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Strronger 'Wind Screen'?

E

E. D. Eliot

Well Known Member
After reviewing several posts about bird strikes, I am wondering what it would take to make our RV windscreens more bird resistant in terms or $$$ and installation practicality?

Seems that every windscreen installation is different so there is no 'one size fits all' solution.

Weight is a genuine consideration also - but, if a more 'bird resistant' wind screen were available either from Van's or an after market supplier, I would buy and install it providing that it would provide real protection.

I realize that speed of the aircraft is very important in computing the amount of damage that is done. I will be flying my RV-12 a lot of the time 'low and slow' so maybe this makes more sense in my case.

Just my thoughts on RV safety. Is this idea practical? Lexan?
 
A friend of my father lost an eye in an F86 from a birdstrike at something over 400 knots. The F86 had a 2 inch thick windshield pane of bulletproof glass... Not sure of the species involved.

Kinetic energy varies as the square of the velocity and the weight of the bird needs to be taken into account to decide your protection criteria. You are not going to stop a Canada Goose at even 150 knots with anything practical attached to an RV airframe. I've used Lexan in race cars and it is impressive stuff compared to plexi as far as ability to absorb impact energy without penetration however then the frame or support structure will have to withstand this force. I believe even 3/8 Lexan on a side by side RV would distort several inches from something like an 8 pound bird impact at 170 knots. Food for thought to design the structure to support that. Not very practical for tip up RVs.

I am sure something of reasonable weight and optical quality could be devised using Lexan to offer a lot more protection that the standard setup does but IMO, you could not protect against really large species.
 
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Lexan tends to yellow over time, even with additives. Not ideal for a windscreen exposed to lot's of UV. It also scratches much more readily and it's optical qualities are not as good.
I think Ross has a great point also.
 
Reinforced windscreen

Mine is set to protect against a 5 pound bird at 150 knots, or a 150 pound bird at 5 knots!

;) :D
 
A helmet with integrated visor may help protect the eyes from flying pieces of plexi.

Bevan
 
From eMail conversation(s) with Todd:
Lighter? No, a little heavier since I use plastic a little thicker. Many people think this is necessary for such a fast airplane.
Stronger? It's a little thicker so it should be.
I think my RV-3 canopy is about .5 pounds heavier than one from Vans.
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Given the above, and Todd's flexibility / ability to do custom shapes / tints, it would seem going that route will get you a stronger canopy if it is your priority.

I would come back to the original point. Has anybody (or even aircraft?) come to serious harm due to canopy penetration in an RV? [I think not]. Are you going to get a significantly stronger canopy (say 50%+?)? Unlikely. Is a stronger canopy the best mitigation to the perceived problem? Probably not - flying higher / slower / avoiding known bird areas / using effective lights are all likely more effective in risk management terms (fly 15K slower = 35% less KE in the bird, before you factor in slower gives bird more time to it's part in the colliison avoidance drill).

I spent a fair proportion of my early flying life at 250' or less / 420K+ and birds were an issue. Canopies did break from time to time, but visor use reduced the hazard, and the biggest danger was engines and/or airframe damage (as seen elsewhere on VAF). The mitigations were lights, lookout, appropriate avoiding action, avoiding bird areas by location / season.
 
Andy Hill said:
...I would come back to the original point. Has anybody (or even aircraft?) come to serious harm due to canopy penetration in an RV? [I think not]. Are you going to get a significantly stronger canopy (say 50%+?)? Unlikely...
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Serious harm? Not yet, but my encounter could have gone very badly. It was pure luck that I got off as light as I did. As a response to this threat I did alter my operational profile some, but I also changed the windscreen, both in geometry and material. I'm not sure how much improvement I made, but I suspect that if I had to repeat my last encounter, I would get away with a blood smear instead of a hole in the windscreen and a permanent scar on my forehead.

I'll tell you this, if my next airplane (Rocket) doesn't have a highly raked, flat wrap windscreen of at least 3/8 inch thickness, it's getting one soon after I get it home. Certainly isn't going to stop a Canadian Goose, but I'd think many of the smaller species will bounce right off.
 
Most certainly people can be seriously injured or killed from a bird strike, not the least of which from plexi fragments.

I think people would be surprised at how much energy is involved here- roughly 11000 J in the case of a 6 pound bird at 180 knots. 3/8 plexi, even with more slope won't withstand this.
 
No, but a 6 pound bird is pretty big. Certainly you're not suggesting an "all or nothing" approach - if we can't protect against a buzzard, we shouldn't even try keep tweety on the outside?

We're talking risk management here - not risk elimination.
 
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Bird strikes

I was wondering what the verdict was on painting one propeller blade a different color to give the birds a clue we are there,
A search thru the photos of bird strikes reveals very little that will stop a large bird from causing major metal damage, even one where the top of the cabin was peeled back a couple of feet,
ONE HALF THE MASS TIMES VELOSITY SQUARED
MAKE SURE YOU INCLUDE BOTH
SCARY:(
 
Windscreen

I think the most practical solution is a thicker windscreen but the same light canopy. I discussed this with airplane plastics but they didn't seem to have a great interest. The original winshield thickness in a Bonanza was about 1/4". Many owners choose 3/8" or 1/2" when replacing the windshield. The extra thickness helps with bird strikes and also reduces noise.

A am leaning towards a similar solution for the RV. If a person wanted to use a flat wrap this would be a fairly easy solution, otherwise it would require pulling a one off windscreen.
 
Toobuilder said:
No, but a 6 pound bird is pretty big. Certainly you're not suggesting an "all or nothing" approach - if we can't protect against a buzzard, we shouldn't even try keep tweety on the outside?

We're talking risk management here - not risk elimination.
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No, as I said before, I think 3/8 Lexan with a revised mounting system would give vastly improved protection against something even quite large like the standard 4 lb. subject often used in jet engine ingestment tests.

For reference, the common large species around my airport- Raven 3 to 3.5 lbs., Hawk 2.5-4 lbs., Gull 2-2.5 lbs. and Canada Goose 7-20 lbs. (heaviest species 24 lbs!) Geese have been observed as high as 33,000 feet- good lungs!

So these are pretty big birds. Most of the other common small bird species with less than an 18 inch wingspan are probably under 1.5 pounds at most.
 
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Lexan looks good on paper (and that was my first choice when doing the -8) but according to my canopy and windscreen engineer here at work, it's not good by itself. First off, it scratches easily without a coating, but most troubling, it is highly sensitive to UV damage. In short order, the UV saps the toughness out of the material, and you are simply left with a easily scratched windscreen that is of comparable strength to Plexi.

The aircraft that use Lexan are UV protected and sandwiched with outer layers of plexi... a very expensive process. WAY outside the scope of the homebuilder.

So thats why I went with 1/4 inch, high quality plexi. Won't stop a bowling ball, but I doubt a quail will make it through again!
 
Lots of brands of UV stabilized polycarbonate available these days without sandwiched construction, can also get a type with hard coating to reduce scratching but not sure if the latter is formable. See these used on OEM auto headlight fairings a lot.

I agree, straight, standard Lexan would have a limited life outdoors in a sunny climate.
 
rv6ejguy said:
... See these used on OEM auto headlight fairings a lot...
Click to expand...

Have you really looked at a 2+ year old headlight cover? Most are etched, warped and yellowing.

...Not exactly a ringing endorsement for a windscreen that has to remain optically pure for its whole life.
 
I have heard that in issue with polycarbonate canopies and bird strikes is that the canopy will deflect inward, strike the pilot, and then rebound to its original shape. While that sounds fine for the canopy, it's the "strike the pilot" part which isn't so good.

More of a problem at jet speeds than ours, I suppose.

Dave
 
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