Hey Jim-Ed:


"Jim-Ed Browne" wrote in message
om...
Is this because none of the ones available as designs currently have
any, or because you feel it's not feasible, or because....exactly why?

I've never looked at any airplane designs that have such features. There is
a huge price to pay in terms of weight, required power and such to provide
pilot protection. Drives up cost a ton, and makes operations more
expensive.

Keep in mind that crumple zones are only really for front impact, too.

Race cars go faster on the ground than some homebuilts will _straight
down_ and, Dale Earnhardt aside, usually people go in the wall and

They have requirements for driver protection. And they have huge budgets to
work with. I don't know about about NASCAR, but, to get the sign-off to
race, the CART guys have to slam a couple of chassis into a wall to show
that the tub holds together. Expensive, expensive, expensive.

I recall that the P-51's designer, Dutch Kindelberger, designed the
cockpit area as the toughest structure, so everything else would
crumple around the pilot and provide protection from the sudden
impact. Is this somehow no longer feasible?

Sure, it's feasible, but it's expensive. How many airframes do you want to
build for the purpose of destroying them to prove the design? Then there's
costs of test facilities. What's the cost in weight, performance, etc.? How
much is it going to cost to design, model, and test? If you see a couple of
zeros being added on to the total cost to build and get the FAA to sign it
off, then you're probably getting a realistic picture.

Even if you could afford to buy one, operation costs of a P-51 is probably
well beyond the average budget of the typical home-builder. Besides, the
P-51 was designed to go to war and get shot at, not for $100 hamburgers.

I guess the question I have is this: How much are you willing to spend to
get an airplane that protects you in case of a crash? If you've got
millions to spend, then you can probably get what you want. But on a $50k
home-built? Forget it. Maybe a certified commercial manufacturer would have
the resources to pursue safety features like this, but I would find it
surprising if people would be willing to fork out the extra bucks for it,
given that the costs would have to be recovered through the sale of a
relatively small number of airplanes.

There are probably much better approaches to achieving leaps in aviation
safety without doing anything about crashworthiness improvments. Think
about the safety improvements you'd get just by having a more reliable
powerplant and fuel delivery system. Think about potential improvements
from sophisticated engine health monitoring (condition-based
maintenance....catch and repair faults before they become
catastrophic...there are some really nice products out there right now)?
Then there are potential benefits for IFR/night flight using synthetic
vision to prevent spatial disorientation. These kinds of improvments might
cost thousands of dollars to the consumer, falling in the range of what is
affordable to the typical RV builder at least.

Anyway, just some things to think about. If you dig around for some of the
data on NASA's General Aviation Revitalization effort (no longer going on, I
think), you can find more comprehensive info on these topics.


Pete

P.S. Just to qualify my views - I'm not an airframe designer, but I do work
in aircraft development. I'm a flight controls engineer (meaning that I'm
one of the guys who's found ways to drive up the costs of an airplane
without driving the weight up) with Lockheed in Palmdale, CA. While I don't
work directly with these design/development trades, I am regularly exposed
to the issues and compromises that they bring up. So...knowledgable, but
not an expert.