The start of certification tests of the Boeing 777-9 remains on hold after the FAA declined the manufacturer’s request for Type Inspection Authorization (TIA), citing concerns over unresolved software and hardware issues.
The move is another blow for Boeing’s long-delayed 777X as TIA marks the milestone when flight tests begin to earn credit towards certification. The FAA issues TIA when its examination of the data required for type certification is completed, or if it has reached a point where it appears that the aircraft will meet the applicable regulations.
Neither of these conditions have been met, according to the regulator. In a May 13 letter to Boeing made public by The Seattle Times, the FAA aircraft certification service aviation safety manager Ian Won said “the aircraft is not yet ready for TIA, even if it is a phased TIA of limited scope with a small number of certification flight test plans proposed.”
Won added the “technical data required for type certification has not yet reached a point where it appears the aircraft type design is mature and can be expected to meet the applicable regulations.”
Boeing declined to comment on the specific issues raised by the FAA. The airframer said it is “fully focused on safety as our highest priority throughout 777X development. As we subject the airplane to a comprehensive test program to demonstrate its safety and reliability, we are working through a rigorous development process to ensure we meet all applicable requirements. We continue to communicate transparently with the FAA and other global regulators about 777-9 certification.”
In all previous Boeing commercial aircraft programs TIA approval has traditionally come within weeks or months of first flight, starting the clock ticking towards the formal completion of type certification or amended type certification in the case of major derivatives. Even the troubled 787 was granted initial TIA within three months of its first flight in December 2009, and full TIA within five.
Despite anticipating heavy regulatory scrutiny in the wake of the 737 MAX accidents, Boeing was initially confident its revised engineering and safety oversight structure would clear the way for TIA approval early in 2021. However, following calls from EASA for modifications to the flight control system and a newly disclosed un-commanded pitch event during a flight on Dec. 8, 2020, Boeing conceded certification would take longer than expected. In January 2021 it announced first deliveries would be delayed until the end of 2023.
Although the $6.5 billion program charge and the 12 to 16-month additional development time was a surprise when revealed in January, the magnitude of the extra cost and delay can now be explained by the issues disclosed by the FAA. Chief issues concern the maturity of the GE Aviation-developed common core system (CCS) avionics; inadequate data to support aircraft level development and safety assessments; and late-running flight control software updates.
Based on a similar system developed for the 787, the 777-9 CCS is an integrated modular architecture that consolidates computing functions for several avionics and utility systems. However, despite years of ground testing and—at the time of the FAA’s letter—15 months of flight testing since the aircraft’s January 2020 first flight, the agency said Boeing had yet to complete the Design Assurance Review for the FAA to conduct compliance findings. Without this, “it is difficult for the FAA to determine if the system is mature and will provide only uncorrupted data for FAA certification testing.”
The letter also raises the specter of potential safety issues with the CCS, despite the good safety record of the closely related 787 system. It says “incorrect reuse of 787 data was noted by the FAA in Boeing’s CCS engineering safety assessment. The assessment also stated that the data is not yet mature enough to show compliance [and] lists many open problem reports against safety documentation, assessments and requirements.”
In addition, the FAA also noted that although Boeing completed a root cause investigation into the un-commanded pitch event, the agency has yet to see “how Boeing fully implements all the corrective actions.” It added that Boeing is expected to “implement a robust process so similar escape (sic) will not happen in the future and this is a not a systematic issue.”
Another factor is the EASA-driven changes to the flight control system actuator controls electronics. The FAA said EASA “has not yet agreed on a way forward on the Model 777-9. The FAA’s concern is due to the addition of late changes. Boeing needs to ensure the changes do not introduce new, inadvertent failure modes.”
According to the FAA, other aspects of the aircraft’s design and certification basis also remain in flux, despite the long-running development effort. “Design maturity is in question as design changes are on-going and potentially significant,” said Won in the letter. Examples of late changes include modifications to the stabilizer design/architecture associated with the removal of the “green band” range of the horizontal stabilizer trim indicator. The green band denotes the take-off trim range and in previous Boeing aircraft sounds a horn if take-off is attempted with the stabilizer trim outside of this range.
Other ongoing design changes cited by the FAA include several modifications to indications and flight deck alerts related to flight control module failures; loss of airspeed protection; failure in flight director-only mode and a variety of other situations.
The FAA said if it issued the TIA prematurely, Boeing would likely have to conduct a significant amount of software regression testing, change impact analysis and add extra certification flight tests. “The additional activity will require the FAA to expend additional resources to review the changes and may reduce our resources to support other certification programs/activities, potentially with a higher priority,” the letter said.
It also stated that—based on Boeing information—the 777-9 amended type certification date “is realistically going to be mid to late 2023.” Boeing said this is consistent with its existing delivery guidance and that it remains on track to begin handing over the first 777-9s in the fourth quarter that year. The airframer also said the extended certification schedule is in line with the message delivered by company CEO Dave Calhoun at the June 3 Bernstein Strategic Decisions Conference.
Commenting at that event Calhoun said: “We are still confident [the 777-9] will be certified in the fourth quarter of 2023.” He added “we don’t have a load of technical glitches and we don’t have a battery issue. We don’t have that kind of stuff because we’ve been flying [and] doing the things that we’ve been doing. I like the status [and] I like the progress we’re making against the certification. We will be subject to FAA’s timeline and we will not question it.”
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