Drift On Landing
Drift angle being the angle between heading and track, he had plenty of drift. I can’t answer for Airbus but one of Mr Boeing’s many approved x wind landing techniques is to land with drift applied up to max authorised x wind limit.
“Three methods of performing crosswind landings are presented. They are the
de-crab technique (with removal of crab in flare), touchdown in a crab, and the
sideslip technique.“. Cut and paste from FCTM. So, no it’s not pretty but it works!
“Three methods of performing crosswind landings are presented. They are the
de-crab technique (with removal of crab in flare), touchdown in a crab, and the
sideslip technique.“. Cut and paste from FCTM. So, no it’s not pretty but it works!
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Drift angle being the angle between heading and track
one of Mr Boeing’s many approved x wind landing techniques is to land with drift applied up to max authorised x wind limit.
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In context, drift is also the angular difference between track and runway centerline heading. if track is along the centerline, there is 0 drift - which is THE MOST IMPORTANT aspect of a landing in high crosswinds.
The most important (as you say) is to maintain the CL (track). To achieve this in a crosswind the ac will need to point into wind (heading). The difference between the two is drift. I’m not sufficiently IT literate to draw the triangle of vectors that we all learn about on Nav 1, but Hdg/airspeed + W/V = Track/GS.
I was on the jumpseat on Saturday watching my colleague landing with 35kt crosswind and trust me - there a whole bunch of drift! Until he neatly removed it in the flare with appropriate use of rudder to align the ac with the runway.
I was on the jumpseat on Saturday watching my colleague landing with 35kt crosswind and trust me - there a whole bunch of drift! Until he neatly removed it in the flare with appropriate use of rudder to align the ac with the runway.
Always remember that on touchdown the aircraft is still mainly wing borne so there's not too much stress on the gear as you straighten her up. Removing drift too early in the flare can be exciting.
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Until he neatly removed it in the flare with appropriate use of rudder to align the ac with the runway.
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Of course, terminology may be different east of the Atlantic...
Aircraft tracking towards a runway appear to 'crab' sideways but that's not exactly what they are doing. You turn into the wind, so that the resulting drift gives you a track down the runway. If there is a change in the wind, you need to turn to fix the effect that the change will have had (it will have moved you in one direction or another before you can correct for it) and re-establish the correct track. At the crosswind limit, that drift will be around 15 degrees.
After the flare you need to use rudder to align the aircraft with the runway but you need to do that smoothly, as a secondary effect of any rudder input is roll and you don't want any roll near the ground, particularly towards the downwind side - and that's the effect that the straightening rudder will have. So, when you start to straighten the aircraft, you cancel out your wind correction, and the wind will start to take you towards the downwind side of the runway. In smaller aircraft you can correct it with a small amount of bank in the opposite direction, but that is not really an option on the airliners, as engine clearance generally becomes an issue.
You also have to allow for the gear which will be considerably on the downwind side from the cockpit. If you put yourself on the centreline as you would normally and you have 15 degrees of drift, the main gear will be displaced by about 25ft to the side for every 100ft cockpit to main gear separation so you need to move yourself upwind by an equivalent amount, to ensure the gear stays near the centreline.
Even when you're down, the wind will still be trying to push you to the side of the runway, so you may have to use quite large and abrupt control inputs to ensure the aircraft stays where you want it.
Boeings can be landed with all of the drift still intact. Airbus are limited to 5 degrees of drift at touchdown
After the flare you need to use rudder to align the aircraft with the runway but you need to do that smoothly, as a secondary effect of any rudder input is roll and you don't want any roll near the ground, particularly towards the downwind side - and that's the effect that the straightening rudder will have. So, when you start to straighten the aircraft, you cancel out your wind correction, and the wind will start to take you towards the downwind side of the runway. In smaller aircraft you can correct it with a small amount of bank in the opposite direction, but that is not really an option on the airliners, as engine clearance generally becomes an issue.
You also have to allow for the gear which will be considerably on the downwind side from the cockpit. If you put yourself on the centreline as you would normally and you have 15 degrees of drift, the main gear will be displaced by about 25ft to the side for every 100ft cockpit to main gear separation so you need to move yourself upwind by an equivalent amount, to ensure the gear stays near the centreline.
Even when you're down, the wind will still be trying to push you to the side of the runway, so you may have to use quite large and abrupt control inputs to ensure the aircraft stays where you want it.
Boeings can be landed with all of the drift still intact. Airbus are limited to 5 degrees of drift at touchdown
