Canopy causes cockpit fire

Yesterday afternoon Mark Mocho (MM Fabrication) opened
the canopy of his Pegasus to get his cell phone. By
the time he made a call to me, his soaring hat, which
was lying atop the glare shield, was smoking. The
canopy was acting like a big magnifying glass and focusing
the sun's rays onto a quarter-size spot just above
the instrument panel. Scary to think what would have
happened if he'd walked away for a few minutes.

Photos are at http://www.silentwingsairshows.com/canopy.html
Notice the burn marks on the instrument panel from
previous solar encounters. One shot is of Mark (no
that's NOT Jack Nicholson) duplicating the sun angle
with a flashlight.

I'd heard of this phenomenon before, but couldn't figure
out exactly how it happened. Seems it's not the light
coming through the canopy, but the light reflected
from the inner surface (which is roughly parabolic
in shape), that causes the problem. At a shallow grazing
angle, enough light is reflected to get smokin' hot.
Nice trick to know if you ever get ants in your cockpit
;o)

Bob

Just take a look at the backseat headrest of most newer K21s - They are all
pitted with burn marks from the magnifying affects of the canopy.
rgds
Stephen

"Bob C" wrote in message
...
Yesterday afternoon Mark Mocho (MM Fabrication) opened
the canopy of his Pegasus to get his cell phone. By
the time he made a call to me, his soaring hat, which
was lying atop the glare shield, was smoking. The
canopy was acting like a big magnifying glass and focusing
the sun's rays onto a quarter-size spot just above
the instrument panel. Scary to think what would have
happened if he'd walked away for a few minutes.

Photos are at http://www.silentwingsairshows.com/canopy.html
Notice the burn marks on the instrument panel from
previous solar encounters. One shot is of Mark (no
that's NOT Jack Nicholson) duplicating the sun angle
with a flashlight.

I'd heard of this phenomenon before, but couldn't figure
out exactly how it happened. Seems it's not the light
coming through the canopy, but the light reflected
from the inner surface (which is roughly parabolic
in shape), that causes the problem. At a shallow grazing
angle, enough light is reflected to get smokin' hot.
Nice trick to know if you ever get ants in your cockpit
;o)

Bob

I'd heard of this phenomenon before, but couldn't figure
out exactly how it happened.

I believe it occurs when the sun angle is parralel with the top of the open
canopy and the magnification is caused by rays passing through the plexiglass
at almost a zero angle. The fire is started on any object that is close to the
focus point, ie. instrument panels, head rest on K-21 or DG-300. I know of an
ASH-25 that was *totaled* after a cockpit fire caused by this phenomenon.
JJ Sinclair

Photos are at http://www.silentwingsairshows.com/canopy.html

what is that, THREE moving map displays on the panel? And what are those wires
coiled around the hat band of the bucket hat-some sort of induction device that
is part of an experimental head-up display?
There is secret experimental nav testing going on here and the cat is out of
the bag....spill the details!!


ps: how does that Ball GC work for you? I sold one to a Russia pilot about five
years ago after I could not make it work with GPS input.

-


-
Mark Navarre
2/5 black ace
LoCal, USA
remove brain to reply
-

I've seen it happen on an ASW-24. The 24 was oriented
with the tail towards the southwest (northern hemisphere,
in North Carolina, USA). The canopy was fully open
and pointed towards the sun and we smelled plastic.
It was melting a portion of the trim around the glare
shield. We then moved the canopy up and down and watched
the bright white spot form on the glare shield when
the canopy was in the 'sweet spot.' It looked just
like it looks when using a magnifying glass out in
the sun when burning paper or ants.

Since my LS-1d has the removable canopy rather than
a hinged one, I guess I don't have to worry about it.
:-)

Ray Lovinggood
Carrboro, North Carolina, USA

At 13:54 04 May 2004, Jj Sinclair wrote:

I'd heard of this phenomenon before, but couldn't figure
out exactly how it happened.

I believe it occurs when the sun angle is parralel
with the top of the open
canopy and the magnification is caused by rays passing
through the plexiglass
at almost a zero angle. The fire is started on any
object that is close to the
focus point, ie. instrument panels, head rest on K-21
or DG-300. I know of an
ASH-25 that was *totaled* after a cockpit fire caused
by this phenomenon.
JJ Sinclair

And thus the checklist for my ASH-26E states "tail NOT pointed at sun".

Last season, the canopy reflected sun burned holes in my little PZL compass on
top of my instrument panel cover. It gets your attention real fast to whiff a
bit of that petroleum based liquid and think you have a fuel leak!

Kemp
9J

I'd heard of this phenomenon before, but couldn't figure
out exactly how it happened. Seems it's not the light
coming through the canopy, but the light reflected
from the inner surface (which is roughly parabolic
in shape), that causes the problem. At a shallow grazing
angle, enough light is reflected to get smokin' hot.
Nice trick to know if you ever get ants in your cockpit
;o)

Bob

I melted the aft facing edge of the GPS antenna that was mounted on the
shroud that covered the instrument panel on my LS-1F. I think it's not
the light passing through the canopy, but reflecting off the inside
surface when the open canopy is facing the sun. My glider was tail
pointed to the east and this was in the morning sun. Fortunately the
design of the LS-1 is such that it's unlikely that anything would find
it's way into the focal point of the beam in most cases.

Bob C wrote:
Yesterday afternoon Mark Mocho (MM Fabrication) opened
the canopy of his Pegasus to get his cell phone. By
the time he made a call to me, his soaring hat, which
was lying atop the glare shield, was smoking. The
canopy was acting like a big magnifying glass and focusing
the sun's rays onto a quarter-size spot just above
the instrument panel. Scary to think what would have
happened if he'd walked away for a few minutes.

Photos are at http://www.silentwingsairshows.com/canopy.html
Notice the burn marks on the instrument panel from
previous solar encounters. One shot is of Mark (no
that's NOT Jack Nicholson) duplicating the sun angle
with a flashlight.

I'd heard of this phenomenon before, but couldn't figure
out exactly how it happened. Seems it's not the light
coming through the canopy, but the light reflected
from the inner surface (which is roughly parabolic
in shape), that causes the problem. At a shallow grazing
angle, enough light is reflected to get smokin' hot.
Nice trick to know if you ever get ants in your cockpit
;o)

Bob

I had the great idea of putting felt on the glare shield of my LS-3 to
hold down reflections. After burning a couple holes in it, I removed it.



Mark Zivley wrote:

I melted the aft facing edge of the GPS antenna that was mounted on the
shroud that covered the instrument panel on my LS-1F. I think it's not
the light passing through the canopy, but reflecting off the inside
surface when the open canopy is facing the sun. My glider was tail
pointed to the east and this was in the morning sun. Fortunately the
design of the LS-1 is such that it's unlikely that anything would find
it's way into the focal point of the beam in most cases.

Bob C wrote:

Yesterday afternoon Mark Mocho (MM Fabrication) opened
the canopy of his Pegasus to get his cell phone. By
the time he made a call to me, his soaring hat, which
was lying atop the glare shield, was smoking. The
canopy was acting like a big magnifying glass and focusing
the sun's rays onto a quarter-size spot just above
the instrument panel. Scary to think what would have
happened if he'd walked away for a few minutes.

Photos are at http://www.silentwingsairshows.com/canopy.html
Notice the burn marks on the instrument panel from
previous solar encounters. One shot is of Mark (no
that's NOT Jack Nicholson) duplicating the sun angle
with a flashlight.

I'd heard of this phenomenon before, but couldn't figure
out exactly how it happened. Seems it's not the light
coming through the canopy, but the light reflected
from the inner surface (which is roughly parabolic
in shape), that causes the problem. At a shallow grazing
angle, enough light is reflected to get smokin' hot.
Nice trick to know if you ever get ants in your cockpit
;o)

Bob

I believe it occurs when the sun angle is parralel with the top of the open
canopy and the magnification is caused by rays passing through the plexiglass
at almost a zero angle.

I've had it happen twice over the many years. I found that it happens when the
open canopy top is almost parallel to the sun rays, which are reflected off the
bottom surface and are focussed somewhere near the instrument panel. I don't
believe it happens if the sunrays pass through the canopy, since the reflected
rays are significantly lower in strength, having had two surfaces to pass
through. Maybe someone would like to experiment?

Bob

On 04 May 2004 13:56:28 GMT, n (Mark Navarre)
wrote:

Photos are at http://www.silentwingsairshows.com/canopy.html

what is that, THREE moving map displays on the panel? And what are those wires
coiled around the hat band of the bucket hat-some sort of induction device that
is part of an experimental head-up display?
There is secret experimental nav testing going on here and the cat is out of
the bag....spill the details!!


It is the experimental thought controlled instrument interface -
obviously.

Mike Borgelt