B777 in Autoland Mode Left Runway When Another Aircraft Interfered With the Localiser Signal (9V-SWQ, SIA)
Boeing 777-312ER 9V-SWQ of Singapore Airlines was flying from Manchester to Munich on 3 November 2011. Shortly after touch-down in Munich the aircraft veered to the left and went off the runway, before veering right and coming to a stop on the grass to the other side next to the runway.
…the co-pilot was initially Pilot Flying (PF) during the flight Manchester – Munich. Based on the latest weather information at Munich, visibility 2,000 m, cloud base 300 ft, the Pilot in Command (PIC) decided to assume the role of PF, as the SOPs (FCOM/NORMAL PROCEDURES/OPERATION) of the operator required, and the co-pilot became Pilot Monitoring (PM). The PIC decided to conduct an automatic approach and autoland.
A BAE 146-RJ85 taxied along taxiway B4 to runway 08R as the B 777 was about 2.9 NM ahead of the runway threshold 08R and 3.4 NM behind the BAE 146-RJ85 when it received take-off clearance.
As the B 777 was about 50 ft above the runway in the flare phase the airplane began to slowly bank left up to 3.5°. As the B 777 flew above the runway threshold 08R, the BAE 146-RJ85 was in front of the localizer antenna and interfered with the localizer signal.
The PIC called out: “Okay, flaps twenty.” At approximately 420 m beyond the runway threshold the airplane touched down with the left main landing gear and 132 kt (KIAS). At that time the Auto Flight System (AFS) switched to rollout mode.
The autopilot was still engaged as the airplane moved toward the left runway edge and veered off the runway with a speed of 123 kt (KIAS) about 944 m beyond the threshold in the area of taxiway B4. For about 400 m the airplane rolled through the grass north of runway 08R in a slightly curved right hand turn. The largest lateral deviation from the runway was reached at about 1,242 m beyond the threshold; speed was 109 kt KIAS. Because of the system design the autopilot disengaged due to crew inputs via the rudder pedals.
The airplane turned right by about 40°, re-entered the runway close to the intersection with taxiway B6, about 1,566 m beyond the threshold. The aircraft crossed the runway with a heading of about 120°. Speed was still 71 kt KIAS.
The airplane veered off the runway again, turned left by about 40°, and came to a stop in the grass south of and parallel to runway 08R.
There were no injuries or apparent aircraft damage.
The crew stated that during the approach and the landing there were no indications as to malfunctions or system failures. The PIC stated he had tried to initiate a goaround procedure by pushing the TO/GA buttons on the thrust levers and thereby triggering the go-around mode once it had been noticed that the airplane banked to the left. But the airplane did not respond. At the same time he retracted the ground spoilers manually which had automatically been deployed at the time of the touchdown.
The BFU say:
The crew did not inform the approach controller of their intention to conduct an automatic landing. The crew knew that under the prevailing CAT I flight operations the safety measures of all-weather operations CAT II/III were not present. Since the controller did not have any information that the crew intended to conduct an automatic landing he did not separate the aircraft in accordance with the required separation minima for CAT II/III but for CAT I conditions; i.e. separation between departing and approaching aircraft was one runway length. The air navigation service provider stated that if the controller had been informed he would not have allowed the BAE 146-RJ85, waiting on taxiway B4, to take off ahead of the B 777. Therefore, the crew had to take into consideration that ILS interferences due to other airplanes on the ground or in the air were possible.
All three receiver antennas of the airplane received identical signals from the localizer on the ground so that on board no malfunction was indicated. Because there was only a short interference of the localizer signal neither the near field nor the far field monitor – which monitor the proper function of the ILS – registered a malfunction of the ILS. This means, the airplane followed the localizer signal. The crew only realised about 30 ft above the runway that something was not correct as the airplane slightly banked to the left and then drifted left. The left main landing gear touched down directly afterwards which resulted in the disengagement of the go-around mode. This prevented the crew from being able to initiate an automatic go-around.
The BFU record the Immediate Causes as:
- The crew decided to conduct an autoland landing even though the conditions on the ground for a safe conduct were not given.
- Shortly before touch-down the airplane was deviated to the left of its flight direction by a disturbed LOC signal. A BAE 146-RJ85 taking off a short distance ahead of the B 777 caused the interference.
- The two 777 pilots could not keep the aircrafton the runway after touch-down because the autopilot was still engaged.
- The crew was confused by the behaviour of the airplane. They had not noticed that the go-around mode had already been deactivated by the initial touchdown of the left main landing gear.
- The recommendation concerning the conduct of autoland landings under CAT I conditions published in the FCOM of the operator allowed the decision for an autoland landing without having to consider the required conditions on the ground.
The air operator implemented the following:
- Additional guidelines for flight crews for the successful conduct of go-around procedures after touch-down.
- Improved simulator training for flight crews during recurring and re-training to train go-around procedures after the aircraft has switched to ground mode.
- Improved simulator training for flight crews to train LOC deviations during flare mode below 50 ft.
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