would an AOA indicator be helpful in a glider?

On Jun 4, 11:22*am, bildan wrote:
On Jun 4, 11:13*am, Andy wrote:





On Jun 4, 9:25*am, "
wrote:

This has all been hashed out before (some interesting threads, those!)
but here is my 2 cents:

AOA can be derived from pressure differential, best way would be to
have sensor ports in both wings (enough to be redundant and avoid yaw
problems. *Nose might also work, but it's the wing you care about,
really.

AOA is really only needed at high angles: Stall, Min Sink, L/D max,
recommended approach speed. *Since these speeds vary with weight and
bank angle, AOA is better than airspeed. *So to keep it simple, with
gear up show min sink (for thermalling) tied to flap setting, and
maybe have an index at L/D max (not really used that often). *Gear
down, show desired approach speed, with warning approaching stall.

I think the military chevrons and doughnut indicator would work just
fine: *On-speed (desired AOA) when center g(green) circle is lit.
Slightly slow when circle and lower up (red) chevron are both lit.
Slow when only red up chevron is lit, slightly fast when circle and
upper down (yellow) chevron is lit, and fast when only down chevron is
lit.

Electronics would need input from gear and flaps, if present, of
course.

Easy to see if on top of panel.

Kirk

I think the tricky part will be calibration. *The device needs to be
set up to a fraction of a degree so I suspect you'll have to do some
fancy measuring of a series of flight tests. You'll also need some
data from the factory about lift coefficient versus alpha.

9B

Actually, calibration is the easy part. *Just load the glider to
maximum gross weight, fly it at the Calibrated Air Speed (From tables
in the POH) for best L/D, for minimum sink and for stall and note the
readings for each. *You probably don't care about actual AoA is in
degrees.

If you want a fancy color LED display that changes color/shape
precisely at each, the electronics package should have adjustments
built in.

Alternatively, *choose a 10 element LED bargraph display where each
element can be red, yellow or green depending on which pins are used.
Once the position of each AoA of interest is known, switch pins to
produce the color desired. *You can also wire in a warning horn to
sound when the red stall LED lights up and the gear is down.- Hide quoted text -

- Show quoted text -

I think you all miss the point that a panel mounted AoA indicator is
not the right way to get this critical information. I don't want some
boob looking in the cockpit while thermaling!! That's why we create
audio variometers! I have been considering this for some time and
unless we want two channels of audio in the cockpit, or we have a very
good heads up display, the AoA info is wasted when you need it most.

Mike

I think the GLIDER is a pretty good angle of attack indicator.

wrote:
I think the GLIDER is a pretty good angle of attack indicator.

Well sure - if you mean in the same sense it also makes a good terrain
alert indicator ("when the fuselage begins to deform at high speed, this is
probably an indication that terrain or an obstruction is very very close.")

On Jun 4, 8:32*pm, Mike Bamberg wrote:
On Jun 4, 11:22*am, bildan wrote:



On Jun 4, 11:13*am, Andy wrote:

On Jun 4, 9:25*am, "
wrote:

This has all been hashed out before (some interesting threads, those!)
but here is my 2 cents:

AOA can be derived from pressure differential, best way would be to
have sensor ports in both wings (enough to be redundant and avoid yaw
problems. *Nose might also work, but it's the wing you care about,
really.

AOA is really only needed at high angles: Stall, Min Sink, L/D max,
recommended approach speed. *Since these speeds vary with weight and
bank angle, AOA is better than airspeed. *So to keep it simple, with
gear up show min sink (for thermalling) tied to flap setting, and
maybe have an index at L/D max (not really used that often). *Gear
down, show desired approach speed, with warning approaching stall.

I think the military chevrons and doughnut indicator would work just
fine: *On-speed (desired AOA) when center g(green) circle is lit.
Slightly slow when circle and lower up (red) chevron are both lit.
Slow when only red up chevron is lit, slightly fast when circle and
upper down (yellow) chevron is lit, and fast when only down chevron is
lit.

Electronics would need input from gear and flaps, if present, of
course.

Easy to see if on top of panel.

Kirk

I think the tricky part will be calibration. *The device needs to be
set up to a fraction of a degree so I suspect you'll have to do some
fancy measuring of a series of flight tests. You'll also need some
data from the factory about lift coefficient versus alpha.

9B

Actually, calibration is the easy part. *Just load the glider to
maximum gross weight, fly it at the Calibrated Air Speed (From tables
in the POH) for best L/D, for minimum sink and for stall and note the
readings for each. *You probably don't care about actual AoA is in
degrees.

If you want a fancy color LED display that changes color/shape
precisely at each, the electronics package should have adjustments
built in.

Alternatively, *choose a 10 element LED bargraph display where each
element can be red, yellow or green depending on which pins are used.
Once the position of each AoA of interest is known, switch pins to
produce the color desired. *You can also wire in a warning horn to
sound when the red stall LED lights up and the gear is down.- Hide quoted text -

- Show quoted text -

I think you all miss the point that a panel mounted AoA indicator is
not the right way to get this critical information. *I don't want some
boob looking in the cockpit while thermaling!! *That's why we create
audio variometers! * I have been considering this for some time and
unless we want two channels of audio in the cockpit, or we have a very
good heads up display, the AoA info is wasted when you need it most.

Mike

You seem to assume a pilot would be fixated on the AoA display.
That's not how it's used. Find the airspeed that corresponds to the
desired AoA and hold that airspeed. The AoA won't change if you don't
change the airspeed or bank angle.

You should be able to hold airspeed, and by extension the AoA by the
sound of the glider and control forces just like you do now - except,
with an AoA indicator, you'd know you were flying exactly the right
airspeed for minimum sink.

wby0n: "I think the GLIDER is a pretty good angle of attack
indicator." This sounds suspiciously like someone is confusing pitch
attitude with AoA.

On Jun 4, 7:32*pm, Mike Bamberg wrote:

I think you all miss the point that a panel mounted AoA indicator is
not the right way to get this critical information. *I don't want some
boob looking in the cockpit while thermaling!! *That's why we create
audio variometers! * I have been considering this for some time and
unless we want two channels of audio in the cockpit, or we have a very
good heads up display, the AoA info is wasted when you need it most.

Mike

An AOA indicator, like the airspeed indicator or even the yaw string,
can easily be used by just glancing at it. Once you have established
the correct AOA, then it's easy to maintain by looking at your
glider's nose position vs the horizon - just as you do now, with that
inaccurate airspeed indicator. The whole point is that you can
quickly set the correct AOA for the bank angle and wingloading you are
flying at (without having to guess what airspeed to use based on some
chart or graph in the flight manual - quick, what is your gliders min
sink speed with 20 gallons of water in a 37 degree bank?).

What would be real nice - and might save a life in the pattern - would
be to have aural Fast/Onspeed/Slow tones that would replace the vario
tones when the spoilers an/or landing flaps are extended (assuming
that once those are out, you are no longer really concerned with
climbing!). Then you could focus all your attention outside the
cockpit on your approach, without having to glance into the cockpit to
check airspeed. That's how we used to land F-4s, and it was a really
comfortable way to fly a visual approach.

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

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.

Bob,

Well it sounds like you fly a HP-18. (How did I figure that out?)

And yes, I thought the AOA in the A-3B Skywarrior and A-6B Intruder were great instruments and would like to have one on MY w/o spoilers sailplane.

Wayne
HP-14 "6F"


"Bob Whelan" wrote in message ...
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.

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 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.