homebuilt safety

guessing you would need quite soft foam, otherwise it wouldn't deform

The foams they use for helmets are pretty hard. They won't deform until you
hit a threshhold. You don't want something that will compress under normal
loads.

Agreed.

I imagine you would want something that would deform around (for the sake
of argument) 10-20Gs. One's back probably has 10-20x the surface area of
one's foot, so my worry is that if you used a foam that was soft enough to
protect your back, it would be easy to put your foot or elbow through it.

Another idea was putting a big chunk of foam at the front of the aircraft
to slow the deacceleration if you hit something frontways. Say you have to

We could be talking about a lot of energy. Might require a lot of foam.

airframe may break. Perhaps a cubic foot of harder, crushable foam in the
nosecone could reduce peak loads on the airframe and spread them more

Where in the nose would you put it?

Behind the canard - in my dreams.

I was thinking of maybe something behind
the instrument panel, maybe attached to the firewall. Speaking of fire....I
think I have an old bicycle helmet laying around. Maybe I'll put a match to
it.

Good point.

Anyway, I'm sure there's data available on foams currently in use.

I have heard that the racing drivers use alu honeycomb. That sounds like
it might be seriously expensive.

AC

"anonymous coward" wrote in message
news
I imagine you would want something that would deform around (for the sake
of argument) 10-20Gs.

Hmm....just shooting from the hip, that sounds like good range.

one's foot, so my worry is that if you used a foam that was soft enough to
protect your back, it would be easy to put your foot or elbow through it.

I'd think you'd put a covering of something rigid over it. Maybe a thin
layer of glass or maybe just some epoxy to make the top rigid enough to
prevent dinging it under normal use.

Behind the canard - in my dreams.

Maybe the thing to do is mount the seat to something that will give somewhat
under crash loads. Might be hard in something like a Long/Vari-EZ, since (I
think, working from memory here) that the EZ seat is mounted directly to
some major structural members. Would need some additional stuff to isolate
the seat with some energy-absorbing stuff that would let it give a bit
(probably don't need more than a couple of inches in a crash).

I have heard that the racing drivers use alu honeycomb. That sounds like
it might be seriously expensive.

There's probably a ton of data on stuff that people have tried for driver
protection in the automotive world. Unfortunately, air-bags are out of the
question for aviation use (for the pilot at least....probably for everyone).
But there must be a ton of other stuff. I'd bet that NASA has sponsored a
bunch of research under the GA revitalization thingy that would be
applicable. Rather than us spend our time speculating here, maybe some
Google time is warranted. There is probably someone at NASA Langley that
would serve as a point of contact, too. There might even be some technology
transfer programs around that we could take advantage of. Not sure how they
would react to helping the average joe home-builder, but I'm sure they make
a lot of data available to certified manufacturers.

Pete

"Pete Schaefer" wrote in message
news:xMprc.4694$ny.935185@attbi_s53...

. . . Unfortunately, air-bags are out of the
question for aviation use (for the pilot at least....probably for
everyone).

Not. See http://www.avweb.com/news/snf2003/184230-1.html - last article,
bottom of page.

Rich S.

Air bags are a factory option on some certified planes, including the
Mooney. The bags are built into the seat belts.

Frank

"Rich S." wrote in message
...
"Pete Schaefer" wrote in message
news:xMprc.4694$ny.935185@attbi_s53...

. . . Unfortunately, air-bags are out of the
question for aviation use (for the pilot at least....probably for
everyone).

Not. See http://www.avweb.com/news/snf2003/184230-1.html - last article,
bottom of page.

Rich S.

wrote:
On Fri, 21 May 2004 03:15:13 GMT, Ernest Christley
wrote:


That's unlikey to be a crumple zone. If you guys are just going to randomly
refer to anything outside the cockpit as a crumple zone, then there's no
basis for communication here.


Well, hell. I didn't mean for you to get your technical panties is a
wad. Anything outside the cockpit IS a crumple zone if

1) it gets between you and the hardstuff, and
2) it's not so strong that you break before it does

By this definition, if something extreme happens and you somehow come
down backwards, landing on your tail with the nose straight up, then the
whole aft fuselage becomes a crumple zone.


Is this what you meant when you said that the P-51 was built with
crumple zones? If that's what you meant, then this is a revisionist
interpretation of how the P-51 was designed and why.

Corky Scott



That wasn't me claiming that, Corky, 'cause I know next to nothing about
the P51's construction or design.

It's just my contention that crash worthiness, called survivability in
the not to distant past, can be increased without a million dollar
budget and without a lot of extra weight. Common sense and load path
analysis are useful in this regime, and you don't have to wear white
coats and carry a slide rule to understand it. It is not hard to do,
produces useful results, and CAN NOT be replaced with electronics.

I would go more into the Delta's features, like how the forward cockpit
tapers back so that the longerons will bend away from the passengers in
the case of a frontal collision, but then I'd have to take more pictures
that show the structure clearly, and finish it up with dropping the
frame off a cliff to prove that the tail will in fact slow down as the
forward fuselage crumples. 8*)

--
http://www.ernest.isa-geek.org/
"Ignorance is mankinds normal state,
alleviated by information and experience."
Veeduber

The Grumman Ag Cat, among others, was designed with a stronger than required
(for mission or for certification) cockpit section/seat/roll-over
protection/restraint system. There are numerous examples of crashes that
pilots walked away from.


BJC



wrote in message
...
On 19 May 2004 12:03:24 -0700, (Jim-Ed Browne)
wrote:

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?

You do? References please. I've studied that fighter for years and
this is the first I've ever heard of Kindelberger designing the
cockpit like a modern car is designed.

Thanks, Corky Scott

On Fri, 21 May 2004 15:41:04 -0500, frank wrote:

Air bags are a factory option on some certified planes, including the
Mooney. The bags are built into the seat belts.

Frank


How are these things controlled? Where is the g-switch that triggers
them? Do they need electrical power to run the system? I wonder what
sort of electrical failures could cause them to fire when they shouldn't?
There have been incidents and accidents where debris in wiring
bundles has shorted a live wire to another wire, thus sending voltage
where it wasn't meant to go. This could potentially cause one of those
air bags to fire when it shouldn't.

I wonder if the air bag would push forward on the yoke if it fired in
flight? If this happened at low altitude, or a high enough airspeed,
could it cause an accident? If so, could installing one of these
air bags actually reduce the level of safety? Of is the perception of
safety more important than actual safety?

Just wondering.

--
Kevin Horton RV-8 (finishing kit)
Ottawa, Canada
http://go.phpwebhosting.com/~khorton/rv8/
e-mail: khorton02(_at_)rogers(_dot_)com

"Kevin Horton" wrote in message
news
On Fri, 21 May 2004 15:41:04 -0500, frank wrote:
I wonder if the air bag would push forward on the yoke if it fired in
flight? If this happened at low altitude, or a high enough airspeed,
could it cause an accident? If so, could installing one of these
air bags actually reduce the level of safety? Of is the perception of
safety more important than actual safety?

There are many "safety" devices, including airbags, safety belts, helmets
etc. that can occasionally backfire in a way to cause a death that might
otherwise not happen. The important thing is that after all is said and done,
the pile of people killed by the device must be much smaller than the pile of
people that would otherwise be dead without the device.


Vaughn

"Pete Schaefer" wrote in message
news:xMprc.4694$ny.935185@attbi_s53...

"anonymous coward" wrote in message
news
I imagine you would want something that would deform around (for the
sake
of argument) 10-20Gs.

Hmm....just shooting from the hip, that sounds like good range.

one's foot, so my worry is that if you used a foam that was soft enough
to
protect your back, it would be easy to put your foot or elbow through
it.

I'd think you'd put a covering of something rigid over it. Maybe a thin
layer of glass or maybe just some epoxy to make the top rigid enough to
prevent dinging it under normal use.

Behind the canard - in my dreams.

Maybe the thing to do is mount the seat to something that will give
somewhat
under crash loads. Might be hard in something like a Long/Vari-EZ, since
(I
think, working from memory here) that the EZ seat is mounted directly to
some major structural members. Would need some additional stuff to
isolate
the seat with some energy-absorbing stuff that would let it give a bit
(probably don't need more than a couple of inches in a crash).

I have heard that the racing drivers use alu honeycomb. That sounds like
it might be seriously expensive.

There's probably a ton of data on stuff that people have tried for driver
protection in the automotive world. Unfortunately, air-bags are out of
the
question for aviation use (for the pilot at least....probably for
everyone).
But there must be a ton of other stuff. I'd bet that NASA has sponsored a
bunch of research under the GA revitalization thingy that would be
applicable. Rather than us spend our time speculating here, maybe some
Google time is warranted. There is probably someone at NASA Langley that
would serve as a point of contact, too. There might even be some
technology
transfer programs around that we could take advantage of. Not sure how
they
would react to helping the average joe home-builder, but I'm sure they
make
a lot of data available to certified manufacturers.

Pete

It would be interesting to build a seat supported by empty aluminum soda
cans. A two-high stack would give a fair amount of deceleration space.
Calibrate for the load by the number of cans you use in parallel.
My experience crunching them for recycling has been that, undented, they're
very consistent in how they crush.
A poor man's honeycomb?

Tim Ward

On Fri, 21 May 2004 19:04:45 -0700, "Tim Ward"
wrote:

:
:It would be interesting to build a seat supported by empty aluminum soda
:cans. A two-high stack would give a fair amount of deceleration space.
:Calibrate for the load by the number of cans you use in parallel.
:My experience crunching them for recycling has been that, undented, they're
:very consistent in how they crush.
:A poor man's honeycomb?

I know one of the missionary flying groups makes seat supports out of
columns of rolled up corrugated cardboard - great energy absorbtion.
Low density urethane foam works nicely too - crushes and doesn't
rebound.

When I was in high school in the 70's in physics class we made a 10
mph bumper for a car out of full soda cans - the energy went into the
soda spraying sideways. Very messy, but lots of fun.