Roll spoilers extended on take off
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Roll spoilers extended on take off
I know it's aileron into wind on take off ( not much if any on Airbus ) but this can't be right can it? They have a lot of spoiler deflection for a take off!
YouTube - Crazy dangerous takeoff 767 in severe storm!!
YouTube - Crazy dangerous takeoff 767 in severe storm!!
Completely normal, cross controls will result in differential spoiler deflection on the upwind wing.
You are trying to avoid too much lift on that side during the take off roll and ensuing rotation.
You are trying to avoid too much lift on that side during the take off roll and ensuing rotation.
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Certainly the technique we use for crosswind takeoffs on the NG is designed to avoid spoiler deployment during the takeoff roll, by limiting the into wind aileron to 1.5 units (about 6 degrees). This is to ensure that the takeoff performance that you calculated remains valid and reduce the risk of tailstrike caused by inadequate lift during rotation caused by the spoiler deployment.
I seem to recall we use to used about 5 degrees wheel movement per 10 knots cross wind on the 747 (waiting to be corrected). As spoilers deployed after 10 degrees, there would be spoliers deployed on the take off roll with more than 20 knots of cross wind. Mr Boeing said this was OK and that the take off run performance wasn't compromised - I was never totally convinvced myself.
Airbus roll control is very different. Sidestick movement demands a roll rate. If you get airborne with the stick deflected, you have roll demanded and the aircraft will start rolling as soon as it's off the ground. But with no sidestick applied you will get airborne with wings level and no correction is required regardless of cross wind. (OK Airbus guys , I know that you effectively take off in direct law and that normal law is blended in gradually up to 50' RA - but this is the official Airbus technique and it seems to work when I try it).
Airbus roll control is very different. Sidestick movement demands a roll rate. If you get airborne with the stick deflected, you have roll demanded and the aircraft will start rolling as soon as it's off the ground. But with no sidestick applied you will get airborne with wings level and no correction is required regardless of cross wind. (OK Airbus guys , I know that you effectively take off in direct law and that normal law is blended in gradually up to 50' RA - but this is the official Airbus technique and it seems to work when I try it).
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Wasn't there something about Boeing having changed the technique for control wheel deflection on takeoff due to tail strikes on the longer 737's. On the old 200 there didn't seem to be anything listed except to keep wings level yet on the 727 with its older FCTM itsays to hold ailerons into wind and use that deflection as your new neutral position.
I see that the 744 FCTM says that excessive spoiler deflection during rotation reduces tail clearance. I suppose during the earlier portion of the roll there is little performance penalty.
I see that the 744 FCTM says that excessive spoiler deflection during rotation reduces tail clearance. I suppose during the earlier portion of the roll there is little performance penalty.
Last edited by JammedStab; 26th Jan 2016 at 03:09.
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Excessive input.
Only input enough to prevent tipping. Do planes tip parked sitting on the ramp? No, so no roll input is needed at the start of the takeoff roll. As the plane accelerates put in just enough roll input to keep the wings level. Typically that means nothing until above 80 to 100 kts and just minor inputs after that. Think "less is more".
Boeing states too much input does reduce tail strike clearance.
Only input enough to prevent tipping. Do planes tip parked sitting on the ramp? No, so no roll input is needed at the start of the takeoff roll. As the plane accelerates put in just enough roll input to keep the wings level. Typically that means nothing until above 80 to 100 kts and just minor inputs after that. Think "less is more".
Boeing states too much input does reduce tail strike clearance.
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Indeed,
B757/767 is/was aileron as needed to keep wings level on takeoff.
B777 is control wheel level at start of takeoff progressively adding aileron only to the extent to keep wings level. Spoiler deflection does indeed reduce tail clearance on the big stuff. Ask the American airline who managed to tailstrike a 777 on takeoff due to agressive aileron input.
B757/767 is/was aileron as needed to keep wings level on takeoff.
B777 is control wheel level at start of takeoff progressively adding aileron only to the extent to keep wings level. Spoiler deflection does indeed reduce tail clearance on the big stuff. Ask the American airline who managed to tailstrike a 777 on takeoff due to agressive aileron input.
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Spoiler deflection does indeed reduce tail clearance on the big stuff. Ask the American airline who managed to tailstrike a 777 on takeoff due to agressive aileron input.
The more drag,the more pull,the more pull at low level,the less tail clearance ...simples
The ailerons and rudder should be put back to neutral positions just as the wheels gets off the ground,then pitch is increased to reach v2+15 inside the FDs.
Last edited by de facto; 14th Oct 2012 at 14:27.
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As has been said 1.5 units is the max deflection on a 737...in reality a lot of people tend to put a lot more in once the nosewheel comes off. Takes a concious effort to avoid doing this (lots of bags in the back and/or lack of people in the front and your in 800/900 tailstrike territory).
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There is no problem on the 737 either,as by the end of the rotation (main whells off the ground),the controls should be set back to neutral,before the pitch is increased further.
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DeFacto
"Only if the ailerons and spoilers are kept in the same position AFTER lift off AND through out the first 10-11 degrees"
Not the case at least on the large Boeings. Leave a large roll/spoiler input in and the aircraft may not leave the ground at VR and thus tail clearance can be compromised. Hence the option to increase VR (performance allowing). Remember tail clearance is a very real consideration in just normal conditions with these machines
"Only if the ailerons and spoilers are kept in the same position AFTER lift off AND through out the first 10-11 degrees"
Not the case at least on the large Boeings. Leave a large roll/spoiler input in and the aircraft may not leave the ground at VR and thus tail clearance can be compromised. Hence the option to increase VR (performance allowing). Remember tail clearance is a very real consideration in just normal conditions with these machines
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Makes sense,i only have experience on the 737.
If the drag is such that a normal pull is not enough,the rotation should be delayed or inputs reduced,in no case should the pilots over pull to try and get airborne.
If the drag is such that a normal pull is not enough,the rotation should be delayed or inputs reduced,in no case should the pilots over pull to try and get airborne.
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Proper roll control during takeoff @5:45 in the video.
Strong crosswinds but a 767 does an excellent crosswind takeoff with NO spoilers visible.
#
Strong crosswinds but a 767 does an excellent crosswind takeoff with NO spoilers visible.
Last edited by misd-agin; 23rd Oct 2012 at 14:18.
