SEVILLE, Spain -- Airbus Military said Dec. 2 that it would resume a series of A400M taxi trials after introducing systems refinements in the run-up to the planned first flight in the second half of next week.

Ground tests since the military airlifter was handed over to the flight-test department Nov. 12 identified several areas where enhancements have to be made in the engines, braking system and other areas of the aircraft. Those issues notwithstanding, chief test pilot Ed Strongman will be at the controls of the first flight aircraft. Preparations have been ahead of expectations, he said.

But Strongman admits the process is fluid. "Something could change, but right at the moment things are going well," he told reporters here at the A400M final assembly site. Rain is forecast for the coming days, but so far Strongman believes a flight by the end of next week remains a possibility.

Taxi tests planned for Dec. 3 aim to validate a software upgrade to the anti-skid braking system, which during early tests showed poor characteristics. Early trials also led to the tachometer reading being lost on some of the wheels because of a connector failure. The cause for the failure hasn’t been identified, but as a near-term fix to get to first flight, those are simply being strengthened.

Other issues have crept up; one is nacelle heating. On the ground, the heat buildup is higher than anticipated -- something already seen on the C-130 flying test bed. As a fix, engineers have figured out they can take some air off the high-pressure compressor for a nacelle ejector system to provide better ventilation at low power. The switch -- only needed on the ground at low speed and low wind -- is currently activated manually, but an automatic function will be developed.

The exhaust gasses are also overheating aft parts of the nacelle in some conditions. As an interim step, Airbus is adding insulation and metal plate protection, with a more permanent fix planned for the third flight-test aircraft. On the other hand, engineers are seeing less heat buildup than expected at the auxiliary power unit exhaust point on the wing, potentially allowing the exhaust to be shortened to reduce drag. Tweaks are also being made to the engine settings. For now, high reverse power is limited to inboard engines. The ground idle position may change for a better neutral thrust position, Strongman says. However, the issue will not affect first-flight plans. Overall, the engines have shown "good response," he notes.

As expected, in ground reverse, the pitot static tubes are receiving confusing airspeed indication data, which is causing them to reject the information. Airbus expected the anomaly, and now officials are trying to apply the proper software fix. "We are solving problems very quickly," Strongman says. In one case, the TP400D turboprop engines had startup problems, but the Europrop International engine consortium was able to deliver a software fix to the full authority digital flight control system overnight. Taxi tests so far have reached 87 knots and also 5 knots reverse.

Photo: Airbus Military