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Windshear recovery

Started by Hardy Heinlin, Tue, 6 Jul 2010 19:27

Hardy Heinlin

I remember in my sim sessions the rule was to pitch the nose up to the limit.

Is this still the basic rule? How do you handle that in your sim check rides?

What if you are near the stall speed and the negative shear has not stopped yet? I think, if you would blindly pitch up in such a case, you would stall and the procedure would be in vain anyway.

Are there not situations where it would be wiser to prefer a descent by a few hundred feet with more IAS over a shallower descent with an immediate stall?


Cheers,

|-|ardy

Peter Lang

Of course, it would never be a wise decision to pitch up and loose your speed. This is the worst thing you could do within some 100 ft above ground.

When you realize after pushing TOGA and gear up, that your speed still does not increase then your only option is a controlled descent. It depends on your height whether your decision is a faster descent rate to increase speed, or a descent rate just to keep your kts, if you are only some feet above ground.

I think the 747 has a very good position to use the ground effect, if its really narrow due to a heavy windshear to savely escape this situation.

Just the thoughts of a single engine pilot
Peter

Will

My training was to level the wings, apply maximum power, and pitch up to "intermittent stickshaker."  If gear is down, it stays down until the event is over, since drag actually increases while the gear doors are opening.  Flaps stay out, since airspeed is low.  The flight path may be a descent, but as Peter says, it's far better to fly a controlled descent into the ground than to stall... so that's what you do.  Once the flight path normalizes, lower the nose, accelerate, and execute a normal go-around.
Will /Chicago /USA

Klausiv

level wings - good.
max power -good.
pitch approx 15 deg. nose up - good.
Follow Flight Director commands smoothly - gooood.

The 747-400 FD has good windshear guidance.
best, Klaus

Jeroen D

From the KLM AOM:

-press TO/GA
-disengage autopilots
-Agressively position the thrust levers full forward to ensure maximum thrust is attained
-Follow FD ptich bar
-Roll wings levels unlesss absolutely required for obstacle avoidance
-do not change a/c configuration

when resulting flightpath is still not acceptable:
-increase pitch in small steps, untill speed is just above stick shaker actuation

From the Boeing Flight crew training manual:

If the pilot attempts to regain lost airspeed by lowering the nose, the combination of decreasing airspeed and decreasing pitch attitude produces a high rate of descent.

Unless this is countered by the pilot, a critical flight path control situation may develop very rapidly. As little as 5 seconds may be available to recognize and react to a degrading vertical flight path.

In critical low altitude situations flight path control must be maintained through the use of pitch attitude and thrust. An increase in pitch attitude even though the airspeed may be decreasing, will increase the lifting force and improve the flight path angle.

In other words; trade airspeed for altitude, if required.

Jeroen
PS: just note all my manuals are a bit dated by now! ;)

Tor

Hallo Hardy,

You are probably remembering terrain avoidance maneuver. A wind sheer escape maneuver may eventually develop into terrain avoidance if the sheer is severe enough and at low altitude. So hence the line may blur.

With the disclaimer that this apply for 737, usually the Boing procedures remain pretty uniform across fleets:
Wind sheer is not as aggressive as terrain avoidance and may in fact be flow on autopilot. Non-Normal Maneuvers section 737 QRH:

AUTOMATIC FLIGHT
• Press either TO/GA switch**.
• Verify TO/GA mode annunciation.
• Verify thrust advances to GA power.
• Retract speedbrakes.
• Monitor system performance***.

Note: ** If TO/GA is not available, disconnect autopilot and autothrottle and fly manually.
WARNING: *** Severe windshear may exceed the performance of the AFDS. The pilot flying must be prepared to
disconnect the autopilot and autothrottle and fly manually.

Terrain avoidance:

• Disconnect autopilot.
• Disconnect autothrottle.
• Aggressively apply maximum* thrust.
• Simultaneously roll wings level and rotate to an initial pitch attitude of 20°.
• Retract speedbrakes.
• If terrain remains a threat, continue rotation up to the pitch limit indicator (if available) or stick shaker or initial buffet.
• Do not change gear or flap configuration until terrain separation is assured.
• Monitor radio altimeter for sustained or increasing terrain separation.
• When clear of terrain, slowly decrease pitch attitude and accelerate.

Note: Aft control column force increases as the airspeed decreases. In all cases, the pitch attitude that results in intermittent stick shaker or initial buffet is the upper pitch attitude limit. Flight at intermittent stick shaker may be required to obtain a positive terrain separation. Smooth, steady control will avoid a pitch attitude overshoot and stall.

Note: Do not use flight director commands.

Note: *Maximum thrust can be obtained by advancing the thrust levers full forward if the EEC's are in the normal mode. If terrain contact is imminent, advance thrust levers full forward.

Note: If positive visual verification is made that no obstacle or terrain hazard exists when flying under daylight VMC conditions prior to a terrain or obstacle warning, the alert may be regarded as cautionary and the approach may be continued.

Hardy Heinlin

OK, thank you all!


Cheers,

|-|ardy

Will

#7
Hardy, it's been a while since the last teaser.  How about a screenshot with relevance to wind shear, but including the "inverted V" style flight director?  (grin)

Tor, you are quite right about the distinction between wind shear and terrain avoidance.  It's completely ridiculous to pull the nose up to a near-stall when you're thousands of feet above the ground and climbing.  The distinction should be made more clearly.
Will /Chicago /USA

Hardy Heinlin

There's no AFDS yet, Will. I'll make the hydraulics first.

I just finished the entire weather system (except volcanic ash and mountain waves). I'll try to take a snapshot during a windshear ...


|-|

Hardy Heinlin

Click to enlarge:


[size=8]

Not really screenshot compatible as the blurr effect requires motion.

By the way, for those new to EGPWS terrain: The tile pattern on the right ND is intentional, it's a digital map, not a radar image like on the left ND (which shows ground clutter in map mode).
[/size]

|-|

Jeroen Hoppenbrouwers

36°C and getting hotter, and he posts rain.

Peter Lang


Hardy Heinlin

#12
Some months ago someone asked why the simulation time can be decellerated down to factor 0.25. Now you have another reason for this :-)

At factor 1.0 the wipers are so fast that they appear almost like a blurred black cloud. I like that because at that speed the engineers won't see the mechanical details of my "provisional" construction :-) (I should remove the wipers from the decelleration feature.)


/-/

Will

Up to Alpha 39, eh?  Nice job as usual!  The artwork is magnificent.
Will /Chicago /USA

Hardy Heinlin

Oops, typo, it's Alpha 38 actually.

OKD

Hardy...

Nice work...loving it...can feel the stalling effect @ 134 knots IAS just by admiring the graphics!!
OK....I am ok, if you are ok...!!

Peter Sagar

A very good mate of mine has just over 14,000 hours on the B747, and has now been a captain for nearly 12 years; over 4 years on the -400. He flies for the white rat airline.  ;)

He has told me in the past that one of the procedures he has practiced in the sim, is flying out of wind shear and other situations "on the stick shaker".

I'll ask him for more details next time we are propping up the bar.

Peter.
Excalibur Beechcraft driver.

\"Cry havoc! And let slip the dogs of war.\"

Walter Kranl

Really stunning graphics, Hardy!

I noticed the left ND is in TRK|MAG mode and the right is in HDG|MAG mode.
I thought this a company option to choose one or the other mode.
BTW, which method has more advantages/disadvantages (If any)?

Cheers
Walter

Hardy Heinlin

#18
Thanks, Walter.

TRK UP is available in MAP mode only. The right ND is in APP mode.

I personally prefer HDG UP because of its orientation and because of the consistency with the other map modes.


Servus,

|-|ardy

Walter Kranl

Thanks Hardy,

Assuming both NDs are in MAP mode, could you mix TRK UP and HDG UP?

Walter