AoA keep it going!

Cats wrote:
On Dec 21, 10:42 pm, Ian wrote:
On 21 Dec, 09:58, J a c k wrote:

Ian wrote:
Seeing other aircraft is often aided by hearing radio transmissions.
Have you literally heard an aircraft you didn't first see?
Are you remembering that in the UK we have a very limited range of
frequencies, and that it is quite possible to be able to hear calls
from gliders at several different airfields at once? I have on
occasion wasted time trying to see the glider which has just called
downwind at an airfield ten miles from the one I am about to land at.

Ian

Gliders at our airfield prefix their downwind call with 'XXX Traffic'
so there is no doubt who they are addressing. OK. sometimes we get
'XXX Base' but it's still unambiguous.

Snap. We make blind calls to "xxx radio" giving approach direction
before joining the circuit and on downwind to give circuit direction and
intended runway. This is in accordance with CAP 413, as all glider
pilots using a radio should know.

Anybody not prefixing the call to a typical glider field with "xxx
radio" is in violation, so a light bollocking would be entirely in order.


--
martin@ | Martin Gregorie
gregorie. | Essex, UK
org |

Mike Lindsay wrote:
Eric,

Just a short observation. If you had an AOA you would notice an AOA
increase as you open your spoilers while maintaining a constant speed and a
decrease as you closed them.

Wayne


Why not? Surely the glider would be sinking quicker so the AoA would
increase when you open your spoilers?

I agree that, once stabilized at the original airspeed with brakes open
the AOA will be a bit higher to compensate for loss of lift, but the AOA
variation during the transition may depend on the glider type.

Some gliders pitch down automatically and accelerate when the brakes are
opened (G103). Others raise the nose slightly and decelerate as the
brakes are opened, so require a good shove on the stick to hold the
airspeed constant (Puchacz). Ditto an ASW-20 as you select landing flap.
The waggling of the AOA needle may be quite different in these cases.


--
martin@ | Martin Gregorie
gregorie. | Essex, UK
org |

Wayne Paul wrote:
"Eric Greenwell" wrote in message
news:gi2bj.303$pi7.43@trndny02...
Nyal Williams wrote:
No one seems to have observed that the AoA is instantaneous
whereas the ASI indicates what the aircraft was doing
moments ago.
I don't think this is true: all the ASI I've had or checked seemed to
respond in less than a second. Surely that's fast enough to keep up with
the glider? Just try blowing gently into a pitot and see how quick the
needle is. If takes "moments" to respond, you should check the indicator
and the pitot line.

The reason we are told to "fly attitude and don't chase the airspeed" is
it takes the glider a while settle down to a steady speed, not because the
ASI is slow.

Eric,

Just a short observation. If you had an AOA you would notice an AOA
increase as you open your spoilers while maintaining a constant speed and a
decrease as you closed them.

True, but the ASI is still indicating correctly, not lagging as Nyal
seemed to suggest.

So, do we fly the same AOA with the spoilers open as when they are
closed? Supposed they are just "cracked" open, half open, fully open -
do I need to know a different AOA for each spoiler position?

And if I use landing flaps for the landing instead of the thermal flap
setting, do I need to yet another list of AOA for different spoiler
settings?

--
Eric Greenwell - Washington State, USA
* Change "netto" to "net" to email me directly
* "Transponders in Sailplanes" http://tinyurl.com/y739x4
* "A Guide to Self-launching Sailplane Operation" at www.motorglider.org

On Sat, 22 Dec 2007 06:39:08 GMT, Eric Greenwell
wrote:

Nyal Williams wrote:
The inside wing; it travels a lesser distance while
sinking the same amount as the outside wing.

No one seems to have observed that the AoA is instantaneous
whereas the ASI indicates what the aircraft was doing
moments ago.

I don't think this is true: all the ASI I've had or checked seemed to
respond in less than a second. Surely that's fast enough to keep up with
the glider? Just try blowing gently into a pitot and see how quick the
needle is. If takes "moments" to respond, you should check the indicator
and the pitot line.

The reason we are told to "fly attitude and don't chase the airspeed" is
it takes the glider a while settle down to a steady speed, not because
the ASI is slow.

That's precisely his point. Change the AoA, and the drag changes.
Change the drag, and the glider accelerates (positively or
negatively). Then the airspeed changes, and only then does the ASI get
a chance to tell you about it.

"Fly attitude and don't chase the airspeed" really means "fly AoA and
don't chase the airspeed", but if you don't have an AoA indicator, you
have to use the attitude as a substitute for AoA. And it's a
second-rate substitute.

rj

Ralph Jones wrote:
"Fly attitude and don't chase the airspeed" really means "fly AoA and
don't chase the airspeed", but if you don't have an AoA indicator, you
have to use the attitude as a substitute for AoA. And it's a
second-rate substitute.

Please pardon me if I sound a bit cranky, but how can attitude be a
"second-rate substitute" for something that we don't even have?

And what would a "first-rate substitute" be?

Not a single poster here has flown with an AOA meter in their glider,
except a few using yarn taped to the side of their canopy. Is that what
we should be using instead of attitude and airspeed?

"Show me the money".

--
Eric Greenwell - Washington State, USA
* Change "netto" to "net" to email me directly
* "Transponders in Sailplanes" http://tinyurl.com/y739x4
* "A Guide to Self-launching Sailplane Operation" at www.motorglider.org

Eric Greenwell wrote:
Not a single poster here has flown with an AOA meter in their glider,
except a few using yarn taped to the side of their canopy. Is that what
we should be using instead of attitude and airspeed?

Actually, I have flown with the factory supplied AoA meter (differential
pressure) in my DG-600, but I could never get the darn thing calibrated
properly...

Marc

Marc Ramsey wrote:
Eric Greenwell wrote:
Not a single poster here has flown with an AOA meter in their glider,
except a few using yarn taped to the side of their canopy. Is that
what we should be using instead of attitude and airspeed?

Actually, I have flown with the factory supplied AoA meter (differential
pressure) in my DG-600, but I could never get the darn thing calibrated
properly...

Bummer. I'm still hoping we'll hear from some pilots with the newest DG
80x gliders, which has it as standard equipment (I think that's right...).

--
Eric Greenwell - Washington State, USA
* Change "netto" to "net" to email me directly
* "Transponders in Sailplanes" http://tinyurl.com/y739x4
* "A Guide to Self-launching Sailplane Operation" at www.motorglider.org

Marc Ramsey wrote:
Eric Greenwell wrote:
Not a single poster here has flown with an AOA meter in their glider,
except a few using yarn taped to the side of their canopy. Is that
what we should be using instead of attitude and airspeed?

Actually, I have flown with the factory supplied AoA meter (differential
pressure) in my DG-600, but I could never get the darn thing calibrated
properly...

Marc

One common problem with many arguments (not just on RAS!) is that people
compare the status quo with an idealized world, and conclude that the
status quo is flawed and must be changed. It seems to me this may be
occurring in the AoA discussion -- many posters have compared a
perfectly functioning AoA indicator with our slow and inaccurate ASIs,
and concluded that AoA indicators are better. But perhaps in the real
world AoA indicators on gliders would be even less accurate than ASIs?

Greg Arnold wrote:
Marc Ramsey wrote:
Eric Greenwell wrote:
Not a single poster here has flown with an AOA meter in their glider,
except a few using yarn taped to the side of their canopy. Is that
what we should be using instead of attitude and airspeed?

Actually, I have flown with the factory supplied AoA meter
(differential pressure) in my DG-600, but I could never get the darn
thing calibrated properly...

Marc

One common problem with many arguments (not just on RAS!) is that people
compare the status quo with an idealized world, and conclude that the
status quo is flawed and must be changed. It seems to me this may be
occurring in the AoA discussion -- many posters have compared a
perfectly functioning AoA indicator with our slow and inaccurate ASIs,
and concluded that AoA indicators are better. But perhaps in the real
world AoA indicators on gliders would be even less accurate than ASIs?

Insufficient evidence. Mine was a 17 year old analog electronic device
hooked up to 17 year old plumbing. It sometimes seemed to work, but not
consistently.

Marc

Eric,

I should have been more precise in my comment. AoA,
as shown by a piece of yarn will be much quicker than
an ASI. The ASI will respond quickly, as you say,
but it will not arrive at a steady-state indication
for a few moments if the AoA change is considerable
and abrupt. I have no opinion about AoA instruments,
for I have never used one.

In my youth, I saw one used on an inboard strut between
the wings of a bi-plane; it was a blade type that floated
in the air. The pilot swore by it.

At 06:42 22 December 2007, Eric Greenwell wrote:
Nyal Williams wrote:
The inside wing; it travels a lesser distance while
sinking the same amount as the outside wing.

No one seems to have observed that the AoA is instantaneous
whereas the ASI indicates what the aircraft was doing
moments ago.

I don't think this is true: all the ASI I've had or
checked seemed to
respond in less than a second. Surely that's fast enough
to keep up with
the glider? Just try blowing gently into a pitot and
see how quick the
needle is. If takes 'moments' to respond, you should
check the indicator
and the pitot line.

The reason we are told to 'fly attitude and don't chase
the airspeed' is
it takes the glider a while settle down to a steady
speed, not because
the ASI is slow.


--
Eric Greenwell - Washington State, USA
* Change 'netto' to 'net' to email me directly
* 'Transponders in Sailplanes' http://tinyurl.com/y739x4
* 'A Guide to Self-launching Sailplane Operation' at
www.motorglider.org