Weird stall recovery technique?

[VNugget]

My CFI taught me to raise the flaps along with the ovious pitch-down and power-up when recovering from stalls. I thought this was a bit, uh.. "weird" to say the least, and when I asked hima bout it, his rationale was that you're getting rid of drag.

But, more importantly, you're losing precious lift, and furthermore, you're increasing your stall speed. I concede that in certain situations that is the right thing to do, but I think that this should be done after things have stabilized, and you have had a chance to analyze the situation and need to do what needs to be done.... not as a part of the "kneejerk" pitch/power reaction. Why would I want to immediately increase my stall speed during a stall recovery?

I haven't presented this argument to him yet because after lessons I always tend to forget to ask the questions that I had "gotten ready" to ask during the actual flight (maybe I should take a notebook, heh) so I decided to run it by all of you before I see him again on Monday.

 

[midlifeflyer]

What kind of airplane and how much flaps? Are we talking about dumping all of them at once?

Or are we talking about moving from 30 or 40° in a C172 to 20°? That's normal stall recovery (and looks just like a go-around)

 

[bobbysamd]

Stall recoveries

Let's say you're flying an old 172. You are doing an approach-to-landing stall with 40°of flaps. You would lower the nose, add full power, pitch up to Vx while raising flaps to 20°. As you are climbing out you milk up the remaining flaps slowly. You do not dump them all after you have lowered the nose and added full power.

Try it sometime. Do it with plenty of altitude. Feeling the airplane drop from under you is disconcerting.

As a suggestion, make sure that what you have written to us is exactly what your instructor said before you confront him.

 

[VNugget]

Midlife, whoops, shoulda mentioned that... 172, and the retraction is from 30 to 10.

Bobbysamd, this isn't about a "confrontation," but rather just some clarification and explanation.

Both of you: After reading around some more on the net, it seems that I jumped the gun and attacked a strawman. My CFI did teach me to raise the flaps in the context of a landing approach stall (which means that it would consequentially lead to a go-around and climbout... all of this of course after making sure you have regained enough airspeed), as did the websites I looked at... and the inference that it should be a part of the intial knee-jerk reactoin was only mine.

At any rate, this will all be clarified tomorrow morning, and thanks for your responses.

 

[stillaboo]

I know this has been cleared up, but for those who don't know:

his rationale was that you're getting rid of drag.

But, more importantly, you're losing precious lift, and furthermore, you're increasing your stall speed.

On most piston aircraft (particualrly small training ones) the first 1/2 of flaps (the 10 and 20 on a C-172 that can do flaps 40) usually generate more lift than the corresponding increase in drag. The second 1/2 generate more drag than they do corresponding lift. That's why you clean up from full flaps on a stall recovery, but never ALL of the flaps.

Extra info for future reference (and for guys more in 'the know'):

"On approach in jets, all of those high-lift, high-drag devices (flaps and leading edge devices) are extended to slow the aircraft to the degree that relatively high thrust must be carried all the way to landing. This aids in go-around situations because, since thrust is already fairly high, spool up time is minimized. Cleaning up the airplane turns out to be faster than waiting for spool up, especially on older turbojet aircraft."
-The Turbine Pilot's Flight Manual, p. 25

For those of you who don't know what 'spool up' is:

"Turbine engines take time to spool up when power is applied. . . . The term 'spool up' refers to the time it takes, after power application, for thrust to increase to the selected values . . . While adding full throttle in a piston aircraft may result in maximum power generation in a couple of seconds, turboprops take a bit longer, and maximum thrust in jet aircraft may not result until five to ten seconds after power application."
-The Turbine Pilot's Flight Manual, p. 24

 

[Timebuilder]

Bobbysamd, this isn't about a "confrontation," but rather just some clarification and explanation.

I think you may be thinking of the word "confrontation" in the contemporary "social" sense of the word, which carries a certain agressive connotation.

You can "confront" someone with sincerity and friendliness, too. Once a word gets used in just one way often enough, it starts to carry an extra meaning.

Bobby was asking you to make clear what you had been told before you possibly embarass yourself when you bring up this topic with your instructor. While it is great to be an "activist" student, remember that you need to have your ducks in a row before you consider arguing against a particular procedure, such as the correct method of stall recovery.

 

[VNugget]

On most piston aircraft (particualrly small training ones) the first 1/2 of flaps (the 10 and 20 on a C-172 that can do flaps 40) usually generate more lift than the corresponding increase in drag.

I've actually heard that from lots of people, including my CFI.

If they add more lift than drag though, why isn't 10 degrees of flaps part of the standard engine-out glide procedure?


As for the original question, I forgot to ask him again. Argh.
Oh well, we ended up with a discussion about thrust vs. power required, and best glide vs. minimum sink speeds, so I didn't go home empty-handed

 

[Timebuilder]

If they add more lift than drag though, why isn't 10 degrees of flaps part of the standard engine-out glide procedure?

Because you no longer have power, you are not seeking additional lift, but the elimination of drag and the prolonged descent necessary for an engine out procedure. Remember, the purpose of flaps is to provide for a steeper descent without an increase in airspeed. In an engine out situation, you don't want a steeper descent, you want one that gives you the greatest choice of real estate for your emergency landing.

 

[VNugget]

Er.... that was plain stupid. I just figured out how it's completely possible (and in this case, the case) that they can add more lift than drag, but still lower the L/D.

 

[avbug]

Stillaboo,

Those things are mesmerizing. (avatar)