10-14-2011, 04:35 AM
Join Date: Jul 2006
Incident: British Airways B772 near Amsterdam on Jun 15th 2010, multiple technical pr
I know this is old but makes interesting reading:
A British Airways Boeing 777-200, registration G-YMMP performing flight BA-16 from Singapore (Singapore) to London Heathrow,EN (UK), was enroute at FL380 overhead Germany just about entering Netherlands when the crew decided to divert to Amsterdam, a few minutes later the crew declared PAN reporting multiple technical problems increasing in number and severity, the crew being unable to pinpoint any specific issues. At the same time the crew reported being low on fuel having about 40 minutes endurance left. The crew requested a long final to be able to configure the airplane early. The airplane proceeded towards Amsterdam, where the aircraft landed safely on runway 27 about 25 minutes later.
After landing it was found, that the right hand engine (Trent 895) suffered substantial damage around the outlet area, both engines had however produced thrust until landing with some higher fuel burn. The engine damage is believed to have happened about 5 hours prior to landing.
The NTSB reported on Jul 7th 2010, that the airplane experienced a vibration shortly after takeoff from Singapore. About 5 hours into the 13.5 hour flight a thud was heard in the #2 engine and the fuel flow rose significantly leaving insufficient fuel to reach the destination. Initial inspection after landing revealed the #2 engine thrust reverser inner wall D-duct had liberated. Damage was also found to the inboard flap fairing and flaperon, engine pylon and inboard flap. The damage is consistent with 9 other previous thrust reverser inner wall failures due to overheating. The incident was initially investigated by the Dutch Safety Board and was delegated to the British AAIB on Jun 22nd.
The British Air Accident Investigation Board (AAIB) released their bulletin reporting the flight crew consisted of two complete crews, the commander and first officer as well as a relief captain and a relief first officer, called the "heavy captain" and "heavy first officer". The aircraft carried 202 passengers and 12 crew.
The aircraft departed Singapore's runway 02L at a high takeoff weight, so that engines were minimally de-rated only and high EGTs were briefed and expected. At 500 feet AGL the right hand engine's EGT fluctuated by about +/- 100 degrees C, an "ENG THRUST R" along with an "ENG RPM LIMITED R" message appeared on the EICAS, the crew noted the right hand engine's N1 showed 100.5%. Neither message required a recall action according to the QRH. After the aircraft climbed through acceleration altitude, the crew engaged the autopilot and reduced engine power to climb power which removed the EICAS messages and brought the parameters of both engines into the normal range. The crew accessed the status page showing an EEC message requiring no crew action and accessed the maintenance access tables which showed a number of discrete faults including a short on the right engine core's fire loop.
After the aircraft passed 10,000 feet the commander decided to conduct a "confidence test", disconnected autothrottle and selected full power for both engines. Both engines spooled up and delivered full power through the right engine's N1 was higher than the left engine's. The autothrottle was re-engaged, climb power selected and the crew decided to continue while assessing the situation. Scenarios like bird strike, fan damage, spurious indications or an EEC failure were considered, however with the only unusual indication of the right engine's N1 being about 3.5% higher than the left engine's, all other right engine parameters including fuel flow were slightly lower than the left engine's. A fan damage was considered likely however the vibration indication showed 0.8 units only well within permitted range. Consultation with the maintenance department of the airline also did not raise any concern.
About 4 hours into the flight an "ENG EEC MODE R" message was displayed on the EICAS indicating the engine had switched to alternate control mode. The crew actioned the relevant checklist and switched the left engine to alternate control mode too in line with the checklist. As the crew had already suspected some engine electronic control (EEC) issue this did not cause any concern with the crew also in view of the many maintenance access table entries. Following the actions the discrepancy between the left and right engine parameters increased as if the right N1 was overreading.
The flight crew operating manual stated that with engines in alternate control a 20 ton penalty was to be applied to performance computations. The crew therefore decided to base step climb decisions based on the higher "assumed weight".
About 5 hours into the flight the fuel estimations for London Heathrow began to drop. The fuel consumption increase was not unexpected due to the performance penalty however the fuel consumption increased above expectation. AS a result reaching Heathrow with minimum fuel required was becoming unlikely. Being over Afghanistan with no reasonable diversion field around and considering that it would take equally long or longer to turn around and return to a suitable diversion field behind, the crew decided to continue with still 52,000 kg of fuel on board at a fuel flow of 8,000 kg per hour.
The "heavy crew" took over and continued to monitor the situation.
In the meantime Singapore ground staff had found debris at the edge of runway 02L during a scheduled check, but was unable to identify the debris.
About 8:45 hours into the flight the commander was woken up in his crew rest bunk from a bang what he believed was an engine surge. The engines however continued running with no change in thrust, so that the commander concluded he had imagined the bang.
The heavy crew heard a thud as well and felt a slight movement of the aircraft. The crew subsequently noticed that the required thrust to maintain altitude as well as the fuel flow had reduced, the deteriorating indications for fuel levels at Heathrow stabilised. The heavy crew suspected a panel had become loose causing an increase drag and had now detached removing the additional drag. As it had already become daylight again the heavy captain visually checked the aircraft exterior but could not see any loose or detached panel. The rear of the engine was not visible. The possibility of a reverser blocker or cascade door detaching was considered, engine parameters remained unchanged however.
The crew decided to divert to Amsterdam (Netherlands) mainly because of the excellent weather there and multiple runways available where the aircraft landed with 2000 kg of fuel above minimum required fuel. Being unsure how many track miles they would need to cover the crew decided to declare PAN and requested emergency services on stand by. After landing the crew had emergency services check the exterior of the aircraft which remained inconclusive however.
Following the clear by emergency services the aircraft taxied to the apron and was shut down. After the passengers had disembarked the crew exited the aircraft and conducted a visual inspection of the aircraft discovering the aft inner nacelle of the right engine was seriously damaged and much of it missing. There was further airframe damage.
After landing in Amsterdam the airline called Singapore Airport reporting that engine parts had been missing upon arrival at Amsterdam. The debris found at the edge of runway 02L was subsequently identified to come from G-YMMP's right engine.
A post flight visual inspection showed the left inner wall "D-Duct" of the thrust reverser of the right engine had separated from the engine and large portion of the turbine exhaust nozzle was missing. There was damage to the inboard flap fairings and flaperon consistent with separation of items from the engine along with sraping and gouge damage on the right lower wing skin and the right horizontal stabilizer.
The engine manufacturer concluded the buckling damage to the inner wall D-duct was consistent with a "typical of loss of stability due to disbond of inner facesheet". This form of failure had already been seen on a number of previous occasions.