The US Federal Aviation Administration is pushing back on a request by Boeing for a temporary exemption from a safety regulation to allow the GE Aviation-powered version version of the 787-10 to enter service on schedule in August.

The GEnx-1B engine has a software bug that in one instance prompted the computer to shut down the engine during a step climb to a higher altitude in ice crystal icing conditions.

GE is working to fix the software bug, but the GEnx-1B-powered version of the 787-10 cannot obtain an airworthiness certificate without an exemption until it is ready.

On 4 March, Boeing applied to the FAA to approve an exemption that would keep the delivery of the first 787-10 with GE engines on schedule for later this summer.

In a letter responding to Boeing dated 1 June, the FAA asks Boeing to back-up its reasons for requesting an exemption.

For example, Boeing said on 4 March that GE’s fix for the shutdown problem is included in a broad software update called “B200”, and it’s not scheduled for delivery until December 2019. But GE has told FlightGlobal and the FAA that the B200 software update will be ready by the first quarter of 2019.

“What justification does Boeing provide for delivering airplanes under an exemption until December 20, 2019?” the FAA asks in the latter.

The FAA also notes that Boeing says that there will be no adverse impact on safety during the exemption period, due to the small chance that the automatic engine restart function won’t work as designed if the software bug causes an engine shutdown.

“Please provide a description of the assumptions and probabilities incorporated in the system safety assessment that determined the risk to be less than extremely improbable,” the FAA says.

The FAA also wants Boeing to back-up its assertion in the application that delaying the overall B200 software update to roll out a fix for the shutdown problem sooner would cause more harm to the public than benefit.

“Please provide a description of the … software changes planned for the version B200 software and how the public as a whole will be benefitted by these changes,” the FAA writes.

Boeing’s responses to the FAA are due by 30 June.

The Rolls-Royce Trent 1000-TEN-powered version of the 787-10 entered service in March with Singapore Airlines.

Source: Cirium Dashboard