A preliminary factual report released today by the Australian Transport Safety Bureau recounts a laudable effort on the part of the five-member flight crew to land the Qantas A380 stricken by the uncontained failure of one of its Rolls-Royce Trent 900 turbofans over the Indonesian island of Batam on November 4.
Minutes after a normal takeoff from Singapore Changi International Airport, the crew reported that they heard two almost simultaneous "loud bangs" while climbing through 7,000 feet msl. Subsequently, the airplane's electronic centralized aircraft monitor (ECAM) system displayed an overheat warning in the Number 2 engine turbine. The crew followed the procedure to move the thrust lever to the idle position and monitor the situation for 30 seconds. During that 30-second interval, the first officer noticed that the ECAM flashed a fire warning for one to two seconds before reverting to the overheat message, prompting the crew to attempt to shut down the Number 2 engine. The ECAM then displayed a message indicating that the Number 2 engine had failed. After determining that serious damage had occurred, the pilots twice tried to discharge one of the fire extinguisher bottles into the affected engine, but they received no confirmation of a successful discharge after either attempt. They then repeated the procedure with the second fire extinguisher. Again, they received no confirmation that it had discharged.
By the time the crew discussed recovery options, including an immediate return to Singapore, the ECAM had displayed numerous systems warnings, including the following:
• Engines Number 1 and 4 operating in a degraded mode
• "Green" hydraulic system – low system pressure and low fluid level
• "Yellow" hydraulic system – engine Number 4 pump errors
• Failure of the AC electrical Number 1 and 2 bus systems
• Flight controls operating in alternate law
• Wing slats inoperative
• Flight controls – ailerons partial control only
• Flight controls – reduced spoiler control
• Landing gear control and indicator warnings
• Multiple brake system messages
• Engine anti-ice and air data sensor messages
• Multiple fuel system messages, including a fuel jettison fault
• Center of gravity messages
• Autothrust and autoland inoperative
• Number 1 engine generator drive disconnected
• Left wing pneumatic bleed leaks
• Avionics system overheat.
As the rest of the crew continued to address the ECAM messages, the flight's second officer entered the passenger cabin to look for signs of damage. From the lower deck, he could see damage to the left wing and a half-meter-wide trail of fluid–likely a mixture of fuel and hydraulic fluid–emanating from the area of the affected engine.
Unsure of the integrity of the fuel system, the crew stopped trying to transfer fuel between tanks. Meanwhile, they couldn't dump fuel due to an ECAM fuel jettison fault.
All told, it took the crew some 50 minutes to complete all of the initial procedures associated with the ECAM messages.
After calculating the landing distance needed for Changi's Runway 20C and determining that they would need all but 100 meters (328 feet) of pavement to stop the overweight airplane, the crew lowered the landing gear using an emergency extension procedure. By that time, the crew knew it had to contend with the lack of reverse thrust from the Number 2 engine, inoperative leading-edge slats, limited aileron and spoiler control, lack of anti-skid braking in the nose gear, limited nosewheel steering and the likelihood that the nose would pitch up on touchdown.
Knowing that failure to maintain accurate speed control on final approach could result in either an aerodynamic stall or a runway overrun, the captain set the thrust levers for the Number 1 and Number 4 engines to provide symmetric thrust and controlled the airplane's speed with thrust from the Number 3 engine. The autopilot disconnected "a couple of times" during the early part of the approach as the speed deteriorated to 1 knot below the required approach speed of 166 knots. The captain tried to re-engage the autopilot, but when it disconnected again at about 1,000 feet, he chose to fly the airplane manually for the rest of the approach.
Upon touching down, the captain applied maximum braking and selected reverse thrust for the Number 3 engine. As the speed approached 60 knots he gradually moved the Number 3 engine out of maximum reverse thrust and continued manual braking until the airplane came to a stop some 500 feet from the end of the runway.
Once the airplane came to a stop, the crew tried to shut down the remaining engines, but the Number 1 engine continued to run and the left body landing gear brake temperature had risen to more than 900 degrees. Meanwhile, the cockpit displays went blank and only one VHF radio still worked. The crew then unsuccessfully tried to use the emergency shutoff and fire extinguisher bottles to shut down the Number 1 engine.
After evacuating the passengers, the crew then tried to reconfigure the transfer valves in the airplane's external refueling panel in an effort to starve the Number 1 engine of fuel. That effort also proved unsuccessful due to a lack of electrical power. Finally, emergency crews drowned the engine with fire-fighting foam, shutting it down two hours and seven minutes after the airplane landed.
The ATSB found that the Number 2 engine had ejected a number of components that struck the aircraft. For example, sections of the intermediate pressure (IP) turbine disc penetrated the leading edge of the left wing inboard of the Number 2 engine, resulting in damage to the leading-edge structure, the front wing spar and the upper surface of the wing. A small section of turbine disc penetrated the left wing-to-fuselage fairing, resulting in damage to several system components, the fuselage structure and electrical wiring. The damage to the wiring affected the operation of the hydraulic system, landing gear and flight controls. Debris also struck the left wing's lower surface, which caused a fuel leak from the Number 2 engine feed tank and left wing inner tank.
Examination of the Number 2 engine revealed that the IP turbine disc, blade and nozzle guide vanes separated into a number of sections, rupturing the surrounding IP turbine casing and damaging the thrust reverser. Investigators also found severed thrust links and extensive damage to the engine cold stream duct and outer cowl panels, the LP turbine nozzle guide vanes and Stage 1 turbine blades.
Although the ATSB expects the investigation into the cause of the engine failure to take roughly a year, it has already identified a potential defect in an oil tube connection to the high-pressure (HP)/intermediate-pressure (IP) bearing structure as a likely culprit.
During an examination of the engine at its Derby, UK plant, Rolls-Royce found an area of fatigue cracking within a stub pipe that feeds oil to the HP/IP bearing structure, which apparently led to an oil leak and fire within the bearing buffer space. Investigators suspect the cracking resulted from a misaligned region of counter-boring within the stub pipe outlet. The misaligned counter-boring produced a localized thinning of one side of the pipe wall.
Qantas has returned two of its A380s to service after conducting further inspection of the suspect oil pipes as ordered by Australia's Civil Aviation Safety Authority (CASA) on December 1. Its other four A380s remain grounded as it scrambles to replace engines that showed any signs of oil leaks.