would an AOA indicator be helpful in a glider?

On Jun 5, 3:46*pm, Bob Whelan wrote:
wrote:

Sensible stuff snipped...
* What is amusing is that pilots who have never had the opportunity to fly an AOA-indicator equipped aircraft seem to be reluctant to accept
it's advantages and cling to their old ways, while pilots who have
used AOA gauges love them.

Apologies for not re-titling this thread, but I've gotta second Kirk's
observation, and, generalize it to include (for example) landing flaps
and 'anything else abbie-normal.'

I haven't flown an AOA-equipped glider, but I'd sure like to. Meanwhile
since 1981 I've been flying a genyoowinely abbie-normal sailplane:
American racing glass (Strike 1!); w/o spoilers (Strike 2!!); and a
side-stick (Strike 3!!!) Oh yeah...while I'm at it, it never had a
chance at obtaining an approved (non-experimental) type certificate,
either. (You're not only out...you're outta the GAME!!!!)

Writ smilingly, with a rueful shake of the head, we pilots as a group
tend to be: a) relentlessly conservative/sheeplike in our 'common
wisdoms'; b) vocal in our (often not-factually-supported) opinions; and
c) 'too-often guilty' of passing off the latter as matters of fact.

Regards,
'Asbestos Bob' W.

Every book on airfoils from the venerable Abbot's "Theory of Wing
Sections" to more modern treatises on aerodynamics show graphs of an
airfoils coefficient of lift vs. angle of attack. The other graphs
have the Cl on the X-axis so everything about a wings performance goes
back to angle of attack. You won't see any airfoil section graphs
showing airspeed. Angle of attack is THE key to knowing what a wing
is doing.

Renowned books on flying from "Stick and Rudder" by Wolfgang
Langewiesche to "Fly the Wing" by James Webb hammer home precisely
that point - angle of attack is everything. Airspeed, while useful,
doesn't come close.

The situation where jets which spend 99% of their time flying fast
have found AOA indicators essential and gliders which spend up to half
their time flying near stall don't have them has always puzzled me.

On Jun 5, 5:27*pm, "
wrote:

What is amusing is that pilots who have never had the opportunity to
fly an AOA-indicator equipped aircraft seem to be reluctant to accept
it's advantages and cling to their old ways, while pilots who have
used AOA gauges love them.

Kirk
66

Me personally ( and I bet most of those reluctant pilots ) are NOT
reluctant to _fly_ with an AOA indicator. I am reluctant to spend
more than a small amount of money on that indicator. I also believe
that an AOA indicator is only a small increase in safety. If my
attention wanders from the airspeed, pitch attitude, stick feel and
position and other indications of low airspeed, I don't think that the
AOA indicator would be exempt from that in-attention. I do believe
that the AOA would allow more precise flying with different wing
loadings, but I don't see many times in soaring that precise AOA
control is needed.

Again, if someone had put one in my panel, I wouldn't throw it away,
but I would not spend a lot of money on it.

Todd Smith
3S

Apologies for not re-titling this thread, but I've gotta second Kirk's
observation, and, generalize it to include (for example) landing flaps
and 'anything else abbie-normal.'

I haven't flown an AOA-equipped glider, but I'd sure like to. Meanwhile
since 1981 I've been flying a genyoowinely abbie-normal sailplane:
American racing glass (Strike 1!); w/o spoilers (Strike 2!!); and a
side-stick (Strike 3!!!) Oh yeah...while I'm at it, it never had a
chance at obtaining an approved (non-experimental) type certificate,
either. (You're not only out...you're outta the GAME!!!!)

Writ smilingly, with a rueful shake of the head, we pilots as a group
tend to be: a) relentlessly conservative/sheeplike in our 'common
wisdoms'; b) vocal in our (often not-factually-supported) opinions; and
c) 'too-often guilty' of passing off the latter as matters of fact.

Regards,
'Asbestos Bob' W.

Bob, did you make it to the Zuni Pow Wow in Moriarty?

The Zuni is a cool looking ship - check out the great photos on the
ASA homepage at http://asa-soaring.org/ - click on the pics for full
screen & enjoy a beautiful finish to a long flight by Randy Acree in
AV8!

Kirk

On Jun 6, 11:35*am, bildan wrote:
The situation where jets which spend 99% of their time flying fast
have found AOA indicators essential and gliders which spend up to half
their time flying near stall don't have them has always puzzled me.

Might that not be because those jets are total pigs when flown at
approach speed? I suspect that if they didn't have the AOA indicator
then either they would get approached way too fast or else the pilot
would be in a constant state of "we're all gonna DIE!!". And they're
going pretty fast while trying to land on small things, such as ships.

They're also landing well below min drag/sink speed, on the "back side
of the drag curve" and depending on big engines to save their bacon if
the AOA starts to get too high. If we did that in gliders then we'd
sometimes have little option but to dive into the ground in a mush
even if we closed the brakes instantly.

Unlike those jets, we in gliders fly the approach faster and with a
lower angle of attack than many other phases of flight, deliberately
sacrificing some ultimate short landing performance for a large
increase in safety.

I can see that an AOA indicator would be useful for establishing
various reference speeds at a particular weight or bank angle, and
then maintain that configuration via our traditional method of
attitude with respect to the horizon. But I don't think it's
something that we'd ever want to use as a primary reference while
flying,

The flight path of a typical glider flown at a fixed angle of attack
is a diverging phugoid. That's not very useful. Least of all on
approach.

There are several thing in this post to which I take exception. However, I will mention one. A carrier approach is NOT flown on the "back-side" of the power curve. They are flown at optimum L/D for the wing when the wing is in its' landing configuration.

Oh, just one more comment..... I have never know a carrier aviation who thought "we're all gonna DIE!!" when the making a carrier approach with an inoperative AOA.



"Bruce Hoult" wrote in message ...
On Jun 6, 11:35 am, bildan wrote:
The situation where jets which spend 99% of their time flying fast
have found AOA indicators essential and gliders which spend up to half
their time flying near stall don't have them has always puzzled me.

Might that not be because those jets are total pigs when flown at
approach speed? I suspect that if they didn't have the AOA indicator
then either they would get approached way too fast or else the pilot
would be in a constant state of "we're all gonna DIE!!". And they're
going pretty fast while trying to land on small things, such as ships.

They're also landing well below min drag/sink speed, on the "back side
of the drag curve" and depending on big engines to save their bacon if
the AOA starts to get too high. If we did that in gliders then we'd
sometimes have little option but to dive into the ground in a mush
even if we closed the brakes instantly.

Unlike those jets, we in gliders fly the approach faster and with a
lower angle of attack than many other phases of flight, deliberately
sacrificing some ultimate short landing performance for a large
increase in safety.

I can see that an AOA indicator would be useful for establishing
various reference speeds at a particular weight or bank angle, and
then maintain that configuration via our traditional method of
attitude with respect to the horizon. But I don't think it's
something that we'd ever want to use as a primary reference while
flying,

The flight path of a typical glider flown at a fixed angle of attack
is a diverging phugoid. That's not very useful. Least of all on
approach.

wrote:
Multi-level snips...

Bob, did you make it to the Zuni Pow Wow in Moriarty?
"Roger that." (And a good time was had by all...)
- - - - - -

The Zuni is a cool looking ship - check out the great photos on the
ASA homepage at http://asa-soaring.org/ - click on the pics for full
screen & enjoy a beautiful finish to a long flight by Randy Acree in
AV8!
It took a while (um...years!) for me to get used to its abbie-normal
lines, but it's always flown beautifully.

Tnx for the link.

Regards,
Bob W.

Some good info on AOA systems for lightplanes, including theory and
installations, at:

http://www.advanced-flight-systems.c...s/AOA/aoa.html

This system uses flush ports on the top and bottom of the wing, along
with pitot and static inputs, to measure the Cl of the wing in real
time (and derive AOA). No probes or vanes needed.

With a glider, you would have to connect the tubing when rigging - but
you could use pitot/static quick connect for that.

Too bad our market is too small - a dedicated system for gliders,
installed at the factory, would be nice - especially if integrated
with an glide computer to share processing power, etc.

There was also a totally passive Cl meter (using pellet-in-tube
technology!) that was described in detail in a old (70s?) issue of
soaring.

Kirk
66

On Jun 6, 5:21*pm, "
wrote:
Some good info on AOA systems for lightplanes, including theory and
installations, at:

http://www.advanced-flight-systems.c...s/AOA/aoa.html

This system uses flush ports on the top and bottom of the wing, along
with pitot and static inputs, to measure the Cl of the wing in real
time (and derive AOA). *No probes or vanes needed.

With a glider, you would have to connect the tubing when rigging - but
you could use pitot/static quick connect for that.

Too bad our market is too small *- a dedicated system for gliders,
installed at the factory, would be nice - especially if integrated
with an glide computer to share processing power, etc.

There was also a totally passive Cl meter (using pellet-in-tube
technology!) that was described in detail in a old (70s?) issue of
soaring.

Kirk
66

I am a bit confounded by the several suggestions that AOA info in the
cockpit would be a bad thing. Frankly a little alarm for stall AOA at
each flap setting would be quite welcome for those moments on approach
where you get distracted.

I am not entirely sure I would use it for cruise, since airspeeds are
quite adequate for this purpose and no one I know flies best L/D or
even precise McCready speeds very much anymore. It might be helpful
in thermalling to get to the precise minimum sink AOA, though I do
wonder again how useful this would be since you typically want to fly
with a bit of margin above the laminar separation speed because
dipping below is quite costly in terms of the accumulated drag losses
before you get the flow re-attached. A cool thing to know for me would
be the maximum AOA for each loading and flap setting that still keeps
you consistently away from separation given gusts, unsteady
aerodynamic effects, etc. Unfortunately, that number doesn't come out
of the POH, so we are back to some form of flight testing I think - or
some sort of rule of thumb.

Even the simple calibration Bill suggests requires three data points
for each flap setting. My glider has 6 flap settings - times three
operating points each yields 18 data points - okay that's not a
ridiculous number, probably a couple of tows on a calm day.

9B

On Jun 6, 6:21*pm, "
wrote:
Some good info on AOA systems for lightplanes, including theory and
installations, at:

http://www.advanced-flight-systems.c...s/AOA/aoa.html

This system uses flush ports on the top and bottom of the wing, along
with pitot and static inputs, to measure the Cl of the wing in real
time (and derive AOA). *No probes or vanes needed.

With a glider, you would have to connect the tubing when rigging - but
you could use pitot/static quick connect for that.

Too bad our market is too small *- a dedicated system for gliders,
installed at the factory, would be nice - especially if integrated
with an glide computer to share processing power, etc.

There was also a totally passive Cl meter (using pellet-in-tube
technology!) that was described in detail in a old (70s?) issue of
soaring.

Kirk
66

Careful reading of their installation manual suggests that it might
work with nose ports.

On Jun 7, 2:14*pm, bildan wrote:
On Jun 6, 6:21*pm, "
wrote:



Some good info on AOA systems for lightplanes, including theory and
installations, at:

http://www.advanced-flight-systems.c...s/AOA/aoa.html

This system uses flush ports on the top and bottom of the wing, along
with pitot and static inputs, to measure the Cl of the wing in real
time (and derive AOA). *No probes or vanes needed.

With a glider, you would have to connect the tubing when rigging - but
you could use pitot/static quick connect for that.

Too bad our market is too small *- a dedicated system for gliders,
installed at the factory, would be nice - especially if integrated
with an glide computer to share processing power, etc.

There was also a totally passive Cl meter (using pellet-in-tube
technology!) that was described in detail in a old (70s?) issue of
soaring.

Kirk
66

Careful reading of their installation manual suggests that it might
work with nose ports.

I just got an e-mail from Advanced Flight Systems indicating that one
of their units has been installed on a glider with top and bottom
nosecone ports. The glider was apparently a Sparrowhawk and the unit
works great.

Since the AFS system is available with flap position sensors and
standard LED displays, it appears to be exactly what we need.