The Federal Aviation Administration (FAA) has ordered inspections of the Gulfstream G500 and G600 fleet in response to a “quality escape” involving improperly installed engine-mounting hardware.

In a 7 June airworthiness directive, the agency says it identified issues with Gulfstream’s installation of engines on new production aircraft and with aftermarket engine installations.

The FAA says aircraft have been found with separated engine-mount fasteners. Its order gives operators 30 days to complete the inspections.

Gulfstream G500 G600

Source: Gulfstream

The order applies to 247 US-registered G500s and G600s

“An FAA investigation discovered numerous discrepancies in the production-engine installation procedures, along with similar discrepancies in the AMM [aircraft maintenance manual] procedures for installing engines” on in-service jets, says the regulator.

The discrepancies included “missing hardware call-outs in the engine attachment instruction text, engine attachment hardware not shown in the AMM graphics, and inconsistencies in AMM image view labelling”.

“Failure of any single engine mount, if not addressed, could result in the separation of an engine from the airplane,” the order says.

Gulfstream did not respond to a request for comment.

The order bypasses the FAA’s typical process for issuing airworthiness directives, which involves collecting public comments before finalising rules. Instead, it made the rule effective immediately and will retrospectively accept comments, a process the regulator can use to address more urgent matters.

The problem became known on 31 January. when pilots of a G600 “noticed a visible misalignment in the pylon area adjacent to the thrust reverser”, says the FAA.

An inspection revealed that a cotter pin had not been installed and that a bolt and nut intended to secure a strut had separated, leaving the strut secured only by a pin. “Migration of the hollow pin out of position was imminent, which would have resulted in the disconnection of the strut from the airplane.”

Gulfstream attributed that event to technicians at a repair station improperly installing fasteners during a previous engine removal and installation. It soon determined that other GVIIs – the model number for G500s and G600s – had “non-conforming” engine-mount hardware.

The company in February sought to address the problem by issuing service bulletins calling on operators to inspect jets within 12 months. It also released revised engine removal and installation procedures.

But subsequent investigations determined that the problem was not limited to aftermarket engine work, but instead “could have originated during production”, the FAA says.

“Some of the non-conformances were found on engines installed in production. This indicates quality escapes exist in both production-engine installation and in-service installation using the AMM procedures.”

The FAA notes that its order applies to 247 US-registered G500s and G600s, including aircraft “that both have and have not had engines replaced since production”.