Another Safety Issue for the 737 MAX

The FAA issued a proposed Airworthiness Directive for the beleaguered 737 MAX program today, not the type of Valentine’s day message Boeing or their customers like to receive. The problem identified was prompted by a Boeing review of the standby power system control unit (SPCU) design that identified a single point of failure.

If not addressed, that unsafe condition could result in the loss of thrust on both engines due to damage from operation in icing conditions without engine anti-ice and “can result in the loss of continued safe flight or landing,” or in plain English, the aircraft could crash.

Boeing

issued a Boeing Alert Requirements Bulletin on November 18, 2022. That bulletin specifies procedures for the installation of four diodes and changing wire bundles in the P5 panel. It also specifies performing an anti-ice diode installation test and an engine anti-ice and wing anti-ice power test and applicable on-condition actions. On-condition actions include doing applicable corrective actions until the tests are passed. The Proposed AD would mandate accomplishing the actions specified in the Boeing Alert Requirements Bulletin, which is optional at the discretion of the airline.

Given the potential dire circumstances that could result from a single point of failure situation, we wonder why the FAA has waited until February 2024 to begin to address an issue that was known in November 2022? The required fix will not impact the entire fleet, but would impact 205 US registered airplanes, and additional aircraft internationally.

This is a different issue involving the engine anti-ice system on the MAX, which could inadvertently be left on and weaken the composite engine inlet. In the event of an un-contained engine failure, the weakened shroud may not hold engine parts, which could penetrate the fuselage and result in a decompression situation.

As the MAX aircraft has no crew alerting system, a message that the engine anti-ice is on is not available, leaving this as another requirement for pilots to monitor. Boeing was issued a waiver for this requirement for the MAX 8 and MAX 9, but has pulled its waiver request for the MAX 7, likely delaying its certification to 2025 at the earliest.

Bottom Line:

More bad news for the 737 MAX program is not what Boeing needs after the MAX 9 incident in early January. While all safety of flight issues need to be addressed, the timing of this announcement, given that Boeing identified the problem and the fix in 2022, needs questioning. If there is a potential safety problem with a single point of failure that could lead to a crash, why has the FAA waited 14 months to propose an action that will not be implemented on an emergency basis?

Safety relies on the entire industry, including manufacturers, airlines, and regulators. In this case, Boeing discovered the problem and took corrective actions. Is the FAA response too slow and risking the safety of the flying public? Was their initial regulatory failure on the MCAS system an isolated event, or a is a pattern emerging. Congressional hearings with the head of the FAA will likely provide additional clarity in the coming months.