LE BOURGET, FranceAirbus is set to restart ground tests of the Pratt & Whitney PW1100G-powered A320neo this week following a six-week hiatus caused by the discovery of a loose ring-shaped component in the combustor section of an engine on one of the two test aircraft

The ground testing will be conducted by an aircraft still powered by the original unmodified engines, and flights will not resume until newly modified PW1100Gs are fitted following their delivery from Pratt at the end of June.  “We will get two retrofitted engines to Airbus at the end of this month and two more in the first week of July,” says Pratt Commercial Engines president Greg Gernhardt.

Issues with the loose component were discovered shortly after the first test A320neo, MSN6101, suffered a bird strike on take-off from Toulouse on April 30. Despite the lengthy interruption to the certification program Airbus says the A320neo will still make its service debut later this year.

The component at the heart of the issue resembles a piston ring, measures 10 in. in diameter and is 2/10th of an in. wide. The part “was not made to correct specifications,” says Gernhardt. “We missed the stress relief during manufacture, and when such a part is at operating temperature the part relieves and falls out of the retaining ring groove.” Adding to the complication was the fact the ring is located by the combustor section.  “So you have to tear into the core, which does take some time,” he adds.

“We have two engines in Toulouse with the current snap ring design and it was jointly decided it doesn’t make sense to fly with those. Those snap rings are still in the groove. So certification testing will resume this week and we can start getting back to ticking off the certification requirements,” Gernhardt says.

“We have pulled two engines back from Toulouse and we are in the process of retrofitting those engines, we have parts available. We have changed the designs slightly, even though we didn’t need to, as all we had to do was make sure it was properly heat treated.  But since we are going in there we have added some positive retention, which is basically a couple of bolts to hold it in place,” says Gernhardt.

Testing will begin again with two weeks of rejected take-offs, high speed taxiing and other higher energy ground maneuvers. “It actually works out well. We shall give ourselves two weeks of ground testing and by the time we’ve done that the retrofitted engines will be available. So it has worked out given the circumstances,” he adds.

Up until the time of the grounding the PW1100G-powered A320s had amassed just over 130 hr. of test-flight time.