The Federal Aviation Administration intends to require airlines to update Boeing 777 software because a previous software update introduced a problem with the jet’s auto-throttle system.
Boeing made that previous update in response to the 2013 crash of an Asiana 777-200ER during landing at San Francisco, the FAA says in a proposed airworthiness directive (AD) released on 22 June.
That previous software update “inadvertently introduced the failure of the [auto-throttle] to disconnect after manual throttle advancement during go-around”, the AD says.
The FAA seeks to require US airlines to update 777s with a new version of the type’s Airplane Information Management Block Point software. The latest update also addresses a separate issue involving failure of the 777’s “wing anti-ice valve”, the FAA says.
The agency’s proposal would apply to 353 US-registered 777s, including 777-200 and 777-300 variants.
Boeing did not immediately respond to a request for comment.
The airframer already developed the software update and issued a related service bulletin in July 2021. The FAA proposes to mandate that update.
The FAA says several issues prompted its action. It notes that a review of fleet data revealed 50 instances between November 2013 and March 2019 of a wing anti-ice valve failing to open. Such failures allow hot bleed air to damage wing slats, the FAA says. The updated software monitors the valve’s function.
The update also addresses the auto-throttle problem, which became known after a troubling 777 incident. During landing, a pilot initiated a go-around while the auto-throttle was at the idle setting.
With the throttles advanced, the auto-throttle should have disengaged, but did not. Instead, it returned the throttles to idle, “causing a low-speed condition during the go-around”, the FAA’s proposal says.
The document notes that the problem is inherent in version 17B of the Airplane Information Management system.
Boeing developed that version in response to the 6 July 2013 crash at San Francisco of the Asiana jet, which led to three fatalities.
Investigators attributed that accident partly to the 777 having “insufficient low-speed protection”, the FAA notes.
That software update “inadvertently introduced the failure of the [auto-throttle] to disconnect after manual throttle advancement during go-around”, the FAA’s document says.
Boeing’s latest update addresses the issue, the FAAs says.