Take a load off!

Angle-of-Attack

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AOA

 

Knowing how and when to unload the wing can save your hide. 

You can stop reading there. The remainder of this post will only seek to emphasize that not-so-subtle point.

 

If you are confused or curious keep reading.

 

Airplanes are fantastically designed machines. They seek equilibrium in virtually all states, alter their control feel at just the right times, and generally fly best when left alone. 

 

Enter el piloto. As pilot in command we are trained to “take charge”, “fly the airplane”, “don’t be a passenger” – all of that is right. Except that sometimes we ask the airplane to do something stupid. In this case it’s simple, we are asking it to exceed the critical angle of attack or critical.  

 

What’s the critical angle of attack? It’s the point at which the angle between the relative wind and the chord line of the wing becomes so acute that lift production drops off dramatically and drag goes up exponentially (both bad things). This is considered a “stalled” condition. 

 

The control surface that let’s us do this is the elevator. Sorry if this is remedial, I feel it’s important that I cover the basics.

 

But this can become confusing because you can exceed the critical AOA in any attitude (with the elevator). You could be pointing straight down, a condition most pilots tend to apply back pressure to remedy, and exceed the critical AOA by pulling too much. 

 

1106p_technique_illustrationYou could be descending nose down to land and exceed critical AOA if you let airspeed get too slow and/or apply a load (G forces) to the airplane – both of these cause the AOA to increase to maintain a given flight path. 

 

The key to all of this is to unload (reduce back pressure). The stall training that was pounded into us from the beginning was good, but it was in a very controlled setting with a strict process for recovery. What you start to learn when you do aerobatic training or all attitude recovery training, is that a stall can be recovered from by simply relaxing the back pressure you have applied – often inadvertently. All acro pilots have stalled going straight down on the back side of a loop or other vertical maneuver when they used too much elevator  too early. They would feel the burble or maybe even get a little wing drop – relaxing back pressure was all it took to correct the situation. They were unloading the wing.

 

The quandary that creates a low altitude critical AOA scenario is generally a botched approach to landing or low altitude maneuvering (buzz job). In these situations the pilot can inadvertently exceed the critical angle of attack reflexively because of the how the perceive their attitude in relation to the ground and/or mismanagement of G loading, airspeed, and pitch control. The easy answer is to not get yourself in a situation like this in the first place, but if you do, relaxing back pressure (or pushing),  whatever it takes to unload the wing and immediately reduce the AOA, is key. 

 

Remember, unless the airplane is grossly out of trim, the only way it’s going to stall is by your inputs. The cure to that is to keep the wing unloaded until it’s flying again. Simple right? Go up and and do some stall recovery practice at a safe altitude (with an instructor if needed) and reacquaint yourself with how it feels. Don’t worry about PTS (Practical Test Standards), just practice what it’s like to just relax the pressure – the airplane just magically starts flying again. 

 

I have taken a topic that experts write entire books about and spend weeks teaching into a few hundred words. This is not a complete picture of stall/spin recovery. I have failed to talk about the throttle, rudder, or ailerons at all. Rather I just want you to think in simple terms when it comes to flying near or in a stall and get comfortable with the big lever that put you into the stall in the first place.

 

by Brent Owens 

 


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