January 12, 2024, ©. Leeham News: We are discussing the different phases of a new airliner program. After covering the Design and Production, we now look at the Operational phase of a new airliner family.
For the operational phase, the airplane must pass scrutiny for Continued Airworthiness. Today, we discuss the different means available to the Regulator, such as Airworthiness Directives ( ADs) and System Bulletins (SBs) to the OEM to make sure any detected issues get noticed and corrected.
During its operational life (which is around 25 years compared to the two years in production), there is regulatory oversight and certification of all aspects of the operation of the aircraft. We have a fresh example from last week with the Airworthiness Directive that the FAA issued for the Boeing 737 MAX 9.
A possible manufacturing lapse to ensure four stop bolts were fitted had the rear plug door on the lefthand side of an Alaska 737 come loose and leave the aircraft during climb-out from Portland International Airport.
The FAA issued an Emergency AD number 2024-2-51 on the 6th of January (Figure 1) to ground all US MAX 9s until inspections have verified they are safe to fly.
The Emergency AD is the highest form of escalation in the Safety Monitoring and Reporting (14 CFR 21.3, 14 CFR Part 39) part of the FAA regulations. The different levels of actions demanded of the operator by the OEM and the Regulator are summarized in Figure 2.
The Airline, OEM, and the Regulator are obliged to continuosly monitor the delivered product in its operation. Depending on the safety risk, different actions are initiated if an issue is suspected or detected:
As can be seen, the certification of an aircraft is the approval of the design. The production certificate is an approval that if the production is done according to the design certificate and with methods and procedures as stipulated in the production certificate, it’s considered safe for use when delivered.
But from the instance of delivery, the airplane is subject to the above monitoring and can at any time receive an SB and AD that require further action to keep the aircraft certified as safe to fly.
Part of the actions to keep the aircraft safe to fly is acted upon during maintenance. Many SBs and ADs are structured so these can be executed at the next hangar maintenance of the aircraft. We look deeper into the maintenance part of Continued Airworthiness in coming Corners.