Guy Norris/DERBY
ROLLS-ROYCE has unveiled improvements to the US Navy's McDonnell Douglas (MDC) T-45A Adour powerplant, as the Royal Australian Air Force (RAAF) nears a final choice of engine for its $1 billion lead-in fighter-trainer contract.
The initiative follows the discovery of cracks and other evidence of "thermal distress" in the combustor and high-pressure nozzle guide-vanes of high-time US Navy F405s. Peter Peck, head of business, North America, for R-R military aero-engines, blames the unexpected problems on "excessive cyclic usage" of the T-45A.
Improved fuel efficiency has resulted in more cycles than anticipated being amassed, forcing the USN, R-R and MDC to revise the original performance specifications. "The rest of the engine has been cleared to 2,000h on condition, whereas the original specification was 1,000h," says Peck.
"We'll have [revised] combustors and nozzle guide-vanes available before the end of the year. By the third quarter of 1996, we'll be validating them and progressively fitting out the fleet," he adds.
The combustor is being upgraded with an improved thermal-barrier coating and modified cooling holes, while a "retuning of cooling holes" is expected to improve the durability of the nozzle guide-vanes. "We've also undertaken to redesign the low-pressure nozzle guide-vanes," says Peck. The low-pressure vanes failed the USN's accelerated simulated mission-endurance test but have not produced problems in the far more rigorous conditions of real-life service. These units are cleared to 1,200h, but will go to 2,000h between overhauls with the redesign.
R-R is also tackling cracks in the jetpipe, and is "looking for alternatives", says Peck. "We've not yet decided what to do. We could go for a corrugated or honeycomb design, or keep the one we have. These are not critical or life-limiting issues."
An RAAF team is due to visit R-R and British Aerospace shortly, to discuss the Hawk bid.
The two UK companies are competing for the RAAF business against the R-R Viper-powered Aermacchi MB339FD, and the T-45A, which has the International Turbine Engines F124 turbofan as the primary engine choice.
The Adour powerplant is also being offered as a second engine choice on the T-45.
Source: Flight International
