Come on, Boeing.

[BEC]

I saw the below diagram posted on facebook. From this and other diagrams it appears that there are 12 bolts and 2 hinges holding the plug in place. Not that you couldn't have a failure at one bolt and then have cascading failures at the others. The written explanation along with the photo sounded to me like facebook BS: "IAW NTSB report what cause de door plug separation on Alaska airlines 1282: The door translated upward direction and disconnected from all 12 door stops which resulted in the upper guide fitting to fracture"
View attachment 623785

Actually, that is a fair description. In order to actually open, the door has to translate upward, which causes the roller pins at the top to go up and out of the guide track. Two of the currently-unaccounted-for bolts trap the roller pins in the guide tracks so that the plug can't move. It has to move up so that the stop fittings on the plug clear the stops on the body frames. Normally the fittings are pressed against the stops and pressurizing the airplane holds them there.

A great video on this here:


Note that he has the door motion (up vs down) but otherwise this is a great explanation. That business gets sorted in the comments....and points out an error in at least some editions of the Airframe Maintenance Manual (yet another can of worms).

It also reminds me that I have been mis-stating the "activated vs. deactivated mid-exit door" business. I had forgotten that there are actually THREE choices here: an activated and therefore usable door, as needed whenever there are more than 189 passenger seats in the cabin, a deactivated door, which is a fully functional door that is completely covered over on the inside (and with no window on the inside) and the plugged option that Alaska and United and Delta (for their 900ERs) use.

An operator or a lease company owner might want the deactivated door option if they expect to be converting the interior from a 189-seats-or-less to one with more during the life of the airplane, as it would be far less costly to basically just reconfigure the interior stuff (and tell the Proximity Switch Electronics Unit what was going on - its job is to, among other things, tell the flight crew about doors ajar) than to add in all the functional door bits later.

But if the owner of the airplane isn't planning any serious interior capacity changes, then taking the plug gives a full-sized window as we have seen in all this discussion.

I should go back to previous posts and fix where I've been calling the plug option a deactivated door option. They are not the same thing as I am now reminded.

 

[user 13]

https://en.wikipedia.org/wiki/British_Airways_Flight_5390
Not a 737, not a Boeing.

 

[smstachwick]

https://en.wikipedia.org/wiki/British_Airways_Flight_5390
Not a 737, not a Boeing.

Also a maintenance error, probably brought on in part by BA’s demanding maintenance schedule.

 

[Sooner Boomer]

Isn't that the way it usually is done- a nut on a bolt or stud gets a cotter pin, bolts are drilled and safety wired. Is there a situation where you safety wire a nut on a bolt or stud instead of using a cotter pin?

I've worked on a lot of nuts with cotter pins, they seem 100% secure to me. I've never seen one come off before you wanted it to come off. Safety wiring is perhaps easier to do if you have a lot of fasteners close together.

I've worked on a lot of cars and never had a problem installing and tightening every fastener that I removed. I did take a car into the dealer for a repair years ago right before the warranty expired. The next morning after I picked it up I got a call from the dealer asking me to bring it back in, the mechanic had woke up in the middle of the night wondering if he had properly tightened the bolts holding the steering rack in. I took the car back and found that everything was done right the first time.

Typically, the shaft of the bolt (or machine screw, or stud) is cross drilled and uses a castle nut/cotter pin. Again, typically, the *heads* of bolts are cross drilled and safety wired. The reason for doing it this way is because when a nut rotates, it can shear off even a cotter pin if enough force (torque) is applied*. Safety wire is much thinner than a cotter pin.
[edit] Bolts that have the head cross /safety wired are typically going into "blind" holes - being screwed onto a solid surface with no way to put a nut on the back side.

*I've seen lazy mechanics do this on purpose, rather than remove the cotter pin.

 

[Bravo52]

Typically, the shaft of the bolt (or machine screw, or stud) is cross drilled and uses a castle nut/cotter pin. Again, typically, the *heads* of bolts are cross drilled and safety wired. The reason for doing it this way is because when a nut rotates, it can shear off even a cotter pin if enough force (torque) is applied*. Safety wire is much thinner than a cotter pin.

*I've seen lazy mechanics do this on purpose, rather than remove the cotter pin.

I get the point you are trying to make, but it clearly doesn't apply here.

I can't conceive of a rotational force that could shear a cotter pin as installed on those through bolts as they were used in the plug application. Even if the heads were safety wired (I don't think they were). Vibration alone would not do it. Pressurization cycles wouldn't do it. The fact there are hundreds (thousands?) of these plugs in service or where in service seems to point to a different direction.

In my opinion, the hardware was missing/damaged/incorrectly installed/sabotaged (take your pick) after the folks on the line at Renton re-installed the plug.

 

[Cape Byron]

Indeed.

I've watched crop dusters in Idaho. The are fearless.

 

[BEC]

Actually, an image posted earlier in this thread shows three of the four bolts whose whereabouts are currently unknown. I have circled them here:

The bottom one, in particular, is hard to see in this view (and its counterpart is hidden by the seats to the left in the image. The top two prevent the guide track from moving up along the roller pins in the door frame. The lower two prevent that portion of the hinge assembly from allowing the door to move up. Both motions are necessary for the door/plug to go upwards (and outwards at the top) enough to get the stop fittings over the stops.

Given the size of the bolts, I will be surprised if they are recovered — assuming they were there before this flight. It’s also hard to imagine any sort of loading that would cause them to turn with enough force to shear the cotter pins.

Here is another picture which has been posted twice (at least) already in this thread, but with the wrong fasteners circled. It’s a much closer view of the bottom one in the picture above:


This bolt (and the one on the other side — to the right on the other side of the door in this picture) prevents the door hinge fitting through which it passes for moving up on the shaft (black area above) which allows the door/plug to move up off the stops before opening.

The NTSB info says they’ll be able to determine from looking at these areas if the bolts were ever there. If they were and they somehow worked loose and fell out that’s one problem. If they weren’t there at all, that’s another. Either way, it looks pretty sorry for Renton Final Assembly. *sigh* again…

 

[bjphoenix]

The bottom one, in particular, is hard to see in this view (and its counterpart is hidden by the seats to the left in the image. The top two prevent the guide track from moving up along the roller pins in the door frame. The lower two prevent that portion of the hinge assembly from allowing the door to move up. Both motions are necessary for the door/plug to go upwards (and outwards at the top) enough to get the stop fittings over the stops.

That's what I was thinking- the facebook report said the door moved upwards. It appeared to me that there were 12 bolts that would act to prevent the door from moving upwards.

 

[BEC]

Kind of. There are four bolts as I mentioned above. The twelve points you see are stops and stop fittings. They are not connected by fasteners between the parts fixed to the door frames and the parts fixed to the airplane frames. They just rest against one another when the door is closed/plug is in place.

 

[Sooner Boomer]

I get the point you are trying to make, but it clearly doesn't apply here.

I can't conceive of a rotational force that could shear a cotter pin as installed on those through bolts as they were used in the plug application. Even if the heads were safety wired (I don't think they were). Vibration alone would not do it. Pressurization cycles wouldn't do it. The fact there are hundreds (thousands?) of these plugs in service or where in service seems to point to a different direction.

In my opinion, the hardware was missing/damaged/incorrectly installed/sabotaged (take your pick) after the folks on the line at Renton re-installed the plug.

I agree with your points above..

(I was just trying to point out how/when cotter pinned nuts/safety wired bolts were used)

 

[ksaves2]

And if you watch those Top Gun movies, you'd think that the Navy would *want* dangerous pilots.

I don't care how good Tom Cruise looks. I don't think the services would allow a 60 year old to fly a high performance fighter!
Maybe a run of the mill transport plane but not a high "G" fighter. I only watched T.G. to see the jets and know that there were
very qualified service pilots who put on the show.

 

[techrat]

I don't care how good Tom Cruise looks. I don't think the services would allow a 60 year old to fly a high performance fighter!

Never mind that. 5 minutes into the movie, I wondered how a Navy Captain can afford a pristine P-51, when actual Billionaires have trouble obtaining them.

 

[ksaves2]

Never mind that. 5 minutes into the movie, I wondered how a Navy Captain can afford a pristine P-51, when actual Billionaires have trouble obtaining them.

Agree whole-heartedly. If the time frame was in the '60's I could see it but in modern times a '51 is a few million dollars. Cruise bought one and that's
probably his in the movie. I saw Cruise online interviewing a NASA astronaut one time and the guy's eyes bugged out when Cruise invited him to come to
California for a ride in his P-51. Cruise prefaced the conversation with, "You're a test pilot aren't you?" The astronaut replied "Yes". Cruise said, "Ever fly a P-51?" The astronaut replied they tried to arrange it for them (test pilot class) but it never came about. Tom Cruise then invited the astronaut to come to
California to fly in "his" P-51. You could see it in the astronaut's face he was amazed! Hope he got his ride. Kurt

 

[Blast it Tom!]

Agree whole-heartedly. If the time frame was in the '60's I could see it but in modern times a '51 is a few million dollars. Cruise bought one and that's
probably his in the movie. I saw Cruise online interviewing a NASA astronaut one time and the guy's eyes bugged out when Cruise invited him to come to
California for a ride in his P-51. Cruise prefaced the conversation with, "You're a test pilot aren't you?" The astronaut replied "Yes". Cruise said, "Ever fly a P-51?" The astronaut replied they tried to arrange it for them (test pilot class) but it never came about. Tom Cruise then invited the astronaut to come to
California to fly in "his" P-51. You could see it in the astronaut's face he was amazed! Hope he got his ride. Kurt

Me too. The Commemorative Air Force will sell you a ride, but it'd be a real "bucket list" item for most, I suspect. Depending on location and length, it's anywhere from $1,895 to $4,000 (40 minute ride, $100/minute!). But proceeds certainly go to a good cause, if you like the old warbirds.

I don't care how good Tom Cruise looks. I don't think the services would allow a 60 year old to fly a high performance fighter!

I have a talk by an ex-test pilot who said that they used to make the older guys step aside, until they realized that they were surprisingly adept, and used to the g's. He related that after helping develop a mission for a new fighter (I suspect by the time frame it was the F-22), he was with a group of young fighter jocks to train them on the aircraft. When told he was their pilot, one of the jocks wisecracked, "Will he need a cane to get to the aircraft?". After said young jock's ride, he was so disoriented he had to be helped from the plane. The old test pilot said he couldn't resist - he leaned over and asked him, "Do you wanna borrow my cane?"

 

[NTP2]

https://en.wikipedia.org/wiki/British_Airways_Flight_5390
Not a 737, not a Boeing.

I didn’t say same it could have had a similar failure.

 

[watheyak]

I didn’t say same it could have had a similar failure.

There is an important distinction between these two accidents that I think needs to clarified.

The BA cockpit window incident was a maintenance issue. Blame was placed squarely on British Airways.

On the Alaska flight were discussing here it was NOT a maintenance issue., It was a Boeing manufacturing issue. Alaska Airlines has outstanding maintenance an I don't want anyone to think otherwise. In the past week I've had to explain this distinction many times to people who only read headlines.

I think most of the people reading this thread understand this, but it's becoming a bit of a hot button item as I find myself having to explain it often.

My wife and I are both Alaska pilots and huge Boeing fans. The 737 has been one of my wife's favorite planes since she was a child (she's weird), so the dinner and social conversation has been interesting as of late.

 

[chuck5395]

Actually, an image posted earlier in this thread shows three of the four bolts whose whereabouts are currently unknown. I have circled them here:
View attachment 623813
The bottom one, in particular, is hard to see in this view (and its counterpart is hidden by the seats to the left in the image. The top two prevent the guide track from moving up along the roller pins in the door frame. The lower two prevent that portion of the hinge assembly from allowing the door to move up. Both motions are necessary for the door/plug to go upwards (and outwards at the top) enough to get the stop fittings over the stops.

Given the size of the bolts, I will be surprised if they are recovered — assuming they were there before this flight. It’s also hard to imagine any sort of loading that would cause them to turn with enough force to shear the cotter pins.

Here is another picture which has been posted twice (at least) already in this thread, but with the wrong fasteners circled. It’s a much closer view of the bottom one in the picture above:

View attachment 623814
This bolt (and the one on the other side — to the right on the other side of the door in this picture) prevents the door hinge fitting through which it passes for moving up on the shaft (black area above) which allows the door/plug to move up off the stops before opening.

The NTSB info says they’ll be able to determine from looking at these areas if the bolts were ever there. If they were and they somehow worked loose and fell out that’s one problem. If they weren’t there at all, that’s another. Either way, it looks pretty sorry for Renton Final Assembly. *sigh* again…

Can someone explain why are these door plugs installed with springs designed to assist in the lifting of the plug out of the tracks when they are never intended to be opened in their final configuration?

 

[NTP2]

There is an important distinction between these two accidents that I think needs to clarified.

The BA cockpit window incident was a maintenance issue. Blame was placed squarely on British Airways.

On the Alaska flight were discussing here it was NOT a maintenance issue., It was a Boeing manufacturing issue. Alaska Airlines has outstanding maintenance an I don't want anyone to think otherwise. In the past week I've had to explain this distinction many times to people who only read headlines.

I think most of the people reading this thread understand this, but it's becoming a bit of a hot button item as I find myself having to explain it often.

My wife and I are both Alaska pilots and huge Boeing fans. The 737 has been one of my wife's favorite planes since she was a child (she's weird), so the dinner and social conversation has been interesting as of late.

I’m not trying to put blame on the maintenance people at Alaska or British, I was wondering more specifically about the bolt failures.

Ps I’m a airbus fan myself…

 

[brockrwood]

One thing is for certain: After all of the groundings and scrutiny, the 737 Max is going to be the safest airplane in the sky.

 

[brockrwood]

I’m not trying to put blame on the maintenance people at Alaska or British, I was wondering more specifically about the bolt failures.

Ps I’m a airbus fan myself…

Airbus uses those weird joysticks. You should have both hands on wheel you are driving a plane. ;-)

 

[smstachwick]

One thing is for certain: After all of the groundings and scrutiny, the 737 Max is going to be the safest airplane in the sky.

More likely it’ll be in compliance with the FAA’s airworthiness standards that apply to every other Part 25 transport-category airplane, which it should have been from the beginning but clearly wasn’t.

 

[BEC]

Can someone explain why are these door plugs installed with springs designed to assist in the lifting of the plug out of the tracks when they are never intended to be opened in their final configuration?

I've been wondering about that a bit. I expect they are part of the activated/deactivated door design that was retained in the plug. The video to the fellow in the UK I posted a bit up the thread said something about them being there to prevent the door/plug from accidentally falling completely closed while work is being done in the opening sort of sounds plausible.

This is a question for my former colleagues in Door Structures....but I expect asking right now is probably not going to yield an answer that would be allowed to go outside the company. I'm sure there are lawyers circling....

 

[watheyak]

I've been wondering about that a bit. I expect they are part of the activated/deactivated door design that was retained in the plug. The video to the fellow in the UK I posted a bit up the thread said something about them being there to prevent the door/plug from accidentally falling completely closed while work is being done in the opening sort of sounds plausible.

This is a question for my former colleagues in Door Structures....but I expect asking right now is probably not going to yield an answer that would be allowed to go outside the company. I'm sure there are lawyers circling....

I think the question of the springs becomes moot if you use all the parts that come in the kit.

 

[BEC]

I think the question of the springs becomes moot if you use all the parts that come in the kit.

Agreed. Use the parts and install them correctly and the plug stays plugged as it should (and as it has been since 2006 on the 900ER).

 

[boatgeek]

I think the question of the springs becomes moot if you use all the parts that come in the kit.

Hey, what are these bolts left over? I'll just drop them off in the recycling, less paperwork that way.

Can someone explain why are these door plugs installed with springs designed to assist in the lifting of the plug out of the tracks when they are never intended to be opened in their final configuration?

I wonder if it's just an ease of manufacturing issue. If installing the plug without springs would take N people 2 hours, and it takes N-1 people 2 hours with the springs, then it makes manufacturing sense to use the springs if they cost less than 2 hours of hourly rate. Of course, that rolls down to whatever maintenance needs doing later in the plane's lifetime, but that doesn't (exactly) matter to Boeing.

A friend asked me an interesting question--is it just one worker who was doing a bad job at tightening bolts? At first, that seemed sort of ridiculous, then I started doing math. With deliveries around 32 jets/month, 8 planes go past a particular station per week. Assuming 4 hours to install and cotter pin 8 bolts (1 plug on each side of the plane, 4 bolts per plug) then we get 32 hours/week. That's a totally reasonable workload for one person once you add training, breaks, stupid corporate BS, etc. I don't know if the manufacturing floor has what amounts to job monopolies ("George here is the best damn plug bolt installer there is!"). I know I would go spare if I was looking at the same four bolts every day for months on end. But maybe going spare/getting burnt out/having a bad month due to personal issues is the root of the problem. On the other hand, for simplicity of training, you'd like to have a relatively small pool of people doing a particular task if it's not a monopoly.

Of course, there's QA/QC that should have caught the loose bolts before they were covered up, but that's another issue.

 

[BEC]

And all the fuselages come to the same big fixed "tool" for systems/insulation installation before being carried off by crane to four final assembly moving lines. So yeah, that's kind of plausible. Especially since probably a good chunk of those 32 airplanes a month are -8s, which don't have these plugs (or real functional doors there) in them.

 

[ksaves2]

Me too. The Commemorative Air Force will sell you a ride, but it'd be a real "bucket list" item for most, I suspect. Depending on location and length, it's anywhere from $1,895 to $4,000 (40 minute ride, $100/minute!). But proceeds certainly go to a good cause, if you like the old warbirds.

I have a talk by an ex-test pilot who said that the used to make the older guys step aside, until they realized that they were surprisingly adept, and used to the g's. He related that after helping develop a mission for a new fighter (I suspect by the time frame it was the F-22), he was with a group of young fighter jocks to train them on the aircraft. When told he was their pilot, one of the jocks wisecracked, "Will he need a cane to get to the aircraft?". After said young jock's ride, he was so disoriented he had to be helped from the plane. The old test pilot said he couldn't resist - he leaned over and asked him, "Do you wanna borrow my cane?"

Glad to hear that. It's a cool story. One thing I wonder is what happens if they develop cataracts? Now I have a lazy/amblyopic right eye and never would have been able to get a 1st class medical. I forsook flying and went into medicine. Never flew again except on commercial airlines. My left eye was rated as 20/12 with correction back then but my brain ignored my right eye. Never had "stereoscopic" vision and supposedly wouldn't be able to judge distance. Thing is my brain compensated and I was able to put a small plane "on the numbers" with practice. I could have obtained a private pilot license with a medical waiver but quit flying when I went to college.
I suspect if a commercial pilot develops cataracts early in life, as long as they get the lens implants, they can use reading half glasses to read the instrument panel.
Also there are lens implants that are flexible that the eye can focus but they cost more $$$$$$ and depends upon the prescription. I'm very farsighted and the opthalmologist said they wouldn't work well for me and go with single vision implants and reading glasses when I had cataracts at age 56. (Which I can buy at Walmart mind you. No more $895.00 prescription glasses anymore.) Oh, the accommodating implants do eventually become less effective with age so I was told. That might have changed now. My late brother was extremely near-sighted and had cataract surgery when he was 50!
Kurt

 

[Reinhard]

One thing is for certain: After all of the groundings and scrutiny, the 737 Max is going to be the safest airplane in the sky.

I had similar thoughts in 2021, when the MAX returned to flight. Apparently, I was wrong then and now I have no idea what to expect from the foreseeable future.
I guess at least in the long run, Boeing will get it's act together again but part of me wonders if this was already the last skeleton in the closet.

Reinhard

 

[brockrwood]

I had similar thoughts in 2021, when the MAX returned to flight. Apparently, I was wrong then and now I have no idea what to expect from the foreseeable future.
I guess at least in the long run, Boeing will get it's act together again but part of me wonders if this was already the last skeleton in the closet.

Reinhard

Surely this has to be the last major problem for the 737 Max? If there is another fatal accident with the Max and it is shown to be a design flaw or manufacturing defect, methinks that is the end of the Max.

Anyway, all of this should prove to Boeing that it is time to get the “Future Single Aisle” (FSA) aircraft development going.

 

[bjphoenix]

Kind of. There are four bolts as I mentioned above. The twelve points you see are stops and stop fittings. They are not connected by fasteners between the parts fixed to the door frames and the parts fixed to the airplane frames. They just rest against one another when the door is closed/plug is in place.

4 bolts? Are there other mechanical devices that hold the door in besides all of the load being on 4 bolts? I'm estimating nearly 10,000# acting on the door which is easy enough for 4 bolts to resist.

Boeing jokes are starting: