Rolls-Royce has signed a memorandum of understanding with Boeing covering the formulation of a flight-test schedule for the RB.211-524HT "hybrid" turbofan, although the timing of the programme remains uncertain as the UK manufacturer works to locate a suitable testbed aircraft.
The -524HT, which uses the core of the Trent 700 fitted to an otherwise-standard -524G/H, is due to be test-cell certificated by the end of April, but R-R's ability to secure an RB.211-powered Boeing 747-400 to use for the flight tests appears to hinge on a customer agreeing to have an aircraft out of service for at least six weeks.
R-R is keen for flight testing to begin as early as September, but Boeing's propulsion-systems division is apparently taking a longer-term view, saying that it is "-looking at a window for flight testing to occur sometime between September 1997 and May 1998".
Boeing adds that the testbed aircraft will probably be a 747-400, saying that no firm decisions have yet been taken and that "-it could either be an in-service or a production aircraft".
British Airways is to take delivery of a 747-400 in September, but has so far been reluctant to commit this aircraft to the test effort because of capacity constraints. This is despite the fact that the UK flag carrier is expected imminently to place the first order for the -524HT, to power 14 747-400s on firm order. R-R is also understood to have approached Hong Kong-based Cathay Pacific to discuss the possibility of using one of its 747-400s as the testbed.
R-R says that it has "-no confirmation" on which aircraft the engine will be used for testing and that it is "-talking to customers".
Before flight testing can begin, Boeing engineers will before June begin carrying out an independent audit of the -524HT to verify its performance. Ground runs of the engine at sea level have shown an initial 1.9% improvement in fuel consumption, compared with the -524G/H, while simulated altitude testing has not yet yielded conclusive results, say sources close to the programme.
Source: Flight International
