homebuilt safety

Pete Schaefer wrote:
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.


Don't mean to tell you your business, but....bulls417!!

See my website for PICTURES of proof. Crumple zones are not only
feasible, reliable, and light, but they've been flying for over 40years.

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.


No extra cost or weight, and why would you get the FAA to sign off on a
homebuilt aircraft design? It won't cost any more to design, model and
test than any other homebuilt design. Why would you need to do
destructive testing? Do I have to break my wings to prove they will
hold me up in flight?

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.


My goal is to stay well under $20k. One builder lost his engine and
didn't make the airport. Buried his Delta in a barnyard silo after
passing it through a bale of hay. Walked away from it. If you can keep
the landing to an acute angle crumple zones WILL help.

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.


From the statistics, the fuel delivery reliability rest most directly
on the pump in the fuel truck back at the airport. There ain't any
hardware that can fix that fault. It's a software problem 8*)

As for the rest of that...now who's talking about spending big dollars?
Crashworthiness should be part of the primary structure. Not a heavy,
expensive afterthought.

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.



When I sit in my incomplete project, I can look around at all the steel
that has to bend before the outside gets to me, I can imagine all the
fiberglass that will have to give way, and even if I'm no safer than in
the aluminum can I trained in, I certainly feel that way. There are not
any electronics or flight systems that will ever make me feel safer than
several feet of protection between me and the hard stuff.


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

"Ernest Christley" wrote in message
. com...
See my website for PICTURES of proof. Crumple zones are not only
feasible, reliable, and light, but they've been flying for over 40years.

There's a lot of stuff on your site. I didn't see anything about crumple
zones. Please provide pointers to what you're talking about. I kept flipping
through your pages, doing searches for "crumple"....no hits.

test than any other homebuilt design. Why would you need to do
destructive testing? Do I have to break my wings to prove they will
hold me up in flight?

As far as I know, crumple zones are not reusable. Isn't that the point of
them? How can you test the design if you don't do it destructively? Am I
missing something here? Or are you saying that analysis is sufficient? Or
are you confusing crumple zones with something else? I don't get your
analogy, either. You test a wing structure by putting it under load and
showing it holds; you test an energy dissipation feature like a crumple zone
by subjecting it to an impact and showing that it crumples by the amount
predicted.

the landing to an acute angle crumple zones WILL help.

I didn't see the crumple zone features of the Delta that you are refering
to.

Crashworthiness should be part of the primary structure. Not a heavy,
expensive afterthought.

ALL of the crashworthiness considerations I've ever seen have been the usual
"this is the max expected design load, so make it strong enough to withstand
XX times that". Often, there is additional strength in components that
protect the pilot. But that's different than crumple zones.

When I sit in my incomplete project, I can look around at all the steel

Fine. If that gives you a warm fuzzy, then good for you. Me? I'll place my
emphasis on accident prevention - both by design, training, and proper
preparation.

There are not any electronics or flight systems that will ever make me
feel safer than
several feet of protection between me and the hard stuff.

Not even an angle-of-attack sensor? Dang. Given that they are available, I
wouldn't consider building a new plane without one. But your Deltas don't
have enough elevon authority to reach CLmax, so that's probably not an issue
for you.

Pete Schaefer wrote:
"Ernest Christley" wrote in message
. com...

See my website for PICTURES of proof. Crumple zones are not only
feasible, reliable, and light, but they've been flying for over 40years.


There's a lot of stuff on your site. I didn't see anything about crumple
zones. Please provide pointers to what you're talking about. I kept flipping
through your pages, doing searches for "crumple"....no hits.

Does it have to be labeled "Crumple Zone" to work?
No, seriously, after looking at the pictures from the perspective of
someone who doesn't look at the plane everyday, the crumple zones are
not quite so obvious. It's best seen in this pictu

http://ernest.isa-geek.org/Delta/Pic...DykeDelta5.jpg

It's especially easy to see in Tom Bauer's red and white Delta on the
bottom. There is about 18" of steel and fiberglass that has to crumple
before outside objects can reach the the internal cage that forms the
cockpit. The cockpit frame has to bend up another foot or so before
reaching the pilot.

A zone of material that has to crumple before outside objects get to
you, ie, a crumple zone.


test than any other homebuilt design. Why would you need to do
destructive testing? Do I have to break my wings to prove they will
hold me up in flight?


As far as I know, crumple zones are not reusable. Isn't that the point of
them? How can you test the design if you don't do it destructively? Am I
missing something here? Or are you saying that analysis is sufficient? Or
are you confusing crumple zones with something else? I don't get your
analogy, either. You test a wing structure by putting it under load and
showing it holds; you test an energy dissipation feature like a crumple zone
by subjecting it to an impact and showing that it crumples by the amount
predicted.


Do you have to know the exact amount of energy the object will absorb
before deciding that you're safer with than without? I'm not saying
that this Delta can take on cliffs, I'm saying that in an off airport
landing, with all other things being equal (they never are though) the
Delta would be safER with it's crumple zone than the typical
conventional GA aircraft, and it cost nothing in additional weight,
labor or money. You don't have to spend millions as you claim to prove
the obvious.


the landing to an acute angle crumple zones WILL help.


I didn't see the crumple zone features of the Delta that you are refering
to.


Crashworthiness should be part of the primary structure. Not a heavy,
expensive afterthought.


ALL of the crashworthiness considerations I've ever seen have been the usual
"this is the max expected design load, so make it strong enough to withstand
XX times that". Often, there is additional strength in components that
protect the pilot. But that's different than crumple zones.


Maybe we should define what we're talking about. In my simplistic view,
a crumple zone is "stuff that breaks, so you don't have to". The front
leading edge is NOT designed to stop the Delta from flying through a
tree. It's designed to hold the nose in the air; HOWEVER, it is
completely willing to sacrifice itself to HELP the pilot survive that
close encounter with the wooden kind. A good design serves its purpose.
A great design will serve many purposes.


When I sit in my incomplete project, I can look around at all the steel


Fine. If that gives you a warm fuzzy, then good for you. Me? I'll place my
emphasis on accident prevention - both by design, training, and proper
preparation.

Building this plane is taking me about 3yrs minimum. I don't see why
there's not time for all of it.

I take the viewpoint that **** is going to happen, no matter how much we
try to prevent it. If I assume that at some point I'll have to put down
when I really don't want to, I have the chance to prepare for it. Try
to prevent the bad stuff, but be ready in case it does finally happen.



There are not any electronics or flight systems that will ever make me

feel safer than

several feet of protection between me and the hard stuff.


Not even an angle-of-attack sensor? Dang. Given that they are available, I
wouldn't consider building a new plane without one. But your Deltas don't
have enough elevon authority to reach CLmax, so that's probably not an issue
for you.




One of the other builders response to my question about AOA indicator
was that the best one for the Delta was the altimeter. If it's
unwinding too fast you need to let the nose down some 8*)

But to answer your question, if you're having to put it down in a small
field cause you blew a jug, how will the AOA indicator help with that
tree that's getting awfully close? When all your altitude and energy
has been spent and your low, slow and close to hard stuff, I'll take a
few pound of steel tube and fiberglass buffer over a ton of fancy
electronics any day.


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

"Ernest Christley" wrote in message
om...
Does it have to be labeled "Crumple Zone" to work?

A crumple zone is a pretty specific type of structure. It's a technical
term.

It's especially easy to see in Tom Bauer's red and white Delta on the
bottom. There is about 18" of steel and fiberglass that has to crumple

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.

A zone of material that has to crumple before outside objects get to
you, ie, a crumple zone.

Please don't make up definitions on your own for technical stuff. It just
confuses everyone.

Do you have to know the exact amount of energy the object will absorb
before deciding that you're safer with than without?

It's about quantifying a benefit. How much benefit -vs- how much weight,
etc. Do the math and make the design decision.

landing, with all other things being equal (they never are though) the
Delta would be safER with it's crumple zone than the typical
conventional GA aircraft, and it cost nothing in additional weight,
labor or money. You don't have to spend millions as you claim to prove
the obvious.

Obvious? I call that speculation without a shred of evidence to support it.

Maybe we should define what we're talking about. In my simplistic view,
a crumple zone is "stuff that breaks, so you don't have to".

There is a ton of good technical info on crumple zones as used in automotive
design. Instead of pulling stuff out of your butt, go look it up.

field cause you blew a jug, how will the AOA indicator help with that
tree that's getting awfully close?

An AOA indicator will help you to precisely select a best-glide speed,
giving you more time and more options.

Pete Schaefer wrote:
"Ernest Christley" wrote in message
om...

Does it have to be labeled "Crumple Zone" to work?


A crumple zone is a pretty specific type of structure. It's a technical
term.


Technical terms have definitions, and believe it or not, I can read.
You can step off the high horse, 'cause we're all human here. If you've
got a definition that will change the definition from what I've stated,
then put it out there. You're liable to teach a whole lot of people a
thing or two, including myself. I've offered a simple, workable
definition below.


It's especially easy to see in Tom Bauer's red and white Delta on the
bottom. There is about 18" of steel and fiberglass that has to crumple


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.


A zone of material that has to crumple before outside objects get to
you, ie, a crumple zone.


Please don't make up definitions on your own for technical stuff. It just
confuses everyone.


Whew!! The snots flying now!

Uh. Excuse me. This IS r.a.h. you know. Making up our own definitions
is what we do best.


Do you have to know the exact amount of energy the object will absorb
before deciding that you're safer with than without?


It's about quantifying a benefit. How much benefit -vs- how much weight,
etc. Do the math and make the design decision.


Uh. Excuse me again. There is NO weight added. You've just put part
of the structure that has to be there anyway between yourself and
obstacles. It's stuff that crumples, and it's in a zone (around here,
we call it "The Stuff to the Front and Side of Daddy Zone", careful I
have that phrase copyrighted, possibly trademark, and I'm gonna talk to
a lawyer about a patent), therefore it's a crumple zone.


landing, with all other things being equal (they never are though) the
Delta would be safER with it's crumple zone than the typical
conventional GA aircraft, and it cost nothing in additional weight,
labor or money. You don't have to spend millions as you claim to prove
the obvious.


Obvious? I call that speculation without a shred of evidence to support it.

Nope no evidence whatsoever, and I'm not about to go out and bend up a
bunch of perfectly good, expensive and increasingly scarce 1" 4130 steel
tube to prove that it absorbs a lot of energy as it's bending.



Maybe we should define what we're talking about. In my simplistic view,
a crumple zone is "stuff that breaks, so you don't have to".


There is a ton of good technical info on crumple zones as used in automotive
design. Instead of pulling stuff out of your butt, go look it up.


Look at all the technical info you want. A zone that crumples. It's
self defining. I don't need a self styled expert to tell me that I'm
safer if I have something other than me to absorb the impact energy.


field cause you blew a jug, how will the AOA indicator help with that
tree that's getting awfully close?


An AOA indicator will help you to precisely select a best-glide speed,
giving you more time and more options.



OK, you've had a perfect glide into the only field in the valley as you
tried to cross the mountain. You're just below the treetops, and the
end of the field is coming quick. How many options will the indicator
give you?

Besides, that's what the airspeed indicator is for.

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

"Ernest Christley" wrote in message
om...
Technical terms have definitions, and believe it or not, I can read.

Well, then look it up. Rather than get offended, go look it up on Google.
You'll get tons of hits, but there will be some gems there that explain the
concept. It wasn't me that started applying the term "crumple zone" to
every part of the airplane.

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

Your definition is way too general and does not match up with common usage
in the engineering circles where the term comes from.A crumple zone is a
structural piece that is designed to compress in a specific way under a load
in a certain direction. Instead of just tearing to pieces, it folds up like
an accordion, thus reducing the peak stresses transmitted to the rest of the
structure. A crumple zone is designed to collapse upon reaching a certain
threshold, usually determined by some maximum impact velocity and the weight
of the rest of the structure. Think about an empty soda can. If you
carefully stand on it, it might support your weight. If you hop up onto it,
the sides will fold up like an accordion. Put a can on it's side, and it
fails in quite a different manner.

Uh. Excuse me. This IS r.a.h. you know. Making up our own definitions
is what we do best.

Yup. It's one of my chief annoyances of newsgroups: very low signal to noise
ratio.

Nope no evidence whatsoever, and I'm not about to go out and bend up a
bunch of perfectly good, expensive and increasingly scarce 1" 4130 steel
tube to prove that it absorbs a lot of energy as it's bending.

If I had an idea for, say, a new engine mount system that could dramatically
increase my chance of survival without increasing weight that much, I
wouldn't hesitate for a second to build a prototype and at least put it
through some static load tests. You wouldn't necessarily have to wreck an
entire airframe, as long as you could demonstrate the behavior with an
appropriate design load.

If you don't want to go through that, then do what everyone else does and
pick a max design load and apply an overdesign factor.

Look at all the technical info you want. A zone that crumples. It's
self defining. I don't need a self styled expert to tell me that I'm
safer if I have something other than me to absorb the impact energy.

Fine, stick to your own definitions if you want. It's not my goal in life to
educate you. And I never claimed to be a structures expert, but I do
interface with guys every day who are. I understand the issues and how they
affect what I do. But I don't go around changing definitions.

OK, you've had a perfect glide into the only field in the valley as you
tried to cross the mountain. You're just below the treetops, and the
end of the field is coming quick. How many options will the indicator
give you?

If you've taken advantage of the best your airframe can do, then maybe
you've arrived above the valley with enough altitude so that you have a
choice as to what direction you're going to land in.

Besides, that's what the airspeed indicator is for.

And how do you chose the best airspeed? Just pick one out of a book? Well,
the best airspeed changes based on your current loadout. The optimum angle
of attack for glide does not change. Without looking at alpha, you're just
going on a rough guess that will likely be off significantly.

"Ignorance is mankinds normal state,
alleviated by information and experience."

Anyway, I've done all the typing on this topic that I'm going to do. If you
want to deviate from the normal state some more, there's plenty of books,
articles, etc., out there for you to read. You don't have to take my word
for anything. Given that you've chosen a low aspect-ratio design, not having
any choices where you set your airplane down may be much more of a reality
for you.

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.

That the P-51 had a monocoque type fuselage and the engine assembly
bolted to it, was just the way fighters were built. It was a
production thing, a compromise between what the engineers really
wanted and what was possible to get the airplanes out the door as
inexpensively as possible and still be lightweight and strong. That
the fuselage was stong was a necessity for combat, withstanding high G
maneuvers and near supersonic speeds, it had nothing to do with crash
safety.

The P-47 Thunderbolt was also designed exactly the same way: monocoque
fuselage and the engine bolted to the firewall. Except that Republic
decided to make the airplane REALLY strong. One example, according to
one of it's more famous pilots, rolled itself up into a ball in Long
Island sound after pulling out of a dive. The pilot was sitting on
the shore somewhat dazed but alive after crawling out of the wreckage
when they found him. Did Republic set out to specifically design the
P-47 to protect the pilot in crashes? No, but it was so strong that
it was more crashworthy than virtually any other fighter in WWII. It
paid for this crashworthiness by being the heaviest single engine
fighter of the war. The phenominal weight made it's climb, for a long
time, it's least impressive feature.

Corky Scott

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

On Thu, 20 May 2004 03:25:58 GMT, Ernest Christley
wrote:


Don't mean to tell you your business, but....bulls417!!

See my website for PICTURES of proof. Crumple zones are not only
feasible, reliable, and light, but they've been flying for over 40years.

Where on your website?

Corky Scott