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