Side Slip (wing down/cross control) Landing Technique on Airbus (A330)
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Airbus tells you that 5 degrees of crab are still acceptable at touchdown to cope with the above mentioned difficulty. Now the question is : do you remember how many degrees of crab you had during your last crosswind landing ? Probably the answer is no, as I believe that you are not watching your ND at that stage, nor is your other CM. If something happens and findings reveal that you were well above these 5 degrees, you can have an interesting debate with whoever is concerned. Finally decrab the airplane following Airbus specs and if it is not feasible then you may want to explore the function enable alternate.
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titaniumwings
Try to do an auto land in the SIM with 20KT crosswind and you will get all the answers. First the auto flight system uses crab and not slide slip, second when it decrabs after flare wings are maintained level by spoilers and aileron activation. I think that is enough to explain the design philosophy and the SOP.
Try to do an auto land in the SIM with 20KT crosswind and you will get all the answers. First the auto flight system uses crab and not slide slip, second when it decrabs after flare wings are maintained level by spoilers and aileron activation. I think that is enough to explain the design philosophy and the SOP.
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scottbill
what is different about washington, landing to the south, is that final approach lasts about three seconds. a very low altitude turn to line up with the runway is required after following the Potomac river for about 6 miles.
if you can obtain a copy of the river visual approach to runway 19 or view someone's video, you might understand.
all the best
CASE ONE
if you use the upwind power technique,/ assymetric/differential thrust, you are making the engine do the work of the rudder...and that gives you more rudder for the instantaneous corrections sometimes required. does that make sense?
what is different about washington, landing to the south, is that final approach lasts about three seconds. a very low altitude turn to line up with the runway is required after following the Potomac river for about 6 miles.
if you can obtain a copy of the river visual approach to runway 19 or view someone's video, you might understand.
all the best
CASE ONE
if you use the upwind power technique,/ assymetric/differential thrust, you are making the engine do the work of the rudder...and that gives you more rudder for the instantaneous corrections sometimes required. does that make sense?
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Airbus asking you to land with 5 degrees crab is another indication that the design does not prefer wing down. You don't need to look at ND to touch down with some crab, looking at the centre line ahead will suffice. The problem in landing with crab is the side load. If you land with drift it will still impose side stress. I remember in 747 classic it was recommended to land with crab on wet runway. On wet runway the aircraft initially skids sideways that reduces the side stress and then the CG position straightens the aircraft.
Vilas---I think you just proved our points. The A330 autopilot can only handle 20 kts of crosswind, which is not a lot. Up to 20 kts the wings can be kept level in the de-crab during the Flare if it's done correctly and you won't need much if any Aileron input. Yes that is how the Autopilot does it in an ideal world.
( then again how do you really know how much Aileron input the A/P makes in the flare as the Sidestick doesn't move and you can't watch the F/CTL page!! )
But at the end of the day in the real world ( not a sim ) you may need to land one wing down in a decent crosswind whilst hand flying.
AS PER THE AIRBUS PUBLISHED FCTM I quoted way back.
Can we move on to something else now?
Close the thread it's running around in circles chasing it's tail.....
( then again how do you really know how much Aileron input the A/P makes in the flare as the Sidestick doesn't move and you can't watch the F/CTL page!! )
But at the end of the day in the real world ( not a sim ) you may need to land one wing down in a decent crosswind whilst hand flying.
AS PER THE AIRBUS PUBLISHED FCTM I quoted way back.
Can we move on to something else now?
Close the thread it's running around in circles chasing it's tail.....
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ACMS
I am talking about a Sim demo and you confirm the behaviour of normal law on the F/CTL page. However as you say in real life you stick to centre line if required by banking into wind.
I am talking about a Sim demo and you confirm the behaviour of normal law on the F/CTL page. However as you say in real life you stick to centre line if required by banking into wind.
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Hi sonicbum,
The Lufthansa aircraft landed on the down wind wheel first, lost half their aileron control, and continued to roll despite full side stick.
See pages 39 & 53 of A320_Hamburg-Crosswindlanding.pdf
"Touchdown
• The aircraft was 4° left wing down at the time the left main landing gear made contact
with the runway
• The horizontal acceleration was 0.17g to the right, the vertical acceleration was 1.68 g
• The rudder was deflected about three quarters of maximum throw to the left. At this time
the yaw rate was about 6° per second.
Between contact by the left main landing gear and contact between the left wingtip and ground:
• The aircraft rolled towards the left
• Both the captain and co-pilot gave sidestick inputs to the right
• The left wing down attitude reached a maximum of 23°, whereupon the left wingtip
touched the ground
• The rudder was deflected about one third of its full throw to the right"
"The system was so designed that when in lateral Ground Mode the ailerons/spoilers kinematics are modified as a function of speed, in the sense to reduce the maximum available ailerondeflection by half (at high speed: > 80k)t. This was also confirmed by the Flight Data Recorderparameter traces, in which aileron deflection was reduced to about half of full travel in responseto full sidestick deflection."
Oops!
With very strong crosswind it may be quite challenging to coordinate it without risking to have one wing down during the flare, as you can see
See pages 39 & 53 of A320_Hamburg-Crosswindlanding.pdf
"Touchdown
• The aircraft was 4° left wing down at the time the left main landing gear made contact
with the runway
• The horizontal acceleration was 0.17g to the right, the vertical acceleration was 1.68 g
• The rudder was deflected about three quarters of maximum throw to the left. At this time
the yaw rate was about 6° per second.
Between contact by the left main landing gear and contact between the left wingtip and ground:
• The aircraft rolled towards the left
• Both the captain and co-pilot gave sidestick inputs to the right
• The left wing down attitude reached a maximum of 23°, whereupon the left wingtip
touched the ground
• The rudder was deflected about one third of its full throw to the right"
"The system was so designed that when in lateral Ground Mode the ailerons/spoilers kinematics are modified as a function of speed, in the sense to reduce the maximum available ailerondeflection by half (at high speed: > 80k)t. This was also confirmed by the Flight Data Recorderparameter traces, in which aileron deflection was reduced to about half of full travel in responseto full sidestick deflection."
Oops!
Last edited by Goldenrivett; 16th Nov 2014 at 12:47. Reason: extra quotes
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vilas,
If you are referring to "Evolution of ground spoiler logic" Airbus%20Safety%20First%20Mag%20-%20Feb%202010.pdf, then that mod was to reduce the height of a heavy landing bounce.
It does not restore full aileron control.
If you are referring to "Evolution of ground spoiler logic" Airbus%20Safety%20First%20Mag%20-%20Feb%202010.pdf, then that mod was to reduce the height of a heavy landing bounce.
It does not restore full aileron control.
Last edited by Goldenrivett; 16th Nov 2014 at 15:56. Reason: Typo
I agree that this thread has probably ended in the usual stand-off between entrenched closed minds on both sides. It can do without this sort of thing
Thank you for the condescension but perhaps allow that after 40+ years in aviation, this does not look like a task for supermen only. Looks like fun, though.
"Three seconds" - really?
The controlled slip I discussed is best initiated at about 100 feet (to allow for low-level windshear). 50 ft perhaps - so long as it is set up before the flare. On Boeings, the important bit that so many get wrong is that the control wheel movement to set the aileron input becomes a new datum which has to be maintained throughout the flare and initial landing run. See-sawing of the ailerons must be avoided.
Could that be relevant to the application of the technique on Airbuses?
scottbill
what is different about washington, landing to the south, is that final approach lasts about three seconds. a very low altitude turn to line up with the runway is required after following the Potomac river for about 6 miles.
if you can obtain a copy of the river visual approach to runway 19 or view someone's video, you might understand.
what is different about washington, landing to the south, is that final approach lasts about three seconds. a very low altitude turn to line up with the runway is required after following the Potomac river for about 6 miles.
if you can obtain a copy of the river visual approach to runway 19 or view someone's video, you might understand.
"Three seconds" - really?
The controlled slip I discussed is best initiated at about 100 feet (to allow for low-level windshear). 50 ft perhaps - so long as it is set up before the flare. On Boeings, the important bit that so many get wrong is that the control wheel movement to set the aileron input becomes a new datum which has to be maintained throughout the flare and initial landing run. See-sawing of the ailerons must be avoided.
Could that be relevant to the application of the technique on Airbuses?
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If you enjoy the approach into DCA, try a "channel visual" approach to 08L at PHNL with a screaming crosswind sometime, or better yet the "Keehi Lagoon" circling approach to 26R the local pilots use on strong southerly-wind days. Thank the China Airlines flight that buzzed downtown Honolulu on a visual approach for getting that one on the books years ago. Watched from Lagoon Drive off the end of that runway many a time over the years as DC-9's and 737's rolled wings-level around 300 or 400 feet on final with a 20 or 25 knot tailwind on base-leg that now becomes a direct crosswind. Many times with many techniques. Most roll out in a crab and kick it strait anywhere between 50 and 100 feet, slip the rest of the way. Some kick it out in the crab, some don't kick it out at all, etc etc etc.
All those techniques seem to work just fine. As long as it is in accordance with the flight manual and SOP, use whichever method works for you. Bottom line, just land on the centerline, keeping the airplane's inertia along that line and the wheels pointed reasonably close to the same direction the airplane is moving.
All those techniques seem to work just fine. As long as it is in accordance with the flight manual and SOP, use whichever method works for you. Bottom line, just land on the centerline, keeping the airplane's inertia along that line and the wheels pointed reasonably close to the same direction the airplane is moving.
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Teaching basic crosswind landings I started with an early sideslip to show how to keep the aircraft straight with the rudders and correct for crosswind with ailerons to stay on centerline.
As they became more experienced I had them delay until late into the flare to make one fluid coordinated rudder and aileron application and then make small adjustments to keep on centerline with no crab. The technique is comfortable for the passengers because you aren't kicking it out but smoothly coordinating the transition from crab to touchdown.
As they became more experienced I had them delay until late into the flare to make one fluid coordinated rudder and aileron application and then make small adjustments to keep on centerline with no crab. The technique is comfortable for the passengers because you aren't kicking it out but smoothly coordinating the transition from crab to touchdown.
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titaniumwings
The thread is split in three parts, cross wind landing techniques in general, individual ideas and lastly Airbus procedure. As far as you are concerned only the last applies to you. I recommend you obtain and read Airbus document 20th Fight safety conference LATERAL RUNWAY EXCURSIONS Cross wind Design and Operational Considerations which was held between 24th and 27th Mar2014. The salient features of that are follow auto pilot logic i.e.
1. Wings level and crabbed approach
2. Flare
3.Decrab
4. Ground control
In high cross wind and especially contaminated runway partial decrab may be required using crab angle and bank angle, use roll control only if required to maintain aircraft on centre line.
In the19th safety conference in gusty wind conditions use of ground speed mini(ATHR in managed speed) is recommended.
If you do something else as suggested by some people here and have an incident you will find yourself a very lonely man.
The thread is split in three parts, cross wind landing techniques in general, individual ideas and lastly Airbus procedure. As far as you are concerned only the last applies to you. I recommend you obtain and read Airbus document 20th Fight safety conference LATERAL RUNWAY EXCURSIONS Cross wind Design and Operational Considerations which was held between 24th and 27th Mar2014. The salient features of that are follow auto pilot logic i.e.
1. Wings level and crabbed approach
2. Flare
3.Decrab
4. Ground control
In high cross wind and especially contaminated runway partial decrab may be required using crab angle and bank angle, use roll control only if required to maintain aircraft on centre line.
In the19th safety conference in gusty wind conditions use of ground speed mini(ATHR in managed speed) is recommended.
If you do something else as suggested by some people here and have an incident you will find yourself a very lonely man.
Last edited by vilas; 19th Nov 2014 at 04:52.
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this is the best info I've seen on airbus crosswind ops
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Originally Posted by scotbill
I agree that this thread has probably ended in the usual stand-off between entrenched closed minds on both sides. It can do without this sort of thing
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Several years ago, when attempting to gather more detailed information regarding the Airbus autoland logic, than is currently available in the FCOM and AMM, an Airbus flight control engineer shared the following:
The autoflight system will utilize a crab to compensate for a crosswind until approximately 45 feet. At this point, the align control law engages. The goal of the align control law is to reduce the crab angle, while maintaining the track of the runway centerline. For the A340-500/600, the autopilot will decrab up to 70 percent of the initial crab angle, with a limiting decrab of 7 degrees. According to the engineer, up to a 7 degree bank angle will be used to counter any drift during the decrab.
It was decided to limit the maximum crab angle during touchdown to 3 degrees. Combine that 3 degree angle with the limiting decrab of 7 degrees, yields a maximum crab angle prior to the engagement of the align control law of 10 degrees. This is what was used to determine the maximum crosswind limit of 23 knots, for an autoland in the A340-500/600.
As vilas has pointed out, Airbus has produced several presentations and documents devoted to crosswind landing techniques. While these sources give a reasonably good explanation of how to deal with crosswinds in the Airbus, I do believe there is room for additional clarity.
There are several potential negative transfer issues for pilots who are transitioning from traditional aircraft to the Airbus. The crosswind landing is one of these potential problem areas. As pilots flare and apply rudder pressure to remove the crab, they often apply and hold an opposite roll input. This leads to a greater bank angle than desired. Attempts to then reduce the bank angle typically are made with sidestick inputs that are too large. The result is PIO in roll, especially in gusty conditions. This type of PIO during the flare has been captured in numerous videos of Airbus crosswind landings.
When a bank angle is required to control drift, only a very small roll input is required until the proper bank has been attained. Once this bank angle (no more than 5 degrees) has been establish, the sidestick roll input is neutralized. At this point you are accomplishing a slideslip, but you are not utilizing the “cross control” technique of a more traditional aircraft.
I have found this thread quite interesting, and hope that it continues.
The autoflight system will utilize a crab to compensate for a crosswind until approximately 45 feet. At this point, the align control law engages. The goal of the align control law is to reduce the crab angle, while maintaining the track of the runway centerline. For the A340-500/600, the autopilot will decrab up to 70 percent of the initial crab angle, with a limiting decrab of 7 degrees. According to the engineer, up to a 7 degree bank angle will be used to counter any drift during the decrab.
It was decided to limit the maximum crab angle during touchdown to 3 degrees. Combine that 3 degree angle with the limiting decrab of 7 degrees, yields a maximum crab angle prior to the engagement of the align control law of 10 degrees. This is what was used to determine the maximum crosswind limit of 23 knots, for an autoland in the A340-500/600.
As vilas has pointed out, Airbus has produced several presentations and documents devoted to crosswind landing techniques. While these sources give a reasonably good explanation of how to deal with crosswinds in the Airbus, I do believe there is room for additional clarity.
There are several potential negative transfer issues for pilots who are transitioning from traditional aircraft to the Airbus. The crosswind landing is one of these potential problem areas. As pilots flare and apply rudder pressure to remove the crab, they often apply and hold an opposite roll input. This leads to a greater bank angle than desired. Attempts to then reduce the bank angle typically are made with sidestick inputs that are too large. The result is PIO in roll, especially in gusty conditions. This type of PIO during the flare has been captured in numerous videos of Airbus crosswind landings.
When a bank angle is required to control drift, only a very small roll input is required until the proper bank has been attained. Once this bank angle (no more than 5 degrees) has been establish, the sidestick roll input is neutralized. At this point you are accomplishing a slideslip, but you are not utilizing the “cross control” technique of a more traditional aircraft.
I have found this thread quite interesting, and hope that it continues.
Last edited by Aztec Kid; 25th Nov 2014 at 09:42. Reason: spelling error
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Aztech Kid,
Really enlightening information. Thank you so much for sharing.
"Incidentally" my SOP requires the call of "BANK BANK" if the bank exceeds 7 degree for landing (for A330). I can see clearer now.
Appreciate the sharing guys!!!
Really enlightening information. Thank you so much for sharing.
"Incidentally" my SOP requires the call of "BANK BANK" if the bank exceeds 7 degree for landing (for A330). I can see clearer now.
Appreciate the sharing guys!!!
