EXECUTIVE SUMMARY of the Test Flights Reports:
The Alpha Systems Angle of Attack (AOA) Stall Warning System offers an accurate, repeatable, and very early warning of impending aerodynamic stall. Such clear stall proximity information mounted prominently on the glareshield in full view of the pilot offers enhanced safety in the operation of general aviation aircraft.
A display of AOA as a cross-check to the primary Airspeed Indicator is particularly useful when operating in steeply banked and/or G-loaded flight conditions because the angle of attack at aerodynamic stall is independent of aircraft weight and/or wing loading.
Specifically, within the scope of these test flights, the following germane conclusions were reached:
• The “Optimum Alpha Angle (OAA) Calibration” technique recommended by the Alpha Systems AOA Stall Warning System Installation Manual is an accurate and repeatable method that can be used to reliably set an AOA target that will be adequately before the aerodynamic stall AOA.
• The target AOA, once calibrated, presents data to the pilot so as to provide early warning of an impending stall, prior to the aircraft stall warning audible system, thereby ensuring a safe margin above stall throughout the entire gross weight envelope.
• The instrumentation provides clear, un-ambiguous, and easy-to-comprehend stall proximity information.
You love your family? You take care of your passengers? Of course you do.
Don't forget that a reliable and effective AOA display that gives a RELIABLE and EARLY warning of stall is available for well under $1,500 plus a few easy hours of installation.
IN-FLIGHT VIDEO of AOA
A brief video of the individual Legacy segments from Cruise to Stall in level flight in a Bonanza.
A 30 deg. banked stall series in a Bonanza as we were calibrating the AOA to the Beech Stall Warning Horn and stall break. We thought the OAA was set a bit too fast at ~90MIAS. Following ths flight, we recalibrated the Legacy for 81MIAS (that's 1.3Vs. Clean configuration)
Then we followed up in the same Bonanza, checking to see if we successfully set OAA for 81 (we did, which gives us an OAA display range of 81-87 MIAS). and then verifying that it was, indeed, a range of OAA being displayed.
So with calibration complete at the early-warning-of stall range we wanted, let's put the Legacy AOA to some real-world work:
Final Approach to touch down in a Bonanza with its OAA calibrated to 81 MIAS (a green donut range of 81-87 MIAS). Interesting... but that was in level flight. Any Airspeed Indicator will give us all we ever need....in level flight.
But here's a Bonanza in very steep banks and pitches and THIS flight regime is where the AOA shines, as the ASI is telling lies in the steepest of the banks. I realize that we all know that, but it's MUCH TOO EASY to forget it. As VERY EXPERIENCED and VERY SKILLED aviators still do, with tragic consequences.
Our second Legacy installation and Test Flight series was in the King Air C90 Blackhawk. We'll skip the calibration process as it's identical, but we did set the King Air for 1.3Vso (Full Flaps with Gear Down). We expected to see a smaller stall margin and we did, but there is plenty of "early-warning-of -stall" remaining...so this King Air will stay set for 1.3Vso .
Lazy eights in a King Air C90. steeper than most King Airs normally fly, but it's a perfectly legal training exercise...and this is a REALLY good place to see the AOA at work
Landing in a King Air C90 from downwind to the rollout.
What did we miss? Ask us, and we'll try to film it for you. (Acrobatic flight? Not in these two aircraft. Inverted? Nope.) What else would you like to see?
DISCLAIMER; Neither Tom Rosen, nor I, nor anyone who helped us with this research (each one helping entirely at their own expense) has ANY financial interest, now or ever, in ANY Angle of Attack manfacturer or in ANY AOA product line. Period. It's simply that...
"This Needs Doing. I'll help"
said Bill Hatfield of Turbine Conversions Ltd. ... just as all the others did too.
This educational effort and flight data research was initiated and funded by friends of skilled aviators gone west. It is placed in the public domain
IN HONOR OF
David Ingalls Brown and Robert H. Baldwin
TWA Captain Ray Rotge and TWA Captain Mack Johnston