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| Date: | Thursday 5 September 1996 |
| Time: | 08:51 |
| Type: |  Boeing 737-59D |
| Owner/operator: | British Midland |
| Registration: | G-OBMX |
| MSN: | 25065/2028 |
| Year of manufacture: | 1991 |
| Engine model: | CFMI CFM56-3 |
| Fatalities: | Fatalities: 0 / Occupants: 70 |
| Other fatalities: | 0 |
| Aircraft damage: | None |
| Location: | Near Lambourne -
 United Kingdom
|
| Phase: | Approach |
| Nature: | Passenger - Scheduled |
| Departure airport: | Brussels-Zaventem Airport (BRU/EBBR) |
| London-Heathrow Airport (LHR/EGLL) | |
| Investigating agency: | AAIB |
| Confidence Rating: |  Accident investigation report completed and information captured |
The crew had flown an uneventful flight from London Heathrow to Brussels during which the aircraft had been fully serviceable. After a normal turnround, the same crew took-off for the return flight. The commander was the handling pilot and he engaged Auto Pilot 'A' soon after establishing the aircraft on the departure from Brussels; in accordance with his company procedures, he had used auto-throttle from the beginning of his take-off roll. The climb and cruise were normal and the automatic control systems were operating correctly. During the descent, the
crew were advised that there was a delay going into Heathrow, and were instructed to enter the 'Hold' at Lambourne. After approximately 15 minutes in the 'Hold', ATC instructed the crew to leave Lambourne at FL80 on a heading of 270°(M) at 220 kt IAS. The commander selected 'HDG SELECT' and '270°' on the Mode Control Panel (MCP) and, as the aircraft crossed Lambourne, it rolled out on the required heading.
With the aircraft still level at FL 80 and clear of any cloud, the crew were not visually aware of any other aircraft in their vicinity. Neither crew member had their feet on the rudder pedals but the commander had his hands lightly on the control wheel. The crew were then cleared to descend to FL 70 and the commander selected the new altitude, Vertical Speed ('V/S') and a descent rate of 1,000 feet per minute on the MCP. As the aircraft started the programmed descent, the Flight Service Manager (FSM) entered the cockpit. Both crew members turned in their seats to talk to the FSM and the commander took his hands off the control wheel as he turned. Shortly afterwards, both of the flight crew were aware of the aircraft banking to the left; the bank appeared rapid but smooth. They both turned back and the commander put his feet on the rudder pedals and his hands on the control wheel. As he did so, his impression was that the wheel and rudder were central. The aircraft appeared to be banked at least 30°and the impression of both crew members was that the aircraft was continuing to roll to the left. The commander immediately disconnected the autopilot and applied right rudder and right control wheel. Response to the control inputs was rapid and accurate and the aircraft was quickly brought back under control. After confirming that the rudder and aileron trim were neutral and that there were no system abnormalities, the autopilot was re-
engaged. It operated correctly for the remainder of the flight although the commander manually disconnected it very early on the approach.
The first officer confirmed the commander's account of the incident. He also reached for the controls following the un-commanded roll, which he estimated as 50° bank. He also thought that the control wheel and rudder were central prior to the commander’s manual input. Both crew members had experienced wake turbulence before but were not fully convinced that this was a wake encounter. They based this assessment on the fact that it was smoother and more extreme than their previous experience.
Accident investigation:
 |
|
Sources:
https://assets.publishing.service.gov.uk/media/5423038140f0b61346000c9d/G-OBMX_500809.pdf
https://www.jetphotos.com/photo/11040618 (Photo)
Revision history:
| Date/time | Contributor | Updates |
|---|---|---|
| 04-Apr-2025 16:14 | Justanormalperson | Added |
| 04-Apr-2025 16:15 | ASN | Updated [Narrative, Accident report, ] |
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