Thai Airways International has unilaterally suspended 120min extended-range twin-engine operations (ETOPS) flights with its six Rolls-Royce Trent 892-powered Boeing 777-300s after the fleet's in-flight shutdown rate rose close to the limit permitted by ETOPS rules.
Boeing is concerned Thai's move could damage its 777 marketing efforts as Airbus steps up its A340 quad-jet sales campaign.
R-R and Boeing are perplexed by the airline's move, which they believe is unnecessary because the shutdown rate, at 0.046/1,000h, remains within the 0.05/1,000h ETOPS limit. In addition, Thai is not operating its 777-300s on routes which require 120min ETOPS.
Thai engineering sources say the airline will only restart 777-300 ETOPS flights after R-R releases a service bulletin to solve a problem discovered with the Trent 892's intermediate pressure compressor (IPC). The manufacturer has asked all operators to inspect, every 250h, first-stage, high-pressure compressor blades for possible damage caused by material leaving the IPC.
On 18 May a Thai 777-300 was forced to divert into Ubon Ratchathani Airport in north-eastern Thailand after suffering a compressor stall in its left-hand engine.
The incident was caused by the failure of an HPC blade. Subsequent boroscope inspections revealed a damaged blade in another Thai Trent 892 that had accumulated only 97 cycles, say the sources.
Thai's fleet of 777-200s, also powered by versions of the Trent 800, remain cleared to operate 120min ETOPS flights because they are treated as a separate fleet and are well within the shutdown limit, say the sources.
Source: Flight International
