Regulators Issue ADs for Gulfstream’s G650, G500 and G600

Both the FAA and the European Union Aviation Safety Agency (EASA) recently issued airworthiness directives to operators of Gulfstream’s fly-by-wire aircraft, with an additional warning of potential applicability to the company’s G500/ G600 fleet. The initial ADs were issued against the G650/G650ER, G500 and G600 fleet regarding continued flight after a flight control surface shutdown. Subsequently, Gulfstream also identified the potential for a hard landing following an in-service incident in unstable air on the G500 and immediately notified all G500 and G600 operators of the potential safety issue as well as published operational guidance to mitigate the hazard.

In February 2020, the FAA published [AD 2020-02-18] that revises the airplane flight manual on the G650/G650ER and the G500/G600 series that “was prompted by reports of continued flight after a flight control surface shutdown. If flight is continued after a flight control surface shutdown, the airplane is left without protection against flight control surface hard-over and force fight events on the remaining, operable flight control surfaces.” The FAA said it had received 30 reports of the G650/G650ER flight control computer commanding flight control surfaces into a damped by-pass mode (surface shutdown). This AD mandated the incorporation of revised procedures governing continued flight operations following a surface shutdown event.

Then, in March 2020, the FAA issued another [AD 2020-05-12] on the G500/G600 series that required revising the airplane flight manual (AFM) to incorporate revised limitations and procedures. This AD was prompted “by a report of a landing incident where the alpha limiter engaged in the landing flare in unstable air while on the approach, resulting in a high rate of descent landing and damage to the airplane.” On March 30, 2020, EASA issued an emergency airworthiness directive [2020-0075-E] for the G500 essentially reprising the early March AD by the FAA. EASA detailed the situation “in which the [Gulfstream’s] alpha limiter (based on angle of attack indicator) engaged in the landing flare in unstable air while on approach. Analysis indicates that this may occur on other aeroplanes. This condition, if not corrected, could limit pilot pitch authority during a critical phase of flight near the ground, possibly resulting in a high-rate-of-descent landing and consequent loss of control of the aeroplane on landing.”

Gulfstream said, “the precipitating event for AD 05-12 came after a G500 operator communicated to us that they had a hard landing event following a circling approach in gusty wind conditions. Working closely with the FAA, EASA and the customer, Gulfstream discovered the Angle of Attack (AOA) limiting feature activated and contributed to the hard landing. Gulfstream also noted that published AFM guidance against making large, rapidly alternating pitch commands and maintaining a proper speed additive during the approach was not followed. Because of these items, Gulfstream released a revision to the G500 and G600 flight manuals to provide updated operational guidance and procedures, focused on maintaining the appropriate speed additives throughout the approach and landing. The AFM revision also includes a temporary 22 kt. crosswind limitation that will be removed once the flight control software is updated later this year.”

EASA offered no reason for why the European community categorized the Gulfstream AD as an emergency, when the FAA did not suggest a similar state of urgency. A Gulfstream spokesman told Flying, “The distinction is one of terminology. The emergency AD process followed by EASA is equivalent to the immediately adopted AD process the FAA used. Both allow the regulator to bypass the public comment period and publish more quickly.”

Editor’s note: This story was updated at 7:45 p.m on Friday, April 10th to reflect new information from Gulfstream.