Lufthansa A320 at Hamburg on Mar 1st 2008 final BFU report
Report: Lufthansa A320 at Hamburg on Mar 1st 2008, wing touches runway in cross wind landing
A Lufthansa A320-200, registration D-AIQP performing flight LH-44 from Munich to Hamburg Fuhlsbuettel (Germany) with 132 passengers and 5 crew, was on ILS approach to Hamburg Fuhlbuettel's runway 23 in strong gusting winds following storm system "Emma" which had battered large parts of Europe with gale force winds. At 13:33L (12:33Z) the airplane flared, the left main gear touched the runway but lifted off again, the right hand wing rose rapidly causing the left wing tip to strike the runway surface and the aircraft veer to the left before the airplane was recovered by the crew and a go around commenced. The airplane landed safely on runway 33 19 minutes later. A video of the approach, touch down, recovery and go-around is available below.
The German Bundesstelle fuer Flugunfalluntersuchung (BFU - Bureau for Flight Accident Investigation) released their final report in German and in in English concluding:
This serious landing incident took place in the presence of a significant crosswind and immediate causes are as follows:
- The sudden left wing down attitude was not expected by the crew during the landing and resulted in contact between the wingtip and the ground.
- During the final approach to land the tower reported the wind as gusting up to 47 knots, and the aircraft continued the approach. In view of the maximum crosswind demonstrated for landing, a go-around would have been reasonable.
The following systematic causes led to this serious incident:
- The terminology maximum crosswind demonstrated for landing was not defined in the Operating Manual (OM/A) and in the Flight Crew Operating Manual (FCOM), Vol. 3, and the description given was misleading.
- The recommended crosswind landing technique was not clearly described in the aircraft standard documentation.
- The limited effect of lateral control was unknown.
The BFU stated, that the flight had been delayed by nearly two hours following ice rain and high winds caused by storm system "Emma", before the airplane could depart with the first officer being pilot flying. While the airplane was already on approach to Hamburg still under control of Bremen Radar, Hamburg tower advised Bremen radar that winds were now coming from 290 degrees and any crew wishing to use runway 33 could be offered runway 33. Bremen radar requested current wind from the Lufthansa crew, who saw present winds at 310 degrees at 60 knots. In his approach briefing the captain advised, that a go-around could well become possible due to the winds and should be no problem.
After the Airbus established on the localizer and after handoff to the tower, the tower controller reported winds from 300 at 28 knots gusting 47 knots. Upon query by the captain the tower reported, about 50% of the preceding aircraft had gone around in the last 10 minutes repeating the wind data 300 at 28 knots gusting 47 and offering runway 33. The captain decided to attempt runway 23 first. The tower subsequently cleared the flight to land reporting winds from 290 at 29 knots gusting 47.
The crew configured the aircraft for landing with gear down and full flaps and continued the approach on autopilot until 940 feet AGL. The first officer took manual control of the aircraft thereafter.
The captain later described the approach as very stable, sinkrate and engine power were stable and the crab angle was appropriate. Shortly before touchdown, when the first officer aligned the aircraft with the runway (de-crab), the right wing was suddenly lifted and the left wing consequently dropped. A ground contact was not noticed by the crew. 2 seconds later the first officer commanded "go-around" and advanced the thrust levers, the captain confirmed "Go-around, I have control", pushed the override button and executed the go-around.
About three minutes after initiating the go-around, ATC adivsed the crew, that an Embraer crew had observed their left hand wing tip contact the ground, a runway inspection however had not found anything. The crew subsequently received approach and landing clearance for runway 33, where the airplane landed safely 19 minutes after initiating the go-around.
The flight data recorder revealed, that immediately preceding the lift of the right hand wing the left hand main gear had briefly touched down and became airborne again, touching down again 2 seconds later already at a left bank angle of 23 degrees. At that point the first officer decided to go-around.
The BFU stated, that at the time of flare and touchdown there was no significant gust. The weather situation was well within the forecasts.
The flight control laws of the Airbus Fly By Wire (FBW) change from flight mode via flare mode to ground mode in the pitch axis and change directly from flight mode to ground mode in the roll control. In ground mode the side stick deflection lead to a direct proportional deflection of ailerons and roll spoilers without computer interaction.
However, above 80 knots the effectiveness of roll control, ailerons and roll spoilers, is reduced by the half (e.g. aileron deflection limited to 50% of maximum deflection).
When the left hand main gear contacted the ground, the radar altimeter indicating less than 50 feet AGL, both landing gear control interface units detecting weight on the left hand wheel, the airplane changed from flight to ground mode, confirmed by Airbus, the effectiveness of the roll control reduced by 50 percent at that point.
The airplane changes back to flight mode within 5 seconds after a takeoff or go-around when the pitch angle exceeds 8 degrees nose up.
The flight data recorder showed, that the airplane started to drift to the left of the runway centerline at 75 feet AGL, to which the first officer reacted by applying right hand sidestick input turning the airplane 10 degrees to the right, reducing the side stick pressure at 50 feet AGL and now applying left hand pressure, at the same time the rudder pedals were moved 28 degrees to the left (align) within the next 5 seconds. The captain applied 4.5 degrees right side stick input at 15 feet AGL, the first officer now also changed her control input from left to the right. The airplane subsequently touched down with the left hand main gear at a roll angle of 4 degrees to the left and got airborne again. The roll angle increased to 23 degrees to the left, first officer and captain each now pushing their side sticks full right, the rudder pedals changed to 14 degrees right. The left hand main gear touched down a second time 2 seconds at a roll angle of 23 degrees and 1.5 degrees nose up pitch at a speed of 144 KIAS. The first officer advanced both thrust levers to TOGA and initiated the go-around, the captain pressed the override button 7 seconds after the first touch down.
Airbus said, that the contact of the left hand wing tip with the ground could have been avoided, if the side stick had been moved to the right earlier. Had the sidestick movement to the right, conducted by the first officer, been applied 1.5 seconds earlier in the present conditions, the left hand bangle would have been limited to 10 degrees (instead of 23 degrees).
The left hand wing tip touched the runway surface about 450 meters/1500 feet past the runway threshold and received damages to the outer area of the wing tip fence, slat #5 and the guide rails #11 and #12 of the slats. No further damages were found in the examination. The components were replaced before the airplane was returned to service.
The Operating Manual described the preferred landing technique align (opposed to crab):
"Crosswind Landings are conventional. The preferred technique is to use the rudder to align the aircraft with the runway heading, during the flare, while using lateral control to maintain the aircraft on the runway centreline. The lateral control mode does not change until the wheels are on the ground, so there is no discontinuity in the control laws. The aircraft tends to roll gently in the conventional sense as drift decreases, and the pilot may have to use some normal cross control to maintain roll attitude.
In strong crosswind conditions, small amounts of lateral control may be used to maintain the wings level. This lateral stick input must be reduced to zero at first main landing gear touchdown. Even during an approach in considerable turbulence, the control system resists the disturbances quite well without pilot inputs. In fact, the pilot should try to limit his control inputs to those necessary to correct the flight path trajectory and leave the task of countering air disturbances to the flight control system.
[...]
Use of rudder, combined with roll inputs, should be avoided, since this may significantly increase the pilot´s lateral handling tasks. Rudder use should be limited to the "de crab" maneuver in case of crosswind, while maintaining the wings level, with the sidestick in the roll axis."
The Lufthansa documentation said, that their limit was 30 knots of cross wind on dry and wet runways. The highest cross wind component demonstrated by Airbus was 33 knots gusting 38 knots.
The Lufthansa documentation stated further, that the airplane is landed safest and easiest employing the de-crab technique.
The BFU conducted a survey of pilot opinions regarding the maximum demonstrated crosswind component (MDCW) being perceived as an absolute limit, recommendation or other concluding, that about 50% of the pilots perceived the MDCW as an absolute limit, while anoter 47% of the pilots perceived the MDCW as a recommendation.
When the BFU raised the scenario of a MDCW 33 knots gusting 38 with a present wind gusting up to 40 knots, 40% of the pilots replied, that landing was permitted if gusts were not perceived as operationally relevant, 36% replied landing was not permitted because the gust would exceed operational limits of the aircraft, 20% said landing was permitted because gusts were irrelevant for computations and only steady wind counted.
The BFU said in their analysis: "This landing in strong gusting cross wind was a highly dynamic and aeronautically demanding maneouver. The investigation has shown, that not a single mistake by involved persons, not a malfunction of the airplane and not a deficiency in the organistation led to the wing contacting the ground, but a combination of multiple factors.
12 safety recommendations were issued by the BFU.
METAR:
EDDH 011220Z 29028G48KT 9000 -SHRA FEW011 BKN014 07/05 Q0984 TEMPO 29035G55KT 4000 SHRA BKN008
TAF:
EDDH 010900Z 011019 28025G45KT 9999 SCT015 BKN025 TEMPO 1019 3000 SHRAGS
BKN008CB TEMPO 1117 29030G55KT=
SIGMET:
EDWW BREMEN FIR SEV TURB FCST BLW FL050, STNR, NC
Fonte: The Aviation Herald
per chi non ricordasse l'evento ecco il filmato del tentato atterraggio:
http://www.liveleak.com/view?i=ddb_1204404185
