jet touchdown and flare
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Join Date: Mar 2001
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jet touchdown and flare
I understand that the preferred way to land a jet is to 'plant' it on the runway, avoiding 'floating' and using up the runway.
Just how firmly are you trained to put the plane down ? Is descent rate (f.p.m.) ever discussed / demonstrated in the sim ?
Mike
Just how firmly are you trained to put the plane down ? Is descent rate (f.p.m.) ever discussed / demonstrated in the sim ?
Mike
Join Date: Apr 2001
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If I remember correctly, and I can't put my hand on the reference right now, anything up to 350fpm instantaneous r.o.d. is acceptable at up to MTOW, and up to 650fpm up to MLW - this is why one can plan to return to land above MLW in emergency, though the aircraft must be checked after each such event.
Accuracy is vital, in terms of speed and position of touchdown, in order to achieve the scheduled landing performance. This is one good reason for putting the thing down positively.
Another issue relates to breaking through the film of water on a wet runway. It is possible to touch down so gently that the tyres end up aquaplaning on the film of water, thus depriving you of braking. So, on a wet runway, it is important to make a firm touchdown.
Trainers look for consistent firm but comfortable touchdowns and will help trainees to achieve them.
However, and there's almost always a 'however' somewhere in my posts
, pilots are skilled people, and on a very long, dry, runway, it can be rewarding to land so smoothly that no-one knows we've touched down until they hear the ground crew applauding. Other PPRuNers will have a go at me for that last comment, no doubt, but I emphasise that this technique is only appropriate where, say, LDA is at least double LDR, and where the correct technique is used. The time spent finely adjusting the flare to achieve the smooth touchdown must be minimised, and the level of skill required to pull this off time and time again is very high. My other top tips for smooth jobs are (i) idle reverse only, and (ii) no autobrake. AMS 19R is an ideal length for small/medium jet pilot to achieve this, if you intend to go over the bridge after landing, and at typical weights the aircraft will each taxi speed before it's time to turn off.
I would not recommend this technique in anything bigger than a B757/A321. Bigger than that, and it just all gets too serious!
[ 14 August 2001: Message edited by: NorthernSky ]
Accuracy is vital, in terms of speed and position of touchdown, in order to achieve the scheduled landing performance. This is one good reason for putting the thing down positively.
Another issue relates to breaking through the film of water on a wet runway. It is possible to touch down so gently that the tyres end up aquaplaning on the film of water, thus depriving you of braking. So, on a wet runway, it is important to make a firm touchdown.
Trainers look for consistent firm but comfortable touchdowns and will help trainees to achieve them.
However, and there's almost always a 'however' somewhere in my posts
, pilots are skilled people, and on a very long, dry, runway, it can be rewarding to land so smoothly that no-one knows we've touched down until they hear the ground crew applauding. Other PPRuNers will have a go at me for that last comment, no doubt, but I emphasise that this technique is only appropriate where, say, LDA is at least double LDR, and where the correct technique is used. The time spent finely adjusting the flare to achieve the smooth touchdown must be minimised, and the level of skill required to pull this off time and time again is very high. My other top tips for smooth jobs are (i) idle reverse only, and (ii) no autobrake. AMS 19R is an ideal length for small/medium jet pilot to achieve this, if you intend to go over the bridge after landing, and at typical weights the aircraft will each taxi speed before it's time to turn off.I would not recommend this technique in anything bigger than a B757/A321. Bigger than that, and it just all gets too serious!
[ 14 August 2001: Message edited by: NorthernSky ]
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Tech should depend on conditions. On a wet or contaminated runway, a slighty firm touchdown allows the tires to punch through the water film and minimize hydroplaning. On a normal dry runway, a smooth touchdown is easier on the airplane structure, gear, etc. Landing jets isn't rocket science. It's mostly power managemet. On an airplane like a 767-300 that is heavily wing-loaded, set the landing attitude, then smoothly retard power will get nice touchdowns. Early power reductions will get you considerable sink prior to touchdown and a startling plop. The 747 has such soft struts (and so many of them) that very nice landings are easily obtained. Very important is getting the wheels on the runway in the touchdown zone, on-speed.
