AoA keep it going!

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

One positive advantage to AoA is that it isn't dependent on a static
pressure source. If the static port becomes blocked, ASI readings go
whacko.

AoA appears to be useful for something since I routinely saw them on
military aircraft (which also always had ASI as well).

AoA may not be the definitive answer, but it is another available tool.

Scott


Nyal Williams wrote:

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






--
Scott
http://corbenflyer.tripod.com/
Gotta Fly or Gonna Die
Building RV-4 (Super Slow Build Version)

Nyal Williams wrote:
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.

Perhaps I misunderstood you. Is the lag you are talking about the time
it takes for the airspeed indication to become steady after you change
the glider's attitude from one steady attitude to another steady
attitude; i.e., from one AOA to another AOA?

If that's what you mean, then I agree: it will take a few moments for
the glider's airspeed to change to the new value.

What I thought you meant was the ASI (airspeed INDICATOR) reacts slowly.

--
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