Decending rw 24 one windy day

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Utvid visningen Emne: Decending rw 24 one windy day

Decending rw 24 one windy day

Innlegg Windshear » Tor Mai 10, 2018 6:37 pm


The technique that I was taught for the 757 was 'wing down' which was something I had been told was 'never' used on 'big' aircraft at training school!!

The technique requires, as always, a stable approach with the correct drift applied to keep the a/c on centreline. At an altitude (personal preference) push out the drift with rudder and put the into wind wing down using aileron to conteract any drift. I usually do this by 200ft to get the feel before touchdown. It will require a slight increase in thrust to maintain airspeed (due to the increased drag of deflected control surfaces). The wing is only down a few degrees and it is kept down until touchdown (on one maingear before the other). The nosewheel is flown on and the into wind aileron deflected to keep the upwind wing firmly on the ground.

As for windshear........just finished the sim today with a mod/severe windshear recovery at rotation. Windshear had been reported, so the first decision would be not to depart......but being the sim we were to go! No reduced thrust being used in the circumstances. After the call of V1 the airspeed stopped increasing thus Vr was not reached. The procedure is that the PNF calls rotate by 2000ft from the end of the runway (you are committed of course since you do not have enough runway left to stop on). At this point the PF rotates to the all engine T/O attitude (calculated prior to T/O) and up to the 'pitch limit indicators' if required with intermittent stick shaker to maintain a positive rate of climb, ensuring max thrust is applied. This gives the best possibility of becoming airborne. Boeing recommend turning off the Flight Directors. It is then important to keep the pitch angle and fly through the windshear with the PNF calling any airspeed and vertical speed deviations. What can happen is the speed stays very low (negative wind component) and then changes rapidly to an increasing airspeed as the winshear is climbed out of. The configuration remains as set throughout, ie gear still down and flaps still in the T/O setting. Boeing recommend flap 20 if departing into known windshear conditions. The thrust remains at max unless the flap limit speed is approached at which point it is 'aggressively' controlled, both off then back on (autothrottle having been disconnected), until the W/S is passed at which point the gear would go up, climb thrust can be set and the a/c cleaned up on schedule. Finally after T/O checks and handing out of fresh underpants.



ps Forgot to mention landing in gusty conditions we add airspeed to our 'Vref' (threshold speed for a/c weight and config) using half the steady headwind component plus all of any gust factor up to a maximum additive of 20kts, bleeding off the gust in the flare. If using autothrottle for the landing (autoland) we just add 5kts to the Vref). Landing in windshear is not a likely course of action as the PF would elect to go around. Anyone who flies into Tenerife South will tell you what its like! The wind changes quite often late in the approach (especially with a wind greater than 20kts). What happens is the airspeed starts to increase markedly and the reaction is to reduce thrust. It depends on how far down the approach you are as to weather you can remain at low thrust (bearing in mind spool up time in the event of a go around). At the same time you need to put the nose down to keep on the glide and can end up in an undesireable, unstabilised scenario of low pitch attitude, idle thrust and still 5-10kts above your desired airspeed. We aim to be stabilised at 1000ft and MUST be by 500ft otherwise we go around.