The belief that flight time qualifies one to make this claim is the epitome of most wrongs in aviation today.
pitch=airspeed; power=altitude
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The belief that flight time qualifies one to make this claim is the epitome of most wrongs in aviation today.
tgrayson
New Member
Here is a chart plotting elevator position with coefficient of lift. It comes from "Airplane Performance Stability and Control", Perkins and Hage, a classic text on the subject used as one of the references in "Aerodynamics for Naval Aviators". The coefficient of lift, of course, is linearly related to AoA, and is related to airspeed via the lift equation I posted earlier. As you can see, the elevator position directly determines the lift coefficient, hence airspeed:
And, if you want to see the equation that it comes from:
wjmiller3
Well-Known Member
WOW!! Lets take two ideas from two separate paragraphs and thoughts, and put them together into one statement so we can manipulate the statement to our liking. You should work for the media!!
And your same quote could be said about 500hr pilots that think they know everything too!!
The point was that pilots, regardless of hours of experience, are not qualified to make such a statement. Instead we should yield our knowledge to members of the technical community in question, such as the repeated sources provided by tgrayson throughout this thread.
nosehair
Well-Known Member
What statement? I read him to say that we are all discussing technique. That his first flight training experience was the pitch to airspeed mantra, then had to learn the pitch to flight path mantra, then after many thousands of hours working both, has learned that it takes experience in both. I thought he was speaking to the experience level, not the knowledge level.
A bold statement he isn't qualified to make and one that is entirely wrong.
Disclaimer: I did not say, nor am I implying that I am qualified to make or dispute this statement. I am merely pointing out that those who are qualified to make such claims, IE the quoted authors in this thread, are in disagreement with the quoted statement.
Wrong, am I? Then why does it work?
You said neither is based on physics. On the contrary, pitch for airspeed is directly derived from the formulae tgray posted. Power for altitude is kind of simple, no engine equates to no climb. I have posted and tgray has spoken about how power required and power available link together for climb rate. Though no formula has been posted for power for altitude so here:
RC = 33,000 [Pa - Pr / W]
Where:
RC = Rate of climb in FPM
Pa = Power available in HP
Pr = Power required in HP
W = Weight in pounds
I presume you are referring to pitching for glide slope, if not ignore this:
P = mV
P = Momentum
m = Mass
V = Velocity
When momentum is enough to overcome weight, it works. When it isn't, if the distracted pilot doesn't realize the situation, it can kill.
I would like to ask you something now (assuming here
that you are or have flown for an airline or with some large turbine): Why do airlines make certain techniques into procedures?
APACHEpilot
New Member
I remember this just a few months earlier, having this same discussion with the DPE on my CFI practical test. There's one thing that is for sure, no matter how much we debate this technique of flying there will never be a clear cut answer. With that being said I teach in light single engine airplanes and have found that pitch=airspeed, power=altitude is the best way to teach it, I also believe it is the safest technique. If you teach a student that pitch = airspeed, if the engine fails you can bet the odds are a lot less that a student will stall-spin the airplane into the ground. That's my two pennies !
tgrayson
New Member
The better answer is that changing our velocity changes the position of the aircraft on the power required curve (or drag curve), producing an excess quantity of power (or thrust) that allows the aircraft to engage in a sustained climb.
This works equally well as changing the throttle settings, if you don't mind the airspeed hit and as long as the aircraft is on the front side of the power curve. If the aircraft is on the backside of the power curve,then increasing the AoA will result in an increase in the rate of descent rather than a reduction, so you can't pitch for altitude by definition, unless you reverse your thinking. Hence the name "region of reverse command", which I find more informative than "backside of the power curve."
Note that even in the region of reverse command, the aircraft has some small ability to convert kinetic energy into altitude before the extra drag kicks in, but this is very transitory and the altitude gain is quickly followed by an altitude loss unless the aircraft has plenty of excess power even in this high drag configuration. Without an immediate threat of hitting some obstacle, when you get low and very slow, the most effective technique is to add full power and push on the yoke to go up. I've watched many pre-solo students continually add power alone in this scenario, resulting in a continually decaying airspeed and further altitude loss. I will not solo them until I see them recover properly from this scenario.
So was my answer wrong or just not as precise as it could have been?
Agree completely, "backside" doesn't tell you anything. Reverse command puts the definition in the title, making it easier to remember IMO.
That's why I like to get them to fly level just above the ground. I make students do a power off approach, flare, and just before touchdown apply this recovery. I always demonstrate it first, but pushing forward only feet from the ground to make you go up is real doozy on the mind.
tgrayson
New Member
The momentum equation is not very explanatory in this case because the velocity in the momentum equation is a vector, meaning it has a direction. What we're really trying to explain is why the velocity vector has the direction it does. If someone asks "why am I going up?" and you say momentum, you're merely saying "you're going up because you're going up".
When we talk about "flight path", what we're really talking about is "velocity vector". If it changes, we need to point to some force that causes it to change. Pulling or pushing on the yoke clearly changes the velocity vector, and load factor is the force that causes it to change. Whether that change in flight path is permanent or not will depend on where that new yoke position (AoA) leaves us on the power required curve. For instance, if you're low and slow, pushing on the yoke causes a brief flight path change in the downward direction due to loss of lift, but then the flight path will change in the up direction due to reduced drag. Likewise, pulling back causes a brief upward flight path change, but then it moves down again, at a steeper angle than before because of increased drag.
Increasing power provides the needed load factor to cause a flight path change by accelerating the aircraft; at a constant AoA, the moment the airspeed increases beyond equilibrium, the aircraft undergoes a load factor greater than one and the flight path starts angling upward. The resulting rearward component of gravity slows the airplane back down to the equilibrium airspeed and the load factor returns to 1. This is why power doesn't produce a sustained increase in airspeed; the airplane gets rid of the increased velocity as quickly as it can by making the flight path as steep as necessary to restore the trimmed airspeed. This is the reason that the formula for angle of climb is related to (Thrust - Drag)/Weight. The excess thrust will exactly match the component of weight that lies along the flight path.
No, I didn't.
I said that neither technique is a law of physics. They are techniques. They both work. I haven't commented on which, if any, I prefer. I've said only that I can fly, and teach, them both.
You seem to be saying that the pitch=flight path/power=airspeed technique does not work. If that is what you are saying then you are unquestionably wrong. Both techniques work and, when applied properly, work well.
[quoteI presume you are referring to pitching for glide slope, if not ignore this:[/quote]
I'm referring to using each technique throughout the entire range of airplane operations.
Standardization.
There is a clear cut answers: Both techniques work when they are applied correctly. Both techniques fail when they are applied incorrectly.
How much time have to spent teaching the pitch=flight path technique? If you have only taught one technique, isn't it difficult to judge which one is better?
I can come up with similar scenarios for, or against, either technique. For example, a student flares too high and is now too high and too slow. If he applies the pitch=A/S technique he'll lower the nose and reduce power. That's not going to be pretty.
My point is that both techniques work and, when properly applied, work well. If someone is saying that only one technique works then that person doesn't understand them both.
And we (me and tgrayson) have both pointed out that this is wrong. One technique is entirely based on physical law.
They are techniques. They both work. I haven't commented on which, if any, I prefer. I've said only that I can fly, and teach, them both.
You cannot use pitch for glide slope (altitude) in the region of reverse command.
It has nothing to do with one technique being deemed safer than another? I am not trying to badger, I legitimately do not know and would like to know. Thanks.
In light pistons, pitch = AS | power = alt, will not fail if applied in any situation ever. Nobody on this thread has yet to come up with an example when it would. (Pick your jaw up till you read the next section
)Why in the heck would the student decrease power. Your scenario accounts for low and slow and the technique, applied properly, would be an increase in power and a decrease in pitch. The student is trying to control their descent rate (power) and increase their airspeed (pitch).
I don't think anyone said that pitch for glide slope doesn't work. What it has to do with, at least in the private level, is habit patterns. Habits are responses (actions/inputs) we develop through practice/use that become subconscious responses to given situations. If you always use pitch when you are sinking to control altitude, that can fail in certain situations. IE region of reverse command, inevitably leading to stall/spin.
SuperCubRick
Well-Known Member
tgrayson
New Member
In the scenario you're describing, the flaw in analysis is once again the conflation of pitch with AoA. Pitch does not control airspeed, AoA does. Anyone who says pitch will keep themselves and others confused forever.
I'd like to wire a 12-volt battery to someone's tongue and each time I hear "pitch", ZAP!The pilot that flares high needs to reduce his AoA to increase airspeed, but he needs to add power to adjust the descent rate to reasonable levels. Or, if he isn't about to stall, he can just fly the airplane to the ground in that horrible attitude with sufficient power. I've done both and seen both.
Larry, you can't come up with a scenario in which using AoA to control airspeed and excess power to control altitude will not work, because that's the way that both techniques work, no matter how the pilot chooses to think about it. I have four shelves of aeronautical engineering texts that say so.
It wouldn't surprise me if you had one lying around that agreed with mine.(caveat: let's ignore flight paths of 90 degrees, okay?
)
nosehair
Well-Known Member
OK, I'm with Larry on this one. And remember, we are talking about primary student reaction based on the rote rule of "pitch to airspeed, power to altitude".
In Larry's scenario, in a ballooning flare, the airplane is slow (pitch down), and high (reduce power). That would be the wrong response, wouldn't it?
I'll give another example. On short short final, the student sees the airplane is going to fly through the power lines at the end of the runway, so he adds power. He's not fast, so there's no pitch up - or increase in AoA, as Tgray likes to say. I prefer to say it that way, also, ..but industry standard slang has sucked me into using the term for convenience. But I always go into extreme detail about how airspeed is an indirect indication of AoA.
So, anyway, when the nose is pointed down and the initial gut level response is to add power when you want the nose pointed up is going to cost you some time and altitude before the power causes an AoA change and a change in vertical velocity. Changing AoA, with a follow-up on power to maintain speed seems the most effective way to go.
wjmiller3
Well-Known Member
And we (me and tgrayson) have both pointed out that this is wrong. One technique is entirely based on physical law.
They are techniques. They both work. I haven't commented on which, if any, I prefer. I've said only that I can fly, and teach, them both.
You cannot use pitch for glide slope (altitude) in the region of reverse command.
It has nothing to do with one technique being deemed safer than another? I am not trying to badger, I legitimately do not know and would like to know. Thanks.
In light pistons, pitch = AS | power = alt, will not fail if applied in any situation ever. Nobody on this thread has yet to come up with an example when it would. (Pick your jaw up till you read the next section
Why in the heck would the student decrease power. Your scenario accounts for low and slow and the technique, applied properly, would be an increase in power and a decrease in pitch. The student is trying to control their descent rate (power) and increase their airspeed (pitch).
I don't think anyone said that pitch for glide slope doesn't work. What it has to do with, at least in the private level, is habit patterns. Habits are responses (actions/inputs) we develop through practice/use that become subconscious responses to given situations. If you always use pitch when you are sinking to control altitude, that can fail in certain situations. IE region of reverse command, inevitably leading to stall/spin.
Who flies an ILS in the region of reverse command? I sure as hell don't! And if you are, you're dangerous!!