Andrew Doyle/LONDON
ROLLS-ROYCE IS under renewed pressure from operators of RB.211-524G/H turbofans to resolve turbine blade problems, after a South African Airways (SAA) Boeing 747-400 came close to suffering a double engine-failure on take-off on 5 September.
The -524H-powered SAA aircraft (ZS-SAY) suffered a high-pressure (HP) turbine blade failure in the No 3 engine at around 750ft (230m), immediately after take-off from New York Kennedy Airport to Johannesburg. The aircraft returned to New York.
Analysis of data from the aircraft's condition-monitoring system prompted engineers to perform a borescope inspection on the No 1 engine. This revealed another HP turbine fracture, although the engine "-had kept going" until the aircraft landed. "The parameter shift on No 1 engine indicated that if it had been taken to take-off power again, it could well have been terminal for the engine," a source says.
Previous failures of the original "2B standard" directionally solidified nickel alloy HP turbine blades on -524Hs, initially involving British Airways 767-300ERs, led R-R to offer a "2C" single-crystal blade for retrofit from early 1994. Meanwhile, carriers such as Cathay Pacific have decided to derate -524Hs on 747-400s to -524G power until the new 2C blades can be fitted.
The SAA aircraft had 2B blades, but was still using the full -524H power rating. R-R says that "-recovery plans are in place and agreed with the airline".
Meanwhile, R-R appears to be accelerating studies of a hybrid RB.211-524G/H engine with a Trent 700 core, following encouraging results from tests (Flight International, 19-25 June). "The hybrid solves all the turbine problems and a lot of smaller ones that could add up to give long-range operators problems," says a source close to the test programme.
Source: Flight International
