Stall Warning Indicators and Your safety

[soartech]

Reading that many lethal accidents are caused by stalls I thought that
a stall warning indicator might be a nice thing to have. After
searching a bit I found this really interesting but sad story on the
subject written by someone at DG sailplanes:
http://www.dg-flugzeugbau.de/ueberziehwarnung-e.html

In it he mentions several significant points: Any experienced pilot
can and will stall the glider at some point. He even admits he has
done it and had a hard landing that cost him $8K in repairs! Humans
make errors!
Modern sailplanes are so clean that they give very little clue before
stalling.
I did a search for such a device. Found some very expensive devices
for general aviation and one device (Redding) for $90 that is just a
microswitch with a vane that requires cutting a hole in the aircraft.
Ugly.
Being an engineer I can envision a simple, cheap (~$200) device that
is "smart", can be automatically switched off at altitude or manually
switched off if you like to thermal below minimum sink (why?) or for
whatever reason, to reduce the annoyance factor.
It could require no panel space other than a switch or knob, run on
12V and tee off the line to your airspeed indicator. It could be
programmed to give warning beeps when approaching a stall slowly or
continuous tone if approaching rapidly.
I'd like to hear pilots thoughts on this idea and if they would be
interested in such a device. For me, I'd rather have something like
this and feel just a little bit less likely to succumb to human error.
Dean

[Andy[_1_]]

On Oct 26, 9:59*am, soartech > wrote:
> I'd like to hear pilots thoughts on this idea and if they would be
> interested in such a device.

To be useful it has to measure alpha or, if pitot based, has to be
compensated for wing loading (ballast and g). I already have a
wingloading and g compensated slow speed warning in my glider
(Cambridge 302). As I mentioned in an earlier thread its main use is
to remind me to adjust the ballast setting if I forget after dumping.


Andy

[Darryl Ramm]

As an engineer your mission, should you accept it, is to build a prototype, show it works well/reliably and without lots of false alarms and then show enough folks to get their endorsements supporting you that it works. Until then you can read all the past threads here where other people have said the same things, and nobody has produced anything that has managed to get any significant number of glider pilots using it or even excited about using it.

As mentioned all those C302s out there have basic stall speed warning capability, and I believe most pilots have it turned off/set to a low speed, I suspect either from ignorance of the feature existing or because (if they find out about the feature) the annoying/false alarms.

Darryl

[soartech]

On Oct 27, 2:09*am, Darryl Ramm > wrote:
> As an engineer your mission, should you accept it, is to build a prototype, show it works well/reliably and without lots of false alarms and then show enough folks to get their endorsements supporting you that it works. Until then you can read all the past threads here where other people have said the same things, and nobody has produced anything that has managed to get any significant number of glider pilots using it or even excited about using it.
>
> As mentioned all those C302s out there have basic stall speed warning capability, and I believe most pilots have it turned off/set to a low speed, I suspect either from ignorance of the feature existing or because (if they find out about the feature) the annoying/false alarms.
>
> Darryl

Thanks for the input guys. I do own a Brauniger flight instrument for
HG and have found the stall indicator on that also is very annoying,
constantly going off while thermalling.So, it turned it off. I
suspect an angle of attack sensor will give better results than
airspeed. I will have to do some research, building and
experimentation to find the answer. Is there anyone out there willing
to defend the warning system in their Cambridge 302?

[Andy[_1_]]

On Oct 27, 9:21*am, soartech > wrote:
> Is there anyone out there willing
> to defend the warning system in their Cambridge 302?

It works as intended and I have not disabled it. It has never warned
me that I am about to stall and spin in because I have never been in
that situation. It seldom gives nuissance warnings. The low speed
warnings I sometimes get when thermalling the 28 are useful since the
28 does not climb well if flown too slowly.


Andy

[Ramy]

On Oct 27, 9:21*am, soartech > wrote:
> On Oct 27, 2:09*am, Darryl Ramm > wrote:
>
> > As an engineer your mission, should you accept it, is to build a prototype, show it works well/reliably and without lots of false alarms and then show enough folks to get their endorsements supporting you that it works. Until then you can read all the past threads here where other people have said the same things, and nobody has produced anything that has managed to get any significant number of glider pilots using it or even excited about using it.
>
> > As mentioned all those C302s out there have basic stall speed warning capability, and I believe most pilots have it turned off/set to a low speed, I suspect either from ignorance of the feature existing or because (if they find out about the feature) the annoying/false alarms.
>
> > Darryl
>
> Thanks for the input guys. I do own a Brauniger flight instrument for
> HG and have found the stall indicator on that also is very annoying,
> constantly going off while thermalling.So, it turned it off. *I
> suspect an angle of attack sensor will give better results than
> airspeed. I will have to do some research, building and
> experimentation to find the answer. Is there anyone out there willing
> to defend the warning system in their Cambridge 302?

I recall an ad for such device in the soaring magazine awhile back.
I turned off my 302 slow speed alarm after trying it few times. It was
a distraction while thermaling unless you set it low enough that it
become useless...

Ramy

[Eric Greenwell[_4_]]

On 10/27/2011 9:21 AM, soartech wrote:

> Thanks for the input guys. I do own a Brauniger flight instrument for
> HG and have found the stall indicator on that also is very annoying,
> constantly going off while thermalling.So, it turned it off. I
> suspect an angle of attack sensor will give better results than
> airspeed. I will have to do some research, building and
> experimentation to find the answer. Is there anyone out there willing
> to defend the warning system in their Cambridge 302?

I didn't find the 302 stall warning useful, and don't use it. I use my
glider's factory supplied angle of attack indicator to avoid stalls
during flight:

* horizon well above the nose - trouble will occur very soon
* horizon just above the nose - safe
* horizon well below the nose - trouble will occur very soon

There is another set of parameters used during landing when the 40
degree landing flap position is selected.

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to
email me)

[Bob Gibbons[_2_]]

On Wed, 26 Oct 2011 09:59:26 -0700 (PDT), soartech
> wrote:

>Reading that many lethal accidents are caused by stalls I thought that
>a stall warning indicator might be a nice thing to have. After
>searching a bit I found this really interesting but sad story on the
>subject written by someone at DG sailplanes:
>http://www.dg-flugzeugbau.de/ueberziehwarnung-e.html
>
.... text deleted

In the interests of not "reinventing the wheel", few likely recall
that the late Dick Johnson published his design for a vane-based stall
warning indicator in the June 1990 (page 25) issue of SOARING
magazine. Dick showed full constructional details of his design in
this article.

The design was the result of a design competition OSTIV announced in
1987, a "Competition for Development of a Special Flight Instrument
for Stall Warning of Sailplanes". The design Dick developed finished
2nd in this competition. While the instrument never found a wide
following, Dick continued to fly with this instrument on his Ventus up
to his untimely death in 2008.

I have reproduced a short note Dick wrote on his instrument, as well
as the winning Polish design, several years before his death.

Bob

======================

SAILPLANE STALL WARNING SYSTEMS

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.

Richard H Johnson

[JohnDeRosa]

On Oct 27, 8:12*pm, Bob Gibbons > wrote:
>
> In the interests of not "reinventing the wheel", few likely recall
> that the late Dick Johnson published his design for a vane-based stall
> warning indicator in the June 1990 (page 25) issue of SOARING
> magazine. Dick showed full constructional details of his design in
> this article.

You were off by a month. The article can be found in the July issue
on the SSA Soaring magazine's G-R-E-A-T archive.

http://ssa.org/magazine/archive/ViewIssue.aspx?year=1990&month=7&page=25

[Bob Gibbons[_2_]]

On Thu, 27 Oct 2011 19:58:07 -0700 (PDT), JohnDeRosa
> wrote:

>On Oct 27, 8:12*pm, Bob Gibbons > wrote:
>>
>> In the interests of not "reinventing the wheel", few likely recall
>> that the late Dick Johnson published his design for a vane-based stall
>> warning indicator in the June 1990 (page 25) issue of SOARING
>> magazine. Dick showed full constructional details of his design in
>> this article.
>
>You were off by a month. The article can be found in the July issue
>on the SSA Soaring magazine's G-R-E-A-T archive.
>
>http://ssa.org/magazine/archive/ViewIssue.aspx?year=1990&month=7&page=25
>
>

John, thanks for the correction. Keyboard dyslexia. Dick had it
correct in his appended note, I mistyped.

Bob