Boeing 737 Airplanes with Collins Aerospace SVO-730 Rudder Rollout Guidance Actuators - NTSB URGENT

 

The National Transportation Safety Board (NTSB) is providing the following information to urge The Boeing Company and the Federal Aviation Administration (FAA) to take immediate action on the safety recommendations in this report concerning the potential for a jammed or restricted rudder control system on certain Boeing 737 airplanes. We identified these issues during our ongoing investigation of the rudder pedal anomaly involving a Boeing 737-8, N47280, while landing at Newark Liberty International Airport (EWR), Newark, New Jersey, on February 6, 2024.

 Federal Aviation Administration:

  Determine whether Collins Aerospace SVO-730 rudder rollout guidance actuators with incorrectly assembled bearings should be removed from Boeing 737NG and 737MAX airplanes and, if so, direct US operators to remove the actuators until acceptable replacement actuators become available for installation. (A-24-29) (Urgent)

If you determine the Collins Aerospace SVO-730 rudder rollout guidance actuators with incorrectly assembled bearings should be removed, notify international regulators that oversee operators of Boeing 737 airplanes about the safety issues involving the SVO-730 rudder rollout guidance actuator and encourage them to require the removal of actuators with incorrectly assembled bearings from 737NG and 737MAX airplanes until an acceptable replacement actuator becomes available for installation. (A-24-30) (Urgent)

 September 26, 2024

Aviation Investigation Report AIR-24-06

 Background and Analysis

On February 6, 2024, about 1555 eastern standard time, the flight crew of United Airlines flight 1539, a Boeing 737-8, N47280, experienced a rudder pedal.

 anomaly while landing at EWR.1 In a postincident statement, the captain reported that, during the landing rollout, the rudder pedals were “stuck” in their neutral position and did not move in response to the “normal” application of foot pressure to maintain alignment with the runway centerline.2 The flight was operating under the provisions of Title 14 Code of Federal Regulations Part 121 as a scheduled international passenger flight from Lynden Pindling International Airport, Nassau, Bahamas, to EWR.3

According to data derived from the flight data recorder, the flight crew applied approximately 32 pounds of force to the rudder pedals before touchdown which yielded no discernible effect on the rudder position or heading.4 The flight crew attempted to clear the jammed rudder controls immediately after touchdown, applying approximately 75 pounds of force to the rudder pedals when the airspeed was about 120 knots, again with no effect on the rudder position or heading.

With the airplane’s airspeed continuing to decrease during rollout, the flight crew applied approximately 42 pounds of force to the pedals, but the jam persisted. The captain elected instead to use the nosewheel steering tiller as the airplane slowed to a safe taxi speed. The captain stated that, after the airplane entered the assigned taxiway, he asked the first officer to check the rudder pedals on his side of the flight deck, and the first officer indicated that the same anomaly was occurring.

Data derived from the flight data recorder indicate that shortly after, with the airplane traveling at a groundspeed of less than 20 knots, the flight crew applied approximately 59 pounds of force on the rudder pedals, and the rudder pedals and rudder surface began to operate normally. The airplane taxied to the gate without further incident, and all airplane occupants (2 flight crewmembers, 4 cabin crewmembers, and 155 passengers) deplaned without any injuries or damage to the airplane.

United Airlines received the incident airplane from Boeing on February 20, 2023. The airplane was equipped with a Collins Aerospace SVO-730 rudder rollout guidance actuator, which was electrically disabled based on the operator’s delivery requirements for the autoflight system.5 Although the actuator was disabled, it remained mechanically connected to the upper portion of the airplane’s aft rudder input torque tube by the actuator’s output crank arm and a pushrod, as shown in figure 1.

 The Collins SVO-730 rudder rollout guidance actuator is installed only on Boeing 737NG and 737MAX airplanes equipped for category IIIB operations. (The incident 737-8 was a MAX variant.) United Airlines does not require category IIIB capability for its Boeing 737 fleet. According to FAA Advisory Circular 120-28D, category IIIB operations involve a precision instrument approach and landing with no decision height and a runway visual range less than 700 ft but not less than 150 ft.

6 Pilot control of the Boeing 737-8 rudder is transmitted in a closed-loop system from the pilots’ rudder pedals in the cockpit, through a single cable system, an aft rudder quadrant, and a pedal force transducer, to the aft rudder input torque tube in the vertical stabilizer. Rotation of the torque tube provides the command inputs to the main and standby rudder power control units to move the rudder surface.