Breaking the "elevator for altitude" habit

[tgrayson]

I've never heard the argument presented otherwise. That's what Deakin was addressing.

Deakin says this:

Assume you're in stable, level flight, constant speed. Your instructor says to increase your speed by 10 knots, while maintaining altitude. Even a moron isn't going to have to think twice about this, he'll add power, there just ain't any other way to get there from here. As the airplane picks up speed, a by-product will be a change in trim, and a small correction with the trim tab would be good. I don't see how anyone can stretch that into the pitch controlling the speed, that's getting the elephant…, er, the cart before the horse, when it should be the other way around.
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Is it not clear that he has no understanding of the physics?

 

[tgrayson]

As soon as the discussion leaves that realm, then this "truism" -- that a lot of CFIs think applies to every aircraft everywhere -- is suddenly *not* true

The physics is the same for all airplanes, only the numerical values of certain parameters changes with wing planform, airfoil, and aspect ratio. (You won't find many pilot training books that slam home the point that AoA controls airspeed more than Aerodynamics for Naval Aviators.)

 

[tgrayson]

I do disagree with you in saying he doesn't have an analytical understanding as that is IMO a bit of an unwarranted assumption. I would reword that to he did not analyze the underlying problem at all but instead, like most high time jet pilots, focused on the plain words of "pitch for airspeed and power for altitude." This as I am sure you realize and others need to begin to realize is not the proble

I spent many years with John Deakin in a forum similar to this and know that he's basically a shoot from the hip sort of guy. He has a good bit of knowledge about engines, but he got that mostly from an engineer, George Braly. On other subjects, he's just a random airline guy, except for having exceptionally strong opinions. If you think that group as a whole fundamentally understands the pitch vs power subject, I think you're gravely mistaken. I'm sure that the vast majoriy fly as if they do, but if you asked them to explain it, they wouldn't be able to so coherently. One very excellent airline pilot of my acquaintance admitted he really didn't understand the difference between AoA and climb angle.

 

[ppragman]

All I see in all of this is that excess power controls sustained rates of climb at a constant airspeed. No power, no climb without trading some airspeed.

I think we can all see this. In level sustained flight, at cruise speeds we decide we wanna go up 100'. Do you mash the throttles forward and wait? No. You raise the nose a wee bit, you lose a little airspeed and you jump up 100'. Then, upon reaching you lower the nose again (thus lowering your AoA), your airplane returns to equilibrium eventually and you are back at the airspeed you started with.

On the back side of the power curve the same is true. Let's say you are exactly dAoA below the critical angle of attack. You need to add power to increase your rate of climb because if you increase your AoA at all, you will stall. Typically, we are not ever this slow, so on short final, we're usually not too deep into the region of reversed command, so even at published shortfield speeds, we still have a fairly wide margin to play with, so average joe pilot doesn't necessarily see the relationship. At real shortfield speeds, you have to "drag it in with power" and bury the airspeed. At those speeds, pitch control stays the same until entering ground effect (typically where it's increased for breaking and flare) and any deviation in airspeed or glide path is controlled by power. If you're too low, you cannot pitch up, so you add power and wait. Too slow and you add power, simultaneously lowering the nose if you have to so you don't stall, while waiting for your airspeed to build so you can return to the original AoA. Low and slow, and if you don't catch it soon enough you can be screwed.

I don't see how the jet could really be all that different, except that in those single seat fighter, the airplane is all motor. Without thrust that airplane becomes a lawn dart, because its wings are designed to go fast, which means that they aren't going to be producing much lift at the lower airspeeds, which to me (correct me if I'm wrong hacker) means the back side of the power curve. Combine this with the fact that almost nothing you do other than change pitch will control things instantaneously (because you don't have propwash to give you that instant response) and your options to maintain an airspeed at any given time will be much much smaller. Your options? add power for pretty much everything. Drive it around with power.

 

[shdw]

I spent many years with John Deakin in a forum similar to this and know that he's basically a shoot from the hip sort of guy. He has a good bit of knowledge about engines, but he got that mostly from an engineer, George Braly. On other subjects, he's just a random airline guy, except for having exceptionally strong opinions. If you think that group as a whole fundamentally understands the pitch vs power subject, I think you're gravely mistaken. I'm sure that the vast majoriy fly as if they do, but if you asked them to explain it, they wouldn't be able to so coherently. One very excellent airline pilot of my acquaintance admitted he really didn't understand the difference between AoA and climb angle.

Well then I retract my statement. I was quite shocked by the arrogance of your original statement because at the time I thought you were basing it purely on that article.

Without thrust that airplane becomes a lawn dart

:rotfl:

 

[Hacker15e]

The physics is the same for all airplanes, only the numerical values of certain parameters changes with wing planform, airfoil, and aspect ratio. (You won't find many pilot training books that slam home the point that AoA controls airspeed more than Aerodynamics for Naval Aviators.)

I was referring to the overall assumption being discussed in the thread, that throttle controls altitude and elevator controls airspeed, period.

It may be that "only the numerical values change", but the result is that if you try to fly a swept wing, symmetrical airfoil, low aspect wing aircraft that way (specifically referring to the approach phase, as that's where this topic is generally discussed) the airplane is very likely to end up not doing what you want it to do, or going where you want it to go.

Elevator (stick position) is far more effective at placing aimpoint, and throttle is far more effective at controlling airspeed, especially in the region of reverse control.

 

[tgrayson]

arrogance of your original statement because at the time I thought you were basing it purely on that article.

The article is purely sufficient. The problem is that you and jrh read an article such as Deakin's and you insert your own knowledge into the missing gaps, because you make the assumption that someone with Deakin's experience could not possibly have a misunderstanding on such a basic topic. I don't do that; I listen closely to what someone says and what they write and sniff for any hint of misunderstanding, because my job as an instructor is to evaluate the understanding of the student, not to figure out some way I can let them be right.

 

[tgrayson]

if you try to fly a swept wing, symmetrical airfoil, low aspect wing aircraft that way (specifically referring to the approach phase, as that's where this topic is generally discussed) the airplane is very likely to end up not doing what you want it to do, or going where you want it to go.

I was pointing out that the Navy taught its pilots to fly low aspect ratio, swept wing, symmetric airfoil airplanes exactly that way, because that's what Aerodynamics for Naval Aviators stresses.

 

[jrh]

Ok, I give up.

 

[dasleben]

Ok, I give up.

You and me both, brother.

Before I leave, let me just say this: Scientific understanding does not take the place of experience in different aircraft types. I mean, an F-15 pilot being called out on the carpet by CFIs about flying his aircraft type? The thoughts of a 35,000 hour airline captain being tossed aside like he's a fool? That's pretty brazen, don't ya think?

Heck, I'm not a super experienced guy myself, but I've instructed, flown 135 commuter, and flown 121 transport jets. I've just been trying to bring my own personal experiences to the table, but each and every time I have, there's another guy without those experiences telling me how wrong I am. Seriously, you guys don't have to listen to anything I say, but everything I've said in this thread has come through experience, not simply a scientific understanding of the principles.

 

[tgrayson]

pilot being called out on the carpet by CFIs about flying his aircraft type? That's pretty brazen, don't ya think?

I think it's a bit brazen that anyone would think that being able to operate a piece of machinery provides much insight into how it works.

 

[Hacker15e]

I was pointing out that the Navy taught its pilots to fly low aspect ratio, swept wing, symmetric airfoil airplanes exactly that way, because that's what Aerodynamics for Naval Aviators stresses.

1. An aerodynamics book would never tell a pilot HOW to fly his airplane. It may give theory behind why, but not how. That's not how military flying training courses work.

2. Not all "Naval Aviators" fly pointy-nosed jets. I know the book of which you're speaking, and don't have any idea if that's actually the book they use in Aviation Preflight Indoctrination down in Pensacola. If they use that book, then it will have to cover concepts that apply to everything from a T-2, to a P-3, to a TH-57, to a F-18. Are you CERTAIN that the section you're reading in that book which talks about alpha and power (and apparently how to maneuver the airplane on approach using them) specifically refers to pointy-nosed jets?

I'd be happy to stand corrected if any USN guys want to pipe up and back up what you're saying.

Until then, I'll stick with what I've been taught in five separate formal aerodynamics courses in the USAF and what I've experienced in 2,000 hours of flying those airplanes.

 

[tgrayson]

any idea if that's actually the book they use in Aviation Preflight Indoctrination down in Pensacola..

Probably not any more. Not that it matters what the book says about it, because AoA always controls airspeed in any conventional airplane, and I don't need that book to say so explicitly. It's too fundamental. But here's what the book says:

Note that for the conditions of steady flight, each airspeed requires a specific angle of attack and lift coefficient. This fact provides a fundamental concept of flying technique: Angle of attack is the primary control of airspeed in steady flight. Of course, the control stick or wheel allows the pilot to control the angle of attack and, thus, control the airspeed in steady flight. In the same sense, the throttle controls the output of the powerplant and allows the pilot to control rate of climb and descent at various airspeeds.

The real believers of these concepts are professional instrument pilots, LSOs, and glider pilots. The glider pilot (or flameout enthusiast) has no recourse but to control airspeed by angle of attack and accept whatever rate of descent is incurred at the various airspeeds. The LSO must become quite proficient at judging the flight path and angle of attack of the airplane in the pattern. The more complete visual reference field available to the LSO allows him to judge the angle of attack of the airplane more accurately than the pilot. When the airplane approaches the LSO, the precise judgment of airspeed is by the angle of attack rather than the rate of closure. If the LSO sees the airplane on the desired flight path but with too low an angle of attack, the airspeed is too high; if the angle of attack is too high, the airspeed is too low and the airplane is approaching the stall. The mirror landing system coupled with an angle of attack indicator is an obvious refinement. The mirror indicates the desired flight path and the angle of attack indicator allows precision control of the airspeed. The accomplished instrument pilot is the devotee of "attitude" flying technique - his creed being "attitude plus power equals performance." During a GCA approach, the professional instrument pilot controls airspeed with stick (angle of attack) and rate of descent with power adjustment.

Maneuvering flight and certain transient conditions of flight tend to complicate the relationship of angle of attack and airspeed. However, the majority of flight and, certainly, the most critical regime of flight (takeoff, approach, and landing), is conducted in essentially steady flight condition.
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[Hacker15e]

Just for S&Gs, I'm cutting-and-pasting from the T-38 manual used to teach students how to fly the jet, called "T-38 Flying Fundamentals".

4.7.1. Glidepath. Use the runway and surrounding environment as the primary reference for establishing a 2.5-3° glidepath. Once the proper aimpoint is set, the HUD pitch scale can be used to check the glidepath – 2.5-3° nose low in the HUD. Trim off stick pressures to aid in glidepath control. Corrections to glidepath are made by increasing or decreasing the current rate of descent until the desired glidepath is regained. A technique for correcting is as follows: if you need to correct for a steep glidepath, aim slightly shorter until re-intercepting a normal 2.5-3° glidepath. If you need to correct for a shallow glidepath (being “drug-in”), aim slightly longer until re-intercepting a normal 2.5-3° glidepath. In either case, do not allow an excessive descent/sink rate to develop.

4.7.2. Aimpoint. The aimpoint is where the aircraft is going (i.e. where you would impact the ground if nothing changed). For a normal (gear and full flap and “on speed”) final approach, the aimpoint will be approximately in the middle of the front windscreen. This will not be a fixed point on the windscreen, rather an approximation which varies based on winds, glidepath corrections, etc. Another way of visualizing the aimpoint is to look for relative movement of objects in the windscreen. The point in the windscreen that appears stationary (it just grows bigger as you approach it) is your true aimpoint. This aimpoint needs to be maintained (assuming on glidepath) until reaching the transition line. When on the proper glidepath, shifting to an aimpoint beyond the desired aimpoint too soon sets up either a long landing (proportional to the amount of shift) or requires a sinking flare to land 500-1000’ down the runway. When using the HUD, the FPM will help you visualize the aimpoint. Placing the FPM just short of the threshold while on glidepath will allow for a controlled transition and flare.

4.7.3. Airspeed. Ideally, the aircraft should be flown at the computed final approach speed and .6 AOA. With gusty winds, increase the final approach and landing speed by ½ the gust factor per the Dash-1. Approximately 90% RPM will maintain on-speed indications on a normal glidepath with gear and full flaps. When making adjustments to glidepath, a power adjustment may also be required. If there appears to be a calibration discrepancy between the airspeed and AOA indications, take all factors (such as aircraft feel) into account to determine the appropriate speed to fly. Flying a higher speed than required is far safer than attempting to fly on speed with suspect indicators.

 

[shdw]

I'd be happy to stand corrected if any USN guys want to pipe up and back up what you're saying.

My chief CFI retired USN and professor Tom Teller also retired USN both have this book sitting in their library. Now I didn't ask professor Teller if thats what he learned from but my chief told me to buy this book when I showed him Flight Theory for Pilots saying, "this is what I learned from."

I don't know if that is all inclusive or if it is still what is currently being used but I don't know of any other books other than Dole and this book to teach this stuff. I know, only hearsay but for now its the best we have and hopefully that will change.



To all of you are arguing that just because pitch for altitude and power for airspeed works better it should be taught that way. Again I will repeat, pitch for airspeed and power for altitude teaches proper physics and thus will never result in a dead pilot if they stick to those parameters. When they get to jets you guys can spend an hour or two teaching them to slightly change their thinking for jet methods.



Das, was 1,700 accident enough or do more pilots have to die for it to sink in. This is not just to you but the rest of the guys that learned in this manner then got to jets and now are standing preaching "well jets fly this way and this is better."

Also yes he is a 35 year captain and I would bet he hasn't picked apart or thought about how his words would be interpreted by a student in 35 years. If he was a 35 year CFI then I would open my ears and be ready to listen. It is painstakingly obvious by the way he posted his general attitude, and tgray can probably back this up, he sounds like an arrogant prick. IMO he should have just kept his mouth shut like he originally planned.

Sure you can. While there are some significant differences (swept wing aerodynamics, turbine spool, etc.), an airplane is still an airplane. The lifties and the draggies still work the same way, and incorporate the same physics.

You forgot the biggest factor, momentum. Momentum is the factor that makes the difference in large jets, not aspect ratio, not delta wing, and certainly not a symmetrical airfoil. These aerodynamic designs, correct me if I am wrong, have little to nothing to do with pitch/power and what controls what.

Want proof, look at the new glasair III with extended wing AR of 7.64 (a B52 AR is 8.56) and a symmetrical wing, everything hacker applied earlier wouldn't be an issue in that aircraft. Why? Well the momentum is drastically less.

What are we talking about when we pitch back? Momentum...




Tgray, interesting point you have their on reading to pick things apart and how that is a job as a CFI. Thanks for the advice whether you meant it to be or not. lol

 

[ppragman]

My chief CFI retired USN and professor Tom Teller also retired USN both have this book sitting in their library. Now I didn't ask professor Teller if thats what he learned from but my chief told me to buy this book when I showed him Flight Theory for Pilots saying, "this is what I learned from."

I don't know if that is all inclusive or if it is still what is currently being used but I don't know of any other books other than Dole and this book to teach this stuff. I know, only hearsay but for now its the best we have and hopefully that will change.



To all of you are arguing that just because pitch for altitude and power for airspeed works better it should be taught that way. Again I will repeat, pitch for airspeed and power for altitude teaches proper physics and thus will never result in a dead pilot if they stick to those parameters. When they get to jets you guys can spend an hour or two teaching them to slightly change their thinking for jet methods.



Das, was 1,700 accident enough or do more pilots have to die for it to sink in. This is not just to you but the rest of the guys that learned in this manner then got to jets and now are standing preaching "well jets fly this way and this is better."

Also yes he is a 35 year captain and I would bet he hasn't picked apart or thought about how his words would be interpreted by a student in 35 years. If he was a 35 year CFI then I would open my ears and be ready to listen. It is painstakingly obvious by the way he posted his general attitude, and tgray can probably back this up, he sounds like an arrogant prick. IMO he should have just kept his mouth shut like he originally planned.





You forgot the biggest factor, momentum. Momentum is the factor that makes the difference in large jets, not aspect ratio, not delta wing, and certainly not a symmetrical airfoil. These aerodynamic designs, correct me if I am wrong, have little to nothing to do with pitch/power and what controls what.

Want proof, look at the new glasair III with extended wing AR of 7.64 (a B52 AR is 8.56) and a symmetrical wing, everything hacker applied earlier wouldn't be an issue in that aircraft. Why? Well the momentum is drastically less.

What are we talking about when we pitch back? Momentum...




Tgray, interesting point you have their on reading to pick things apart and how that is a job as a CFI. Thanks for the advice whether you meant it to be or not. lol

Famous last words.

 

[shdw]

Famous last words.

I challenge anyone here to give a scenario in any aircraft under 12,500 lbs non jet where pitch done strictly for airspeed and power done strictly for altitude can or has killed anyone.

 

[tgrayson]

Just for S&Gs, I'm cutting-and-pasting from the T-38 manual used to teach students how to fly the jet, called "T-38 Flying Fundamentals".

I don't see anything in the manual you quoted that contradicts what I have stated.

Corrections to glidepath are made by increasing or decreasing the current rate of descent until the desired glidepath is regained.

That part is true by definition and so is self evident. The question is, how to increase or decrease your descent rate? There is really only one way: you need to change your quantity of excess power. You can do this by either making a throttle change, or changing your AoA to change airspeed. The guidance you posted doesn't recommend a technique for doing so, from what I can see.The aiming point will change with either procedure.

Approximately 90% RPM will maintain on-speed indications on a normal glidepath with gear and full flaps. When making adjustments to glidepath, a power adjustment may also be required.

Again, I don't see a conflict. In a C152, for instance, maybe 1500 RPM will maintain proper glidepath at a final approach speed of 65 knots.

 

[tgrayson]

I challenge anyone here to give a scenario in any aircraft under 12,500 lbs non jet where pitch done strictly for airspeed and power done strictly for altitude can or has killed anyone.

Well, there was that Mission Impossible movie where the aircraft flew into the side of a mountain. The pilot was lying unconscious, then woke up and saw the mountain looming. His sole action was to advance all the throttles. Realistically, he should have done that and hauled back on the yoke until he got the stick shaker.

 

[Hacker15e]

You guys are right. I have no idea how to fly my own airplane. It's amazing that I haven't ended up a smoking hole in the ground since I'm apparently using my controls incorrectly.