What happened
On 13 November 2017, a Boeing 777-236, registration G-VIIJ, was performing a scheduled passenger flight from Houston to London Heathrow. During the descent phase, approximately one hour before arrival, a strong smell of fumes became noticeable in the flight deck and the passenger cabin. The crew implemented the Smoke, Fire or Fumes checklist, and due to the intensity of the fumes, the pilots utilized oxygen masks. An urgency message was transmitted to Air Traffic Control, and the aircraft completed an automated landing at Heathrow.
Following this event, the aircraft experienced subsequent issues during following operations. On its next flight, an oily smell was detected during the engine start, leading the aircraft to return to the stand. Despite maintenance involving the replacement of the APU and air conditioning components, fumes were identified again during ground runs, with the left engine identified as the source. During a subsequent flight from Seattle to Heathrow, the crew received an overheat indication for the left engine. Although parameters appeared normal, a post-flight inspection revealed significant damage.
The investigation
The AAIB investigation focused on the source of the fumes and the subsequent engine damage. Examination of the left engine revealed sooting, heat damage, and a hole in the combustion chamber case located just behind a fuel nozzle.
Technical analysis by the engine manufacturer determined that a swirler retainer had detached due to a broken weld. This loose component eventually chafed through a fuel nozzle, causing the fuel spray to ignite and burn through the combustion chamber case. The investigation also reviewed the application of the Fault Isolation Manual. At the time, the manual prescribed different inspection paths depending on whether fumes were perceived as oil or fuel-based. Because the initial events were attributed to oil, the fuel nozzles were not inspected during the earlier maintenance intervals.