AlliedSignal claims that its "get-well" effort for the once-troubled LT101 turboshaft has begun to pay dividends, with 1996 reliability levels improving by nearly 50% for the civil fleet compared with 1995 results, and by 20% for engines in service with the US Coast Guard.
Specific improvements to the engine included power-turbine-thrust kits, improved bearings and better power-turbine design. A year-long test of 50 engines with the new power turbine revealed that "blade walking", the excessive movement of turbine blades in the retaining turbine disc, has dramatically reduced. Since the introduction of the improvements, engine removals for blade walking have been cut by between 40% and 60%, says the company.
Allison is introducing enhancements to its Model 250-C20R Series II engine in a programme designated the C20R+. The engine will be capable of better hot-and-high performance with up to 15% increased shaft horsepower. Increased compressor and turbine efficiencies are also expected to cut fuel consumption by up to 10% compared with the C20R.
The change components include a larger throat area centrifugal diffuser, new first- and second-stage gas-generator nozzles and discs and new third- and fourth-stage power-turbine nozzle and discs. The improvements will be ready by early 1998.
Source: Flight International
