TUI Airways B789 at London on Jul 6th 2018, deteriorating flight controls

Last Update: February 14, 2019 / 19:42:43 GMT/Zulu time

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Photo of TUI Airways G-TUIM, Boeing 787-9 Dreamliner — TUI Airways G-TUIM, Boeing 787-9 Dreamliner (Photo credit: Alec BHX/KKC / Flickr / License: CC by-sa)

Incident Facts

Date of incident
Jul 6, 2018

Classification
Incident

Airline
TUI Airways

Flight number
BY-4535

Departure
Tenerife South, Spain

Destination
London Gatwick, United Kingdom

Aircraft Registration
G-TUIM

Aircraft Type
Boeing 787-9 Dreamliner

ICAO Type Designator
B789

A TUI Airways Boeing 787-9, registration G-TUIM performing flight BY-4535 from Tenerife South,CI (Spain) to London Gatwick,EN (UK) with 353 passengers and 11 crew, was on approach to London Gatwick's runway 26L in clear weather (CAVOK) and light wind when the crew selected flaps 1 and received "SLATS PRIMARY FAIL" and "FLAPS PRIMARY FAIL" EICAS messages. The crew extended the flaps to 20 degrees using the alternate electrical system while flying an orbit and following delay vectors. After intercepting the localizer for runway 26L the crew selected the gear down, however the nose landing gear remained in transit, a fault with the nose wheel steering was indicated. The crew decided to go around, lowered the nose landing gear with the alternate electrical system, the crew discussed and prepared for the lack of nose wheel steering. The aircraft positioned for another approach, the autopilot was disconnected at about 1000 feet AGL and the aircraft continued for a safe landing on runway 26L coming to a complete stop on the runway about 5500 feet down the runway.

The UK AAIB released their bulletin concluding the probable cause of the serious incident was:

The incident was caused by the NLGIV failing to open when commanded which meant that the leading-edge slats, trailing edge flaps, nose landing gear and nosewheel steering would not operate normally. The alternate electrical system was used to select flaps 20 and lower the nose landing gear.

The AAIB reported:

This was the third incident involving G-TUIM in a week where similar indications of system degradation had occurred but it was the first where problems with the nose landing gear and nosewheel steering were indicated.

- On 30 June 2018, on the base leg to LGW a slats primary fail message was displayed on the EICAS. The approach was continued to a normal landing and rollout.

- On 4 July 2018, left downwind for Runway 09L, on selection of flaps 1, an EICAS message slats primary fail was displayed and the ECL actioned. On selection of flaps 5, the flaps primary fail caption was displayed. The approach was delayed and, after completion of the ECL and a recalculation of the landing distance required, a flaps 20 landing was carried out.

The engineering department carried out the required system and serviceability checks which were passed satisfactorily. It was decided to order a replacement Hydraulic Control Unit (HCU) and maintenance action was planned for the aircraft.

During the event on 6 July 2018 there were similar slats and flaps system failures but, additionally, there were gear disagree and nose wheel steering EICAS messages. The reported failures also highlighted that the hydraulic synoptic page displayed an ¡®amber cross¡¯ through the Nose Landing Gear Isolation Valve (NLGIV). The NLGIV subsequently failed a serviceability test and was replaced.

Following engineering tests the AAIB reported:

A response from the manufacturer received on 10 October 2018 regarding the NLGIV advised that the NLGIV was cold tested to -40¢ªF. The unit failed to open under those conditions and the failure was repeatable. This finding will support future work and potential mitigating actions, which were being examined. A FIM revision is being made and an amendment to the Aircraft Maintenance Manual to add an operational test of the valve.

The AAIB analysed:

The flight crew were confronted with an escalating degradation of normal systems that progressed from an initial failure of the primary slats and flaps systems. When the landing gear was selected down, a gear disagree message was displayed on the EICAS indicating that the nose landing gear had not achieved the selected position. The alternate landing gear lowering system was used to lower the nose landing gear into the correct position, but a further message indicated a fault with the nosewheel steering. ATC was used to assist the crew by directing them to fly orbits during which they were able to action the ECL and discuss their plan for the landing. The commander carried out a NITS brief for the SCCM, briefing a precautionary landing. With the additional problem of the nosewheel steering, however, this was upgraded to a briefing for an emergency landing, and the SCCM carried out the required cabin briefing and actions. When the SCCM realised that the aircraft was close to landing and no orders had been received from the flight deck, he issued the ¡°brace, brace, heads down, heads down¡± command which ensured that those in the cabin were properly prepared. The landing rollout was safely accomplished using the rudder for aerodynamic directional control followed by differential braking to maintain the runway centreline. The engines were stopped on the runway and the aircraft towed to the parking stand and the passengers disembarked normally.