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speedracer1407
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Posts: 330
Joined: Fri Dec 24, 2004 4:19 pm

Windsheer (or Microburst) Recovery Techniques

Tue Jul 25, 2006 5:57 pm

Hey folks,

Of course, modern weather prediction and analysis, pilot training, and lessons from past disasters go a long way to ensure that todays airliners and their pilots are (hopefully) never put into a situation where they have to recover from serious windsheer conditions on final approach. But, I'd imagine such scenarios are practiced in the sims, and have probably been experienced by some of the pilots around here. BTW, I'm considering rapid windspeed changes strong enough to cause a go-around, perhaps 20kts or more.

So my question is what are the techniques involved in recovering from a rapid, significant change in local windspeed/direction? I suppose a sudden tailwind of 20 Knots or more is potentially catastrophic, or at the very least, the technique is rather straight foreward: stand the throttles up and try not to stall.

But what about big windspeed shifts from the left or right? Can a 20Kt or more windsheer from the side, or perhaps, from a 4 or 8 o'clock direction effect more than just lateral directional control? Besides a likely go-around scenario, do pilots try to turn the plane into the wind? What control movements are requered? What sort of communactions should transpire to allow for a wandering plane?

And finally, what about a sudden headwind windsheer? Seems like a scenario that lacks immediate danger, but are there dangers that I'm not considering? Thanks for any replies,

O
Dassault Mercure: the plane that has Boeing and Airbus shaking in their boots.
 
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Jetlagged
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Joined: Sun Jan 23, 2005 3:00 pm

RE: Windsheer (or Microburst) Recovery Techniques

Tue Jul 25, 2006 10:41 pm

Current windshear detection systems are only concerned with longitudinal and vertical wind changes, not lateral wind. A lateral gust complicates things, but a sudden loss of airspeed is the most serious problem.

Typically the recovery technique is to apply initiate a go-around and pull the column until the stick shaker triggers, at which point you have the maximum safe lift coefficient. With EFIS, the pitch angle will correspond to the "eyebrows". In a fly by wire Airbus all you would need to do would be apply full aft sidestick and put the thrust levers to TOGA, the EFCS will do the rest.

Headwind, followed by downdraught, then tailwind is the classic microburst windshear profile and highly dangerous. All modern simulators have such training scenarios so pilots can practice escaping windshear.
The glass isn't half empty, or half full, it's twice as big as it needs to be.
 
YYZYYT
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Joined: Tue Apr 05, 2005 12:41 am

RE: Windsheer (or Microburst) Recovery Techniques

Wed Jul 26, 2006 3:37 am

Quoting Speedracer1407 (Thread starter):
I suppose a sudden tailwind of 20 Knots or more is potentially catastrophic

indeed:

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Photo © Lee Thomas


sudden swing to a tail wind while over the threshold was possibly one of the contributing factors, as found by the inital report....
 
flymatt2bermud
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RE: Windsheer (or Microburst) Recovery Techniques

Wed Jul 26, 2006 5:26 am

We had an aircraft system initiated wind shear alert on final at 200'. Confused I thought 'what the heck is that' but went ahead and called for a 'go around' about 4 seconds later it felt like King Kong had hit our right wing with his hand. We were already about 17 degrees nose up though I do not recall any altitude loss, the turbulence was extreme. The tower asked why we went around and what our intentions were. I told him we had a wind shear alert followed by moderate to severe turbulence. I heard the controller say "check that out!" We had been requested to make a 90 degree left turn and I looked back on the final approach path and could see what appeared to be a large dust devil churning up rocks and debris at the approach end of the runway. There was a Thunderstorm with tops to FL450 about 10 miles East. We eventually came back around and landed without any more wind effects at all.

We just wanted to avoid the ground and take it out of there like they train us to do in the sim as described in Reply 2.
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