The Aviation regulator of the United States of America, Federal Aviation Administration (FAA) has said that an operator of a B737 Max plane found loose bolts in a rudder control system, and they are adopting a new Airworthiness Directive (AD) on this.
In its release, FAA said,
The FAA is adopting a new airworthiness directive (AD) for certain The Boeing Company (Boeing) Model 737-8, 737-8200, and 737-9 airplanes. This AD was prompted by a report of a missing washer and nut and consequent migrated bolt discovered by an operator during scheduled maintenance. This AD requires a one-time inspection of the aft rudder quadrant and applicable on-condition actions. The FAA is issuing this AD to address the unsafe condition on these products.
The FAA said it received a report about a missing nut, washer and “migrated” bolt in the system from an operator in December of last year.
It said Boeing then inspected all 737 Max 8, 737 Max 8-200, and 737 Max 9 planes in production and turned up another “under-torqued nut at the same location.”
Boeing subsequently inspected all Model 737-8, -8200, and -9 airplanes in production and found one additional under-torqued nut at the same location. It was discovered that the required run-on and final torques had not been applied to the nut in production.
The FAA is issuing this AD to address improper torque of the aft rudder quadrant output rod fasteners, which may cause a disconnect between the aft rudder quadrant and the output rod, which would result in loss of rudder control via the rudder pedals to counter an engine-out scenario during takeoff/climb out or to counter a high crosswind during landing.
The disconnect between the aft rudder quadrant and the output rod (due to the bolt falling out) would result in loss of rudder control via the rudder pedals. In that scenario, Rudder surface position would then be based only on the rudder trim and yaw damper systems.
The pilots would be able to slowly move the rudder surface by adjusting the rudder trim position but would be limited by the maximum rudder trim authority. In the event of a disconnect, and with the limited rudder trim authority, there would not be enough rudder control to counter an engine-out scenario during takeoff/climb out or to counter a high crosswind (above 20 kts) during landing. This condition, if not addressed, could result in the loss of continued safe flight and landing.
The FAA said to have reviewed the Boeing Multi Operator Message MOM-MOM-23-0993-01B, dated December 27, 2023. The service information specifies performing a one-time detailed visual inspection or remote video inspection of the aft rudder quadrant for any missing bolt, nut, or washer; any gap between the bolt/nut/washer and quadrant; and insufficient thread protrusion.
The FAA, meanwhile, said in a statement Thursday that inspections recommended by Boeing in December had been completed by all U.S. airlines in early January.
“The FAA carefully reviewed the inspection results, which found no missing or loose rudder bolts,” the FAA said.
The service information also specifies the following corrective actions if necessary: inspection of the bolt and nut for damage and replacement as needed; torque application; and a rudder travel test.
An airworthiness directive from the FAA that will require “a one-time inspection” of the system in which the loose bolts were discovered for certain Max airplanes is being published.
Within 30 days after the effective date of this AD, perform a one-time detailed visual inspection or remote video inspection of the aft rudder quadrant for missing bolts, nuts, and washers; a gap between the bolt/nut/washer and quadrant; and insufficient thread protrusion.
If any discrepancy is found during the inspection as above, operators need to carry out a detailed inspection of the bolt, washer, and nut for damage and, before further flight, replace any missing or damaged bolts, washers, and nuts.
After the detailed inspection ,operators to install each bolt, washer, and nut with a torque of 65 in-lb and perform a rudder travel test to ensure that the rudder is operating correctly. If the test fails, before further flight, corrective actions and repeat test to be done, until passed.
The latest directive is being published after last month’s incident in which a decompression and emergency landing occurred on an Alaska Airlines B737 Max 9 flight from Portland to Ontario, Calif., when a door plug blew off mid-flight.
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