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.

The Latest Update: November 4th, 2011

I flew the Cessna 205 back to its home in Connellsville, PA (KVVS) yesterday. I had to wait for the fog to clear before I took off from the lonely Donegal Springs Airport (N71) which is a mere 4 miles from our place in Mount Joy.

Donegal Springs looks like an airplane graveyard -- there are more airplane carcasses  falling apart amid weeds then there are flyable types. The hangars are in terrible shape -- several have doors permanently open with all sorts of rusting trash laying about. The runway is clear but the markings are gone. There has been no surface treatment in a very long time. I counted four airplanes that looked like they might be flyable. The rusting fuel pumps have a twin parked in front. Several aerostars site on flat tires around what looked like an FBO.

There are a few trailers next to the parking area that have a sign for the Donegal Springs Skydivers Club. I don't thin there's been a jump in a couple of decades.

I've flown in a couple of times and it's a nice enough strip -- clear approach either end, with the first half of runway 10 slightly downhill. Too bad there's nothing else to recommend the field except proximity.

Anyway, I bid adieu to this sad little airfield and climbed to 4500'. I requested advisories from Harrisburg Approach and stayed with them until I cleared Blue Mountain. They gave me a switch to Johnstown but I was too low and too far to make contact.I tried a couple of times and then just switched back to 1200 and descended to ridge skimming altitude.

Three Mile Island behind the strut, Harrisburg Airport (KMDT) in front

 I had a conference call at 1130 so I landed at Bedford (KHMZ), parked, and set up on the lone picnic table near the ramp. It was warm enough to conduct my meeting outside with cell phone and wifi provided by the FBO.

Three Mile Island, Susquehanna River

I launched an hour later and now the air was rougher. I followed the Turnpike for a while, then turned left at Somerset towards Connellsville. I've done the flight enough times to know a straight shot to Seven Springs then the next to the gap in the ridge formed by the Youghigheny would take me right to the airport. I was high (as I usually am to clear the ridge), slowed to 100 MPH, dropped 20 degrees of flaps, and slipped a bit to reach pattern altitude. I turned final and had a nice gentle landing on runway 23.

Endless Ridges seen from 4500' somewhere near Shippensburg, PA (Looking west)

Somerset, Pennsylvania and Pennsylvania Turnpike

I put the airplane away with Bill's help. We wiped off the bugs and loaded up and headed to Dairy Queen for some fast food.

It looks like he has a motivated buyer for 8104Z, and though I'm sad to see her go I'm happy that Bill can finally sell her. He hasn't flown much the past year and hangar fees, insurance, annuals, subscriptions and the rest can add up quickly.

I had to go pick up the trailer from U-haul so headed off to Hopwood where the process took four times longer than necessary. Finally I was able to hook up and roll out 45 minutes later. I drove straight to Waynesburg where I planned to do 1/2 the loading, park the trailer in the hangar, and finish loading Saturday. But there was no way to unhitch the trailer solo with all the weight in it, so I committed to loading the rest of the stored items boxes.

I checked in on John and saw my engine back on its mounts on 24286. He was looking for a few parts so he could finish. I didn't have them in the hangar (he later called to tell me he found them). The annual should be complete Sunday and I should be able to fly it home anytime after Monday, weather permitting.

He said some of the valve clearances were way out of spec. So with the valves adjusted to book spec and the new head gaskets preventing blow-by I should have a smoother running, more powerful engine -- and every additional horse is welcome when you only have 65 to start with!

We also replaced all the pushrod tube seals (which was the cause of the nuisance oil leak).So I'm looking forward to flying behind an engine that has essentially had a top overhaul completed.