homebuilt safety

On Sun, 30 May 2004 18:44:20 +0000, Richard Lamb wrote:

Ok, enough abstract thinking.
Let's see what you guys can dream up for a specific airframe.

With your weight budget I guess it's useless to try to design a plane that
you can nosedive in at Vne and walk away from... Probably better to
concentrate on the low-hanging fruit (assuming there is some).

My guess is that the best place to look for this, would be in injuries
that are neither fatal nor insignificant - though I guess there may also
be fatalities that have been prevented just as easily.

I don't trust my intuitions on the subject - does anyone know of any
sources that say what the most common non-fatal injuries are in GA
accidents? My guess is that they'd need to be pretty specific - 'back
injury' would not be much help; 'lower back injury due to high descent
rate at landing' would be.

I'm happy to browse a database if someone can point me in the right
direction - I just don't know where to look.

This is a proposed single seat all metal low wing sportster.

Power is intended to be 2180 VW or Rotax 912.

Figure 550 empty weight, 900 gross?
I've got 33 pounds budgeted for payload.

The hang-glider pilot in me says that's enough for a camera, some
lunch and a flask with plenty to spare. The long-distance cyclist within
me says that's not even enough for a tent, lunch, a stove, a toolkit, a
coat and a bicycle pump.

How much of that do you guys thing should be spent on
crash protection?

I guess the question is, 'how much of that can we persuade you to spend on
crash protection?'

And is there anything else you'd rather put in than 'structural
protection'? - e.g. a ballistic 'chute (if you believe in them).

http://home.earthlink.net/~n6228l/l-one.htm


The CAD drawings look sweet...

AC

With your weight budget I guess it's useless to try to design a plane
that
you can nosedive in at Vne and walk away from... Probably better to
concentrate on the low-hanging fruit (assuming there is some).

Go buy an old cropduster -- they're far and away the most crashworthy
aircraft out there

Ed Wischmeyer

On Mon, 31 May 2004 06:58:35 -0700, Ed Wischmeyer
wrote:

With your weight budget I guess it's useless to try to design a plane
that
you can nosedive in at Vne and walk away from... Probably better to
concentrate on the low-hanging fruit (assuming there is some).

Go buy an old cropduster --

How much is BOb going for? :-)

Ron Wanttaja

Nose in at Vne, you are gonna get what you deserve!
Let's look at the things we CAN survive and try to improve our
poor sucker's chances.

I already have four compression fractured vertebra, so this is not
just an academic exercise. (From my fun summer vacation in Viet Nam)

Sitting on the main spar like that, there just isn't a lot of
'crumple space' between the warm pink bottom and the cold hard ground.

So any landing that wipes out the gear could be pretty serious.

BTW, that is one of the things we are looking at very carefully.
In the event of a gear failure, where will all the big pieces go,
and will they go thru anything soft and squishy on the way out(?).

Beyond pilot comfort, I think this is a good place for a layer of
Temperfoam (seat bottom). It's heavy stuff for its size, but
Temperfoam will absorb quite a bit of energy in an impact situation.
Anything that can slow down the energy transfer - even a few more
milliseconds - will reduce back injuries significantly.
It shouldn't take more than six pounds for the foam.

After that, the most serious threat is smacking the head on something
hard or pointy. This cockpit is close enough that a good shoulder
harness should be mandatory. But that brings up the age old question
of where to attach the harness so that it can actually take the impact
load without failing the attach structure.

I'm guessing 30 G's (eyeballs forward) for 50 milliseconds?

Next, I worry about fires. Been there, singed holes in my T shirt.
A big gas tank in front of the panel is the simplest lightest way
to store gas, but it is also vulnerable in an accident. Cracks in
the tank, broken out fittings, or fuel line torn loose? None of
these are pleasant options when the gas is sitting in your lap.

However, on this plane, there is no way to put 20 gallons (120 lbs)
in a nose tank and still be within the CG range. For that one reason
we have decided to put the tanks in the wings. Ok, so now, do we
still want to have a header tank at the firewall (for a gravity feed),
or feed directly from the wing tanks (gotta have fuel pumps anyway!)?

Lastly, reducing the amount of commanded energy at touch down is
probably the best way to improve survivability. Get the stall speed
down as much as practical.

My first wing estimates indicated stall speed about 65 mph.
(I had some rather impressive fantasies about cruise speed)
That's just way to very dam fast (for this old fart, any way).
Another 12 sq ft of area, and a slightly different airfoil
got it down to around 52 mph.

Only way to improve on that is to add flaps.
Flaps could cost as much as eight or ten pounds...
But getting the landing speed down to 45 MPH or so?
Hard call there. (compromise)

I'm afraid a ballistic parachute is way over weight budget.
It certainly won't help you get over the trees at the end of the
runway...



Richard Lamb


http://home.earthlink.net/~n6228l/l-one.htm

How much does a parachute weigh?

"Richard Lamb" wrote in message
...
I've got 33 pounds budgeted for payload.

On Thu, 03 Jun 2004 02:42:50 GMT, "Pete Schaefer"
wrote:

How much does a parachute weigh?

"Richard Lamb" wrote in message
...
I've got 33 pounds budgeted for payload.



Twice as much as one chute...

Sorry, but I had to do that...

John

I shall look forward to seeing how it all turns out.

Good luck, & keep us posted.

AC


On Mon, 31 May 2004 18:31:59 +0000, Richard Lamb wrote:

I already have four compression fractured vertebra, so this is not
just an academic exercise. (From my fun summer vacation in Viet Nam)

Sitting on the main spar like that, there just isn't a lot of
'crumple space' between the warm pink bottom and the cold hard ground.

So any landing that wipes out the gear could be pretty serious.

BTW, that is one of the things we are looking at very carefully.
In the event of a gear failure, where will all the big pieces go,
and will they go thru anything soft and squishy on the way out(?).

Beyond pilot comfort, I think this is a good place for a layer of
Temperfoam (seat bottom). It's heavy stuff for its size, but
Temperfoam will absorb quite a bit of energy in an impact situation.
Anything that can slow down the energy transfer - even a few more
milliseconds - will reduce back injuries significantly.
It shouldn't take more than six pounds for the foam.

I never heard of it before - but it looks just the ticket.

After that, the most serious threat is smacking the head on something
hard or pointy. This cockpit is close enough that a good shoulder
harness should be mandatory. But that brings up the age old question
of where to attach the harness so that it can actually take the impact
load without failing the attach structure.

I'm guessing 30 G's (eyeballs forward) for 50 milliseconds?

Next, I worry about fires. Been there, singed holes in my T shirt.
A big gas tank in front of the panel is the simplest lightest way
to store gas, but it is also vulnerable in an accident. Cracks in
the tank, broken out fittings, or fuel line torn loose? None of
these are pleasant options when the gas is sitting in your lap.

However, on this plane, there is no way to put 20 gallons (120 lbs)
in a nose tank and still be within the CG range. For that one reason
we have decided to put the tanks in the wings. Ok, so now, do we
still want to have a header tank at the firewall (for a gravity feed),
or feed directly from the wing tanks (gotta have fuel pumps anyway!)?

Lastly, reducing the amount of commanded energy at touch down is
probably the best way to improve survivability. Get the stall speed
down as much as practical.

My first wing estimates indicated stall speed about 65 mph.
(I had some rather impressive fantasies about cruise speed)
That's just way to very dam fast (for this old fart, any way).
Another 12 sq ft of area, and a slightly different airfoil
got it down to around 52 mph.

Only way to improve on that is to add flaps.
Flaps could cost as much as eight or ten pounds...
But getting the landing speed down to 45 MPH or so?
Hard call there. (compromise)

I'm afraid a ballistic parachute is way over weight budget.
It certainly won't help you get over the trees at the end of the
runway...

I loooked up BRS systems - 34lb lol.



Richard Lamb


http://home.earthlink.net/~n6228l/l-one.htm