A very good question that I expect is being asked at airline HQs all over the world. Boeing’s management must be apoplectic, but at this point there is nothing they can believably say except “We now know we are out of control but we trying to regain control. We’ll keep you posted.”
In the immediate aftermath of the first MAX accident some airlines took to explicitly proactively informing folks they were on a MAX with the intent of smoking out any nervous bail-outs early, not at departure time. As best I could tell at the time, the effort yielded near zero results. So was quietly abandoned as unneeded. Some carriers restarted it when the MAXes came back from the long grounding, but again any passenger nervousness was near zero and the effort was quickly forgotten.
So the evidence is that by and large passengers simply assume somebody at the airline or at FAA is minding that store so they don’t have to. Which generally speaking has been and still is true. Until it isn’t.
Two-ish months ago there was another assembly anomaly discovered with loose or missing fasteners. It was Boeing, but I don’t now recall which model. It also didn’t get much traffic outside the airline maintenance / engineering trade press. Nor was there much detail on what exactly was loose or missing how.
If indeed something is very out of control at the factory(ies) and their build quality is both bad and unknown amounts of bad, that could kill the whole program.
Airlines believing they needed to perform a whole full-teardown D check upon delivery of each new plane would be the end. The industry simply doesn’t have the capacity for that extra work even if they had the financial willingness to pay for it and the time to waste between delivery and first revenue flight.
So at what point do these aircraft need to be extensively torn down and inspected? After finding QC problems in multiple places, I hope the plan isn’t just to fix the latest discovered issue and then let them fly again. There are bound to be other issues lurking.
It’s sad that airplanes have to be destroyed. There are DC-3s/C-47s, DC-4s, & DC-6s that are still in commercial service. But with pressurised jets and the metal fatigue that can happen over many cycles, there is too great a possibility of catastrophic failure to keep flying them. Not to mention noise regulations with the old engines, the expense of operating less-efficient aircraft, etc. But still, I find it sad when an aircraft is broken up.
All this, taken in the context of the turbine hub story, where the factory didn’t have the inspection data they claimed to have, does not make the industry look like they have their shit together.
For clarification - not having an inspection report is a failure at multiple levels, even beyond the engineering failures. Something like that should trigger a full audit, not just by the customer, but any regulatory agencies as well. It’s an egregious loss of control - multiple heads should roll. It really appears that Boeing has been just sliding by for awhile. It may not be TRUE, but perception drives business.
A question I saw in a news video completely escaped me. If this had happened at 35,000 feet it would have been a different news story. That might have crushed the hull enough to instigate a cascade failure similar to the early Comet breakups.
Even if they can certify the lower bolts are secured I don’t have a lot of confidence in the 2 upper attaching points. That tiny stud riding in a channel looks like something that is subjected to a lot of stress that’s begging to fail. At this point I’d like to see a thick rod that runs the width of the door and well into the door frame. If you’re going to lock an outward panel in place then don’t be shy about over engineering it.
I think Boeing gets a lot of leeway because they are a major defense contractor that is too important to fail, and because it is hugely politically connected.
This does not serve Boeing well, as everytime they hang themselves the government gives them more rope. They’d be more disciplined or bankrupt if they weren’t so powerful.
I hear ya. If it is going to be a fixed plug that is only to be accesible for removal in the shop, then add extra immobilizing hardware, remove the hinge assist springs, whatever, make the failsafe mode be “if something breaks, this can’t move from fully seated w/o using tools”. So it’s then more complicated/expensive to convert from plug to proper hatch if you want/need to… so be it.
That smells pretty implausible to me. If it had failed at a higher differential pressure it would have departed more violently once it had swung out. But it was already separating along fully designed edges of the hatch plug and door opening.
If anything, I’d be more concerned about IAS than diff pressure. But max IAS would apply from ~11,000 when they got up to cull climb speed through about 25K when the IAS starts to drop as you climb at a constant Mach.
For darn sure, had the skin started tearing it coulda got real bad. I just don’t see how a higher altitude, more diff pressure, and less IAS makes that tearing more likely, not less likely.
IMO, YMMV, etc. For sure some engineer at FAA or Boeing has or will run the calcs.
As to over-engineering the dummy plug, there’s a lot of advantage in doing what you do with the real door to the degree possible. Whatever engineering they did for one should be adequate for both. You don’t want to do a whole separate set of engineering; that just introduces more ways to screw up. To the degree they’re the same, any in-service experience with one is applicable to both.
I wonder how the real hatch mechanism prevents it from sliding upwards? Duplicating that to the degree possible with the dummy hatch seems the path of least potential surprise.
I was thinking of the Comets that came apart from windows blowing out. It’s got to be a dramatic shift in structural integrity to have that happen at 500 mph.
And look at the damage done to a DC-10 when the cargo door came off. The floor buckled from the depressurization and jammed control cables. And that was at 11,000 feet.
This is not something that can be tested for with a real model. they had to build water tanks to simulate structural failure with the Comets and that didn’t involve exposure to high velocity winds.
Hard to say it would destroy the plane for certain but there’s history backing up the severity of such an event.
The difference is that the Comet’s windows blew out because its structure was unsound. The fundamental structure of the door and frame is sound, the problem is just that the door fell out.
The fuselage skin tore from one window corner to the next and the fuselage came apart like a long perforation in a piece of paper, jumping all but instantly from weakened window corner to weakened window corner. The window itself was immaterial. It was just the place where ignorant structural design had concentrated more stress than the metal could handle. So the metal tore where it was overstressed.
As well, the Comet lacked any kind of rip-stop structure. Which later airplanes have. Yes, that can be partly overwhelmed. But when the corroded raggedy Aloha 737 lost a big hunk, the rip stops held after just a few feet.
For sure your larger point that greater diff pressure and or greater IAS would be adverse inputs into the failure, and more altitude would be an adverse input into the recover maneuver and cabin survivability is 100% legit. I just question whether the difference is big enough to matter. All guesswork by both of us.
