..Blueskies. wrote:
"Montblack" wrote in message ...

First time I've stumbled across one of these:

Lift Reserve Indicator

http://home.hiwaay.net/~sbuc/journal/liftreserve.htm
"One of the AOA systems that has been around the longest is the Lift Reserve Indicator. This unit was developed in the
1970's and has been offered in a couple of different variations since then. There is considerable controversy over
just what the LRI actually measures and how it operates, but when the price of the analog unit was recently reduced
substantially, it got my attention. Since the panel of 399SB is rather unconventional, I had included a small backup
airspeed indicator. However, the AI was never used since I rely on the RMI uEncoder for pitot info, so I decided to
replace the AI with the LRI since it could also serve as a backup airspeed indicator. The decision was easier since
the LRI would fit in the same space as the little AI and was in the pilot's angle of vision."

http://www.liftreserve.com/
Company website - InAir Instruments


Montblack


Interesting, delta P between two sources, one more or less pointing forward and one more or less pointing downward. I
suppose the indicator has a pressure diaphragm inside it linked to the needle...

I want an AOA indicator for the BD4 someday...

Hmmmmmm.......



A couple of years ago Kitplanes had an article about and AOA sytem
that used 2 ports flush with the wing surface near the wing tips. It's a
simplified version of a system the military has been using for decades.
The military version uses a conical probe sticking out of the side of
the fuselage. There are two sets of slots a few degrees part facing
towards the front of the airplane. These slots are ports that send air
pressure to two sensing chambers. Here's where they decided to get
complicated: the cone is then driven until the chamber measure equal
pressure. The cone's position is then transmitted to an indicator.
Obviously the system isn't for single engine tractor airplane. The
3.125" indicator is a tad big for most homebuilts, but does contain
switches for stall warning and AOA indexer lights. It seems to me some
enterprising electronics genius should be able to design a simple system
that does all this in solid state.

Dan, U.S. Air Force, retired