
That is a very good question and I did the math some time ago.
Brief explanation: after seeing a story on TV about a birdstrike in a Baron which injured the single pilot, I wondered about whether a prop in front of a windscreen spins fast enough to chop up the bird into smaller chunks, thus reducing the risk of the plexi breaking. (which would be a big advantage to twins)

The calculations yielded a surprising (to me) result that a small enough bird can pass through the prop arc unscathed and hit the windshield/cowling/whatever whole. The slower the prop turns, the bigger the bird that can pass through. So on final approach with the engine RPM very low, is the highest chance for a bigger bird to pass through the prop arc. In a climb, with maximum engine RPM and at low speed, the chances are much smaller for bigger birds but small birds can still pass.

Example math for cruise (using made-up numbers since I do not know your RV's performance):
aircraft speed: 150 kt
engine RPM: 2400
bird speed: negligible
number of prop blades: 2

To get a common denominator (not literally), you can calculate everything per second.
aircraft travels 150 nm in an hour and that translates to ~ 250 fps
prop spins at 2400 rpm which translates to 40 rps or 80 blades per second
So while your aircraft travels 250 feet, a blade passes in front of your cowling 80 times, once per 3 feet (approx) of travel.
A small bird can pass by the spinner while a bigger bird could pass in the tip arc.

Anyway, enough math. Glad it was a non-event.
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Interesting post, Lou.

I'm still amazed that it didn't even scratch the paint. To cleanly slip through that intake, which is maybe 4 times bigger than the bird, after passing through the prop arc at the thickest segment, is truly one in a million.

I'll bet you could throw a stone at a whirling prop a thousand times, and not get the stone to pass through, let alone get into the engine compartment.
 
Yes, it's possible to have a no-damage bird strike.

One of the places I rent from had a 172 prop-strike a small bird on takeoff over a salt marsh. No damage, no engine hiccup, nothing but bird guts sprayed all over the place. Though we couldn't identify it (nothing but small bits left), it couldn't have been very large. I doubt it was a seagull or pelican or plover. Something smaller.

Good God that was nasty. Good thing it wasn't my job to clean it up. :) No involvement, just a bystander.
 
MAKG1 said:
Yes, it's possible to have a no-damage bird strike.

One of the places I rent from had a 172 prop-strike a small bird on takeoff over a salt marsh. No damage, no engine hiccup, nothing but bird guts sprayed all over the place. Though we couldn't identify it (nothing but small bits left), it couldn't have been very large. I doubt it was a seagull or pelican or plover. Something smaller.

Good God that was nasty. Good thing it wasn't my job to clean it up. :) No involvement, just a bystander.
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Had that happen to me during my primary training, was on takeoff roll in a 172 just at rotation and caught a small one (sparrow?) on the prop - spread him out quite nicely over the right half of the windshield. Instructor laughed and told me to make the pattern and fullstop, was a nonevent.

Well, it was a nonevent for ME anyway - I didn't have to clean the plane! :goofy:
 
jsstevens said:
My primary instructor said "Don't dodge them. They'll dodge you." So far, so good. But I'm not as confident now that he was telling the truth.
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Someone once told me that when trying to avoid a bird, it's better to climb than to dive because birds will dive to avoid the airplane. After some highly scientific research (i.e., five minutes of web searching just now) I read several articles which refute that claim, or at least say that it is not always true. However, this AOPA article from 2005 has some interesting data, including the notion that above 500 feet, climbing over birds is probably the better decision, but below that the birds are as likely to climb as not. Of course, if I'm below 500 feet, I probably don't want to do any sudden dives, either. :)

The article also references bird strike information in the AIM, which I had completely forgotten. It (the AIM) also mentions climbing to avoid birds, but for a different reason: the distribution of birds in a flock.

It also occurred to me that climbing would expose more of the underside of the airplane, hopefully reducing the chance of hitting the windscreen.

Anyway, I've had a few fairly close encounters with birds, but fortunately no strikes. Around here (5C1) I worry more about deer strikes, especially at dusk. Diving to avoid deer is not usually an option, unless perhaps to avoid reindeer on Christmas eve. For those who live near the coast like Jay, though, I imagine bird strikes are a constant concern.

Lee
 
airguy said:
Had that happen to me during my primary training, was on takeoff roll in a 172 just at rotation and caught a small one (sparrow?) on the prop - spread him out quite nicely over the right half of the windshield. Instructor laughed and told me to make the pattern and fullstop, was a nonevent.

Well, it was a nonevent for ME anyway - I didn't have to clean the plane! :goofy:
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The only animal strike I've had while PIC wasn't nearly so messy.

I saw the squirrel sitting on top of a taxi light as I taxied by, then he ran off. A second or so later, I felt the telltale thump coming from the left side. Asked Ground if I got him, answer was in the affirmative.

I suppose I should have filled out a form 5200-7. Didn't even think of it at the time.
 
MAKG1 said:
The only animal strike I've had while PIC wasn't nearly so messy.

I saw the squirrel sitting on top of a taxi light as I taxied by, then he ran off. A second or so later, I felt the telltale thump coming from the left side. Asked Ground if I got him, answer was in the affirmative.

I suppose I should have filled out a form 5200-7. Didn't even think of it at the time.
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In my youth, I ran over a squirrel with my bike tire. He scampered on. True story. Poor bastards. :)
 
asechrest said:
In my youth, I ran over a squirrel with my bike tire. He scampered on. True story. Poor bastards. :)
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I once had a squirrel try to jump through my front bicycle wheel while I was riding down the street. The poor guy got caught in the spokes of course, and whirled around a few times before I could stop to let him off. I don't know where squirrels rank on the intelligence scale, but I suspect he was intelligent enough to never try that trick again.
 
Most RV windshields have been penetrated at 140-150 kts below 3000 agl. I try to slow under 120 kts below 5000' agl and keep my lights on after seeing a friends RV-10 damage. It is better for big bird avoidance too and I am below Va if I need to pull up hard.
 
Jay Honeck said:
I'll bet you could throw a stone at a whirling prop a thousand times, and not get the stone to pass through, let alone get into the engine compartment.
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Depends on how fast you throw, I guess. Roland Garros had pretty good luck shooting machine gun a machine gun through the prop disk, with just metal wedges to deflect the few bullets that would have hit the blade. Tougher nearer the hub, of course.

My Fly Baby had a birdstrike, once. Took me an hour to clean the guts off the trailing edge.

Ron Wanttaja
 
azure said:
I once had a squirrel try to jump through my front bicycle wheel while I was riding down the street. The poor guy got caught in the spokes of course, and whirled around a few times before I could stop to let him off. I don't know where squirrels rank on the intelligence scale, but I suspect he was intelligent enough to never try that trick again.
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You must have really spoked him.

(I'm here all night.)
 
There must be something about squirrels and bicycles. I was riding on a trail and a suicidal squirrel tried darting across through my front spokes, too. It didn't get caught, but it did get bounced off pretty good.
 
Matthew said:
There must be something about squirrels and bicycles.
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You might be onto something here.

Ever since I put my mountain bike on the back patio this winter for easy access (as opposed to keeping in in the garage, hanging behind the truck), the local squirrels started bringing their loot (pecans) onto the deck and cracking them open and eating them there. Evidenced by a huge mess on the deck, close to the bicycle. Lots of shells scattered everywhere in that corner.
What's up with that? :dunno:
 
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