Over the past few weeks, there has been a lot of focus on the rudder and its contribution to loss of control in-flight (LOC-I) accidents.

The month of April began with an article entitled “Use of Rudder” in Safety First, the Airbus Safety magazine, that issues a stern warning to pilots: “The use of rudder by the flight crew on Airbus aircraft is limited to the takeoff and landing roll, crosswind landings, or to counteract the yaw effect caused by an engine failure until the rudder is trimmed.”

According to the manufacturer, “Several events have been reported where the flight crew used rudder inputs after encountering turbulence, causing unnecessary trajectory deviations and loads on the aircraft structure.”

Next, aircraft upset prevention and recovery training (UPRT) specialist Aviation Performance Solutions released “The Rudder—Critical, Powerful, and Often Misunderstood” on YouTube. In this video, APS CEO Paul “B.J.” Ransbury reviews several case studies where the rudder contributed to loss of control or near loss of control events. “These events, mechanical, uncommanded, and pilot-induced,” according to Ransbury, “all reinforce one thing: the rudder is powerful and must be treated with respect.”

He continues by explaining the foundational role of effective UPRT in building manual flight skills, flight envelope awareness, and resilience. Specifically, ICAO and FAA guidance on rudder use during upset prevention and recovery is discussed, underscoring the necessity of a comprehensive UPRT program.

Airbus Case Studies

In its rudder story, Airbus highlights a recent event involving an A320 that encountered turbulence when climbing through FL300 to its FL360 cruise altitude. Passing 31,600 feet, the aircraft began to roll to the right, reaching a maximum of 52 degrees.

According to the article, the pilot flying (PF) reacted with full left and nose up sidestick and light left rudder input that disengaged the autopilot, leading the aircraft to bank to the left. Next, the PF reacted by applying a full right sidestick and approximately half right rudder, causing the aircraft to bank “severely” to the right and triggering the “STOP RUDDER INPUT” warning.

These actions were followed by a series of alternating full left and right sidestick and near-half rudder inputs, causing the aircraft to bank left and right and triggering three additional “STOP RUDDER INPUT” warnings. The PF was finally able to stabilize the aircraft using only light sidestick inputs.

Upon landing, the flight crew reported “heavy turbulence” to maintenance but made no reference to the “STOP RUDDER INPUT” warnings. Maintenance performed inspections related to excessive turbulence but did not perform the inspection related to high lateral loads.

Later, following a routine review of flight data, it was discovered and confirmed that the lateral acceleration of 0.41 g during the event corresponded to a “red level” event requiring further inspection. Upon inspection, it was determined that “flight loads were in the vicinity of design limits but did not exceed them.”

This event is significant for two reasons. First, even the latest-generation jet transports are vulnerable to in-flight upsets. The A320 is a fourth-generation aircraft design incorporating fly-by-wire technology and flight-envelope protection. These advancements, according to Airbus, have reduced loss of control in-flight (LOC-I) incidents by 90% when compared to third-generation aircraft.

Second, the “STOP RUDDER INPUT” warning is significant to Airbus pilots since it is a reminder and the result of an accident that killed 260 people. On Nov. 12, 2001, an American Airlines Airbus A300-600 crashed shortly after taking off from New York JFK International Airport (KJFK). During its initial climb, the aircraft encountered wake turbulence from a preceding Boeing 747-400.

According to the NTSB, “the aggressive use of the rudder controls by the first officer stressed the vertical stabilizer until it separated from the aircraft.” In addition, due to excessive lateral forces, both engines separated from the aircraft before impact. The first officer’s actions may have been a result of the airline’s training programs. Prior to the accident, the airline promoted rudder use to recover from inadvertent aircraft upsets.

In its final report, the NTSB determined that the probable cause of this accident “was the in-flight separation of the vertical stabilizer as a result of the loads beyond ultimate design that were created by the first officer’s unnecessary and excessive rudder pedal inputs. Contributing to these rudder pedal inputs were characteristics of the Airbus A300-600 rudder system design and elements of the American Airlines Advanced Aircraft Maneuvering Program.”

Boeing Case Studies

During the 1990s, a series of issues affecting the rudder systems of Boeing 737s resulted in multiple incidents and two fatal accidents. In two separate accidents, pilots lost control of their aircraft due to sudden uncommanded rudder movement, resulting in crashes that killed 157 people.

The NTSB determined that the accidents were the result of a design flaw that could result in an uncommanded movement of the aircraft’s rudder—in the opposite direction—as commanded by the pilots. Following the investigation of these accidents, the FAA mandated modifications for all 737 aircraft in service. Since the modifications, there have been no additional rudder-reversal incidents.

In addition to the rudder modifications, a new concept—crossover speed—was introduced to the industry. Crossover speed is the airspeed that requires full lateral (roll) control from the ailerons and spoilers to counteract roll due to yaw caused by full rudder input. At speeds less than crossover speed, with full rudder input, the roll induced by the rudder starts to exceed the lateral control authority of the ailerons and spoilers.

More recently, an issue was identified with the 737 Max’s rudder system (this system differs from the classic 737 aircraft, described above). In February 2024, a Boeing 737-8 Max experienced a “stuck rudder” during the landing rollout at New Jersey’s Newark Liberty Airport (KEWR). According to the NTSB report, the captain stated that “during the landing rollout, the rudder pedals did not move in response to the normal application of foot pressure while attempting to maintain the runway centerline.”

The captain was able to use the nosewheel steering tiller to keep the airplane near the runway centerline and exit the runway once the aircraft slowed to a safe taxi speed. Shortly after landing, according to the report, the rudder pedals began to work normally. Flight data analysis corroborated with the captain’s report regarding the malfunction of the rudder system.

Investigators determined that water intrusion, and the subsequent freezing, of a rudder “rollout guidance servo” restricted the rudder pedals on the incident aircraft. As a result, of the investigation, the NTSB issued an urgent safety recommendation to replace the affected components (only one U.S. airline was affected) and cautioned pilots on abrupt rudder control movements that could cause “sudden large, and undesirable rudder deflections that (could) unintentionally cause a loss of control or departure from a runway.”

Handle with Care

Airbus cautions pilots on the risks of structural overload due to opposite rudder inputs: “Aircraft structures are designed to sustain loads caused by normal use of the rudder in a wide range of conditions and speeds. However, aggressive, rapid, full or nearly full travel, and rapidly pressing one rudder pedal then the other in opposite succession can lead to rudder inputs that will cause loads higher than the design limit and can result in structural damage or failure.”

It notes, “The rudder travel limit system is not designed to prevent potential structural damage or failure caused by such forceful rudder pedal inputs by the flight crew.”

Even the latest Airbus aircraft with electric rudder systems have flight control laws that may reduce structural stress caused by forceful or alternating rudder pedal inputs, but this is not protection against structural damage or failure, the manufacturer said.

Industry Guidance on Rudder Use

APS’ Ransbury cites industry guidance (ICAO document 111 and FAA AC 121-111, AC 120-109A, and AC 121-123) on the proper use of rudder during upset prevention and recovery. In the video Ransbury mentions these salient points:

• Rudder control is still effective at a high angle of attack, and special care must be taken in the use of rudder during upset prevention and recovery.
• Excessive use of pitch trim or rudder during the recovery may aggravate the upset condition and/or may result in exceeding aeroplane structural limitations.
• It is important to guard against control reversals. To maintain structural integrity, avoid rapid full-scale reversal of control deflections.
• Extreme care must be taken whenever a pilot chooses to use rudder to correct sideslip.

General Aviation Accidents

Sadly, earlier this month, a malfunctioning or “stuck rudder” may have contributed to a tragic general aviation accident in Florida. On April 11, a Cessna 310R crashed near Boca Raton Airport (KBCT) in Florida. Preliminary accounts of the crash detail the short 11-minute flight that killed three people. Shortly after takeoff, the aircraft entered a series of left-hand turns in the vicinity of the airport at varying altitudes.

Interviews with air traffic control specialists, witness accounts, and video show the aircraft “yawing” to the left in continuous left-hand turns, and with both engines operating. According to some reports, one air traffic controller said the pilot—an accomplished aerobatic pilot—had “no rudder control” and “had difficulty controlling the aircraft.” After several attempts to land at the airport, the aircraft crashed about 3,500 feet southwest of Runway 05 at KBCT.

LOC-I Almost Always Fatal

Loss of control is a leading category of aircraft accidents worldwide. These accidents are almost always fatal and affect every aircraft type and every segment of aviation.

According to IATA, the most prominent contributing causal factors of these events involve the pilot, including those human-induced loss of control causal issues such as manual handling errors, poor energy management, the effects of automation, and spatial disorientation and procedures. Meteorological conditions and aircraft malfunctions (such as the rudder) are among the primary contributing threats to these human-induced incidents.

One of the best ways to mitigate the LOC-I threat is a comprehensive UPRT program. These programs enhance the pilot’s toolbox by promoting an approach that helps avoid, detect, and recover from a loss of control event.

The opinions expressed in this column are those of the author and are not necessarily endorsed by AIN Media Group.