737 Max: Loose Rudder-Control Fastener Issue.

[BlankBox]

Boeing Urges Airlines to Inspect 737 Max Planes for Possible Loose BoltsThe F.A.A. said it was monitoring inspections after an airline discovered a bolt with a missing nut in the plane’s rudder-control system.


​​​​​​​https://www.nytimes.com/2023/12/28/business/boeing-737-max-faa-inspections.html

[Thirsty]

LOOSE BOLTS:
"The inspections were prompted by an airline finding a bolt with a missing nut while performing routine maintenance.

FAA said it was an international operator that made the discovery.

A nut that was not properly tightened was also found on a second undelivered aircraft."

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?

[WillowRun 6-3]

FAA Closely Monitoring Inspections of Boeing 737 MAX AirplanesThursday, 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".

[Thirsty]

....and to provide the agency with details on how quickly these two-hour inspections can be completed.
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?

[DType]

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

[Nil by mouth]

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

[DaveReidUK]

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 ?

[tdracer]

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...

[gums]

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.org-vbulletin/333x240/rightwing_e536b16fc9ceb5fc6389ccde1d0bbeb66f891700.jpg

Gums sends...

[Thirsty]

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?

[Consol]

Salute!

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

So my 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.org-vbulletin/333x240/rightwing_e536b16fc9ceb5fc6389ccde1d0bbeb66f891700.jpg

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

[tdracer]

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:

[gums]

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...

[NWA SLF]

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?

[+TSRA]

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

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).

[Geriaviator]

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.

[gums]

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...

[Big Pistons Forever]

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......

[Lonewolf_50]

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:

[Herod]

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.

[Equivocal]

So design/manufacture and maintenance are not my area of expertise, but I offer a few thoughts…. Whilst, clearly, aircraft that are in service need to be checked, I would like to think that a thorough investigation is carried out at Boeing to understand how such a manufacturing error made it through to delivered (and delivery-ready) aircraft. Although this particular error may, arguably, not be critical, what confidence is there that other, more critical errors are not being made. And, further, is there a weakness in the FAA oversight processes which could/should have picked this up at an earlier stage.

[classic200]

A dual inspection.

[classic200]

Its a flight control, its a dual inspection.

[N707ZS]

The big question, was it fitted/manufactured incorrectly or has it worked loose due to system use.

[Uplinker]

Good spot, finding this fault. A disaster averted.


..........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.


Not necessarily terrifying; we hardly touch the rudder with the foot pedals in normal (jet transport) flight - the yaw damper puts in most rudder movements that are required for turn coordination and yaw damping.


Cross-wind take offs and landings, and of course engine failure are another matter. You obviously wouldn't take off with this fault; but to get you back on the ground; losing foot control of the rudder in flight would not be a biggy, as long as the yaw damper and trim were serviceable, and providing the rudder itself didn't go hard over, which would be unlikely if the control rods just became disconnected. It would certainly allow an into-wind landing

[Big Pistons Forever]

The big question, was it fitted/manufactured incorrectly or has it worked loose due to system use.


Since Boeing found a loose bolt on a new airplane that had not been delivered yet, it seems to be a manufacturing problem.

[N707ZS]

Ah, thanks, missed that bit.

[DaveReidUK]

Since Boeing found a loose bolt on a new airplane that had not been delivered yet, it seems to be a manufacturing problem.

And, given that we're told the issue isn't something that's detectable between C checks, I'd hazard a guess that the in-service aircraft found without a nut at all was delivered in a similar state.

[WOTME?]

It was drilled into me,firstly by the RAF & then by the CAA that any disturbance of safety critical parts had to be a duplicate inspection by two suitably type qualified engineers.
Don't Boeing do that on manufacture?

[Geriaviator]

Quite: from my post #16: 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.
Glad to see someone else raising this basic regulation (not a rule).

Exam answer from memory of 60 yrs ago: What is a duplicate inspection? Answer: A duplicate inspection is first made by a licensed engineer or qualified person and certified, and then made by a second licensed engineer and again certified. Basically it meant two heads on the block if something went wrong.

[gums]

Salute!

As a fellow, really old aviator, with Geri, I would really be "concerned" in a multi engine plane without a rudder when one motor quit. Especially if I could not feather the prop, although a pure jet/turbofan might be slightly easier,but not so with swept wings ( roll due to yaw worse on bent wings).

All the yaw dampers and aileron-rudder interconnect and FBW control laws are no substitue for cranking in some rudder when it is required to keep the pointy end forward.

Just my thots from a mostly single-engine or multi-engine, centerline thrust dude, although the over-powered A-37 needed an awful lot of rudder on a single engine go-around (lost two that way, but then trained folks to use lottsa rudder early). My LEF adventure also required plenty of rudder that the FBW laws did not command.

Gums sends...

[TURIN]

Is this just another indication of the decline in quality standards? Not just at Boeing.

[blind pew]

Decline in standards..nah..
in the early 1970s after a DC10 had a cargo door locking mechanism fail after being hit by a coffin there was a mandatory modification. A new DC10 destined for Turkish airlines had the mod signed off and inspected which hadn’t been carried out. The aircraft ended up in a forest outside of paris with 346 dead.

[nonsense]

Decline in standards..nah..
in the early 1970s after a DC10 had a cargo door locking mechanism fail after being hit by a coffin there was a mandatory modification. A new DC10 destined for Turkish airlines had the mod signed off and inspected which hadn’t been carried out. The aircraft ended up in a forest outside of paris with 346 dead.
https://en.wikipedia.org/wiki/Turkish_Airlines_Flight_981

[megan]

Our Navy had a Sea King accident in Indonesia while on a humanitarian mission following an earth quake, nine deaths and two seriously injured. Caused by a missing split pin on a castellated nut in the cyclic control system.

The investigation found that meeting the mission had priority and things such as maintenance, training and leadership took a back seat. Maybe Spirit (Boeing) is suffering the same pitfalls, get the aircraft out the door and focus being lost on the process.

[DaveReidUK]

Our Navy had a Sea King accident in Indonesia while on a humanitarian mission following an earth quake, nine deaths and two seriously injured. Caused by a missing split pin on a castellated nut in the cyclic control system.

The investigation found that meeting the mission had priority and things such as maintenance, training and leadership took a back seat. Maybe Spirit (Boeing) is suffering the same pitfalls, get the aircraft out the door and focus being lost on the process.

I think pointing the finger at Spirit might be a tad premature.

By all accounts the final rigging of the door plug is done at Boeing, and that's after the locking bolts have been removed and later replaced so the plug can be opened to improve access to the rear cabin while the interior is being fitted out.

[Phantom4]

Is this a design fault,quality control,inspection or maintenance.
FAA conspicuous by their absence
Boeing should be held to account.

[Semreh]

A dual inspection.

As an ex technical auditor, speaking with my nit-picking audit hat on, no.

A dual inspection does not prevent collusion, witting or unwitting. You need evidence. A signed entry in a log-book is suggestive, but is certainly not proof that something was done.

Where possible, it can be good to take a photograph of the finished job. It documents that the job was done at the date and time the photograph was taken. Ideally, you have a tamper-resitant display in the image that shows the current date and time. It does not provide proof that the finished job was not disturbed later.

In nuclear weapons installations, tamper evidence can achieved by sealing equipment with epoxy which has glitter mixed in with it. A stereoscopic picture of the seal is then taken, and subsequently it can be compared to the in-situ seal to show if the epoxy has been removed and replaced. Unsurprisingly, much work has gone into working out how to duplicate or move these apparently unreproducible seals.

I'm not suggesting that glitter epoxy is used to seal locking bolts. It's almost certainly over-egging the pudding and would add unnecessary mass to the airframe; but there are ways of providing physical/documentary proof of things that don't reply so much on fallible humans.

For example, you can keep an accurate inventory, so if you see that four bolts, castellated nuts and length of locking wire and/or cotter-pins have not been used, you don't roll out the airframe. Keeping such an inventory is non-trivial.
Or, you can mark each item with a unique serial-number (or pattern) and keep track of them - if the S/N shows up in a photograph, so much the better. Larger items can have RFID tags attached. They are cheap enough to be used in inventory management for fashion clothing.

Professional aircraft technicians will do their best to not leave jobs incomplete or make mistakes, but they are human, and our experience of having humans 'in the loop' is that they tend to generate mistakes or mishaps, so we need compensating systems. Dual sign-off is better than nothing, but by no means infallible,

[Geriaviator]

As you mention nit-picking, may I question your use of the term "dual sign-off" which implies the engineers perform the inspection together? In my day we didn't: we went by the book definition which stated "A duplicate inspection is first made by a licensed engineer or qualified person and certified, and then made by a second licensed engineer and AGAIN certified." The point being that there are two separate operations confirmed by two signatures on the log book or works record, and two heads to roll if something goes wrong. Of course this implies extra cost, extra delays in production and similar stuff to annoy the bean-counters.

[Semreh]

As you mention nit-picking, may I question your use of the term "dual sign-off" which implies the engineers perform the inspection together? In my day we didn't: we went by the book definition which stated "A duplicate inspection is first made by a licensed engineer or qualified person and certified, and then made by a second licensed engineer and AGAIN certified." The point being that there are two separate operations confirmed by two signatures on the log book or works record, and two heads to roll if something goes wrong. Of course this implies extra cost, extra delays in production and similar stuff to annoy the bean-counters.

Quite right, and great that you pick up on it.

But the point stands that one signature, or two signatures, in a log does not mean that the job was done.

People who have worked together for a period can build up a level of trust. Bob can say to Fred that Bob has done Job No. XP/371A and present the log book. Fred can go back to the aircraft, unscrew the access panels that Bob has replaced and check the job was done, or just take Bob's word for it. Of course he should check. But it is human nature: they have a good working relationship, and Bob has never made a mistake before...

Yes, it is unprofessional, and it should never happen. But it, or something very like it, happens often enough that we need systems to detect and prevent it. Ideally, no-one is ever tired, or under pressure to meet a deadline, or makes a mistake looking at panel C instead of panel D, or misses the fact that Job XP/371A opens three panels, not two because one page of the worksheet goes missing.

As an auditor, I was actively disliked because I distrusted people professionally. It didn't matter how well-intentioned people were, or professional, they still made mistakes. And so did I. Questioning peoples procedures is often taken personally: questioning the integrity of the process is often taken as questioning the integrity of the person following the process. Eventually I learned enough 'people-skills' to depersonalise the issues for most.

We should not expect people to do things without error. We should design systems that effectively and efficiently identify when things go wrong, and provide effective and efficient mitigation. Relying on humans to get things right every time is unreasonable.

[MechEngr]

Let he who has never lost track of car keys cast the first stone.

This may turn on the curve of experience.
1) On the first few times the task is new and everyone is on edge to check everything.
2) Then there is the dangerous period, where some are thinking "I've got this" and they don't.
3) This is followed by the long term, where the repetition is such that missing a task practically makes people itch; they don't even have to consciously be aware, they just have a built in reflex to know they missed something and to turn around and look.

Since this door is installed and then removed and then reinstalled, but everyone knows it won't really be used, there is a good slot for the second state to happen.

I'd like to be looking at the procedures and sign-offs that go along with that re-install. Like, is there a re-install checklist taped to the door with a list of all fasteners that need to be put in, like a more sophisticated tag-out operation when servicing a machine. And a placard permanently on the door that the door shall not be removed without first affixing the checklist.

[Vasco dePilot]

Boring seems to have lost focus on the importance of engineering quality. Without that, zero profit can be made. It was drilled into me,firstly by the RAF & then by the CAA that any disturbance of safety critical parts had to be a duplicate inspection by two suitably type qualified engineers.
Don't Boeing do that on manufacture?

[m0nkfish]

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).


Off course if you discount the two fatal crashes and other safety issues this aircraft has had in its vast 7 years service life (almost 2 of which were spent grounded) its got an impeccable safety record...

[hoistop]

It was drilled into me,firstly by the RAF & then by the CAA that any disturbance of safety critical parts had to be a duplicate inspection by two suitably type qualified engineers.
Don't Boeing do that on manufacture?
I believe they do - or should do it. But on my "Human factors in maintenance" lectures, I am telling students that there is 10% chance that duplicate inspection will not catch the fault - this comes from serious research. Hovewer, in this case, there must be more systemic problem, as there was not one-off problem, but was repeated. I agree somewhat that media is jumping up on MAX excessivelly - we do not need that each SB or even AD is trumpeted all over. (Eventhough Boeing management somewhat deserves it for what they did.) Just look on FAA or EASA website for AD issued against each type - there are hundreds and I do not need to read about each one in the media. And this is not the first time I heard about such problem. I am well aware of an instance where brand new helicopter from well known manufacturer produced intermitent chip light in main transmission - only to discover that "chip" was actually a nut that fell off from somewhere inside the transmission.

[Semreh]

I believe they do - or should do it. But on my "Human factors in maintenance" lectures, I am telling students that there is 10% chance that duplicate inspection will not catch the fault - this comes from serious research. Hovewer, in this case, there must be more systemic problem, as there was not one-off problem, but was repeated. I agree somewhat that media is jumping up on MAX excessivelly - we do not need that each SB or even AD is trumpeted all over. (Eventhough Boeing management somewhat deserves it for what they did.) Just look on FAA or EASA website for AD issued against each type - there are hundreds and I do not need to read about each one in the media. And this is not the first time I heard about such problem. I am well aware of an instance where brand new helicopter from well known manufacturer produced intermitent chip light in main transmission - only to discover that "chip" was actually a nut that fell off from somewhere inside the transmission.

I'm always looking for good examples where 'obvious' control measures are not as good as people expect: could you give me a pointer/link to the relevant research providing evidence that "there is 10% chance that duplicate inspection will not catch the fault". A quick Internet search hasn't given me any obvious candidates - and a lot of procedures are designed around (semi-)independent sign-off, as in: A does the job and logs it as done, B checks and logs that it has been checked. It's relevant in many areas, not 'just' aircraft maintenance.

[T28B]

Please read the first post in this thread. This thread is not about the Alaska Airlines plug/door, it is about bolts.
The thread about the Alaska Airlines plug/door, and the 737 issue surrounding it, is here: https://www.pprune.org/accidents-close-calls/656760-alaska-airlines-737-900-max-loses-door-flight-out-pdx.html

[island_airphoto]

I am going to fly a $30,000 C-150 if the weather clears for an hour of fun and all the nuts are safety-wired and get checked by an A&P every 100 hours. Is this too much to ask for Boeing to do? WTF?
* in my previous career of being an "A&P+Avionics" guy on yachts, once I found ONE thing done that badly we would tear into everything to see what else had got screwed up by an obviously incompetent builder or previous firm.

[74757677]

It’s all about the culture of the organisation. Yes, a mistake was made by someone. This applies to the plug door issue as well, obviously. Was that (the mistake) because of work pressure, arrogance, incompetence, fatigue, issues at home or any other of a myriad of reasons? We all make mistakes, I certainly have in my 30 year flying career and I know nobody sets out to make a mistake. We all want to do the best job possible but external factors can prevent that.

My concern about Boeing is that there seems to be a disconnect between what they say and what they do. I know that there are thousands of Boeing employees that work tirelessly to ensure that everything is as it should be but recently I get the impression that other factors are at work.

I read here and in the Seattle Times, about the engine anti-ice issues with the Max, that they applied for an alleviation to certification rules to allow certification with an AD (airworthiness directive) in place.
If this is true I will be horrified and appalled. I think that an organisation that claims to have moved on and learnt lessons from previous incidents should understand how ridiculous their strategy appears to the outside world.

[055166k]

Bits can drop off aeroplanes for a variety of reasons.......and not just Boeing's. Read UK AAIB Special Bulletin S2/2023 Airbus 321-253NX G-OATW.

[Shehasblueeyes]

Has the EASA also ordered a check on the rudder bolts of European MAXES? Cannot find it on their AD list

[Busbert]

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 ?

Nope.
That requirement was introduced into 14 CFR 25.607 at Amdt 25-23 in August 1970.
BOEING HAS BEEN GRANTED AN EXCEPTION TO THIS REQUIREMENT ON 737NG and 737MAX. ‘Grandfathering/Changed Product Rule’ at it’s finest.
The fastener has a 1/4” UNF-28 stiff nut.
All clear as day in the TCDS.

I’ll let you draw your own conclusions about the mindset at Boeing.

[Big Pistons Forever]

Airplanes are complicated to build, especially with composite structures and computerized systems. But tightening bolts and then having a QC process to make sure it happened is manufacturing 101. This is a failure of the most basic manufacturing processes.

The recent plug door failure now seems most likely to the failure to ensure 4 bolts were in place and properly tightened.

The steady drip drip of QC escapes in the 737, 767, and 787 lines isn’t getting better. Boeing seems to be sleep walking to catastrophe

[megan]

I'm always looking for good examples where 'obvious' control measures are not as good as people expect: could you give me a pointer/link to the relevant research providing evidence that "there is 10% chance that duplicate inspection will not catch the fault"Here is a report just released. Take off crash of a DA42 because rudder control was reversed. Finding,Certification of work accomplished by another person

In this occurrence, the rudder cable guide tube replacement and the installation of the rudder cables were performed by individuals other than the person certifying the work. The ACA holder who certified the work was not present during the performance of the work and was not aware of the guide tube replacement before certifying the work. Even though it is possible to inspect most of the work after it has been completed, there are some aspects of the rudder cable installation that may be difficult to validate due to their location on the aircraft, especially when the person certifying the work is not aware of the work performed on the system.

For the steps that are difficult or impossible to validate once the work is completed, it may be necessary for the person signing the maintenance release for the certification of the work, to observe the work being completed, to the extent necessary to ensure the work meets the applicable standards of airworthiness.

Finding as to a risk

If the person signing a maintenance release for work accomplished by another person does not observe the work to the extent necessary to ensure that it is performed in accordance with the applicable standards of airworthiness, there is a risk that the aircraft will not be airworthy when it is returned to service.

https://www.tsb.gc.ca/eng/rapports-reports/aviation/2022/A22O0060/a22o0060.pdf

[illusion]

Here is a report just released. Take off crash of a DA42 because rudder control was reversed. Finding,

https://www.tsb.gc.ca/eng/rapports-reports/aviation/2022/A22O0060/a22o0060.pdf

Boeing has sent a team of accountants to investigate. Until these idiots give back control to engineers and recruit, train and retain properly experienced assembly line workers (not recruited from Maccas) the long term decline of their civil aircraft business will continue. The commonality of the A318/319/320/320Neo/321/321Neo
etc endorsement is what has pushed Boeing into dunce's corner. Until they they develop a new generation greenfield design (big bucks) Airbus will continue to increase their market share and deservedly so.

[421dog]

Y’know, I haven’t seen a lot of Southwest pilots here griping about 737’s…

[Count of Monte Bisto]

The danger of a discussion like this is that it quickly degenerates into tribal loyalties - in this case Airbus v Boeing. Full disclosure - I am an Airbus pilot and have been for the last 22 years. I had the opportunity to fly the 737 at the time and chose Airbus - just personal preference. Trying to stand back from this and take the big picture is hard as we do not have all the facts. What I do know as a Brit is that when the de Havilland Comet had 2 fatal crashes in the 1950's, the UK commercial jet market was destroyed just about overnight and Boeing won the world with the 707. Clearly vested interests came into play, but the undeniable fact was that square windows rather than round ones caused metal fatigue failures resulting in the loss of many lives. It got fixed, but no one wanted the revised product. The rest, as they say, is history.

Move now to the 737 MAX, which has had two fatal crashes caused by Boeing's failures at many levels - not least of which was to not tell the pilots that flew them about the existence of a critical safety feature in the form of MCAS. It also transpired that to save money it was only connected to one of three possible systems - something Airbus had had in place from the beginning back in the 80s. My observation would be that, rather than humbly deal with the issue, much very unhelpful talk has taken place within the US about how, 'this is all about terrible African pilots' and 'us Americans would never have that'. Rather than just say, 'we blew it' and just get on and sort it, some of the political rhetoric from uninformed people has been nothing short of embarrassing to an industry that should be above all that. That said, it transpired that Airbus's stall recovery training was woefully inadequate, as I discovered when I did my type rating back in 2001. The training at the time was not far from, 'Don't worry - the Airbus does not stall' and we moved on. This lack of adequate training and suitably qualified simulators contributed hugely to the Air France 447 A330 accident in 2009 and the Indonesia AirAsia Flight 8501 A320 accident in 2014. Therefore Airbus has to have some degree of humility here - as I think they do. Most Airbus pilots who have been on the type for many years will have observed radical changes in training from when they first did the type rating to what happens now in both initial and recurrent training. Airbus has also been very fortunate not to lose aircraft under similar circumstances and, frankly, got lucky when the AoA probes froze up on a couple of occasions.

However, it is the 737 MAX that is in the glaring light of publicity right now and the optics are not good. Two fatal crashes and now a terrible bit of manufacturing/maintenance that should simply never have happened. The Airbus A320 Series NEO is already a mature product that requires virtually no extra training from a regular A320 CEO. It has been a seamless success in terms of entry into service. Unless Boeing do something very quickly to sort this mess out and restore confidence, their 737 MAX is well on the way to suffering the same fate as the Comet. Time is not on their side to do so.

[Sailvi767]

Airbus is not without fault. They knew well before the AirFrance accident that the pitot anti ice system was inadequate and could lead to serious consequences yet failed to address the issue in a timely manner.

[xetroV]

Y’know, I haven’t seen a lot of Southwest pilots here griping about 737’s…
I personally prefer the 737's that I fly to remain in one piece, but perhaps Southwest pilots are more tolerant than I am regarding minor annoyances such as doors falling from their aircraft or primary flight controls becoming unusable due to loose bolts. (I don't believe that for a second, though.)

[TURIN]

Y’know, I haven’t seen a lot of Southwest pilots here griping about 737’s…
How would any of us know? Do SW Pilots have a special emoji identity card?

[421dog]

I would merely suggest, that as an intimate companion of multiple SWA pilots, they never had a 737 max issue that scared them, and they were trained in the sim for a trim runaway related to an AOA sensor failure.
Nobody died over here…..

[T28B]

Back to the bolts, if you please.

[Count of Monte Bisto]

Airbus is not without fault. They knew well before the AirFrance accident that the pitot anti ice system was inadequate and could lead to serious consequences yet failed to address the issue in a timely manner.

Did I not just say that?

421dog - I think you will find that the problem is that plenty of people have died. Given recent events, it is extremely fortunate that a whole lot more did not. I think the MAX has now run out of rope. If some other significant incident/accident occurs that can be reasonably laid at the feet of the manufacturer or the aircraft itself then it will have a catastrophic effect on the willingness of passengers to fly on those aircaft. Whether that is fair or not becomes a moot point. Consumer confidence is very hard to define in absolute terms. However, we all know when it is exists and when it does not.

[turbidus]

Airbus is not without fault. They knew well before the AirFrance accident that the pitot anti ice system was inadequate and could lead to serious consequences yet failed to address the issue in a timely manner.

You are aware of the anti-ice issues on the MAX aircraft?

Its one of the reasons holding up cert on the MAX 7.

On the MAX door plug bolts...the FAA has rejected Boeings inspection procedures.

Its a door plug, not a plug door...that difference in design is significant.

Trying to find a discussion oN pprune about the flight deck door opening on decompression.

this appears to be a significant design flaw....

While "loose lips sink ships"
loose nuts crash aircraft

[PAXboy]

Airline regulators will not be rushed into clearing grounded Boeing 737 Max 9 planes after a mid-air blowout, the US government has said.
As reported on BBC Web News (https://www.bbc.co.uk/news/business-67943988)
The aircraft, which were suspended in the US following an incident on an Alaska Airlines flight "need to be 100% safe", said Transportation Secretary Pete Buttigieg.It is unclear when the planes will be allowed to fly again.

Boeing's boss, Dave Calhoun, described the incident as a "quality escape".
Well, at least it was not a 'failure' Phew.

[Lonewolf_50]

PAXboy, I guess you aren't up on maintenance and production jargon.
Quality Escape is a professional's term that applies to cases like this, and it isn't limited to Boeing-speak.
Here is some reading material for you to take a look at.
The-Analysis-of-Quality-Escapes-in-the-Aerospace-Defense-Industry.pdf (ren-services.com) (https://www.ren-services.com/wp-content/uploads/2014/10/The-Analysis-of-Quality-Escapes-in-the-Aerospace-Defense-Industry.pdf)

In gross terms, quality escapes are nothing more than inability to manage the details. Not surprisingly, the root causes of numerous quality escapes are found in the flow and interpretation of technical requirements. These root causes often take the form of ambiguity in the original requirements, failure to adequately evaluate the results of requirements interpretation, or simply overlooking the requirements.
And a bit of motherhood
In fact, the current quality imperative across all industry sectors has focused a harsh light on quality escapes.
Six Sigma has become the stated objective of prime contractors and their suppliers across the aerospace supply chain. Industry sponsored organizations which formulate quality policies and procedures have instituted strict standards (e.g., AS9100) which exceed ISO in their requirements.
This is particularly true in areas such as management of characteristics, control of manufacturing processes, adherence to specifications, and configuration management. Aerospace prime contractors are increasingly requiring their suppliers to achieve AS9100 registration.

The industry is also applying the first article inspection methodology prescribed in AS9102 which places strong emphasis on characteristic accountability. This emphasis is largely based on the recognition that many quality escapes happen with the very first production unit as a result of an inadequate first article inspection. {Renaissance Services White Paper: The Analysis of Quality Escapes in Aerospace & Defense 2} With all of this emphasis on quality, the continued occurrence of escapes is a driving factor in the establishment of programs such as e-LINCS. While AS9100 and related standards seek to legislate a certain level of quality behavior, the tools needed to ensure confidence in their compliance are largely absent from the primes and their supply chain.
The Qantas A380 flight over Malaysia (much discussed on PPRuNe) whose RR/Trent turbofan lost a turbine disc was, all said and done, a RR Quality Escape. (Investigatore eventually found out the root cause for why the lube line failed which led to the chain of events that resulted in the turbine disc leaving the aircraft...uncontained...)

(In comparison, the MCAS mess was a combined design and systems training system error, or at least that how I'd categorize it).

[hoistop]

I'm always looking for good examples where 'obvious' control measures are not as good as people expect: could you give me a pointer/link to the relevant research providing evidence that "there is 10% chance that duplicate inspection will not catch the fault". A quick Internet search hasn't given me any obvious candidates - and a lot of procedures are designed around (semi-)independent sign-off, as in: A does the job and logs it as done, B checks and logs that it has been checked. It's relevant in many areas, not 'just' aircraft maintenance.

I took it from my "Human Factors in Maintenance" training book, but unfortunatelly it only says it came from a 1960s research on work on electronic and missile systems, with no direct pointer to the research. I take it as such. In my 30+ years in aviation maintenance I was involved in more than one investigation, (politely said) where a maintenance incident was not prevented by duplicate inspection, so I can attest that such omissions are not extremely rare.

[Semreh]

T28B; I'm reading your posts. It could be I'm the only one? :confused:
No, you are not.
However, I think it would be useful if the thread title were changed to 737 Max: Loose Rudder-Control Fastener Issue.

It is unfortunate that the Alaska airlines door-plug blowout seems to be narrowing down to loose or missing fasteners as well. While it is possible that there is a common Quality Control / Quality Assurance issue at play, it is confusing.

[601]

routine presence of foreign object debris [FOD] in Spirit products, missing fasteners, peeling paint, and poor skin quality.

Are they all actually "defects"

Some would appear to be "human error" in that a human did not insert a bolt, torque the bolt to the correct value and insert a cotter pin.
Some of the terminology coming from the FAA is disheartening.
"bolt with missing nut" Obviously the "missing" nut was found!
"a plug type passenger door". Surely it is "a emergency exit plug "

[bri21]

As a long retired 80-something engineer in both the aviation and nuclear industries, as both a producer and an inspector, I suspect that there has been too much attention paid to posh-sounding jargon and too little attention to the nitty-gritty detail of turning out good-quality work. Too much focus on money always produces these issues.

[Lonewolf_50]

As a long retired 80-something engineer in both the aviation and nuclear industries, as both a producer and an inspector, I suspect that there has been too much attention paid to posh-sounding jargon and too little attention to the nitty-gritty detail of turning out good-quality work. Too much focus on money always produces these issues. Indeed, sir. Jargon and technical language can create their own difficulties. But among professionals, coining particular terms can allow for a common understanding. To give particular things usable definitions, and to differentiate one thing from another similar thing, is useful.
(See the back and forth about door plug and plug door as but one example).

As I suggested above, it is useful in this case, I think, to differentiate between a design error (MCAS), a training system error (MCAS) and a process error (these bolts). Why? Because getting the right solution/correction is aided by identifying the problem and the cause.

(And of course, some the jargon is tribal short hand which doesn't help much ... )

[golfbananajam]

https://www.faa.gov/newsroom/faa-increasing-oversight-boeing-production-and-manufacturing

WASHINGTON, D.C. — After taking decisive and immediate action to ground approximately 171 Boeing 737-9 MAX planes, the Federal Aviation Administration (FAA) today announced new and significant actions to immediately increase its oversight of Boeing production and manufacturing. These actions come one day after the FAA formally notified Boeing that the FAA has launched an investigation into the company as a result of last Friday’s incident on a Boeing Model 737-9 MAX in which the aircraft lost a passenger door plug while in flight.

The actions announced today include the FAA conducting:

An audit involving the Boeing 737-9 MAX production line and its suppliers to evaluate Boeing’s compliance with its approved quality procedures. The results of the FAA’s audit analysis will determine whether additional audits are necessary.
Increased monitoring of Boeing 737-9 MAX in-service events.
Assessment of safety risks around delegated authority and quality oversight, and examination of options to move these functions under independent, third-party entities.

"It is time to re-examine the delegation of authority and assess any associated safety risks," FAA Administrator Mike Whitaker said. "The grounding of the 737-9 and the multiple production-related issues identified in recent years require us to look at every option to reduce risk. The FAA is exploring the use of an independent third party to oversee Boeing’s inspections and its quality system."

Yesterday, the FAA announced an investigation to determine if Boeing failed to ensure completed products conformed to its approved design and were in a condition for safe operation in compliance with FAA regulations. The letter to Boeing is available here (https://www.faa.gov/newsroom/updates-grounding-boeing-737-max-9-aircraft).

The safety of the flying public, not speed, will determine the timeline for returning the Boeing 737-9 MAX to service.

[T28B]

However, I think it would be useful if the thread title were changed to 737 Max: Loose Rudder-Control Fastener Issue.
Good suggestion, and done! :ok::)

[BFSGrad]

A quality control lapse at Boeing discovered in December has proved less significant than it at first appeared. Airlines worldwide have inspected the rudders on the more than 1,400 Boeing 737 MAX aircraft in service globally for loose bolts and found no faults.

Rudder bolts inspected on all Boeing 737 MAXs; no more faults found (https://www.seattletimes.com/business/boeing-aerospace/rudder-bolts-inspected-on-all-boeing-737-maxs-no-more-faults-found/)