Glider angle of attack indicator by SafeFlight

Bill Daniels wrote:
"Ralph Jones" wrote in message
...
On Thu, 06 Dec 2007 16:25:30 -0700, Ralph Jones
wrote:

On Thu, 6 Dec 2007 15:28:23 -0700, "Bill Daniels"
bildan@comcast-dot-net wrote:

I was very pleased to see the advert in the December issue of "Soaring
Magazine".
See: www.safeflight.com

Does anybody know more about this device - especially the price?

Hope it works out. A design for an AoA indicator appeared in _Soaring_
twenty or thirty years ago, but it was really crude. IIRC, it had its
own separate pitot and static sources, and connected them across a
vertical, tapered tube similar to one side of a pellet vario. A solid
metal ball rode in the tube, its mass serving to sense acceleration,
and its vertical position gave a measure of AoA.

The vane types found on jets work splendidly, but they're mounted high
up on the airplane where people and vehicles don't bump into
them...the equivalent on a glider wouldn't last long!

I presume the Safeflight device uses the pitot/static/acceleration
principle...that should be relatively easy with contemporary sensor
technology and chips.

Oops, no, I see on the website that it uses a vane. That's likely to
be a problem...

rj

Note that they say the vane is removable. You would probably install it as
you would a TE probe just before flight and remove it just after landing.

Pity they don't say which sensor they use on the glider AOA instrument.
If its the type with 360 degree rotation, it could easily be using an
optical sensor (Grey encoded rotary position sensor or similar), in
which case the system could be quite robust and friction-free,
especially with a removable vane.


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

When dealing with AoA sensors it is very important to consider how it
is to be used. If it is intended to be a Go - NoGo stall warning
device, that is one thing. If it is intended to be used to measure
and be proportional to a range of AoA that is quite another. The
mounting becomes quite critical because the airflow may be such that 1
degree of AoA change does not translate into 1 degree of sensor
movement (in the case of a vane for example) . As a young flight
control engineer I learned this the hard way when an AoA vane mounted
near the nose of a test vehicle actually changed 5 degrees for every
degree of AoA change of the aircraft.

Greg

"gfoster07k" wrote in message
...
When dealing with AoA sensors it is very important to consider how it
is to be used. If it is intended to be a Go - NoGo stall warning
device, that is one thing. If it is intended to be used to measure
and be proportional to a range of AoA that is quite another. The
mounting becomes quite critical because the airflow may be such that 1
degree of AoA change does not translate into 1 degree of sensor
movement (in the case of a vane for example) . As a young flight
control engineer I learned this the hard way when an AoA vane mounted
near the nose of a test vehicle actually changed 5 degrees for every
degree of AoA change of the aircraft.

Greg

Good point.

Lets say that you will be interested in only stall, min sink, and best L/D
at each flap setting. Can it be calibrated for that?

Bill Daniels