I agree almost completely with RAVI on this, and I've said it before. If you make this stuff uncomfortable enough, you won't wear it. The day those two crashed it was 85 degrees. Think about why they weren't wearing their vests. Sparky's PLB was IN a very large, very bulky VEST, hanging on the seatback of his airplane.
I agree with AH64 on fabrics as well. If you want to try to swath yourself in Nomex, get military or custom made flight suits--they are expensive, and not very comfortable, though you can get custom ones in lighter Nomex material.
But, just DON'T wear nylon, rayon, or other synthetic fibers if you can avoid it. Cotton will protect you nearly as well in a flash fire as Nomex. Nylon will go up like a torch and embed itself in your skin.
Let me tell a story, and my apologies if this sounds off track:
One winter, the Kodiak Coast Guard FLying Club was able to park all our aircraft (four) inside a C-130 hangar-heated, instead of tied outside. CG had lost a Herc in an accident. We moved the airplanes inside. Huge hangar doors, BUT equipped with big electric motors to open them for you, absolutely a piece of cake. At the end of a flight, each airplane had to be bonded to the hangar floor with a cable, and a drip can had to be hung under each fuel vent.
Flying activity dropped to near zero. Me and another fellow were the only ones flying. Couldn't figure it out, and it went for almost three months, weather was NOT a factor.
One guy suggested we put the planes outside again and see what happened. We did and flight activity went right back up to normal levels.
Just that little bit of extra hassle kept people from flying.
Flying for many of us is fun and transportation. Don't make it any more painful or uncomfortable than is necessary.
You don't need a full medical kit carried in your vest, nor do you need all sorts of appliances. I've siwashed at 48 below zero, and didn't use but about four items in my vest and a couple from the plane.
You can't plan for every single contingency. I would argue that not many if ANY on this list carries all that stuff in their cars, and you're a lot more likely to need it there than in your plane, if not for you, for others.
Keep it light, stick to the basics. As I noted before:
A GOOD knife
THree ways to start a fire: Lifeboat matches or match safe, blast match, Bic lighter
Parachute cord-25 feet or 50
Signal mirror-THAT alone would have got these guys out 20 hours earlier.
PLB
Some BASIC trauma stuff--blood stopper powder, blood stopper bandage
Smoke canisters-tiny
a lightweight mylar "space" blanket.
A multi tool
I know--it doesn't cost a fortune, you can buy most of the stuff at Cabela's. It won't cover EVERY contingency.
You can't, and never will.
Keep it simple, keep it light and ENJOY flying.
Oh, yeah, I forgot the IPOD

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MTV