Sundstrand's Auxiliary Power International (APIC) plans to boost the in-service life of its APS 3200 auxiliary power unit on the Airbus single-aisle aircraft family with a block upgrade in the next few months. APIC is confident of growing business on the 100-seat A318 after being selected by International Lease Finance for its first purchase.

The San Diego, California-based company is introducing advanced hot section improvements, including coated turbine materials and cooled turbine blades and nozzles.

The block upgrade, to be launched officially in April 1999, is aimed at extending life on wing to "10,000 hours first-run reliability", says APIC. The current mean time between unscheduled removal rates (MTBUR) for the APS 3200 worldwide is more than 7,700 flight hours.

Existing in-service engines will also be upgraded with durability improvements to a similar modification standard, starting early in 1999.

"We are working with DaimlerChrysler Aerospace to define the performance requirements for the APU on the A318," says the company. "Our contract with ILFC puts us on the A318 automatically, but we haven't finalised a deal to define performance ratings.

APIC says the higher pressure ratio N2 (core) spool of the new Pratt & Whitney PW6000, which powers the A318, will demand higher torque input during engine start than is usually expected.

"APIC is actively engaged in definitive APU discussions with P&W and their starter supplier, Hamilton Standard, and is very comfortable with the starter sizing and bleed flow requirements," says the company.

Because the environmental control system bleed air requirement will be lower for the A318 size of cabin than for other aircraft in the Airbus single-aisle range, APIC plans to incorporate special derating software to control cabin air to the lower level. This is expected to result in a "substantially" larger deterioration margin, resulting in longer time on wing and lower costs. By the end of 1998, there will be 385 APS 3200s in service on the A320 family of aircraft with 30 operators, says APIC, which plans to make the 500th APS 3200 in January 1999.

More than 1,200 APS 3200s have been chosen by the airlines, including 716 in direct competition with AlliedSignal's 131-9A, adds APIC.

The APU has accumulated 1.5 million hours and 2 million cycles in service to date.

Source: Flight International