Alaska Airlines flight forced to make an emergency landing... 82

[waross]

Those spare doors have been around for a long time since the 737-900 I think so many hours of service and they haven't fallen off before...

It's only recently that they stopped putting the retaining bolts in place.

Sensors and pressure:
I surmise that it wasn't a failure as much as slightly slower pressure build-up due to an unseated door.
One sensor may have been slightly differently calibrated or differently placed.
Example:
A burner in an oil heater had a tendency to build up soot on the fire eye.
Eventually, the soot build-up would prevent a successful start.
Solution;
The fire eye had 7 seconds to see the flame else it aborted the start.
We programmed an alarm at 3 seconds.The alarm simply latched a pilot light that indicated;
"Slow Light-Off."
When the "Slow Light-Off" light came on the tech's could clean the fire eye at their convenience.
The Max was probably showing slow pressure build-up rather than failure to build pressure.
Not a faulty sensor, but slightly different calibration of the sensors.
That's easy do diagnose in hind sight.
Much harder to find in the shop.

--------------------
Ohm's law
Not just a good idea;
It's the LAW!

 

[LionelHutz]

Respectfully, it may have been a good part of that 9 seconds or even a little more before the pilots started the 5 second "recognition" time.
That's strange the controls are getting heavy, to the controls are too heavy to manage.

Did you forget there are trim wheels that spin when the trim is changing? The pilot and copilot should be capable fairly easily figuring out that trim wheel movement + heavier stick = trim has moved in the wrong direction.

 

[3DDave]

I did not forget - I don't need to repeat the entire contents of all the reports; just the highlights. They could be blind and still feel the controls getting heavy.

 

[Alistair_Heaton]

the 737 trim wheels are constant movement with the auto pilot in. Forwards and backwards. And they are rather fast and the trim window for manual handling is rather small. In fact uncertifiable small, for the regs just after the 737 NG was certified, never mind when the MAX was certified.

Startle is a known human performance issue.

There are several things happen.

Adrenaline discharge. Which triggers heart rate increase, your liver dumping glucose, and a few other things. One of them being the front lobes of your brain shutting down which are the part which deals with analytical thought and data processing.

Depending on the level of "flight or fight response" and other physiological factors depends how long it takes your front lobes to start working again at full capability.

So yes they might have felt them getting heavier but the analytical capacity just wasn't on line. So the fight or flight response was pull to lift the nose so that's what they did and it didn't work which prolonged the phycological effects.

to be honest it doesn't really matter it has been proved without a doubt it should never have been certified in the first place.

And the way things seem to be going trying to correct the certification issues with the 7 and the 10 they won't be certifiable until 2025, and then they will have to fix all the 8's and 9's. And that will be nearly over 6 years after it was grounded.


And there seems to be some movement in corporate ethics but there is a long way to go.

 

[Alistair_Heaton]

pilot black humour

 

[Murph 9000]

Three pressure controllers on the Max?

I could be wrong (certainly not an expert on it), but I believe it's 2 automatic controllers (which automatically alternate on each flight), and a manual system consisting of a double throw momentary switch (3 position; close/-/open) and a position indicator for the outflow valve. It's essentially the same setup that has been on the 737 from the beginning, changing to a digital version with the NG.

See

http://www.b737.org.uk/pressurisation.htm

for lots of detail.

 

[Alistair_Heaton]

That's how I understand it as well Murph.

They basically haven't changed the system since the 1960's or the outflow valve.

The double throw is just a motor controller to power the valve open and closed.

There is another valve which is an emergency depressurisation which is an on off button.

And I think 2 sprung pressure relief valves to deal with ultimate over pressure negative and positive which are just dumb springs with no control over.

its 2 controllers alternating controlling the singular valve, a manual method of controlling that valve, another separate valve which is binary open or closed, and the sprung valve or valves for hull integrity.

So it hits 3 level.

 

[1503-44]

So everything in the pressure monitoring and control system is working just fine. Pressure indicators and controllers. That's just great. The only thing remaing to do is start believing in the alarms.

--Einstein gave the same test to students every year. When asked why he would do something like that, "Because the answers had changed."

 

[zeusfaber]

Anybody else noticed a natural tendency for technicians to want to change the unit that has the warning light on it? Even if that's just the alarm panel. One of a long list of random lessons I would love to weave into basic technical education is "When complex systems go faulty, the cause may be miles away from the symptom" - and for engineers "design it so the technician has some chance of seeing what's going on inside the system"

 

[3DDave]

I have been watching South Main Auto for a long time now and - yup - whatever the idiot light says is broken is what they want to replace. Top of the heap so far was a dealer wanting to replace the power steering, the trailer controller, and what else I forget - about $5000 in components that all simultaneously reported problems. Actual problem? Bad ground strap between the body and the frame leading to a large voltage on the ground side of the components due to the resistance of the strap to high current.

There does seem to be a tendency in aviation to make everything a procedure. It seems to work for those who follow them - apparently no deaths from commercial aviation crashes anywhere in 2023. 2024 started rough though. It all goes south if there is something that has not been anticipated as the lack of adaptability leads to an inability to manage even small disturbances.

Not only do procedure writers need to anticipate potential problems, they have to also guess what pilots will think the problem is based on the symptoms and, if a pilot misses a symptom and guesses the wrong procedure, then it's all for naught.

 

[Alistair_Heaton]

pretty much the way its gone in the 20 years I have been flying.

And actually the A220 has the least number of procedures of all the aircraft I have flown.

The ECAM system schedules the order you deal with things.

And it is obvious that Bombardier spent a lot of time and resources planning the human interaction with the machine and the presentation of data to the pilot.

And we have absolutely zero memory items. Jetstream we had 16 sets of them.

 

[3DDave]

When something not on ECAM comes up, expect pilots to freeze at the controls and blame the makers for the crash.

Does ECAM prompt to put the oxygen mask on when the plane explosively depressurizes? How long does it say the pilot can take? Does it detect when the pilot doesn't put the mask on and go to Plan B?

 

[Alistair_Heaton]

like what?

We have a Emergency descent mode which arms above FL230 which if the pressurisation warning triggers with a cabin alt of 14500ft it squawks 7700 and then puts the alt select to FL150 and starts a emergency decent. We don't have to touch anything.

The ECAM check list tells us to done the masks and establish coms. Then gets into the guts of the rest of it.

Memory items for similar on other types had the none flying pilot putting the mask on then swapping controls and then the other did. Then establish coms.

History has shown with slow depressurisation the pilots get into troubleshooting trying not to declare a mayday. Then they pass out and when the fuel runs out that's when they descend.

So the A220 declares a mayday for you like it or not with the 7700 squawk.

 

[3DDave]

So the ECAM doesn't detect that the pilots just didn't put on masks? Would it auto-descend into a mountain face?

Would ECAM have told Sullenberger to go for the harbor? You already mentioned he didn't follow the procedure when he started the APU.

Would the ECAM have helped the DC-10 that lost an engine? Yes - like that. Even though it was found in simulators that the flight was recoverable if only the pilots had retracted the slats, pushed over and throttled up. What ECAM writer would consider that entire sequence?

 

[Alistair_Heaton]

more humour.

 

[Alistair_Heaton]

"So the ECAM doesn't detect that the pilots just didn't put on masks? Would it auto-descend into a mountain face?"

The not descending into a mountain face is on the cards with a link to the MSA for the alt select from the FMS. In Europe we only have 2 peaks above 4500m which would be an issue.

Those examples are airmanship decision making. ECAM's function is not for that. Its system diagnostics and appropriate actions, and tracking so miss configurations do not occur later.

It is a tool. and an extremely good one I have found so far in the sim.... No where near as many checklist screw ups that were common on other types.

The Q400's bus fail was just an nightmare if you didn't spot it within the 5 seconds before bus shedding started. And they always gave you it when you were busy with something else like a TCAS event which takes priority over a master caution or warning.

737 doesn't even have a central annunciator panel, its system status lights are like a Christmas tree all round the cockpit. That setup hasn't been certifiable since Late 70's early 80's on a new type certifications.

 

[JohnRBaker]

Adding insult to injury...

Secretary Antony Blinken’s Boeing 737 out of Davos had a critical failure. He had to switch planes

https://www.cnn.com/2024/01/17/busi...ge-planes-after-boeing-breaks-down/index.html

An excerpt from the above item:

Secretary of State Antony Blinken was forced to change planes to return to Washington from Davos after his plane suffered what the traveling press was told was a critical failure related to an oxygen leak.

Blinken and the traveling party boarded the modified Boeing 737 jet in Zurich on Wednesday after a day and a half of meetings at the global summit in Davos.

The plane suffered the issue after boarding and the party was forced to deplane, according to traveling press.

A new, smaller aircraft was being sent for Blinken, and many in the traveling party will now be returning to Washington commercially, according to the traveling press.

John R. Baker, P.E. (ret)
Irvine, CA
Siemens PLM:

The secret of life is not finding someone to live with
It's finding someone you can't live without

 

[Murph 9000]

A new video is out on the 737 tech channel. No big surprises, just a quite detailed review of the various pieces of mounting and securing hardware around the plug door and their operation. He then goes on to cover the post-incident findings so far, and the pressurisation system including some discussion of the problems experienced prior to the incident.

737 Technical Aspects of AS1282 Updated

 

[3DDave]

Oh no - another breathless expression of stupidity from the press looking to gin up more airtime filling content.

An old plane in military service, likely maintained by the military or by military contract has a dispatch problem?

The same military cannot get the F-35s in order and they are newer and have all that electronic crap so beloved by the magenta line followers.

 

[Murph 9000]

Yeah, it sounds like just a routine problem discovered during the pre-flight checks. Probably related to the oxygen bottles for the flight deck masks. Sounds like an embarrassing incident for the USAF, not something that should be used to add to Boeing's current troubles.

The plane was likely a C-40B or C-40C. They are 737NGs with a 737-700 hull on 737-800 wings & gear, elements of the Boeing Business Jet programme, auxiliary fuel tanks for extended range, and various military upgrades.