'stuck' rudder pedal during landing roll out; Boeing 737 MAX 8

[LaissezPasser]

Originally Posted by SLF3

As I understand it the actuator is only used on roll out but if stuck due to icing the rudder would be inoperable in flight.

Is that correct?

Is the rudder required in flight or an optional extra? Asymmetric thrust on engine shutdown / failure?

The actuator is used also during final approach and landing, as well as on rollout. But you are correct that if moisture accumulates inside an actuator with an incorrectly assembled bearing, it can freeze and render the rudder controls inoperable in flight.

Rudder is not typically used in cruise. Rudder is used in phases of flight like final approach and landing, which is why pilots are only likely to discover this particular failure scenario (i.e., jammed rudder controls due to frozen rudder rollout guidance actuator) at the last moment, during a critical phase of flight. There is greater need for rudder in situations like an engine out or crosswind landings.

The NTSB sent a follow-up letter to the FAA.

Originally Posted by DaveReidUK

That's an unlikely scenario, given that it's a rollout guidance actuator, though a runway excursion is serious enough.

Dave, your comments have generally been on target in this thread, but I’d like to respectfully point out that this last post of yours evinces a misunderstanding of the scope of the concern. The “smoking hole” scenario is an equal concern. As the NTSB report notes, the rudder rollout guidance actuator remains mechanically connected to the rudder control system even when it’s not active. (In fact, on the United Airlines planes, the rudder rollout guidance actuators had been electrically disconnected but still remained mechanically engaged with the rudder control system.) This means that if moisture freezes in the actuator gearbox, it can jam the whole rudder control system, regardless of whether the rudder rollout guidance actuator is active or not, and regardless of whether the airplane is flying in the air or rolling on the ground. According to the NTSB report, there is concern about the potential for loss of control in flight, during landing, and on rollout—both because the rudder controls can jam but also because Boeing’s procedure for clearing the jam could produce the same result (loss of control) due to a large, sudden, and undesired input and resulting rudder deflection. The scenario could be exacerbated by an engine-out or high crosswind condition.

[tdracer]

Originally Posted by SLF3

So it’s happened three times, the NTSB say it’s dangerous, the fix is obvious but only applied for US carriers. Which non US regulator will move first?

This is actually quite normal. NTSB has no rule making authority - they can only make recommendations - it's the FAA that must take actual action. Further, if the FAA issues an AD or other action, it only applies to US operators - they have no authority over non-US operators (although they can ban specific non-US operators from US airspace if they believe the operator is unsafe). What normally happens is - after the FAA has issued an AD or other action - the other affected airworthiness authorities will take duplicate (or at least similar) action.
Same thing with EASA - they only have authority over the operators in EASA countries.

[MechEngr]

Originally Posted by SLF3

So it’s happened three times, the NTSB say it’s dangerous, the fix is obvious but only applied for US carriers. Which non US regulator will move first?

Only the US carrier was properly reactive without the FAA demanding action. The foreign carriers, yet again, don't seem to care.

This should require exactly zero regulators to deal with, except giving Collins a colonoscopy to figure out why this defective assembly could leave their hands and why the design allows this to even be possible.

[SLF3]

There was a post above suggesting the NTSB is grandstanding. Their follow up letter (link in post 82) reads like a regulator doing their job.

If you want the NTSB to stop firing, stop handing them bullets.

51 foreign regulators (starting with the Chinese) grounded the Max after MCAS 2 before the FAA acted. So I do not buy the arguments above that foreign regulators are obliged to follow the FAA lead.

[DaveReidUK]

Originally Posted by LaissezPasser

Dave, your comments have generally been on target in this thread, but I’d like to respectfully point out that this last post of yours evinces a misunderstanding of the scope of the concern. The “smoking hole” scenario is an equal concern. As the NTSB report notes, the rudder rollout guidance actuator remains mechanically connected to the rudder control system even when it’s not active. (In fact, on the United Airlines planes, the rudder rollout guidance actuators had been electrically disconnected but still remained mechanically engaged with the rudder control system.) This means that if moisture freezes in the actuator gearbox, it can jam the whole rudder control system, regardless of whether the rudder rollout guidance actuator is active or not, and regardless of whether the airplane is flying in the air or rolling on the ground. According to the NTSB report, there is concern about the potential for loss of control in flight, during landing, and on rollout—both because the rudder controls can jam but also because Boeing’s procedure for clearing the jam could produce the same result (loss of control) due to a large, sudden, and undesired input and resulting rudder deflection. The scenario could be exacerbated by an engine-out or high crosswind condition.

Thanks, yes I stand corrected.

[LaissezPasser]

Originally Posted by SLF3

Which non US regulator will move first?

India: https://timesofindia.indiatimes.com/.../114016780.cms

[MechEngr]

The reported Indian response seems stupid. The affected device can freeze at any time, so:

The regulator has also asked operators using B737s with affected Collins rudders to stop low visibility CAT 3B landings on these planes apart from conducting risk assessment and special rudder control training for pilots.

doesn't deal with the problem.

The only temporary safe option is removal of the system. The risk is not limited to CAT 3B landings, it affects all landings of equipped aircraft.

[safetypee]

fix the machine not the human

Mech, your argument is sound; however the DGAC's proposal appears to follow the Boeing / FAA view that the human can be relied on to safely intervene with increasing visibility.

The assumption in principle, of appropriate, timely, and correct intervention, in all situations - even as a stop gap measure, is flawed as demonstrated by recent high profile accidents.

We, humans, are not as good as we think we are; fix the machine not the human

[WillowRun 6-3]

FAA SAFO

FAA Flight Standards Service has issued an SAFO, 24006 Oct. 7 2024.

Tried posting the link but not with proper results; easy enough to find on FAA website (and widely reported in many media and news sources).

[LaissezPasser]

Originally Posted by WillowRun 6-3

FAA Flight Standards Service has issued an SAFO, 24006 Oct. 7 2024.

Tried posting the link but not with proper results; easy enough to find on FAA website (and widely reported in many media and news sources).

Here it is: https://www.faa.gov/sites/faa.gov/files/SAFO-24006.pdf