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Status quo, you know,
is Latin for ‘the mess we’re in.’
- Ronald Reagan
Tail Stall
Do you know how to recognize a tail stall? What if your wing deice works, but the tail deice fails? What happens? A tail stall-- and the indication and recovery procedure are exactly the opposite from a wing stall. Ever had an autopilot malfunction and rapidly pitch up? How about asymmetric speed brake or spoiler deployment? I’ve been at or beyond 60 degrees of bank, unintentionally, three times in transport category airplanes. Once was due to wake turbulence at a high altitude, another at a low altitude. I had asymmetrical spoiler deployment the third time due to a failing auxiliary hydraulic pump. I’ve talked to colleagues who have had asymmetrical deice problems as well. Lots of ice on one wing, little on the other. And while I hope to never have it in real life, I’ve trained in several different jets for inflight thrust reverser deployment, and in the sim, it’s dramatic.
Well, I Never!
If you have never been beyond 60 degrees of pitch or bank, you need to. As a part 135 or 121, two-pilot crew, the chances of being in a ‘very’ unusual attitude are slim. The odds are higher in single-pilot part 135 or part 91 operations, but it’s still rare. But don’t convince yourself that as long as you pay attention to your attitude, you’ll be okay and that upset training is just for fun. If for no other reason, it will help you recognize your condition more quickly, and more importantly, you won’t be as inclined to soil your trousers when it does happen. And with clean trousers, you can more confidently get to the task of executing a recovery.
The basic thought process of unusual attitude recovery is similar to an engine failure in a multi-engine airplane: recognize the condition, verify the condition, pick a plan, execute the plan, and verify that you got the desired results.
The first thing is to recognize the condition. It’s normal to feel and hear things in your plane and react. The sound of airspeed or engine noise increasing or decreasing, a variation in cabin pressure, sudden turbulence, or the sen- sation of more or less g force. If you fly over mountainous terrain, the signs of mountain waves may be your warning. If it’s night or you’re in IMC, your reaction should be to check the panel. Hopefully, you’ve recognized the condi- tion rather than getting a call from ATC. That call would be well into your deviation from level flight.
No Need To Panic!
noun - sudden uncontrollable fear or anxiety, often causing wildly unthinking behavior.
Some type of attitude indicator (PFD, MFD, ADI) is the first place to look—and look at more than one if you have several. If you find two that agree with each other, you can move on to the pick-a-plan phase. If they disagree, you
must find one or more indications to determine which at- titude indicator is right; a third artificial horizon, the VSI, IVSI, airspeed, and altimeter, should do. There’s no need to panic, really. You have some time. You don’t want to get this one wrong by using ‘wildly unthinking behavior,’ so take a few (3-5) seconds.
Picking a plan will depend on what you see the airplane doing. You will have the urge to ask yourself why it’s hap- pening—fight that urge until after the wings are level. The easiest unusual attitude from which to recover is one in the roll axis, even if you’ve made it all the way around to inverted. Rolling the shortest direction upright is the accepted course of action. Depending on the plane, you may use a combination of yolk and rudder. Follow your manufacturer’s recommendation regarding the rudder, though; in some airplanes, you can break things using too much rudder or with rudder reversals (rapidly transition- ing direction in yaw--- e.g., AA 587 November 12, 2001).
Corner Velocity
The more dangerous unusual attitudes are extreme deviations in pitch. Usually, if you’re nose high, you’ll be slow, and if nose low, fast. However, it’s possible to have a nose-low attitude with slow speed and a nose-high at- titude with high airspeed. With this in mind, you need to understand the concept of corner velocity or corner speed.
Corner velocity is used in fighters, aerobatics, and air- plane racing. It’s the speed at which you can generate the highest turn rate and, therefore, the smallest turn radius. If you’re faster than corner, your radius is larger. If you are slower than corner, your radius is, again, larger. Generally, this speed is the square root of your g-limit times stall speed:
Vc = VS x √Gmax (e.g., 6g limit and 60-knot stall = 146 corner, 4g and 80 kt stall=160).
This matters because we want to recover from this bad attitude with the smallest loss or gain of altitude. Especially
April 2023 / TWIN & TURBINE • 25