As the Air France 447 accident investigation continues forward, a few themes apply to all aircraft regardless of size. Unexpected stalls are bad, the indication of the stall should be unambiguous, and perhaps most importantly, the wing needs to be unloaded to resume flight. It seems so basic and yet every week, at least in GA, somebody exhibits poor airmanship that results in at least damage to the aircraft and sometimes worse.
There have been calls for improved airmanship since the Colgan Q400 accident in Buffalo where the captain allowed the aircraft, on autopilot to level off and, under reduced power, settle into a stall. The stick shaker and then the stick pusher activated but the captain may have believed that they were in a tail stall. He pulled hard and used considerable aileron to attempt recovery with discouraging results.
Two high tech glass cockpit airplanes with professional crews somehow fell victim to basic aerodynamics. In the case of the Airbus 330 in the AF 447 accident, three airspeed probes apparently froze up, the computer got confused and handed the aircraft back to the pilots. There were some conflicting indications but in the calm of hindsight it could be said that had they merely gone with pitch and power indications everything would have remained manageable. That will come out in the final report. A totally separate question is why three separate probes took a powder at the same time.
Now step back into the low tech world where the Air Safety Institute’s Piper Archer has been equipped with a state of the art Angle of Attack (AOA) system by Alpha Systems. In last week’s blog we discussed my flight review with stalls, slow flight and multiple landings. To be sure,there is a huge difference between the Archer at low altitude and the “Bus” at high altitude but the concept is essentially the same.
The Archer’s AOA which is mounted next to the windshield post, was a confidence builder in helping to fly the Archer more precisely and slowly. It was calibrated at stall or alpha floor as the jet types like to call it. Too fast and there is an upward pointing yellow arrow, exactly in the groove and just above stall, there’s a green doughnut and too slow will yield a red downward pointing arrow and a voice reminder that you’re too slow. There’s also a warning warble when alpha moves into the yellow arrow range.
Airspeed is an approximation of alpha and the numbers change depending on aircraft weight and wing loading in turns. Wouldn’t it be better to teach from the beginning with alpha awareness? I think so, but it’s never caught on with the light aircraft crowd. Apparently, it’s beginning to be an issue with the big iron folks. Navy pilots are taught AOA right from the beginning and they operate from some really short floating airstrips.
Using Alpha, I consistently flew the Archer 5 knots slower on short final—which translated into better landings, less float, less tire wear and one of the best spot landings in memory. I should have bet some adult beverage on that but it just garnered a “nicely done.”