Are we at ‘back of the drag curve’ during approach and landing?

8 Answers

1. Best Answer
   
   

   
   

   Mark Kolber on Jul 23, 2013

   Yes, on short final you are the back of the power curve just as you are in slow flight.

   But, unfortunately, what you are being exposed to in the worst way is one of the great religious battles in aviation – whether pitch controls airspeed and power controls altitude or vice versa.

   Bottom line is that, whether ahead or behind the power curve, powered flight involves a balance between pitch and power. It takes both.Which predominates is strictly a matter of teaching technique, nothing more. If you think in terms of power controlling airspeed, you will still need to make a pitch input to get the result you want. If, otoh, you think in terms of pitch controlling airspeed, you will still need to make a power input to get the result you want. If you’re flying the aircraft properly, which way you choose to look at it will have zero effect on the result, so long as you are consistent.

   This is one of those unfortunate nonsensical disputes in aviation. My favorite example is the time I was told in no uncertain terms that I can’t possibly be alive because the day the bottom came out on final due to windshear, I looked at it the “wrong” way and that my uneventful landing was impossible.

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   Jim F. on Jul 23, 2013

   As an added question, is the “back of the drag curve” just another name for the “region of reverse command?” Seems like according to the explanation it is, but just wanna check…

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   CrashDamage on Jul 23, 2013

   Yes, Jim, I believe they mean the same thing.

   Tried the ‘new’ method today. (The method new to me i.e. POWER=AIRSPEED and ATTITUDE = GLIDEPATH).

   Struggled with it – perhaps I’m finding it difficult to get out of old habits.

   Do students find one method easier than the other? Any tips?

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   Mark Kolber on Jul 24, 2013

   Jim, yes, they pretty much refer to the same thing. “Region of reverse command” may have the benefit of being descriptive in the sense that in region of “normal” command, one would reduce power to maintain altitude at a slower airspeed; in the region of “reverse” command you need to add power to maintain altitude at a slower airspeed. But they are referring to the same concept.

   Crash, I feel your pain. The truth is that unless there is something wrong with your control or your instructor is forcing you to say what you are doing out loud, your instructor should not even be able to tell the difference.

   Take that landing approach you described in your first post. Let’s say, for example, that your airspeed is ok but you are getting too low. You would use both power and pitch control pressure to correct it, right? Here’s the difference:

   In “pitch=airspeed, power=altitude” you would describe it as adding power to reduce the rate of descent and raising the nose to maintain the proper airspeed.

   In “pitch=altitude, power=airspeed” you would describe it as raising the nose to reduce the rate of descent and adding power to maintain the proper airspeed.

   See what I mean? No difference in what you do. In both cases, you add power and add back pressure to the yoke. The only difference is in the way you think about it.

   You ask whether students find one method easier than another I have a preference for one over the other when teaching primary students but always ask a student who has taken lessons before which they were taught. Overall, I think students find the one they learned first to be the easiest and making an unnecessary change difficult.

   And you are only (and naturally) getting confused by trying to change your thought process. There is no good reason whatsoever for you to change that particular “old habit” unless you are doing something potentially dangerous, like doing one of the control inputs but not the other.

   What to do about it? Speak to your instructor. Tell him that you learned it the other way and that you are getting confused by trying to mentally reverse it. Ask him to let you think of it in your way and to correct errors in the approach with “too slow” or “too low” rather than “add power” or “push down.”

   Hopefully your instructor is flexible enough to change his ways instead of messing with yours, at least to the extent of testing it out. If not, well, I always hesitate saying “change instructors” when I don’t know the pilot or the CFI or the situation, but IMO, forcing a pilot (student or otherwise) to change a technique that works, not for safety but just because the instructor likes it another way, is one of the very worst things an instructor can do (and yes, I was once a victim of that instructor attitude)

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   JTX on Aug 01, 2013

   In my point of view there is a big reason for teaching attitude=> airspeed & power=> RoD, and I think it is universal.

   Mainly because the biggest danger during the critical phases of the flight – take off and landing – the stall.

   For example, during a landing approach. You go below the approach speed, closer to the Vs. If you use power to accelerate, the aircraft will want to pitch even more up, getting you closer to the critical AoA.
   The right thing is pitch down, and, almost at the same time but as a second step you have to judge if you are high or low, and then you use power.

   This applies to the Warrior. Maybe for some peculiar and rare aircrafts it can be the other way, only maybe.

   About the back of the drag curve during an approach, thats true. But it doesn’t change the method of attitude-airspeed, power-rod

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   augerk on Aug 01, 2013

   I prefer to think of it as power for airspeed and pitch for your aiming point. The airplane is not on the backside of the power curve during approach, so even though the other technique works, it seems a bit backwards to me. But as others have stated as long as you pick one and stick with it, your landing will look the same either way.

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   Sean Falzarano on Aug 10, 2013

   I used to teach the whole “pitch for airspeed-power for altitude” method until I realized it is better to teach students how to land using the very same techniques CFIs are teaching their students before they come into the traffic pattern and learn how to land- Constant Speed and Rate. Instead of confusing them with “pitch for airspeed-power for altitude” or vice-versa, I’ve been explaining that the landing is a constant speed descent and once you have the power set appropriately to the configuration of the plane (flaps, gear…) the rate of descent should be pretty stable, as well. Of course, in the end it’s pretty much the same thing..you are adjusting pitch and power slightly to make corrections, but the idea of constant speed and constant rate comes from what the student already knows from the “practice area”. Introducing “pitch for airspeed-power for altitude” is like introducing a whole new concept to students and they seem to over think something they already know how to do. I’ve seen this make a world of difference for my piston and turbine students.

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   David Eberhardt on Aug 25, 2013

   JTX (on Aug 01, 2013) comments were spot on.

   For all you pitch for glide path, power for airspeed advocates I ask:

   1) what do you teach your students about how to “stretch” a glide to make it to the runway if you are coming up a bit short? Same question applies to power off and power on.

   a) if power off – raising pitch will only slow you down. If you are on speed or slow, it won’t help you at all.

   b) if power is available, simply adding a bit of power will carry you further and the nose will tend to rise just a bit in response anyway. see my video on youtube (dkeberhard)

   most adjustments to glide path and airspeed require a coordinated power and pitch but power dictates altitude control.

   Here’s a question for you – what controls altitude control when flying a loop? power, pitch?

   correct answer is the amount of g’s pulled.

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