Breaking the "elevator for altitude" habit

[shdw]

This has been haunting me since I started teaching and I have been testing ideas read from books and my own to try and find an efficient way to break my students of this habit. It is a natural human habit and we all have it which makes it increasingly more difficult to break than many other habits.

First I tried power only for any altitude change and I have had my students fly cross countries using only the power to change their altitude. I thought this was working till I had my student fly the flare (I recommend everyone does this) and sure enough he kept pulling to try and hold us off which inevitably left us to touch down.

IMO this is a great way to see if your student has this habit or not, there is no time a person will be more scared in a typical flight than when a foot off the ground. If they have the capacity to recognize the sink toss in the power and throw the nose forward when only a foot off the ground then my assumption is they have formed a pretty good habitual response. Oh, don't forget to tell your student to use nearby trees, houses, buildings and other things that protrude into the horizon as we sink lower for touch down as a reference to judge height above the ground.

I plan to test this further with surprises like having a normal approach to land then suddenly telling the student just before touchdown (full stall landings non of this wheel crap) not to land we aren't cleared. I will post up some results here as I come up with more results.



I theorize that our having the student descend to land and letting them nose up at all will enforce this habit because the nose up will give an initial climb. They don't care about the descent after, their brain sees that initial climb and primacy kicks in, the rest is ignore.

So I have recently started acting as a vice on the controls with my students. First off I teach the horizon, my students don't use instruments with the exception of the altimeter and when low or maneuvering the ASI. If they are not holding the horizon I hold the yoke so it can't move till they are 10 feet off the runway and I make power the only control they have. I have found at least in the limited testing I have done that this drastically improved the 3 students approaches that I have done it with so far.

I do it every single time the nose starts pitching up and down I grab it and make it so they can't move it forward or back again. Just like anything it needs to be done more with some than others, but I think it helps avoid/prevent erroneous reinforcement of pitch equals altitude.



I will let everyone know as I test this further but I would love to hear from the rest of you as to what has worked for you in this area. How did you test if it was working? What did you do if it didn't work to fix it and so on.

 

[jrh]

Maybe it's because I haven't been getting enough sleep lately, but your post didn't make much sense to me.

What I'd like to add is that I think using pitch for altitude / power for speed, or power for altitude / pitch for speed is an oversimplification and I rarely use either explanation.

The reality is that pitch controls both speed and altitude and power controls both speed and altitude. They are linked together during all phases of flight. You can't change one without influencing the other.

If you're high during an approach, but want to maintain a constant airspeed, you need to lower the nose and reduce the power. Vice versa if you're low.

If you're on glidepath but too fast, you need to reduce the power and raise the pitch attitude. Vice versa if you're too slow.



This is like debating if ailerons or rudder make an aircraft turn. I could say it's all rudder or all aileron, and I'd be right, to some extent. I could use a single set of controls and the aircraft *would* turn. But to teach it correctly, it should be a simultaneous application of both rudder and aileron. Same deal with pitch/power...use them both together to achieve what you want.

 

[tgrayson]

It is a natural human habit and we all have it which makes it increasingly more difficult to break than many other habits.

It's difficult to break because it does work...on the front side of the power curve. But I really don't think you want to break the habit completely; if you made throttle changes for every altitude deviation on a turbulent day, the throttle would have a continuous back and forth movement, which would be annoying.

I set an arbitrary limit of 100 ft altitude corrections with the yoke while in level flight, and even then I expect *small* AoA changes to fix it. While on approach, if a student fixes glidepath with the yoke, I will point out the airspeed penalty he paid by using this technique. Eventually the habit fades.

 

[shdw]

I set an arbitrary limit of 100 ft altitude corrections with the yoke while in level flight, and even then I expect *small* AoA changes to fix it. While on approach, if a student fixes glidepath with the yoke, I will point out the airspeed penalty he paid by using this technique. Eventually the habit fades.

I do the same, but I use 200 feet. I wasn't referring to making every single little change with it. Though I was referring to that method for approach to land with me holding the stick and not allowing them to have any elevator control.


If my theory holds true as I continue to test it than it would prove wrong your thinking on telling the students about airspeed on approach. If we look outside and pitch up on approach the first thing we see is a climb and that is what our mind saves IMO because of primacy. The student knows this is bad because they loose airspeed, but when they are nervous and acting on habit they don't think (won't check the airspeed) and they pitch back. When they pitch back they get what they wanted, a climb, as you know this repeats and continues till...

At least if all they ever did on approach was use power to go up and down than if things went bad my hope is their instinct would just be to hold pitch. Not to mention, this is a much much easier way for a student to learn to see a glide path and properly fly a glide path (regardless of glide angle) because pitch changes screw up the perception of glide path. Now if they loose an engine their only instinct needs to be holding pitch, there is no thinking about altitude or airspeed involved, just pitch/AOA.


For the bold, I think stall spin statistics show otherwise, thats why I made this post. Your students may be a different story, but the majority I don't think are changing this habit. I would say that it is likely because one we don't have an accurate and effective way to test this and two we don't study it or focus on it to figure out how to fix it. It has been a know problem since the birth of aviation and yet we still have engine failures on takeoff commonly result in stall/spin.

Aircraft stability and engine reliability has improved so much that I think this bad habit has nearly been forgotten by most. The problem is airplanes still stall, they still spin, and engines still fail and this habit must be broken to help a pilot avoid these situations.



For clarification: The bold in this post is what the whole topic is about, how to test the human habit that pulling back = up and how to help a student break this deadly habit.

 

[tgrayson]

The student knows this is bad because they loose airspeed, but when they are nervous and acting on habit they don't think (won't check the airspeed) and they pitch back.

I don't find this a problem past, oh, the 7 or 8 hour mark, except maybe within 50 feet of the ground, there is an unconscious tendency to start pulling back on the yoke. Not really dangerous at this point, but it can cause a firm or short landing. I expect to extinguish this prior to solo, but it can reoccur.

I focus on ensuring that the student is trimmed for the proper airspeed and is holding the yoke lightly in the hand; this allows the airplane to fly itself and makes it hard for him to inadvertently start applying back pressure.

 

[Douglas]

I agree with JRH, I wouldn't get too hung up on it. They both pitch the airplane and a moderate dose of both is best. I would like to hear more about it though when you try it out on more primaries. I like the idea of holding the yoke fixed to get the message across on final.

I use what TGRAy mentioned.

 

[ProudPilot]

Ok, I over complicate things a bit, but it seems to work with students from initial to commercial.

Physics, and steep turns get this demonstration done. You have potential energy (altitude) and Kinetic Energy (speed) and your power adds total energy. So, you need to balance things, but you can always have your power go to one or the other more with pitch.

The example:

In a steep turn, if you are low and fast, your total energy is correct but in the wrong place. Bring the pitch up and exchange the kinetic (speed) energy into some potential (altitude) energy and everything will be fine. Same for vice versa if you're high.

If you're both low and slow, you need more total energy. Bring up the power, and the nose, but not so high that you don't gain any airspeed. Just enough so that you speed up and climb. When on altitude, you would now have too much energy so bring back the power to counteract your drag (important otherwise students go idle thinking they have enough energy... man I wish more people too high school physics).

If you're high and fast, you have too much energy, bring back the power and pitch down a little to convert some potential energy into kinetic energy to maintain speed as you descend.

This works with students on approach and flare as well. As they now see power as a total energy, they control their pitch and make fewer power changes to get their total picture correct.

 

[shdw]

except maybe within 50 feet of the ground, there is an unconscious tendency to start pulling back on the yoke.

In my opinion this applies at altitude in an emergency, the student ultimately is scared of hitting the ground even though they are at a higher altitude. This tendency is what I am seeing if I can find a way to fix in my students. That is why I mentioned testing it in the flare as a possible way to test this habit or "unconscious tendency" to be broken.


I teach the reverse, I trim nose a touch nose up and make them push down all the time. The unnatural tendency is to push down, why not show them it is safe and works fine? I personally would rather if they jumped to press down, when at altitude on descent in, than pull back. Once over the threshold around 50 feet hand in front holding back as you reduce power for flare/touchdown.

 

[shdw]

Ok, I over complicate things a bit, but it seems to work with students from initial to commercial.

Physics, and steep turns get this demonstration done. You have potential energy (altitude) and Kinetic Energy (speed) and your power adds total energy. So, you need to balance things, but you can always have your power go to one or the other more with pitch.

The example:

In a steep turn, if you are low and fast, your total energy is correct but in the wrong place. Bring the pitch up and exchange the kinetic (speed) energy into some potential (altitude) energy and everything will be fine. Same for vice versa if you're high.

If you're both low and slow, you need more total energy. Bring up the power, and the nose, but not so high that you don't gain any airspeed. Just enough so that you speed up and climb. When on altitude, you would now have too much energy so bring back the power to counteract your drag (important otherwise students go idle thinking they have enough energy... man I wish more people too high school physics).

If you're high and fast, you have too much energy, bring back the power and pitch down a little to convert some potential energy into kinetic energy to maintain speed as you descend.

This works with students on approach and flare as well. As they now see power as a total energy, they control their pitch and make fewer power changes to get their total picture correct.

This works great when they are thinking, what happens in an emergency when the chances of them being able to think about mathematical relationships and imaginary numbers when they are under 1000' above the ground is not likely.

I am not speaking of how it is taught and explained on the ground. What procedures specifically do you do in the air to try and eliminate this "back = up" habit? Tgrayson gave a great example, "I focus on ensuring that the student is trimmed for the proper airspeed and is holding the yoke lightly in the hand; this allows the airplane to fly itself and makes it hard for him to inadvertently start applying back pressure."

I certainly hope you don't speak with them about their potential/kinetic energy and have them making constant altitude/pitch changes to make it work. It would be fun to see someone learn this way flying a vertical S approach chasing kinetic then potential. This kind of thinking is wonderful for instrument/commercial students trying to balance the total energy their aircraft to make approach decisions. I would think it a bit too complex to teach an 8 hours student how to land like this.

 

[tgrayson]

As they now see power as a total energy

While the energy paradigm is useful in some flight scenarios, I believe it fails to capture several important parameters for the approach. Specifically:

1. It implies that the aircraft has an unlimited ability to exchange kinetic and potential energy, when in fact that capability is limited by the stall,
2. it ignores the role of AoA in controlling airspeed, and
3. it ignores the AoA's contribution to the energy budget by not drawing the distinction between the front and back sides of the power curve.

All three of these problems are evident with your resolving the "low and slow" scenario by pitching up and adding power:

1. If the aircraft is slow enough, increasing the AoA may result in a stall;
2. if the aircraft is slow, the airspeed will only get slower if you increase the AoA, no matter how much power you add, and
3. if the aircraft is behind the power curve, increasing the AoA will only result in a more rapid destruction of energy by the aircraft due to the increased drag.

The best solution to the low and slow scenario is to apply full power and push on the yoke to reduce the AoA to increase airspeed. That will shift the aircraft to the right along the power required curve and increase its ability to climb. Failure to do so could make recovery impossible if the aircraft is in a high drag configuration.

I won't solo a student until I seem him recover from low/slow situation by pushing, both the yoke and the throttle.

 

[shdw]

The best solution to the low and slow scenario is to apply full power and push on the yoke to reduce the AoA to increase airspeed. That will shift the aircraft to the right along the power required curve and increase its ability to climb. Failure to do so could make recovery impossible if the aircraft is in a high drag configuration.

This is evident in that flared flight scenario I gave, a foot off the ground in flare just above stall having the student get into level flight a foot above the runway. It requires a good, excessive boost of power to stop the sink, while at the same time nosing forward, and finally reducing power to prevent climbing out of ground effect. It is quite a difficult little maneuver to perform, but on a calm day it can does a great job of demonstrating that the nose going forward won't result in a loss of altitude if subsequent power is added to compensate.

Edit: I am going to see if I can grab a plane for 15 minutes tomorrow and have a CFI record me doing this, from outside, it might be fun to show to my students but I will post it here if you guys would like.

 

[woutlaw]

I won't solo a student until I seem him recover from low/slow situation by pushing, both the yoke and the throttle.

+1

Once they do that on their own they're ready to solo, or at least pretty darn close.

 

[splash]

If you're high during an approach, but want to maintain a constant airspeed, you need to lower the nose and reduce the power. Vice versa if you're low.

hummm, at this stage the power is already low. Reducing power to idle will not suffice for the nose down attitude and you will gain airspeed. I say reduce power to idle and keep the nose up and pay close attention to airspeed shoot for Vx then you will not have a bunch of airspeed to bleed off. This way you gain sink rate with out increasing airspeed. What do I know though, I never come in too high or too low.

 

[jrh]

hummm, at this stage the power is already low. Reducing power to idle will not suffice for the nose down attitude and you will gain airspeed. I say reduce power to idle and keep the nose up and pay close attention to airspeed shoot for Vx then you will not have a bunch of airspeed to bleed off. This way you gain sink rate with out increasing airspeed.

Ok, if a person is drastically high or low my advice won't work, but I was referring to more routine situations. In the example you gave, I'd recommend executing a go around rather than intentionally gliding down final on the back side of the power curve.

Also, for what it's worth, I wouldn't use Vx in order to increase drag. Vx is fairly close to the minimum drag speed in many aircraft and it would actually keep you in the air longer...resulting in remaining too high, just at a lower airspeed.

 

[MidlifeFlyer]

Also, for what it's worth, I wouldn't use Vx in order to increase drag. Vx is fairly close to the minimum drag speed in many aircraft and it would actually keep you in the air longer...resulting in remaining too high, just at a lower airspeed.

Although Vx is also pretty close to short field airspeed, the whole idea of which is to steepen the descent. And that's what I teach for being too high (other than going around) - short field configuration and if that doesn't bring you down, a slip.

On the main topic. The human tendency to pull back so the houses get bigger is one reason why pitch for airspeed can be an effective initial teaching technique even though the end result will ultimately be the proper application of both.

 

[jrh]

Although Vx is also pretty close to short field airspeed, the whole idea of which is to steepen the descent. And that's what I teach for being too high (other than going around) - short field configuration and if that doesn't bring you down, a slip.

Do you happen to have any info on how much drag is actually added to the aircraft by flying Vx?

My understanding is that the slower speed used on a short field approach is to minimize floating during the roundout and flare, not to add drag to the plane.

In looking at numbers for a C-172S, it looks like best glide speed is 68 and Vx is 62. Since I know best glide speed falls slightly ahead of the minimum drag speed, I can't imagine there is more than a 5 knot spread between the minimum drag speed and Vx. This is why I agreed with Splash in principle, that flying on the back side of the power curve could steepen the approach angle, but Vx is not the speed to use--it has to be slower to have an effect.

If a person really wants to lose altitude using this trick, they should pitch up to the edge of a stall (slow flight with power at idle), mush down to within 100 feet of the ground, shove the stick forward to gain a little speed, then pull back to flare. The problem with that technique is that it's not very safe in the real world with inexperienced pilots at the controls. They might unintentionally stall and lose control close to the ground, or misjudge their height above the ground and pound it in hard.

That's why neither option here is good...going slow enough to sink is risky, while going faster is ineffective. Thus, I still recommend a go around.

 

[tgrayson]

that flying on the back side of the power curve could steepen the approach angle, but Vx is not the speed to use--it has to be slower to have an effect.

Vx and Best Glide are irrelevant here, since both speeds are without flaps, and Vx assumes full power. In low power airplanes most of our speeds are close together since our range of flight speeds is pretty small to begin with; the closeness doesn't necessarily indicate a relationship.

With full flaps, the recommended glide speed in a C172 is about 60 knots; any speed slower (or faster) than that is steeper, by definition. Since we only have about 10 knots to spare on the slow side, you clearly have an ability to lose a lot more altitude by flying at the top of the white arc, rather than the bottom. In a dire situation, you might ought to be clean and fly at the top of the green arc. Combining any of the above with a max performance slip (with S-turns) can lose a phenomenal amount of altitude.

 

[ppragman]

Do you happen to have any info on how much drag is actually added to the aircraft by flying Vx?

My understanding is that the slower speed used on a short field approach is to minimize floating during the roundout and flare, not to add drag to the plane.

In looking at numbers for a C-172S, it looks like best glide speed is 68 and Vx is 62. Since I know best glide speed falls slightly ahead of the minimum drag speed, I can't imagine there is more than a 5 knot spread between the minimum drag speed and Vx. This is why I agreed with Splash in principle, that flying on the back side of the power curve could steepen the approach angle, but Vx is not the speed to use--it has to be slower to have an effect.

If a person really wants to lose altitude using this trick, they should pitch up to the edge of a stall (slow flight with power at idle), mush down to within 100 feet of the ground, shove the stick forward to gain a little speed, then pull back to flare. The problem with that technique is that it's not very safe in the real world with inexperienced pilots at the controls. They might unintentionally stall and lose control close to the ground, or misjudge their height above the ground and pound it in hard.

That's why neither option here is good...going slow enough to sink is risky, while going faster is ineffective. Thus, I still recommend a go around.

I did that just the other day coincidentally (not to 100' more to like 400 or so) so I could get down from 3500 to sealevel in about 7 miles.

 

[jrh]

Vx and Best Glide are irrelevant here, since both speeds are without flaps, and Vx assumes full power. In low power airplanes most of our speeds are close together since our range of flight speeds is pretty small to begin with; the closeness doesn't necessarily indicate a relationship.

I agree. I only referenced Vx in order to address Splash's point, and best glide as a way to estimate the minimum drag point since it's not published for most aircraft.

With full flaps, the recommended glide speed in a C172 is about 60 knots; any speed slower (or faster) than that is steeper, by definition. Since we only have about 10 knots to spare on the slow side, you clearly have an ability to lose a lot more altitude by flying at the top of the white arc, rather than the bottom. In a dire situation, you might ought to be clean and fly at the top of the green arc. Combining any of the above with a max performance slip (with S-turns) can lose a phenomenal amount of altitude.

Again, I agree. I wasn't suggesting that slowing down to the edge of a stall is necessarily the *most effective* way to lose altitude, but using the back side of the power curve to steepen the approach is certainly one way to go about doing it. As you say, a steep dive will lose more energy and is my second most preferred method...right behind a go around

 

[ppragman]

Vx and Best Glide are irrelevant here, since both speeds are without flaps, and Vx assumes full power. In low power airplanes most of our speeds are close together since our range of flight speeds is pretty small to begin with; the closeness doesn't necessarily indicate a relationship.

With full flaps, the recommended glide speed in a C172 is about 60 knots; any speed slower (or faster) than that is steeper, by definition. Since we only have about 10 knots to spare on the slow side, you clearly have an ability to lose a lot more altitude by flying at the top of the white arc, rather than the bottom. In a dire situation, you might ought to be clean and fly at the top of the green arc. Combining any of the above with a max performance slip (with S-turns) can lose a phenomenal amount of altitude.

The angle of attack to lift curve is not linear at slow airspeeds, so theoretically there should be an very very high AoA that gives you the same lift that a very low AoA. The problem with diving and driving in on the approach is that you might not be able to slow down enough to land in some airplanes, thus negating the effectiveness of being on glideslope, depending on how high you are.