Thermal right, land left

In article ,
Eric Greenwell wrote:
Mark James Boyd wrote:
It might be useful to look at small airplane accidents, since they DO
have stall warning horns. I'm under the impression that stall/spin
accidents are a big cause of fatal accidents also. Do you have any numbers?


I looked up the last ten years of gliders (49 fatalities)
and then I looked up a three month window of airplane fatalities
from 3/94 to 6/94 (102 fatalities). I got lazy and didn't want
to look through more than 100, but I wanted to see final reports, so...

Gliders: 21 stalls of 49 fatalities = 43%

If you eliminate midairs and disconnected controls, 21 of 42 = 50%

Airplanes: 9 stalls of 102 fatalities = 9%

If you eliminate midairs and disconnected controls, 9 of 91 = 10%

A bunch of the airplane ones were also night and/or IFR (less than
half). But it seemed real clear that more of the glider fatalities
could have been stalls. Anyway, I concluded that airplane guys
don't stall very much close to the ground...

I was also VERY surprised to find a lot of medical problems
with airplenes, and I don't think even one fatal glider accident
due to a medical condition. This is really surprising...I'll
need to look at all 250 fatal glider reports at some point to
see if there are ANY medical fatalities...

Anyway, yes glider pilots die from stalls as a real big
factor. I think it's because they don't have warning devices.
Hells bells, just hook 'em to the gear down and spoiler cracked
switches, so they're off the rest of the time (thermalling).

Or maybe somebody has a better idea. I dunno, I'm just real
surprised we don't have any stall horns at all on any gliders...

I'm not suggesting this isn't a good idea, but I do wonder...

Why do airplanes have ANY stall/spins during landing? Typically, they
have full control of their pattern (altitude, entry point), while the
glider accidents most often occur when the pilot can't do the desired
pattern because he returns too low.

Maybe we don't need a stall warning for gliders: perhaps a simple
airspeed alert would do everything that is needed, as long as it was
enabled by the gear being extended. I think it should alert regardless
of the spoiler position, since a low, slow pilot isn't likely to open
the spoilers.

DG sailplanes makes such a device, called the DSI. Take a look he

http://www.dg-flugzeugbau.de/dsi-e.html
DG Flugzeugbau GmbH / DSI - Digital Soaring Indicator

Is anyone using one of these? Maybe we already have what we need, but
not enough people are using it.

Well, some of the power accidents are just newer pilots that
weren't trained to properly react to the horn. In some
I suspect the horn wasn't even working (I've been surprised by
failed horn a few times).

The airspeed idea is good (better than nothing) but doesn't
tell the AOA at both wingtips, and doesn't seem to account for the
G loading in a tight turn. Also, as another poster pointed out,
the horn detects gusts, which is pretty useful IMHO.

In any case, I'd just love to have a glider with an AOA tab
(each with a different tone) on each wingtip, and teach some spins in it.
I'd also love to see how well it does when thermalling. Maybe
Andreas is right and one can't tell horn vs. vario, but it would be
a kick to try...

Anyway, just another fun idea...now let's cut out this
nonsense and get back to implementing the turbine powered sparrowhawk ;P

--

------------+
Mark Boyd
Avenal, California, USA

Mark James Boyd wrote:
Well, some of the power accidents are just newer pilots that
weren't trained to properly react to the horn. In some
I suspect the horn wasn't even working (I've been surprised by
failed horn a few times).

The airspeed idea is good (better than nothing) but doesn't
tell the AOA at both wingtips,

This probably won't be useful for landing, since the selected airspeed
should be high enough to make the AOA at the tips irrelevant.

and doesn't seem to account for the
G loading in a tight turn.

Take another look: both the DSI and the 302 have accelerometers that let
them account for G loading. Anyway, the stall/spins typically aren't
from tight turns, but shallow ones.

Also, as another poster pointed out,
the horn detects gusts, which is pretty useful IMHO.

I think any gusts that affect your landing will be readily apparent as
the glider twitches and bobs in response to them. Certainly they are
noted by the pilot while thermalling.

Maybe it's time to give airspeed alerts in the pattern a chance.


--
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change "netto" to "net" to email me directly

Eric Greenwell
Washington State
USA

Looks to me that having AOA indicators in the IP for both wingtips to
optimize climbing performance and avoid the onset of spin would be great .

Karel, NL


"Mark James Boyd" schreef in bericht
news:4053a369$1@darkstar...
In article ,
Eric Greenwell wrote:
Mark James Boyd wrote:
It might be useful to look at small airplane accidents, since they DO
have stall warning horns. I'm under the impression that stall/spin
accidents are a big cause of fatal accidents also. Do you have any
numbers?


I looked up the last ten years of gliders (49 fatalities)
and then I looked up a three month window of airplane fatalities
from 3/94 to 6/94 (102 fatalities). I got lazy and didn't want
to look through more than 100, but I wanted to see final reports, so...

Gliders: 21 stalls of 49 fatalities = 43%

If you eliminate midairs and disconnected controls, 21 of 42 = 50%

Airplanes: 9 stalls of 102 fatalities = 9%

If you eliminate midairs and disconnected controls, 9 of 91 = 10%

A bunch of the airplane ones were also night and/or IFR (less than
half). But it seemed real clear that more of the glider fatalities
could have been stalls. Anyway, I concluded that airplane guys
don't stall very much close to the ground...

I was also VERY surprised to find a lot of medical problems
with airplenes, and I don't think even one fatal glider accident
due to a medical condition. This is really surprising...I'll
need to look at all 250 fatal glider reports at some point to
see if there are ANY medical fatalities...

Anyway, yes glider pilots die from stalls as a real big
factor. I think it's because they don't have warning devices.
Hells bells, just hook 'em to the gear down and spoiler cracked
switches, so they're off the rest of the time (thermalling).

Or maybe somebody has a better idea. I dunno, I'm just real
surprised we don't have any stall horns at all on any gliders...

I'm not suggesting this isn't a good idea, but I do wonder...

Why do airplanes have ANY stall/spins during landing? Typically, they
have full control of their pattern (altitude, entry point), while the
glider accidents most often occur when the pilot can't do the desired
pattern because he returns too low.

Maybe we don't need a stall warning for gliders: perhaps a simple
airspeed alert would do everything that is needed, as long as it was
enabled by the gear being extended. I think it should alert regardless
of the spoiler position, since a low, slow pilot isn't likely to open
the spoilers.

DG sailplanes makes such a device, called the DSI. Take a look he

http://www.dg-flugzeugbau.de/dsi-e.html
DG Flugzeugbau GmbH / DSI - Digital Soaring Indicator

Is anyone using one of these? Maybe we already have what we need, but
not enough people are using it.

Well, some of the power accidents are just newer pilots that
weren't trained to properly react to the horn. In some
I suspect the horn wasn't even working (I've been surprised by
failed horn a few times).

The airspeed idea is good (better than nothing) but doesn't
tell the AOA at both wingtips, and doesn't seem to account for the
G loading in a tight turn. Also, as another poster pointed out,
the horn detects gusts, which is pretty useful IMHO.

In any case, I'd just love to have a glider with an AOA tab
(each with a different tone) on each wingtip, and teach some spins in it.
I'd also love to see how well it does when thermalling. Maybe
Andreas is right and one can't tell horn vs. vario, but it would be
a kick to try...

Anyway, just another fun idea...now let's cut out this
nonsense and get back to implementing the turbine powered sparrowhawk ;P

--

------------+
Mark Boyd
Avenal, California, USA

SAILPLANE STALL WARNING SYSTEMS - Recent History

Because of concern about sailplane stall accidents, during early 1987
OSTIV announced that they would sponsor a "Competition for Development
of a Special Flight Instrument for Stall Warning of Sailplanes". We of
the Dallas Gliding Association decided that entering that competition
was certainly a worthwhile project. The offered prize for 1st place
was 2,550 DM, and 1,000 DM for 2nd place. Those prizes were awarded
after flight-testing judging and during the 1989 OSTIV Congress at
Weiner Neustadt in Austria.
Over a 2-year period we studied various candidate configurations, and
performed developmental flight-testing with 5 or 6 different
experimental stall warning systems. While most of the flight-testing
was performed with my Ventus A, several other sailplanes ranging from
a Schweizer 1-26 to a Nimbus 3 were included. Flight testing included
flying into moderate rain showers, and flying with many natural bugs
along the wing leading edges.
We judged our best overall stall-warning configuration to be a small
floating vane mounted well aft on the top surface of the wing, and
entered that configuration into the 1998 OSTIV Competition fly-offs at
Weiner Neustadt. The Polish entry was judged to be the winner there,
but our configuration placed 2nd. The weakness in our design was that
its external mounting was subject to damage during club use.
The Polish design used the differential pressure measured between the
fuselage nose pitot tube and a small flush orifice located on the
bottom of the nose several inches aft of the pitot. It is essentially
an angle-of-attack indicator, and I believe that it is still marketed
today.
Although its external mounting makes it subject to handling damage,
the DGA design performs well in my opinion, even in rain and with bugs
and various flap settings. I have used it on my sailplanes
continuously since its development, and feel my flying is safer for
that. Its design is shown in the 7/90 issue of Soaring, and I believe
it was also published Sailplane & Gliding about that time.
Dick Johnson

We judged our best overall stall-warning configuration to be a small
floating vane mounted well aft on the top surface of the wing,

Beechcraft used this system on the early models of the Bonanza.

Robert Mudd

Wow, there have been some absolutely excellent posts on this
thread. Thank you to all those who contributed...
--

------------+
Mark Boyd
Avenal, California, USA

I forgot to mention that the stall warning unit, set normally to about
10% stall margin. appears to be of help while thermalling also. Going
too slow and/or pulling too many "G" will increase drag, besides being
dangerous. A prompt easing of the stick back-pressure quickly silences
the small piezo horn's warning signal.
Dick Johnson