Microburst recovery

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10-16-2012 | 07:15 PM

Denver

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From: Lunar Lander Commander

Microburst recovery

Why is it that they teach micro burst recovery as slowing down (pitching) for a climb to where if need be the pitch attitude is about to induce a stall in an attempt to get a climb/stop descent. And if an imminent stall is indicated reduce pitch sufficiently to avoid a stall. This is a speed far lower than the aircraft's Vx/Vy/Vld speed. Seems like you would want to be in a Vx/Vy maximum performance climb speed instead of incurring a big induced drag penalty.

Is it because it is better to trade all the money in the bank on a bet that the encounter will end before you go broke?

Just speculatizing

10-17-2012 | 04:15 AM

Duckdude

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From: B767 Captain

I have wondered the same thing before. Could it have anything to do with minimizing energy in the event you crash? And why do you keep the same configuration? I would think reducing one notch of flaps, if landing with full flaps, would be a good idea to reduce drag with only a small increase in stall speed.

Looking forward to a good answer on this one!

10-17-2012 | 05:03 AM

dustrpilot

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From: AT802

Quote:

Is it because it is better to trade all the money in the bank on a bet that the encounter will end before you go broke?

Just speculatizing

Yes! In a wind shear recovery event it's important to get every once of lift available to stop the decent and the only way to do that is ride the shaker until your clear of the event. It is operating on max performance and not done often, so it can be uncomfortable to some people.
I never think about crashing, but if I had to, I'll take under control and as slow as possible

10-17-2012 | 05:15 AM

9kBud

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From: yes

Quote:

Originally Posted by Duckdude

Recovery depends on what the manufacturer finds best; you don't keep the configuration the same in every airplane.

10-17-2012 | 12:02 PM

Yazzoo

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From: 747

Quote:

Originally Posted by Denver

Why is it that they teach micro burst recovery as slowing down (pitching) for a climb to where if need be the pitch attitude is about to induce a stall in an attempt to get a climb/stop descent

To answer your original question, a microburst is basically a big "downforce" acting on the entire airplane, so the idea is to go max power and pitch as far up as possible to generate as large an opposing "upforce" as possible. You're trying to turn the airplane into a rocket and blast away from the ground.

The procedure does vary from airplane to airplane. Someone correct me if I'm wrong, but when I rode in a 737 sim I was told the procedure is to follow the FD because it calculates the best path possible (in the 120 you just pitch as far up as possible without stalling).

10-17-2012 | 12:12 PM

USMCFLYR

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From: FAA 'Flight Check'

It is all about AOA.

USMCFLYR

10-17-2012 | 03:55 PM

JamesNoBrakes

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From: Volleyball Player

Quote:

Originally Posted by Yazzoo

The guidance for a severe downdraft (like lee-side mountain turbulence) is to ride it down, gain speed, increase horizontal distance, and use excess energy to climb out of it and past it. I think the main problem here is the proximity of the ground and inherent problems with reducing configuration/drag significantly(increasing AOA, sink rate momentarily as wind sheers to an even stronger TW, and so on). You simply can't "ride it out" as in the more optimal thousands of fpm DD lee-downdraft. 2000' up or lower on the ILS, you don't have far to go or much time.

10-17-2012 | 05:11 PM

Yazzoo

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From: 747

disregard this post....

Last edited by Yazzoo; 10-17-2012 at 05:45 PM. Reason: James, my bad man, I shouldn't post when I'm this out of it!

10-17-2012 | 10:41 PM

Swedish Blender

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From: fins to the left, fins to the right

Quote:

Originally Posted by Duckdude

And why do you keep the same configuration? I would think reducing one notch of flaps, if landing with full flaps, would be a good idea to reduce drag with only a small increase in stall speed.

I have been told it to stop a pilot from dorking it up. While it may not apply to your aircraft, many have multiple flap settings. I believe it was found to be better leaving things alone rather than trying to change configurations and screw things up. Ala missing a gate and raising the flaps too much.

10-19-2012 | 12:53 AM

#10

okawner

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From: Awa(k3rE3

Quote:

Originally Posted by Denver

Seems like you would want to be in a Vx/Vy maximum performance climb speed instead of incurring a big induced drag penalty.

These speeds, while touted as "max performance" speeds, all have a certification-mandated safety margin above stall added to them. So they are not truly the maximum performance numbers, they are the "safe" maximum performance numbers. Good enough for departure climb, but you can do better if you need to. Same for engine thrust. Unless governed, turbofan engines can make better than take off or max rated thrust, but for long term safety and reliability they are capped.

I agree with SB regarding the configuration. Never ceases to amaze me how unplanned go arounds tend to flummox even experienced pilots.