The NTSB says the rudders on "more than" 353 Boeing 737NG and MAX aircraft can freeze stuck and it's suggested the manufacturer come up with a solution besides stomping on the pedals to free them up. The board issued an urgent safety recommendation Thursday resulting from its investigation of an incident in Newark last February in which the rudder pedals jammed on a United MAX after landing. The pilots couldn't budge the rudder so the captain kept the plane on the runway using the tiller.
Iâm confused. During manufacture, install, or operations?!?!
An old Director of Maintenance I worked with used to refer to it as âthe convincerâ.
I canât believe I am reading the suggested solution is to overpower, or, at least to try until you break something else, or, jam it. Utterly dumbfounding. But, this is the world we live in today.
The suggestion for pilots (the flight manual tells pilots) to âuse maximum forceâ to free a stuck rudder on the Boeing 737NG or MAX could be extremely risky, especially when you consider what happened to American Airlines Flight 587 over Jamaica Bay in 2001. In that accident, the first officer applied aggressive rudder inputs after takeoff, which caused the vertical stabilizer to snap off the aircraft. The excessive side-to-side rudder movements created more force than the stabilizer was designed to handle. Without the stabilizer, the plane crashed, killing everyone (265) on board.
Just like the Airbus A300 in the AA587 crash, the 737 MAX has limits on how much force its vertical stabilizer can handle. When Boeing tells pilots to stomp on the pedals to free a jammed rudder, theyâre setting the stage for a potentially dangerous situation. If the rudder suddenly becomes unstuck, it could swing all the way to one side, causing an abrupt, extreme deflection. This could put massive stress on the vertical stabilizerâjust like what happened on Flight 587. The stabilizer might not be able to handle the sudden force, leading to structural failure or loss of control.
In simple terms, âpushing with maximum forceâ could make things much worse. Instead of solving the problem, it risks breaking the planeâs structureâa lesson we should have learned from AA587. The NTSB is right to be concerned, and Boeing needs to find a better solution than âjust push harder.â
Donât understand âThe board is suggesting the faulty actuators be removed (presumably limiting low-visibility operations)â. The rudder is critical especially for crosswind landings, unrelated to low-visâŚ
Just like thereâs a Va/Maneuvering Speed at which an aircraft will stall before the structure is damaged by excessive loads (https://www.faasafety.gov/files/notices/2015/Nov/V_Speed_Review.pdf), might there theoretically also be aâIâll call it âVmrâ, e.g. V-maximum-rudderâa speed below which no combination of maximum rudder deflections would damage the vertical stabilizer?
Looking at the far ends of the speed spectrum, certainly jamming the rudder back and forth at 0 kias wonât cause vertical stabilizer damage. Doing so at 120 kias would probably be structurally sound but produce some terribly dangerous yaw and stall condition. Jamming it back and forth at 350 kias likely would do damage to the vertical stabilizer. Raf references AA587; what would itâs approximate airspeed have been about 1m:30s after departing the runway? 180kias? That airspeed would obviously be beyond my theoretical âVmr,â for a loaded A300 at least, given the outcome. So⌠maybe around 150-170 kias for my theoretical âVmrâ?
Bottom line, they have known defective parts on in-service airframes, and apparently have issued no specific recommendations on how to deal with it. The NTSB points out that the recommended action in the event of rudder freezing during landing, per the flight manual (not a specific recommendation to this situation), is potentially dangerous and could result in sudden, uncontrolled extreme rudder deflection and loss of control on roll out. Given Boeingâs recent history - especially around the Max - how could this possibly have slipped through and gotten to the point where the NTSB had to issue a public news release? At this point, one would expect that even a totally dysfunctional organization would be on high alert to mount an âall hands on deckâ response to anything associated with the words âdefectiveâ âMaxâ âsafetyâ. Boggles the mind.
The NTSB Urgent Safety Recommendations News Release is here: NTSB Issues Urgent Safety Recommendations on Boeing 737 Rudder System
Raf, it wasnât a single forceful application of rudder that brought down AA587, it was the repeated reversals of the rudder that snapped off the tail. One application of âmaximum forceâ wonât do it.
It is a different 737 rudder actuator problem, but doesnât this bring to mind USAir Flight 427? I knew several people who perished on that flight. It seems like this would be a ground the fleet and fix it fast issue.
David, youâre absolutely right that the AA587 crash wasnât caused by a single forceful rudder application, but rather by repeated and aggressive rudder reversals. The NTSB investigation concluded that the rapid, alternating rudder inputs created extreme lateral forces that exceeded the vertical stabilizerâs design limits, causing it to snap off.
One application of full rudder might not have caused structural failure, but the repeated inputs amplified the aerodynamic forces beyond what the aircraft was designed to withstand. This highlights both the sensitivity of the rudder system and the importance of understanding how multiple inputs in quick succession can have a cumulative effect on the structure. Airbus made significant design and training updates to address these concerns after the incident, recognizing that even within normal operating parameters, repeated rudder use could lead to catastrophic results under certain conditions.
Following the AA587 accident, Airbus made changes to its flight control systems to prevent pilots from over-stressing the vertical stabilizer with excessive rudder inputs. These changes include modifications to pilot training and flight control system logic.
Iâm not sure what bearing this has on the rudder issue but a quick and inexpensive stopgap that Boeing could use to address this might just be a slow anti-icing drip using a good lead based (and might be toxic) solution until the affected bearings are replaced. A more permanent solution would be to use mega heating pads (that keep my cat warm on those cold winter evenings) adjusted for the ambient tail temps. Somehow I donât think heated rudder pedals would do the trick, but who knows?
Hardly old news. The incident happened in Feb of this year and the preliminary report identifying the cause was issued in March. The NTSB just issued their âurgentâ news release. The point, is that Boeing did not get in front of this issue or the story. The NTSB clearly feels it is an urgent safety issue and that Boeing has not addressed it. At a minimum, a PR failure on Boeingâs part and at worst another example of not moving swiftly to address a real safety issue. Either way, inexcusable in light of their current reputational crisis.
