Alaska Airlines 737-900 MAX loses a door in-flight out of PDX
Both the principal FDR/CVR vendors (Honeywell and L3/Harris) have (different) 2-hour and 25-hour CVRs in their product lines. AFAIK there is no provision for restricting newer 25-hour units so that they only record 2 hours.
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The zip wire
Just a question. If that zip-wire was in place when the aircraft was flying, and the major thing blocking vertical movement of the door-plug, would there be wear and tear marks in the paint, or is the material too soft?
ZIp ties are usually made of Nylon - at least the white ones are. It would be possible for it to leave a mark on paint. However, I would question the tie having the strength to do very much (as others and I commented earlier).
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There is a reason they are used as handcuffs. It is sharp edges and sunlight over time that weakens them. And they do stretch with a constant very strong pull.
Psychophysiological entity
I'm aware that among others I've locked horns with a good technician when I again become vociferous about that tie. It's not the strength but the angle of the loops. Has my brain finally failed or would we be looking at the cosign of the angle when it comes to plain old tug? It would rotate a long way before stopping that vertical movement.
I'm aware that among others I've locked horns with a good technician when I again become vociferous about that tie. It's not the strength but the angle of the loops. Has my brain finally failed or would we be looking at the cosign of the angle when it comes to plain old tug? It would rotate a long way before stopping that vertical movement.
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To simplify, say the support of the stop pin and the stop pad are 1" long and high, and the gap is 0.7". The whole "circumference" when they are aligned is 6" + 2 x 0.7" for the gap, that is 7.4".
If the door rise half of the height of the stop pad, the circumference becomes 4" + 2 x sqrt[(1+0.7)^2 + 0.5^2]. With sqrt(2.89 + 0.25) = 1.772, the circumference becomes 7.544" which is 2% more. Not much, but for the door blows out, it has to rise 1":
For the door rises 1" the tie has to stretch to:
4" + 2 x sqrt[(1+0.7)^2 + 1^2] that is 4" + 2 x 1.972 = 7.945
which is 107.3 % of the original length.
Is that enough to keep the door closed? I don't know for sure, but is seems possible if the tie has been tightened well.
But a problem remains. If you look again at the post #1751 pic, the tie has to be put a little "sideways". There is nothing to prevent it from slipping on the outside side of the stop pad, because on the non visible side (on this pic) of the stop pad, there is only a hole (see the second pic of the post #1620). But anything put in the hole can do the job! One of the missing bolts?
Anyway, it is strange there is noting about this possible tie in the preliminary report. Could it be a scratch on the pic? It is hard to believe.
Sorry for not having the links to the pics (or the pics) in the post, but I believe I am not allowed to do it.
Regards,
PL
I think Loose Rivets is suggesting that the tie would not be in the position it appears to be in the picture if it were the only thing resisting the spring force.
There's a similar possible objection even if it were in a figure 8. In that case the door could move up unit the pad cleared the stop without changing the overall length of the 8. One of the two segments that cross at the center of the 8 would have to lengthen, but the other would want to get shorter by the same amount.
Of course, either configuration would be possible if the spring were weak enough, or if there were enough friction between the pad and the stop, between the tie and the metal parts, or somewhere else in the system.
There's a similar possible objection even if it were in a figure 8. In that case the door could move up unit the pad cleared the stop without changing the overall length of the 8. One of the two segments that cross at the center of the 8 would have to lengthen, but the other would want to get shorter by the same amount.
Of course, either configuration would be possible if the spring were weak enough, or if there were enough friction between the pad and the stop, between the tie and the metal parts, or somewhere else in the system.
Psychophysiological entity
No, in fact I know so little about the residual sprung up-force despite all the calculations, that I still don't know what the door would do without restraint(s) of some kind. We've seen a feeler gauge in one shot which really surprised me having felt sure there'd be a residual pin/pad pressure to align the plug with the fuselage. But it seems not. So, no bolts, and no mystery ties, and there's a high probability the door will 'float'. Which makes a pair of firmly pulled ties a significant, quote, 'smoking gun'.
Dave's picture shows the ties 3-ish pixels across. Knowledgeable information tells us that it was on the right edge (forward) of the accident aircraft, but not when. What is certain is that if it was there when the plug departed, the tie would have marked the paintwork. That it would have held the plug down for >hundred flights. Meh, still don't think so. But that's all, just a gut feeling.
So much of my engineering came from disappointment. You know, the clatter of exhaust pipes that had hither to been held on with Terry clips. That kind of learning. Looking at that tie, I'm not convinced it would have to follow the cos of the angle of the loops, but 'only' the pin across the pad? It would be very near the edges when it/they became tight. But then, pad edges were damaged.
It's important because it/they could be the answer to how the plug stayed down for so long. If they were there, then it's certainly worth some involved experimentation.
Dave's picture shows the ties 3-ish pixels across. Knowledgeable information tells us that it was on the right edge (forward) of the accident aircraft, but not when. What is certain is that if it was there when the plug departed, the tie would have marked the paintwork. That it would have held the plug down for >hundred flights. Meh, still don't think so. But that's all, just a gut feeling.
So much of my engineering came from disappointment. You know, the clatter of exhaust pipes that had hither to been held on with Terry clips. That kind of learning. Looking at that tie, I'm not convinced it would have to follow the cos of the angle of the loops, but 'only' the pin across the pad? It would be very near the edges when it/they became tight. But then, pad edges were damaged.
It's important because it/they could be the answer to how the plug stayed down for so long. If they were there, then it's certainly worth some involved experimentation.
No, in fact I know so little about the residual sprung up-force despite all the calculations, that I still don't know what the door would do without restraint(s) of some kind. We've seen a feeler gauge in one shot which really surprised me having felt sure there'd be a residual pin/pad pressure to align the plug with the fuselage. But it seems not. So, no bolts, and no mystery ties, and there's a high probability the door will 'float'. Which makes a pair of firmly pulled ties a significant, quote, 'smoking gun'.
Dave's picture shows the ties 3-ish pixels across. Knowledgeable information tells us that it was on the right edge (forward) of the accident aircraft, but not when. What is certain is that if it was there when the plug departed, the tie would have marked the paintwork. That it would have held the plug down for >hundred flights. Meh, still don't think so. But that's all, just a gut feeling.
So much of my engineering came from disappointment. You know, the clatter of exhaust pipes that had hither to been held on with Terry clips. That kind of learning. Looking at that tie, I'm not convinced it would have to follow the cos of the angle of the loops, but 'only' the pin across the pad? It would be very near the edges when it/they became tight. But then, pad edges were damaged.
It's important because it/they could be the answer to how the plug stayed down for so long. If they were there, then it's certainly worth some involved experimentation.
Dave's picture shows the ties 3-ish pixels across. Knowledgeable information tells us that it was on the right edge (forward) of the accident aircraft, but not when. What is certain is that if it was there when the plug departed, the tie would have marked the paintwork. That it would have held the plug down for >hundred flights. Meh, still don't think so. But that's all, just a gut feeling.
So much of my engineering came from disappointment. You know, the clatter of exhaust pipes that had hither to been held on with Terry clips. That kind of learning. Looking at that tie, I'm not convinced it would have to follow the cos of the angle of the loops, but 'only' the pin across the pad? It would be very near the edges when it/they became tight. But then, pad edges were damaged.
It's important because it/they could be the answer to how the plug stayed down for so long. If they were there, then it's certainly worth some involved experimentation.
No, in fact I know so little about the residual sprung up-force despite all the calculations, that I still don't know what the door would do without restraint(s) of some kind. We've seen a feeler gauge in one shot which really surprised me having felt sure there'd be a residual pin/pad pressure to align the plug with the fuselage. But it seems not. So, no bolts, and no mystery ties, and there's a high probability the door will 'float'. Which makes a pair of firmly pulled ties a significant, quote, 'smoking gun'.
Dave's picture shows the ties 3-ish pixels across. Knowledgeable information tells us that it was on the right edge (forward) of the accident aircraft, but not when. What is certain is that if it was there when the plug departed, the tie would have marked the paintwork. That it would have held the plug down for >hundred flights. Meh, still don't think so. But that's all, just a gut feeling.
So much of my engineering came from disappointment. You know, the clatter of exhaust pipes that had hither to been held on with Terry clips. That kind of learning. Looking at that tie, I'm not convinced it would have to follow the cos of the angle of the loops, but 'only' the pin across the pad? It would be very near the edges when it/they became tight. But then, pad edges were damaged.
It's important because it/they could be the answer to how the plug stayed down for so long. If they were there, then it's certainly worth some involved experimentation.
Dave's picture shows the ties 3-ish pixels across. Knowledgeable information tells us that it was on the right edge (forward) of the accident aircraft, but not when. What is certain is that if it was there when the plug departed, the tie would have marked the paintwork. That it would have held the plug down for >hundred flights. Meh, still don't think so. But that's all, just a gut feeling.
So much of my engineering came from disappointment. You know, the clatter of exhaust pipes that had hither to been held on with Terry clips. That kind of learning. Looking at that tie, I'm not convinced it would have to follow the cos of the angle of the loops, but 'only' the pin across the pad? It would be very near the edges when it/they became tight. But then, pad edges were damaged.
It's important because it/they could be the answer to how the plug stayed down for so long. If they were there, then it's certainly worth some involved experimentation.
Psychophysiological entity
SRMman Yes, I recall. However, while I've done some 'just for fun' PAT tests involving Ideal Springs, your calculations and knowledge of the materials was well out of my pay scale. If it had been Jet Blast, I'd have been looking for the Python, 'Sorry, don't understand the banter' link. :-) Anyway, door held fully up seems most probable, while deepening the mystery.
DTA
I'd love to know about the trim panel. 'Something no one has thought about' teases as well.
DTA
Maybe the tie, the insulation material, the decor/trim panel, stickiness of the seal, perhaps paint and perhaps something no one has thought about.
Hinge Fitting Spring Extension.
If you refer to Figure 15 of the Prelim Report, you can see that the spring is at its max extension and on the stops of the fitting, ie they cannot extend any further because of the washers and nuts on the end of the fitting.
Curiously it also shows that the door is unrestrained by the Lanyard/Strap Assemblies, and the weight of the door appears to be taken by the hinge fittings sitting on the door aperture rim/Seal..
If you refer to Figure 15 of the Prelim Report, you can see that the spring is at its max extension and on the stops of the fitting, ie they cannot extend any further because of the washers and nuts on the end of the fitting.
Curiously it also shows that the door is unrestrained by the Lanyard/Strap Assemblies, and the weight of the door appears to be taken by the hinge fittings sitting on the door aperture rim/Seal..
The plug (it's not a door!) may well be resting on some kind of support/cushion on the gantry outside the fuselage. However, being more or less horizontal it is putting no weight on the spings and so it is not a surprise that they are fully extended. It also means the bottom edge of the plug is held away from the fuselage when opened. The spring compression issue, subject to much speculation on this thread, is only relevant when the door is vertical.
We know the plug weighs 67lb (if I recall correctly) and that the springs are termed by Boeing as "lift assist springs". We also know that the four (missing) retaining bolts carry no vertical load in normal service. The plug is only 2ft wide externally and therefore perhaps only 18 - 20 inches wide in terms of its internal structure (painted green in the images). I suggest this is a bit narrow for a 2-man lift from inside the fuselage (there are no external handles or hand-holds). Hence I assume the plug is designed to be lifted by one person up and over the stop pads in order to open it. In the UK (and probably many countries) lifting a 67lb weight as a one-man lift would not be acceptable on health & safety grounds. So taking all these factors into account, I conclude that the spring lift force must logically be less than 67lb, and would guess it is perhaps around the 40lb mark.
We desperately need someone "in-the-know" to give us the true answer in order to end all this speculation, including mine!
We know the plug weighs 67lb (if I recall correctly) and that the springs are termed by Boeing as "lift assist springs". We also know that the four (missing) retaining bolts carry no vertical load in normal service. The plug is only 2ft wide externally and therefore perhaps only 18 - 20 inches wide in terms of its internal structure (painted green in the images). I suggest this is a bit narrow for a 2-man lift from inside the fuselage (there are no external handles or hand-holds). Hence I assume the plug is designed to be lifted by one person up and over the stop pads in order to open it. In the UK (and probably many countries) lifting a 67lb weight as a one-man lift would not be acceptable on health & safety grounds. So taking all these factors into account, I conclude that the spring lift force must logically be less than 67lb, and would guess it is perhaps around the 40lb mark.
We desperately need someone "in-the-know" to give us the true answer in order to end all this speculation, including mine!
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PL
Wow
The FAA moved to halt planned production increases at Boeing until it was "satisfied that the quality control issues uncovered during this process are resolved." FAA Administrator Mike Whitaker told CNBC in Jan24 that the FAA would keep "boots on the ground" in monitoring Boeing's production, incl factory-floor inspections. In the company's 31Jan2024’s Q4 conference call, CEO Dave Calhoun said, "I'm sort of glad they <the FAA> called out a pause because that's a good excuse to just take our time, do it right."
Note that no system can compensate this, so both an SMS and QMS will turn out to be both costly and useless paper tigers.
We might start calling ‘Boeing Bank’, … high bonus, high risk, high stacks of paper, too big to fail supported by taxpayer guarantees and dollars.
Incredibly sad after reading this.