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.

VOEPASS 2283 [PASSAREDO CALLSIGN] PRELIMINARY REPORT - LOSS OF CONTROL IN-FLIGHT (LOC-I)

 

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SOURCE: CENIPA

LOC-I LOSS OF CONTROL IN-FLIGHT

Date: 9 August 2024

(UTC): 9 August 2024

Time: 16:22

City: VINHEDO - SÄO PAULO - BRASIL

Aerodrome: OUTSIDE THE AERODROME

Local: RESIDENTIAL AREA OF THE CITY

Damage to third

parties: YES

Injuries Function on Board Quantity

FATAL CREW 4

FATAL PASSENGERS 58

 

History

 

At 14:58 UTC, the aircraft took off from SBCA (Coronel Adalberto Mendes da Silva Airport, Cascavel, State of Paraná), bound for SBGR (Guarulhos - Governador André Franco Montoro - Airport, Guarulhos, State Of SOO Paulo) on a public regular passenger transport flight with 04 crew and 58 passengers on board. With the aircraft flying along the route, and after encountering icing conditions, control Of the aircraft was lost and it crashed into the ground.

 

Aircraft Involved

Registration marks: PSVPB

Location of latest takeoff: SBCA - ADALBERTO MENDES DA SILVA

Location of intended landing: SBGR - GOVERNADOR ANDRÉ FRANCO MONTORO

Type of operation: REGULAR

Phase of flight: CRUISE

Aircraft damage: DESTROYED

 

Sequence of events

Based on the information collected at the initial field Investigation, as well as recordings from the Flight Data Recorder (FDR) and Cockpit Voice Recorder (CVR), the Investigation Committee identified the sequence of events preceding the aircraft's collision with the ground. The time reference utilized is UTC (Universal Time Coordinated).

• 14:58:05 - the aircraft initiated takeoff from the runway 15 of SBCA, with 58 passengers and 04 crew on board;

• - the PROPELLER ANTI-ICING 1 and 2 were turned on;

• 15:14:56 - the Electronic Ice Detector connected to the Centralized Crew Alert System (CCAS) emitted an alert signal upon passing FL130;

• - the AIRFRAME DE-ICING was turned on;

• 15:15:42 - a single chime was heard in the cockpit. Subsequently, the crew commented on the occurrence of an AIRFRAME DE-ICING Fault, and that they would turn it Off;

• 151549 - the AIRFRAME DE-ICING was turned off,

- the Electronic Ice Detector ceased emitting the alert signal.

• 1516125

• 1517:08

- the Electronic Ice Detector emitted an alert signal.

- the Electronic Ice Detector stopped emitting the alert signal;

- the Electronic Ice Detector emitted an alert signal;

- the Electronic Ice Detector stopped emitting the alert signal.

- the Electronic Ice Detector emitted an alert signal;

- the Electronic Ice Detector stopped emitting the alert signal;

- the Electronic Ice Detector emitted an alert signal;

- the SIC (pilot Second in Command) made radio contact with the airline's operational dispatcher at

Guarulhos airport, for coordination of the aircraft arrival;

• - At the same time of the SIC's coordination with the operational dispatcher, a flight attendant called

over the intercom. The SIC asked her to hold on moment and continued speaking with the dispatcher,

• - the Electronic Ice Detector stopped emitting the alert signal. At this time, the SIC was asking the

flight attendant for information that would be passed to the operational dispatcher;

• 16:17:32 - the Electronic Ice Detector emitted an alert signal; at this time, the PIC was informing the passengers about the SBGR local conditions and estimated time of landing,

• 16:17:41- the AIRFRAME DE-ICING was turned on;

• 16:18:41 - at a speed of 191 kt., the CRUISE SPEED LOW alert was triggered. Concomitantly, the SIC was about to finish relaying some information to the operational dispatcher;

• 16:18:47 - the PIC started the briefing relative to the approach for landing in SBGR. Concomitantly, APP-SP made a radio call, and instructed him to change to frequency 123.25MHz;

• 16:18:55 — a single chime was heard in the cockpit. At this time, the communication with APP-SP was taking place;

• - the AIRFRAME DE-ICING was turned off;

• 16:19:16 - the crew made a call to APP-SP (Sao Paulo Approach Control) on the frequency 123.25 MHz;

• 16:19:19 - APP-SP requested the PS-VPB aircraft to maintain FL170 due to traffic;

• 16:19:23 - the crew replied to APP-SP that they would maintain flight level and that they were at the ideal point of descent, waiting for clearance;

• 16:19:28 - at a speed of 184 kt., the DEGRADED PERFORMANCE alert was triggered, together with a single chime. The alert was triggered concomitantly with the exchange of messages between APP-SP and the Crew;

• - APP-SP acknowledged the message and requested the aircraft to wait for clearance;

• 16:19:31 - Passaredo 2283 aircraft reported receipt of the message and thanked ATC;

• - the PIC resumed delivering the approach briefing;

• - the Second in Command (SIC) commented, "a lot of icing";

• - the AIRFRAME DE-ICING was turned on for the third time;

• - APP-SP cleared the aircraft to fly direct to SANPA position, maintaining FL170, and informed that the descent would be authorized in two minutes;

• 16:20:39 - the crew acknowledged the flight instruction received (last communication performed by the flight crew);

• - the aircraft started a right turn in order to fly to SANPA position.

• 16:20:57 — during the turn, at a speed of 169 the INCREASE SPEED alert was triggered, in conjunction with a single chime. Immediately afterwards, vibration noise was heard in the aircraft, simultaneously with the activation of the stall alert;

• 16:21:09 - control of the aircraft was lost, and it entered an abnormal flight attitude until colliding with the ground. The aircraft rolled to the left to a bank-angle of 52 degrees, and then rolled to the right to a bank- angle of 94 degrees, performing a 180-degree turn in a clockwise direction. Subsequently, the turn was reversed to an anticlockwise direction, with the aircraft completing five full rotations in a flat spin before crashing into the ground.

Click on image to see it isolated

The ICING light would blink with the detection of an Icing condition and the Anti-Icing and/or De-lcing  (AIFRAME) were not selected to ON, followed by single chime. The light would remain illuminated in a continuous fashion with the systems turned on.

 

Anti-Icing and De-Icing Systems

 

The Anti-lcing functions were energized electrically, whereas the De-icing ones were provided by means of pneumatic pressure.

 

The APM system needed to be checked by the crew on a daily basis, and in case of a failure, an amber-colored FAULT message would illuminate on the APM panel.

If the aircraft's drag increased due to ice accumulation and performance was degraded, resulting in loss of cruise speed, alerts in three levels were triggered and presented to the pilots on both alert panels Of the APM, as follows:

• 1st Level - CRUISE SPEED LOW

The blue-colored message would indicate performance degradation Of around 10%, with reduction Of the Indicated Air Speed (IAS) during the cruise phase by at least 10 kt. below the speed computed by the APM.

This alert would be triggered only during the cruise phase.

• 2nd Level - DEGRADED PERFORMANCE

The amber-colored message would be followed by a single chime and a master caution alert, indicating a significant performance degradation in the range between 22% and 28%, induced by a significant increase in aerodynamic drag, causing a drop in cruise IAS of around 15 to 20 knots below the speed computed by the APM. This alert could be triggered during climb, cruise, Or descent.

• 3rd Level - INCREASE SPEED.

The amber-colored message would appear flashing, followed by a single chime and a master caution alert, indicating that the degraded performance condition had worsened , reaching an IAS value below the ICING BUG + 10 kt. This alert could be triggered during climb, cruise, or descent.

 

The pilot has set the ICING BUG SPEED for SEVERE ICING CONDITION to 165 Knots.

In addition to the speed alerts (emitted by the APM), the airspeed indicators of the left- and right-hand cockpit stations had BUGS for reference, particularly for minimum speed maneuvers at low bank, flaps O', and icing conditions (VMLBO ICING), The said BUGS could be adjusted manually.

 

The ICING BUG needed to be adjusted by the pilots for each flight in accordance with the aircraft's weight, in order to indicate the minimum speed for a flight in icing conditions and with flaps retracted. The VMLBO ICING.