Introduction
An Air Canada Airbus A330-300, registered as C-GHKX and operating as Flight ACA216, departed Vancouver International Airport at 1423 Pacific standard time on a scheduled flight to Calgary, Alberta. The aircraft carried 6 crew members and 92 passengers. Shortly after take-off, Vancouver tower informed the pilots that a substantial amount of smoke or vapour was emanating from the number 2 engine. Despite no abnormal engine indications or cockpit warnings, the pilots declared an emergency and advised they were returning to Vancouver.
Maintenance Error
The day before the occurrence, during a routine service check, maintenance personnel discovered a fuel leak from the drain mast on the number 2 engine (a Rolls-Royce RB211 TRENT 772B-60/16). The leak originated from the air/oil heat exchanger, which on the Airbus A330 uses high-pressure fuel to control oil temperature. The leak exceeded limits in the Airbus A330 troubleshooting manual (TSM). Maintenance entered the defect into the aircraft maintenance logbook and removed the aircraft from service at approximately 1300 PST, towing it to a hangar for replacement of the air/oil heat exchanger.
However, a notation was mistakenly made on the maintenance office duty board indicating a required replacement of the fuel/oil heat exchanger instead of the air/oil heat exchanger. A team of three licensed aircraft technicians, starting work at 2030, was assigned to replace the fuel/oil heat exchanger. Due to the conflict between the duty board and the logbook, and because the technicians did not use the TSM, they unnecessarily disconnected the low-pressure (LP) fuel line to the fuel/oil heat exchanger. During reinstallation, they did not refer to or follow all procedures in the available Aircraft Maintenance Manual (AMM). While waiting for replacement seal rings, the retainer—which cannot be removed from the fuel line—slid down and became obscured. The LP fuel-line coupling was reassembled without the retainer.
Sequence of Events
During the required idle engine run after maintenance, the fuel pressure and low fuel-flow rate, combined with minimal engine vibration, were insufficient to simulate in-flight conditions. Thus, the LP fuel line did not detach despite the missing retainer. After the run, the reconnected components were inspected for leaks from the ground, not from an elevated position as required by the AMM. A developer that would have made fuel leaks easier to detect was not used. The coupling appeared secure even without the retainer, and the technicians were unfamiliar with the fitting. The seal rings had compressed enough to prevent any leaks, rendering the developer ineffective.
On the day of the incident, as the engine power levers were advanced for take-off, increased fuel pressure, flow rate, and possibly engine vibration caused the LP fuel line to detach from the fuel/oil heat exchanger because the retainer was missing. This resulted in a large vapour trail noticeable to other aircraft crew and observers on the ground. The vapour trail was brought to the crew's attention, and they took appropriate action. An uneventful landing followed, and the crew shut down the number 2 engine. Aircraft rescue and firefighting services observed fuel leaking but no fire. The aircraft was towed to the terminal, and passengers deplaned without injuries or damage.
Investigation Findings
The Transportation Safety Board (TSB) completed an engineering laboratory report (LP 132/2003) and identified causes and contributing factors: an incorrect entry on the maintenance office duty board and technicians not following the TSM led to unnecessary removal of the LP fuel line; unfamiliarity with the coupling, the retainer being hidden, and failure to refer to the AMM resulted in improper reconnection; upon application of take-off power, fuel pressure, flow rate, and engine vibration caused the LP fuel line to detach, causing a substantial fuel leak.
Findings as to risk included that a high-power engine run was not performed (nor required by the manufacturer) that would have simulated take-off conditions; correct inspection would have required an elevated platform both before and after the engine run; and Air Canada had not implemented Airbus Service Bulletin (SB) A330-28-3080, which alerts pilots to a potential fuel leak after a loss of 3500 kg of fuel. On this flight, a fuel loss of 3500 kg occurred in fewer than five minutes after departure.
Other findings noted that the removal and reinstallation of the LP fuel line were not documented as required by Air Canada's maintenance policy manual and Transport Canada regulations.
Aftermath
On 16 December 2003, Air Canada issued a Maintenance Alert to all A330 technicians, emphasizing the importance of consulting appropriate technical publications and recording all work. An internal safety review was conducted, and by the report's release, Air Canada had implemented SB A330-28-3080 on approximately 50% of its A330 fleet, with plans to complete the remainder by autumn 2004.
The TSB sent a Safety Advisory to Transport Canada on 3 March 2004, recommending a review of maintenance practices for engine run-up procedures. Transport Canada responded on 16 June 2004, finding existing procedures sufficient if followed, and planned to publish an article on fuel/oil leak engine test runs in the Aviation Safety Maintainer.
The TSB authorized the release of this report on 7 September 2004.