ASN Wikibase Occurrence # 235618
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| Date: | Sunday 9 June 2019 |
| Time: | 15:59 |
| Type: |  Boeing 747-436 |
| Owner/operator: | British Airways |
| Registration: | G-BNLN |
| MSN: | 24056/802 |
| Year of manufacture: | 1990 |
| Engine model: | Rolls-Royce RB211-524G2-T-19 |
| Fatalities: | Fatalities: 0 / Occupants: 338 |
| Aircraft damage: | None |
| Category: | Serious incident |
| Location: | North of Blackburn, Lancashire -
 United Kingdom
|
| Phase: | En route |
| Nature: | Passenger - Scheduled |
| Departure airport: | London-Heathrow Airport (LHR/EGLL) |
| Phoenix-Sky Harbor International Airport, AZ (PHX/KPHX) | |
| Investigating agency: | AAIB |
| Confidence Rating: |  Information verified through data from accident investigation authorities |
British Airways flight BA289, a Boeing 747-400, was on a scheduled flight from London to Phoenix, USA, with the commander and co-pilot being line-checked by a training captain, who occupied the jump seat. The aircraft took off at 14:28 hrs with the co-pilot acting as pilot flying (PF). It had just reached the top of climb at FL330, with the right autopilot and autothrottle engaged, when the Master Warning activated. The crew reported that a line appeared through the Vertical Navigation (VNAV) path on the Flight Mode Annunciator (FMA) and that the Engine Indication and Crew Alerting System (EICAS) indicated a red overspeed warning, ALT disagree, IAS disagree, Rudder Ratio Single, Airspeed Low and Altitude Alert. The crew also reported feeling ear discomfort from a change in cabin air pressure.
The co-pilot recognised the airspeed had become unreliable, notifying the other two pilots before carrying out the recall drill. In doing so, he noted that the autothrottle had reduced thrust to 1.2 EPR before it was disengaged. He set a pitch of 4° nose-up and thrust of 80% N1, as required by the drill.
The crew declared a PAN with ATC and were cleared to remain on their current heading with a block altitude cleared for them to operate within. The commander and training captain then referred to the “Unreliable Airspeed Table” in the Quick Reference Handbook (QRH) from which they determined the required pitch attitude under the prevailing conditions was 3.5° nose-up and the required thrust setting was 87.5% N1.
While the datums were being agreed, and with the aircraft maintaining a pitch attitude of 4° nose-up and engine power setting of 80% N1, the stick shakers activated. The crew briefly discussed whether to maintain the ‘Airspeed Unreliable’ datums or carry out the stall recovery manoeuvre. They agreed that the stall recovery would be appropriate, and this was carried out by the co-pilot. He decreased the pitch attitude to 1° nose-down, at which point the stall warning ceased, which the crew considered confirmed their belief that the stall warning was genuine. He then slowly increased the pitch and engine power to the datums required in the QRH, however, as he did so the stall warning reoccurred, so the co-pilot reduced pitch again until the warning ceased. As the airspeed increased, the co-pilot gradually increased pitch, however the stick shaker activated once again, causing him to reduce the pitch angle until it stopped activating. He repeated this process several times until the QRH datums were finally attained and there were no further stick shaker activations.
The aircraft had lost about 2,800 ft during these manoeuvres. With the aircraft now stable, the crew completed the rest of the ‘Airspeed Unreliable’ checklist with the air data source being changed from the right to the centre Air Data Computer (ADC). This allowed the autopilot and autothrust to be re-engaged. The crew also contacted the operator’s maintenance office by radio which was able to confirm, via the aircraft health monitoring system, that the right ADC had failed.
The crew and maintenance office both assured themselves that the aircraft was still able to comply with the Required Navigation Performance and Minimum Navigation Performance Specifications and, having done so, the flight continued to the destination with no further incidents".
Twelve days later, on June 21, 2019 British Airways Boeing 747-436 G-BNLN was withdrawn from service at London Heathrow after arriving as BA58 from Cape Town. This reduced the British Airways Boeing 747-400 fleet to 33 aircraft.
Three days later, on Jun 24, 2019, withdrawn British Airways Boeing 747-400 G-BNLN positioned London Heathrow (LHR) to RAF St Athan late in the afternoon as BA9179 for parting out and scrapping.
Accident investigation:
 |
|
Sources:
1. AAIB Final Report: https://assets.publishing.service.gov.uk/media/5f451241d3bf7f69a89b6c1c/Boeing_747-436_G-BNLN_05-20.pdf
2. AAIB Annual Safety Review 2020 pp.104-105: https://assets.publishing.service.gov.uk/media/60d2e72ed3bf7f4bd4662d67/Annual_Safety_Review_2020.pdf
3. https://www.flightradar24.com/data/aircraft/g-bnln#20d41eac
4. http://thebasource.com/aircraft/b747-400/g-bnln/
4. https://avherald.com/h?article=4d6a301b&opt=0
Images:
Discrepancy between the right and left ADC (AAIB)
Media:
Revision history:
| Date/time | Contributor | Updates |
|---|---|---|
| 30-Apr-2020 16:48 | harro | Added |
| 30-Apr-2020 16:52 | harro | Updated [Photo, Accident report, ] |
| 26-Jun-2021 22:13 | Dr. John Smith | Updated [Location, Source, Narrative] |
| 26-Jun-2021 22:22 | Dr. John Smith | Updated [Source, Embed code, Narrative] |
| 26-Jun-2021 22:24 | Dr. John Smith | Updated [Narrative] |
| 26-Jun-2021 22:25 | Dr. John Smith | Updated [Narrative] |
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