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        Looking at Stalls in a new light

Printed in National Association of Flight Instructors - Mentor -December 2008

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MooneyInFlight

Stalls. - For all that has been written about them, they still seem to vex student pilots more than anything else. When I talk to students about stalls, I find that students invariably can discuss all of the "book-learning" They can talk about exceeding the critical angle of attack and loss of lift. They can talk about signs of an impending stall, such as the stall warning horn, the mushiness in the controls, and the wing buffeting. And yet, when I ask students to perform a stall recognition and recovery maneuver, it often seems to be haphazard. And, even more seriously, when I see student and even private pilots get into a potential stall situation in the traffic pattern, they often do not relate their learning to the situation at hand. So, let me make a few suggestions that might help you see stalls in a slightly different light.

First of all, I have come to realize that we are really trying to teach four totally different things when we teach "stalls". But not only do we instructors not clue you in on this fact, some of what we are trying to teach is totally opposed to some of the other things we are trying to teach. For example, on one hand, we say we are teaching you how to avoid stalls, and then in the next breath, we teach you how to actually perform them.

Second, we want you to understand where in normal flight where these situations might occur. We want you to see the potential trap in the distance as you walk along the path, so to speak, so that you can avoid the situation long before it occurs.

Third, we want you to be able to return the aircraft to "normal" before the situation occurs, when it is still just a possibility, and we want you to be able to safely return the aircraft to "normal" even after you fall into the trap

And fourth, we want you learn how to perform a particular maneuver to the standards set in the Private Pilot Airman Certification Standards (ACS) So, let's look at these topics individually instead of pretending that they are all the same.

When I look at these topics individually, I first like my student to see that the stall situation is generally not going to occur in cruise flight. No one has ever stalled an airplane with the power set at a cruise RPM and the trim set for a level flight attitude. No, when you read accident reports in the flying magazines, the word "stall" always seems to be associated with either "takeoff", "landing" or "coming out of the clouds". I am going to set the third situation aside, because that is a separate topic and just talk about recognizing the stall situation in the takeoff and landing phases of flight.

CriticalAngleOfAttack

On every flight we transition through the "stall area" as we accelerate and take off, and as we slow down and land. So why are stalls a problem on some takeoffs and landings, but not on others? This question leads me to the first fact I like to point out. When performed correctly, these everyday stall situations do not lead to disaster. So, with the knowledge that the stall that is most likely to occur is the one in the traffic pattern, and that takeoffs and landing can occur without a stall disaster, I think that you need to really understand first what a normal takeoff and traffic pattern and landing look like. Therefore, I like to wait to introduce power-on stalls until we really understand what a correct takeoff and climb-out look like. And likewise, I wait to introduce power-off stalls until we can better understand a correct traffic pattern and landing.

Although all instructors have their own way of explaining things, one thing you have invariably heard your instructor talk about is "sight picture" or "nose relative to the horizon" or "attitude picture". All flying, whether looking outside at the real horizon, or inside at an artificial horizon, is based on setting the power where it needs to be, and setting the aircraft attitude where it needs to be. So, as we talk about power-on stalls, we are really talking about a stall which would potentially occur with full power. And that means takeoff and climb-out. So, before talking about power-on stalls in the practice area, work with your instructor to get a pitch picture firmly in mind of a perfect takeoff and climb-out. Get the sight picture in mind for the takeoff and the changing pressures on the controls that occur. Get the picture firmly set in mind for a normal climb, for a climb at the best rate (Vy) and a climb that gets you up and over obstacles (Vx). You will not really recognize the potential stall situation on takeoff and climb-out until you have the normal picture firmly in mind.

Once you have the "correct picture" set in your mind, it is time to look at takeoffs and climb-outs gone bad. And since we need some room to breathe, we are going to look at these "bad" takeoffs and climb-outs with some spare altitude below us. So, out to the practice area.

I like to start off by bringing the power back to idle and slowing down toward a slow-flight airspeed, and then performing a normal takeoff. Now obviously, we are not going to slow down to zero, but we are going to perform the maneuver just like we do on the ground. We add power, we bring the nose up to the takeoff picture, and then we hold a climb-out attitude and pretend that we are climbing out of the traffic pattern. Finally, after all of this, we are ready to look at the first of topics we are trying to teach. That is, how can a normal takeoff and climb-out become a stall situation? This is what your instructor is demonstrating when he brings the nose up higher than a normal climb picture. And now that you understand what a correct picture is, you can understand what an abnormal picture is. But, it is hard to understand the "abnormal" situation if you don't have the normal picture firmly in mind

I often have students ask me, "Chris, this climb-out attitude is so obviously wrong. How can anyone fail to see the picture when it occurs?" Well, in real life the situation is going to occur in several different ways. First of all, at some point in your flying experience, the aircraft will not climb out as it normally does. You will be taking off on a hotter-than-normal day, you will be taking off with a heavier load than you normally, do, the engine will have some mechanical problem that keeps it from developing full power, the kids in the back seat will distract you, or a door pops open and distracts. Something out of the ordinary will occur to cause you to get a different picture than you normally see - like leaving the flaps extended or the carb heat ON after a touch-and-go..

So this is "lesson first" of the power-on stall: We want you to see and understand a normal full-power climb situation and then we want you to understand all of the differences with the stall situation

Second, we want you to be able to recognize those differences as they occur for real, and then make the corrections as necessary to get back to "normal". We hope that you don't wait for all of the impending-stall signals to occur before you start to take corrective action. We hope that you recognize first that if the power is too low or the pitch picture indicates higher-than-correct, you will immediately take action. We hope that you don't wait for sluggish controls, warning horns or wing buffeting. But, like that alarm clock that gets louder and louder as you ignore it in the morning, we want you to recognize the full extent of the warning you will receive before the event finally occurs. So, your instructor will help you become aware of all of clues as they occur. But just as you probably do not wait for the alarm clock to reach its loudest point, in a real potential stall situation, we do not expect you to wait until the last minute to recover from the situation when it occurs for real.

The third thing we want to get across is how to recover from the situation once you recognize it. If the thought "stall" passes through your mind as soon as you see the nose slightly high and airspeed 10 knots lower than you want, and if you then lower the nose a touch to get the airspeed back and check that the throttle is full forward, you have just recovered from an impending stall. And in reality, this is exactly the point where we hope you will recover. If you recognize the potential problem before you come close, you don't even have to display your new talents.

But we are going to go farther than this. Remember when you asked, "How could anyone even get to this situation?" We are going to assume that at some time in your flying career you miss those early signs of an impending stall, so we show you the all of the follow-on signs. And then, your instructor will show you how to correct the situation if you see it when you are closer to a problem, and how to correct it if you totally fail to see all of the warning signs and the stall actually occurs. And, you will realize, that this corrective action is exactly the same as it would be if you noticed the situation in its very early stage: that is, you will release some back pressure to get the nose back to a level flight attitude, roll out of any bank you might have, and ensure that the throttle is full forward. (And actually, I add one more step here. Depending on the airplane, you may or may not have these additional knobs: mixture, carburetor heat, and prop control. If you have any of those, push them full forward as well. Just shove everything forward to go faster. And check that the flaps are up. Ever forgotten to raise them after a touch and go?)

Since we have been talking about this situation occurring on takeoff or climb-out, it is time to throw in one more pesky fact. The ground will not care if you hit it in a stalled or an un-stalled situation. It is going to hurt if you hit it at all. So, not only do we need to get ourselves out of the situation, but we need to do so without losing one foot of altitude more than necessary. And this is where knowing that level flight picture really comes in handy. If we add full power, and lower the nose to a level flight picture, we will regain flying airspeed and the airplane will once again be under control. There is no need to lower the nose to a diving attitude

Up to this point, I have been talking about how your instructor will guide you through this set of lessons to help you recognized the difference between normal flight settings and potential stall settings, and how your instructor will help you get the airplane back to a safe attitude, no matter where you become aware of an unsafe situation. But the time will come when you have to demonstrate to a designated examiner that you can recognize the stall (and potential stall) situation and that you can recover from the situation at whatever point you recognize it. Section VII-C
Private Pilot Airman Certification Standards (ACS) is pretty explicit of what a power-on stall demonstration maneuver is supposed to look like. But once you realize that we are asking you to accomplish an everyday maneuver (takeoff and climb-out) incorrectly, the maneuver falls into place.

I ask my students to demonstrate a normal takeoff and climb-out – that is, to reduce the power and slow down toward the slow flight airspeed, then to increase the power and raise the nose to the takeoff picture.  The ACS guidelines states that you "exhibit knowledge of the elements related to power-on stalls." So, this is where you mention signs of impending stall as they occur, and you can state that, in a real situation, you would be recovering at "this point" rather than later. Then, at the point where the stall finally does occur, you will release back pressure to put the aircraft in that level flight attitude and ensure that all of the knobs and levers are full forward. (And note that I did not say, "Dump the nose.") Then, as the airplane accelerates, you can raise the nose slightly and begin a slight climb.

I have been talking only about power-on stalls, but the issues surrounding power-off stalls are similar. The power-off stall is most likely going to occur in the pattern and landing phase of flight. (When else are you flying with the power at or near idle, and the airspeed decreasing?)

Reading the accident reports month after month, it is obvious that when a power-off stall occurs, it occurs in one of two places – the turn from base to final, or over the runway during the landing itself. So, let's look at those two situations.

First, the turn to final. We are back to "sight-picture" and "proper attitude." I find that it is much easier to understand what a potential stall attitude picture looks like if you recognize a normal sight picture for the turn to final. Therefore, with your instructor, work on developing a consistently correct turn to final before you try to recognize and understand the incorrect turn to final. You will come to understand that a normal turn to final consists of the nose somewhat below the horizon and a particular airspeed, suitable for your aircraft. The turn is initiated prior to the runway centerline so that the turn becomes tangent to the center line as you turn to the runway.

Once you understand what the turn is supposed to look like, we can introduce some dangerous variables – those pitfalls along the path. What happens if you have a tailwind on base and you roll out of the turn past the centerline? What happens if your eye is focusing on a parallel runway or taxiway that is past the desired runway? What if we just plain mis-judge the point where we should have started the turn, and just roll out late? The correct answer to all of these situations is "GO AROUND and try again." But, in some cases a pilot might think that an acceptable solution would be to pull the turn a touch tighter. And often, when this happens, the pilot realizes that he is descending so he holds the nose up "just a little" as he slowly tries to correct the overshoot. Your instructor will show you this, not to show you how to correct from an overshoot, but to demonstrate how this pitfall can occur so that you can totally avoid it

And like the power-on stall that you see coming, this should be a power-off stall situation that you see coming. Ideally, you will begin to recover as soon as you see yourself overshooting. But like the power-on stall situation, your instructor will help you see all of the warning signs that begin to pile up before you.

There is one more power-off stall that I like to help my students with, and that is the straight-ahead power-off stall. This is a stall that we will actually perform everyday, because it is the stall that allows us to land. The difference here between a "good stall" and a "bad stall" is merely the height above the ground when it is performed. If we perform this power-off stall lined up with the centerline, airplane aligned with the runway, and our altitude about two or three feet off the of the ground, we call the stall a "perfect landing". However, if we perform the same maneuver ten feet in the air, or not over the center of the runway, or not aligned with the centerline, we call it "a fiasco" (or more properly, "a go-around situation".) So therefore, it seems to me that we can better understand this stall situation once we understand what a good landing is supposed to look like. Then, anything else is probably a "bad stall".

The next thing that your instructor will show you, after demonstrating all of the signs of the impending stall, is how to recover. Fortunately, you pretty-much already know this – Use the yoke (stick) and rudders to put the aircraft in a wings-level, level flight attitude and smoothly push the throttle lever / knob fully forward. (and check to ensure that all of the other knobs and levers are full-forward). And then, the one difference from the recovery from a power-on stall – Raise the gear and flaps as recommended by the aircraft manufacturer.

With this understanding, flying a power-off stall demonstration for an examiner is a snap. Just get yourself up to altitude and fly a normal traffic pattern (with a serious error in the turn to final.) I like to suggest that you get about 2,500 to 3,000 feet above ground level. (This maneuver will be an altitude loser.) Then, configure the aircraft exactly as you do for downwind – same airspeed and everything. When you are ready, turn base, just as you normally do – same pitch picture, power setting, carb heat, flaps, etc. Make it look like you do it everyday. Then, instead of executing your perfect turn to final that you do at your home airport, you can find a point out toward the horizon on the wingtip, and imagine that that was the runway that you overshot. And, then you can tell yourself that you are low, but if you are verrrry slow and verrrry deliberate, you can carefully bring the nose around safely. And this is where you can explain to the examiner all of the ways that you can tell that this is an unsafe situation, and that if you saw this situation occurring in the pattern, you would be adding power and going around. If asked, you can maintain the picture until the stall occurs, and then simultaneously add power, roll to wings level, and release back pressure to maintain level flight.

Finally, there is one more power-off stall that you can be asked to demonstrate, and that is a straight-ahead or wings-level stall. Again, simple, because you do it every day. We just need to be organized. Imagine yourself on final approach to your favorite airport, power, flaps, gear, carb heat and pitch picture all set as normal. Now imagine yourself coming across the end of the runway, raising the nose as you always do for that perfect landing. Now, hold the nose off, hold it off, hold it off. Now is the point where you say to yourself, "Oh no, I am rounding out too high. I need to go around!" And that is all that you are going to do. Simultaneously bring in full power, use whatever back-pressure you need to hold the nose at the takeoff attitude, and let the aircraft fly out. You will find that you will lose only a few feet of altitude as you perform this maneuver, and when you are safely climbing, you can raise the gear and flaps in accordance with the flight manual.

And there is a bonus lesson when you learn to perform this power-off stall demonstration. You have just practiced the perfect landing and the perfect go-around.

Once you can demonstrate that you can recognize all of the signals that the aircraft provides prior to the stall, and then recognize and recover from the stall itself, you will have accomplished all four tasks. You will understand what a correct takeoff and climb-out look like, and what a safe turn to final and safe landing look like. You will then be able to differentiate between a safe situation and an unsafe situation. You will be able to recover from the situation should it occur in the future, and you will be able to demonstrate all of those items to anyone who asks

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