Solutions Found for A400M Engine Problems
Although it gained EASA certification in May, the Europrop International (EPI) TP400-D6 engine that powers the Airbus Military A400M airlifter subsequently encountered two problems. But according to EPI’s president, Simon Henley, they have both now been resolved.
The first problem concerned a fatigue crack in the idler gear that occurred at cruise propeller speed. This led to an in-flight shutdown and also caused the cancellation of the A400M’s appearance in the flying display at Paris as a precautionary measure. With the fault located, EPI instigated a redesign to shift the resonance point out of the running range.
Blade fatigue in the high-pressure compressor was the second problem. This was traced to resonance occurring in a very tight speed band at ground idle, generated by wake separation from the variable inlet guide vane (VIGV) located upstream. A temporary software patch was applied to the four test aircraft to avoid the resonance speed, while for production engines EPI has devised what Henley termed “a double fix.” The company has implemented a permanent logic change in the control system to prevent operation in the problem speed range and redesigned the VIGV to eliminate the wake separation.
Meanwhile, Airbus Military revealed that the active noise cancellation system planned for the A400M will not be required, leading to a weight savings of about 550 pounds. Noise levels in the cabin are lower than expected, thanks to insulation.
The first aircraft to have a representative cabin is the fifth test aircraft, MSN6. It is complete and could fly in a matter of weeks, if required. However, a decision has not yet been taken on whether to wait for further modifications to be applied before first flight. In that case MSN6 would most likely join the test fleet in early 2012.