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This issue has resulted in unintended rolls during flight
and poses a risk of pilots losing control of the aircraft.
FAA: 737 MAX Spoilers Issues
The FAA’s issuance of this airworthiness directive was
prompted by a report detailing “a non-conforming installation of spoiler wire
bundles that led to unintended spoiler motion, including one instance of
spoiler hardover.”
Spoilers, which are panels mounted on wings, disrupt airflow
over the wings when extended, causing increased drag and reduced lift. If a
spoiler experiences a ‘hardover,’ it has reached its maximum limit and becomes
effectively jammed.
The FAA has received reports of “multiple instances of
unusual spoiler deployments, resulting in an uncommanded roll to the right”
during the cruise phase of flight.
The FAA investigation has highlighted the potential for a
hardover of more than one flight spoiler on the same wing, exceeding full
lateral control capability and leading to a loss of control of the airplane.
In the reported cases, the aircraft’s “spoilers” warning
light illuminated, and the spoiler control electronics issued a spoiler fault
code. The FAA noted that the fault was intermittent and occurred on multiple
flights.
The root cause was identified as “wire chafing damage
resulting from spoiler control wire bundles riding on the landing gear beam rib
in the right wing trailing edge due to non-conforming installation of spoiler
wire bundles during production.”
Service Bulletin (SBs) Addressed this Issue
The FAA has initiated a notice of proposed rule-making,
asserting that the “unsafe condition…is likely to exist or develop on other
products of the same type design.”
On July 14, 2023, Boeing issued an alert bulletin addressing
this concern. The bulletin is a notification to operators and maintenance
organizations about necessary inspections and repairs. It outlines procedures
for measuring the clearance of spoiler control wire bundles and provides
instructions on ensuring adequate clearance when a fault is identified.
The FAA’s proposed airworthiness directive (AD) would
mandate the completion of tasks specified in Boeing’s alert bulletin to rectify
the identified “unsafe condition” on Boeing’s 737–8, 737–9, and 737–8200 MAX
planes.
In its advisory bulletin, the FAA acknowledges the inability
to determine the exact number of aircraft requiring these repairs. The
estimated costs for inspection are $85, and repairs are anticipated to be $425.
Furthermore, the FAA has requested Boeing to rectify a
design flaw in the 737 MAX that could compromise the aircraft’s anti-ice
system, potentially resulting in a “loss of thrust on both engines.”
Additionally, Boeing is mandated to resolve a distinct de-icing issue affecting
Boeing Model 787–8, 787–9, and 787–10 Dreamliner airplanes currently in
service.