B737 WINDSHEAR ESCAPE MANEUVRE

[de facto]

Despite what Boeing says, anyone leaving the automatics engaged during a Windshear escape manouvere is perhaps being a little bit too trusting IMHO.

True.
On the other hand pilots may believe their skills on that day may bring a better outcome.Maybe,maybe not.
Never experienced a strong downdraft shear in real life.
What i can say is during low altitude phase,(take off/landing)with AT engaged already,disengaging it is not making use of your resources properly.
If GA thrust is not enough at that time and the ground is coming back at you then yes firewall the damn thing.

[737OPR]

Pontius,

Send you a pm.

[RAT 5]

Regarding A/T on/off: I digress slightly as this comment is not specifically about W.S. escape. And firstly I have to disagree with Boeing's 1 size fits all philosophy.
On the B737 classic the TCAS RA manoeuvre was disengage A/P and follow the red prism guidance. You left A/T engaged, which I thought a splendid idea. In the stress of the moment speed control was one less thing to relax about; the escape and the recovery afterwards.
On the NG Boeing disconnects A/T. When I asked Boeing pilot he said it was to comply with Boeing's philosophy of manual flight = manual thrust. How pedantic is that? I suggested they had introduced a massive threat, and perhaps after the first RA followed by stick shaker they would be reviewing their procedure. There was little reaction, but a note was made. On your day, when you are at the sharp end wrestling with the bronco you may choose to use the depth of airmanship you have and do what is necessary rather than dither around.

[B737900er]

Like Rat5 said Boeings philosophy is manual flight = no A/P no A/T.

Regarding the W.E.P in manual flight; if you are flying single channel and hit TOGA the A/P kicks out reverting you to manual flight with A/T engaged this would be contradicting their philosophy about manual flight.

Automatic flight or Dual Channel: by pressing TOGA will allow a full automated GA, but like a previous poster said ' be prepared to go manual flight and don't rely solely on the automatics'.

[Checkboard]

On the NG Boeing disconnects A/T. When I asked Boeing pilot he said it was to comply with Boeing's philosophy of manual flight = manual thrust. How pedantic is that? I suggested they had introduced a massive threat, and perhaps after the first RA followed by stick shaker they would be reviewing their procedure. There was little reaction, but a note was made. On your day, when you are at the sharp end wrestling with the bronco you may choose to use the depth of airmanship you have and do what is necessary rather than dither around.

Say you're in a LVLCHG descent, autothrottle commanding idle thrust, Flight Directors showing, say 8º down pitch for the descent - and a "TCAS Climb" event occurs. You disengage the autopilot and pitch up, away from the Flight Director command, and follow your pre-decided non SOP action of leaving the autothrottle engaged.

What does the autothrottle do? Does it remain in idle thrust, attempting to follow the valid Flight Director commands for the idle descent? Are you only hoping for the Alpha floor function to save your stall as you pitch up without adding power?

[de facto]

Flight Directors showing, say 8º down pitch for the descent

Quite a steep descent there.. 2 deg from an upset recovery..

and a "TCAS Climb" event occurs. You disengage the autopilot and pitch up, away from the Flight Director command, and follow your pre-decided non SOP action of leaving the autothrottle engaged.

B737NG:RA= AP+AT OFF.

Are you only hoping for the Alpha floor function to save your stall as you pitch up without adding power?

This 'alpha floor' doesnt work if your aircraft altitude is above your MCP altitude.

[Cornish Jack]

Could I suggest that an exceptionally good training video on windshear, produced by an AA training captain, should be required viewing for ALL. We used it at Virgin for recurrent training and the specifics of what was recommended were succinctly laid out, with reasoning and inarguable! "Stow the boards, Thrust to maximum, auto throttle OFF, wings level, pull to stick shake, if necessary". The accompanying video of the example W/S event at Dallas(?) L1011 should reinforce the necessity for fast, instinctive reaction.

[de facto]

Stow the boards

You are flying Airbus?

Once Max thrust is set with AT OFF, does your SOP require both hands on the wheel or not?
I would think pitch control near the PLI would be smoother with both hands ON.
What you think?

[Ditched]

Windshear Escape Manoeuvre

..From my QRH (737NG)

Push TOGA, this puts the AFDS in G/A mode,
Disconnect AT and AP! (AP drops off anyway if youre single channel)
MAX Thrust, (manually)
Aggressively pitch up to 15 deg or stick shaker wichever comes first. Disregard the Flight Director.
Pray you've got enough air under the wings
Wait untill youre out of the WS
Then clean up and have a chat with ATC

I would never leave automatics in, you'll need both hands on the control column with the stong pitch up moment cauesed by the engines. No time to start messing around with the autothrottle if its not doing what you want.... anything other than full thrust.

hope it clears some things up. seems to be quite a bit of confusion around here.

be safe!

[Pontius]

In the case of an AP engaged and AT engaged,if you see alt acq,and you are still in the windshear, by all means disconnect the automatics.

Thank you for stating the obvious, De Facto, but you've conveniently avoided the technical aspects of the scenario I postulated. I imagined such a situation to counter your suggestion that my G/A knowledge was lacking and that my technical savvy not up-to-scratch. Now, that's a fair call but if you're going to do that, then at least have the decency to tell me how the A/T remaining engaged in auto flight will solve the problems of, effectively, a low level altitude capture situation which could really cheese you off in a windshear situation, which wouldn't happen with the A/T disengaged. Just as a reminder; I am not advocating disconnecting the A/T. I am saying I will stick to the QRH but I would like to know why the difference

You guys scare me, is not TOGA thrust, wings level and 10 deg nose up standard for all aircraft?

No, Grounded, that is not standard for all aircraft. Luckily for you we do know what is required of our aircraft, so you can rest assured and feel less scared

When I asked Boeing pilot he said it was to comply with Boeing's philosophy of manual flight = manual thrust.

This may very well be the answer and that's an end to it. I know the guys with big brains in Seattle/Toulouse figure this stuff out and I'll do what they say but I sometimes like to know why and this is one of those times. As I said to 737OPR in my PM, 99.9% of this is theoretical and the scenarios are quite contrived. You're pretty well going to end up going manual anyway (my 3 events did), so the point is almost moot. However, as this is the tech forum I'm going to suggest that disengaging the A/T will stop the power coming back when (theoretically) you don't want it to and this is good in manual flight, so why not click them out once thrust is set by the A/T in auto flight? If manual flight = manual thrust and auto flight = auto thrust is the answer to my question, have the big brains thought about the unwanted thrust reduction suggested in my (pretty farfetched) scenario or have I failed, again, in my ability to see the Big Picture and risk assess

"Stow the boards, Thrust to maximum, auto throttle OFF, wings level, pull to stick shake, if necessary"

But not if the auto pilot is engaged I know I'm being trite....but that's what's written in my QRH

[Denti]

@Ditched, that seems to be a company specific maneuver, it is not the standard boeing one which has two different ones for using automatics or not.

[wiggy]

grounded27

You guys scare me, is not TOGA thrust, wings level and 10 deg nose up standard for all aircraft?

No.

Next question.

[Centaurus]

I suggested they had introduced a massive threat,

Not if you are competent at hand flying the aircraft in all respects. On the other hand if you are one of the automatics addiction mob (and I am sure you are not of course), then any change from automatics to manual will have the potential to introduce a massive threat

[Centaurus]

say 8º down pitch for the descent

With THAT sort of pitch attitude you are courting serious trouble within a few seconds...

[sheppey]

"Stow the boards, Thrust to maximum,

I note the AA pilot advice was to first "stow the boards" by which one presumes he means retract the speed brakes first.

In contrast, that personal advice perhaps for his own aircraft type, is at odds with the windshear advice published in the the Boeing 737 QRH . There, it states the speed brakes are retracted after the autopilot is disconnected, max thrust is applied and after rolling the wings level, and rotating towards an initial pitch attitude of 15 degrees. Of course all this happens very quickly.

The GPWS pull up manoeuvre is slightly different in that the initial pitch attitude is 20 degrees but the speed brakes are still retracted in the same order of events as the windshear escape manoeuvre.

The 20 degrees attitude was introduced after the Air New Zealand Mount Erebus crash when the DC10 hit Mt Erebus following a GPWS warning. At the time the GPWS pull up policy set by the major manufacturers was to select go around attitude of 15 degrees. Later research into CFIT accidents revealed that statistically 20 degrees gave you a better chance of getting away with it.

[ImbracableCrunk]

This 'alpha floor' doesnt work if your aircraft altitude is above your MCP altitude.

Are you saying that because he's now attempting a climb? Min Speed Reversion definitely works when you're above your MCP alt, but the A/P kicks out if you can't - in a climb - maintain a min airspeed and climb rate.

[737OPR]

Does everybody realize how far the thread has drifted from the OP's original question?

[Cornish Jack]

Apologies, don't want to continue off topic, but the"Stow the boards" etc. was this instructor's suggested sequence to ensure that there would never be a repeat of past errors - viz. attempted go-around with the speed brakes deployed and/or auto throttles retarding (Uncommanded by crew) It happened, and with Murphy ever present, book or no book, I know which sequence I would prefer!

[latetonite]

The TOGA gives you a 15 degrees FD command, for guidance. Trust is manually firewalled.........come on guys..

[de facto]

Are you saying that because he's now attempting a climb? Min Speed Reversion definitely works when you're above your MCP alt, but the A/P kicks out if you can't - in a climb - maintain a min airspeed and climb rate.

I am saying that as he mentionned pitching up without adding thrust.

The 737 auto-throttle system will increase thrust to maintain its minimum speed (the books say approx 1.3 v/s) however what the book does not say is that if the MCP altitude is above current altitude that is true.However if the aircraft is below the current altitude then the thrust will close and the elevator will pitch down to minimum speed. Min Speed reversion is an MCP SPD mode.


Pitch 15 then firewall? How about max thrust initially?