First flight of the Rolls-Royce Trent XWB aboard a dedicated Airbus A380 flying testbed brought the engine to "the edge of the flight envelope of the A350" and generated "very encouraging, satisfactory results", is the verdict of Airbus flight test engineer Emanuele Costanzo.

Such anomalies as arose during the 18 February sortie can be addressed within "the standard development flight test activity for this kind of exercise", added Costanzo. They included "very gentle oscillations, visible on a plot" when the engine was at minimum idle.

Costanzo was aboard the 5h flight from Toulouse. A Trent XWB development engine, fitted with test sensors, was mounted on the A380's inner-left pylon, replacing one of the aircraft's Trent 900s.

"Flying the actual engine of the A350 on one of our airplanes one year before the first flight of the A350 gives us a tremendous opportunity to identify the engine behaviour, to identify the handling and operability of the engine, and to bring the engine to extreme conditions," said Fernando Alonso, Airbus's head of flight operations.

Alonso stressed that the flight focused not just on the engine itself but also on the engine's interfaces with the aircraft. The A350's generators, bleed system and hydraulic pumps had been fitted. "This is a major contributor to the maturity of the A350 XWB right from its very first flight," he said. "The bulk of the first flight on the flying testbed was about opening the flight envelope."

The A380 reached its maximum operating speed of Mach 0.9 and normal operating ceiling of 43,000ft. It was also operated at high angle of attack and at the minimum speed that would be encountered in normal service. "The engine was fully functional and gave us exactly the performance that we would have expected at Flight Level 100 [10,000ft] and 108kt," said experimental test pilot Terry Lutz.

"When we did the simulator preparation for this particular flight, we noticed that engine acceleration and deceleration characteristics were just slightly better than the Trent 900's, and we were very pleased to find that those characteristics were almost identical on the actual flight," added Lutz.

The flight kick-started a seven-month test campaign Airbus is pursuing jointly with Rolls-Royce. This is set to accumulate 175h, "some three times more airborne flying hours than on previous programmes", and will include hot weather testing likely to take place in the United Arab Emirates in the summer, plus tests intended to support Rolls-Royce's efforts to secure European Aviation Safety Agency certification - for example, identification of the re-light envelope and demonstration of compressor surge margins. "We will make the compressor surge in flight to determine the surge line of each compressor in new and deteriorated condition," said Costanzo.

Cold weather testing additional to that already carried out by Rolls-Royce is unlikely to happen until the A350 airframe is in flight testing.

A350 systems to be deployed within the flying testbed campaign include the air data computer and a Goodrich nacelle and thrust reverser.

Source: Air Transport Intelligence news