737 Max: Loose Rudder-Control Fastener Issue.
 

​​​​​​​https://www.nytimes.com/2023/12/28/b...spections.html

LOOSE BOLTS:
Could we issue a spare bolt and nut to every air hostess, so they can fit it if they hear a rattle? I'm not kidding as I recall that flight in the '80s downunder on TAA (now defunct) where the rear aisle fluorescent light started to flicker somewhat annoyingly. No problems - the air hostess leaned up, undid the two fasteners on the cover with a fork (metal in those days) and removed the offending tube. Was mighty pleased at that point that she showed some initiative and consideration for the passengers. To my shock and horror, she reappeared soon after, brandishing a new fluorescent tube which she promptly fitted and refastened the two mounting screws on the cover! Never flew TAA again, when cabin staff (trained for the procedure or not) perform rolling maintenance while in-flight!

Boeing says there are 1,370 737 Max aircraft out there that need to be checked. The check takes approximately two hours. Do you get a sticker inside the front door pillar that the check has been made like my car dealer does for car recalls?

Should the entire 737 Max fleet be grounded until the checks are made? Would you fly without a reassurance the bolts were done up correctly on YOUR rudder?

From FAA website
 

FAA Closely Monitoring Inspections of Boeing 737 MAX Airplanes

Thursday, December 28, 2023
"The FAA is closely monitoring targeted inspections of Boeing 737 MAX airplanes to look for a possible loose bolt in the rudder control system.

Under consultation with the FAA, Boeing has issued a Multi-Operator Message (MOM), urging operators of newer single-aisle airplanes to inspect specific tie rods that control rudder movement for possible loose hardware.

The FAA will remain in contact with Boeing and the airlines while the inspections are underway. The agency is asking the airlines to work through their approved Safety Management Systems to identify whether any loose hardware has been detected previously and to provide the agency with details on how quickly these two-hour inspections can be completed.

The FAA will consider additional action based on any further discovery of loose or missing hardware. Boeing recommended the inspections after an international operator discovered a bolt with a missing nut while performing routine maintenance on a mechanism in the rudder-control linkage. The company discovered an additional undelivered aircraft with a nut that was not properly tightened".

Can I make an uneducated guess? Two hours? All 1,370 of them.

If it was the aircraft you were about to take to the skies in, knowing your rudder may be faulty and uncontrollable, would you like the inspection to be superficial and hasty?

Will Boeing be providing pilots with a half inch spanner to tighten the nuts if they hear a rattle in flight?

Try "how soon" they can be completed on all relevant aircraft?

It would have been a lot cheaper if they had spent an extra two or three cents using captive nuts?

Hasn't it always been mandatory for any removable fasteners in the flight control linkages to have positive locking, for example castle nuts/split pins, locking tabs, etc ?

I have a vague memory of being told Boeing doesn't like to use 'lock nuts' (i.e. those with some sort of deformable aspect that keeps them from loosening) because people tend to re-use them and they wear out, instead using things like castle nuts with pins or lockwire for positive retention.
However that only works if someone actually installs the lockwire/pin...

Salute!

Yeah Dave, except when the wrench bender doesn't use the safety wire or lock nut or....

So the trusty team working my leading edge flap fails to use a "keeper bolt/nut" to keep the flap drive tube connected to the flap drive motor shaft (spline fitting, so tube can slide out fairly easy). Sucker slides off the drive shaft at 160 KIAS just after takeoff and I become Chuck Yeager to get the jet back on the ground for the picture.
https://cimg9.ibsrv.net/gimg/pprune....b66f891700.jpg

Gums sends...

As an aside, has anybody else got this error message when attempting to go to Boeing's website? "An error occurred during a connection to www.boeing.com. Peer’s Certificate has been revoked." Maybe loose bolts is the least of their problems?

Great picture and achievement to get that back on the ground.

Pretty sure it was going to end up on the ground regardless. Gums accomplishment was getting back on the ground intact (more or less).:ok:

Salute!

There's a reason, and a pretty good one, to follow the repair/maintenance checklist. And on some procedures, even have two or more folks verify.

Next flap failure was a mechanical problem and pilot couldn't land it on first try, then got tired and bailed. You see, you had to hold almost the max limit of force - figure 15 - 16 lb for over 10 or more minutes. And then do not get slow or try to flare for touchdown. First failure like mine was fatal, as jet began a sharp roll below 170 knots or so and the guy ejected sideways too low. Accident board for second one( not long after mine) resulted in a video of what I did, as it was not widely publicised originally. All Viper units got the video and we never lost another plane to a leading edge flap problem/failure.

I have always thot that the MCAS debacle was an example of not making widely known of a potential problem and a fairly simple procedure to safely return. And then, of course, fix the system!!

Gums sends...

The problem is a loose nut in the rudder mechanism, but is it right to assume there are an abundance of fasteners in the rudder system, and failure critical fasteners are wired? In this case the nut was missing (bad) but the plane did not crash (good). The problem was found upon inspection and Boeing notified. Boeing immediately checked planes in inventory and found one fastener not tightened to spec. Since the bolt was found during an inspection, and apparently the airplane had not experienced a control problem, is it not likely the bolt was not safety critical for some reason? Are there not hundreds of bulletins issued by all manufacturers every year to follow up on something unusual found during routine maintenance?

The recommended compliance date is 10 January 2024.

The media is playing the 'Max bad, Max evil' narrative again. Since the MOM was published, the original operator has inspected the remaining 110+ aircraft in its fleet with zero findings, my airline has inspected 17 of our Max-8s (half the Max fleet) with zero findings, and this very washer and nut combination is checked as a component of every C-Check, meaning the vast majority of flying aircraft will have already had this checked as part of routine maintenance and this is just the normal 'out of abundance of caution' that we've been used to. I'd also point out, from the memo we got: "The rudder will no longer respond to pilot pedal inputs and will center relative to the current rudder trim neutral position. Rudder trim control and yaw damping will be available and function normally. Pilot response to this failure includes executing the Jammed or Restricted Flight Controls NNC." So bad that the rudder won't respond, but good that we already have an existing and well-trained (at my spot) NNC. Granted, I'd hope that if this were to happen, I hope the wind is right down the pipe or nil and that it doesn't decide to separate at VR.

I'm not suggesting that a missing nut and washer are not problematic and that we should not be concerned as pilots when manufacturing defects are found. Quite the opposite. Our professionalism should have us looking closely at the issue and thinking aloud what our actions would be should we encounter the fault. This is why I am angry about the MCAS issue - we were not advised of the potential for the fault and, by extension, could not talk about what our actions would be, despite there being an existing NNC. But the media running to the hills screaming every time a Max MOM or AD is put out is getting a little old, especially when procedures exist that help us control the potential fault. Save for two horrific flights, it has an otherwise seemingly impeccable safety record (knocking on wood right now).

Old fart here recalling his early days and a quaint Air Registration Board (predecessor to CAA) regulation that splitting or installation of any primary control MUST be signed off with a duplicate inspection by another licensed engineer. This long-retired pilot and LAE thinks that a "rudder will no longer respond to pilot pedal inputs" would have terrified him. He certainly would not have flown with it.

Salute TSRA!

Some good points, especially about not being advised of a potential or worse, a known fault. I would have been angry too.

I agree about media overkill on the type plane, however, we had the rudder actuator problem years ago and then the new problem with max. So my gut tells me that management got in the way of the procedures used for decades when a tech order action went out or we at least got a heads up on a potential problem.

That memo you got was scary - loss of rudder seems harsh, and seems the plane had some kinda redundancy, huh?. OTOH, that problem I faced was not supposed to happen because there was supposedly asymmetric flap brakes to stop one of the things if it got more than a few degrees from the other. But nope, and only reason I manually turned off the auto flap system was to keep the other one from doing something wierd. The design measured flap position at one place and it was upstream of the connection of one tube/rod to another. After all, the two were connected with a very good spline and it had a "keeper bolt" that prevented one component from sliding away from the other. Easy fix and have not heard of another problem since back then. Plus, emphasis upon a second mechanic checking first one as another old fart has just stated. And I don't know any of we single seat guys that don't not put our hand on the grear lever many times before landing, even if we are in the family model.

Gums sends...

Boeing has a world renown QA system with a history of finding and correcting these kind of build mistakes before the airplane gets delivered to the customer........Oh wait.......

Hat. coat, umbrella, briefcase, roller bag, emergency slide......

You are on PPRuNe, amigo. You are now going to be lectured for taking your bags with you during an emergency evac. :p

For +TSAR: thanks for the inputs from how your company is handling it. :ok:

Many years ago, on a different type, I had a rudder failure to remember. The rudder itself broke and ended up some 120% of full deflection. That could be controlled (just) with full aileron, but of course you have to level the wings for landing. "Hello, grass". The good news was that everyone walked away and with a new rudder the aircraft flew again.