Stall Recovery

So now that we've had a few fatal air carrier crashes we're re-thinking how we train stall recovery...?

From the FAA Publication: Pilot's Handbook of Aeronautical Knowledge (PHAK)

It's about time.

Here's what the PHAK says about stalls:

An aircraft stall results from a rapid decrease in lift caused by the separation of airflow from the wing’s surface brought on by exceeding the critical AOA. A stall can occur at any pitch attitude or airspeed. Stalls are one of the most misunderstood areas of aerodynamics because pilots often believe an airfoil stops producing lift when it stalls. In a stall, the wing does not totally stop producing lift. Rather, it can not generate adequate lift to sustain level flight.

So the wing doesn't suddenly stop flying -- rather, it flies less and less well until it can't support the airplane.

I've been perplexed by the FAA PTS standards for stall recovery for a while now. Here's an extract from both Private and Commercial Pilot PTS:

Recognizes and recovers promptly after the stall occurs by simultaneously reducing the angle of attack, increasing power to maximum allowable, and leveling the wings to return to a straight-and-level flight attitude with a minimum loss of altitude appropriate for the airplane.

This is the ideal method of recovery but not necessarily the best way to train.

Why?

Most student pilots have expereince driving cars. Push the throttle to go faster, release to slow down. The airplane throttle effects are not as simple. One clear difference is change in airflow over the inboard parts of the wings and tail with and without power.

So the student learning about stalls equates power with recovery, which tends to confirm a wrong thought -- that increased power equals not stalling, and that only power can recover, and that stalls are somehow related to the application of power.

I propose a more simple progression:

1. Power to idle stall and recovery using only changes in Angle of Attack to cause the stall and recover from the stall. This exercise continues until the student understands the relationship between flying and not-flying and Angle of Attack. Power is not part of this equation until AoA is understood.
2. Power to idle stall, power added as Angle of Attack is reduced. Once the student understands AoA, then we can introduce power as a vector in the AoA equation.
3. Power on stall and recovery.

Some will complain that we'll confound student's in that the Law of primacy will be broken.

So what? The current primacy we're teaching is inculcating a flawed understanding of stalls and recovery. My proposal re-sets the student's experiences with stalls so that Angle of Attack becomes the control over stall/ not stalled.

Here's an excerpt from FAA Advisory Circular 61-67C (Change 1)

105. STALL RECOVERY. The key factor in recovering from a stall is regaining positive control of the aircraft by reducing the AOA. At the first indication of a stall, the aircraft AOA must be decreased to allow the wings to regain lift. Every aircraft in upright flight may require a different amount of forward pressure or relaxation of elevator back pressure to regain lift. It should be noted that too much forward pressure can hinder recovery by imposing a negative load on the wing. The next step in recovering from a stall is to smoothly apply maximum allowable power (if applicable) to increase the airspeed and to minimize the loss of altitude. Certain high performance airplanes may require only an increase in thrust and relaxation of the back pressure on the yoke to effect recovery.

 (Emphasis mine)
Notice how power is used to "increase airspeed and minimize loss of altitude." This makes much more sense and fits into the proposed training emphasis.

Nice Evening to Fly

Had some time for a lesson late this afternoon. We had the airplane started by 415 and rolling by 420. The air was smooth and clear and the moon hung like a silver-rimmed jewel above the haze layer in a clear, sapphire sky. I had Rick practice steep turns and slow flight and speed control in level flight as I enjoyed the view.

It would be dark all too soon so I asked him to head to the airport. There's no GPS in this bird so it's pure terrain association. Fortunately Lancaster County has plenty of landmarks visible from 1500' up. After a bit of coaching we were downwind for runway 10.

Rick's getting the pattern and approach sequence. Landings are progressing but will take some practice. This is always a hurdle as it's rather unnatural to fly directly at the ground and then do big control movements while at slow flight. But then the moment comes when the light bulb clicks on and we all wonder, "Why did I ever think this was hard?"

No news today on the annual, which is not good news, as John was going to let me know his IA's schedule so we can have 24286 inspected so I can fly her home. This weather won't last -- of that I'm certain.