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-   -   737 Windshear escape maneuver (https://www.pprune.org/tech-log/612093-737-windshear-escape-maneuver.html)

stilton 12th August 2018 05:59
737 Windshear escape maneuver
 
Normal practice is to leave gear down in this maneuver to avoid drag from opening doors during retraction


However the 737 has no main landing gear doors, just the nose gear


So do you retract the gear during this maneuver on this aircraft?

Wizofoz 12th August 2018 06:12
No. No configuration change until clear of windshear.

Goldenrivett 12th August 2018 13:52
b) help make the aircraft a bit more controllable speed wise with high amounts of positive sheer by making it a bit more draggy.
Hardly! The idea is to avoid ground contact (i.e. crash) during the recovery. Whilst landing flaps are "draggy", the reduction in stall speed compared to a GA flap setting means less of a height loss during -ve wind shear when flying on the edge of the stall warning.
"No configuration change" including leaving the landing gear down is to KISS for all situations incase of contact with the runway during recovery.

The recovery procedure was developed after the TriStar crash in 1985 at Dallas http://libraryonline.erau.edu/online...s/AAR86-05.pdf

Edit. Thanks ImbracableCrunk (below) - you are correct.

ImbracableCrunk 12th August 2018 14:37
I was told by an instructor that it was to use the same procedure as the other Boeings (which do incur a climb penalty as the doors actuate).

BluSdUp 12th August 2018 18:20
Please correct me if I am wrong, but the few modern types I have it is all the same; Max pwr, pull up. use all the energy if needed. NO config change!

Onceapilot 12th August 2018 19:34
Windshear G/A was designed to give the best chance of avoiding unintended flight into terrain, when appropriate windshear parameters were recognised. Agree with comments about common drill, value of gear in unintended touchdown and possible performance issues.

OAP

A Squared 12th August 2018 23:05
Originally Posted by TangoAlphad (Post 10221460)
Full thrust is adequate even with the gear down to escape ...
If that were true, we wouldn't have the whole routine with trading airspeed up to the shaker if necessary. Wind-shear escape maneuver would be to pitch to best rate of climb airspeed ... period.

vilas 13th August 2018 05:55
D191 crash triggered development of the Predictive Wind Shear system.

Capn Bloggs 13th August 2018 07:20
Originally Posted by Tangoalpha
yes there may come a day full thrust isn't enough but 99% of the time it will be far more than enough.
The concept of thinking about what thrust to use is very suspect when it comes to windshear. If you've identified it as windshear, give it all you've got and ask questions later. Have you never been shown a marginally survivable windshear in the sim?

wiedehopf 13th August 2018 07:51
Originally Posted by Capn Bloggs (Post 10222229)
The concept of thinking about what thrust to use is very suspect when it comes to windshear. If you've identified it as windshear, give it all you've got and ask questions later. Have you never been shown a marginally survivable windshear in the sim?
The debate is about "would raising the gear be beneficial on the 737 as it reduces drag". Which is indirectly a debate about how much excess thrust is available.

No one is thinking about using anything but TOGA. He just said that it is plenty even with gear drag.
In this case he suspected windshear before the plane annunciated it and had already firewalled the throttles.

So how is he thinking about not using TOGA?

vilas 13th August 2018 09:27
Wind-shear escape maneuver would be to pitch to best rate of climb airspeed ... period.
No particular speed can be identified for wind shear escape but maintaining a climb by doing whatever it takes right up to stick shaker speed which is not the best ROC speed.

A Squared 13th August 2018 15:44
Originally Posted by vilas (Post 10222314)
No particular speed can be identified for wind shear escape but maintaining a climb by doing whatever it takes right up to stick shaker speed which is not the best ROC speed.
Right. That was kind of my point. If thrust was always enough to outclimb shear as TA claimed, you’d just pitch to best climb and climb out of it. But It isn’t always enough. Windshear can and does exceed an aircraft’s steady climb ability. DAL191 is an example. That’s why we have a procedure in which we exchange airspeed for climb, even past best ROC airspeed if necessary. It’s not sustainable but hopefully it will keep you from hitting the ground long enough to fly out of the shear.

vilas 13th August 2018 17:13
That’s why we have a procedure in which we exchange airspeed for climb, even past best ROC airspeed if necessary
Actually in commercial jet you take TOGA and just fly the FD. Only in case of momentary rapid speed increase you fly above the FD to convert speed into height and then back to FD. In Airbus stall is taken care of by the computer so lower speed doesn't bother you. No particular speed is targeted.

Vessbot 13th August 2018 17:51
What does the FD tell you to do? Exchange airspeed for climb.

Switchbait 14th August 2018 10:16
Boeing B737NG is levers fully forward and auto throttle off.

15 degrees nose up until the PLI becomes the limiting pitch.

Extract all the performance you need to avoid hitting the ground, and don’t stall the airplane. If ya gonna hit the ground, having the gear out is an advantage.

vilas 14th August 2018 11:38
Small cog
I should have said in airbus.TOGA is also Max thrust in Airbus.


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