Quote:
Originally Posted by Alfisti
Reports sayin there was a pressurisation light noted three times on previous flights and Alaska had deemed the aircraft not fit for travel over water and limited it's altitude.
So..... if this is true... i mean ... jebus.
Speaking at a news conference, Ms Homendy said pilots reported pressurisation warning lights on three previous flights made by the specific Alaska Airlines Max 9 involved in the incident.
The decision to restrict lengthy flights over water was so that the plane "could return very quickly to an airport" in the event the warnings happened again, the NTSB chief added.
It is not clear if there is a link between the issues that led to those warnings, and the issue that caused the blowout on 5 January.
"An additional maintenance look" was requested but "not completed" before the incident, Ms Homendy said.
|
No, no, no.
The light had NOTHING to do with the door.
Literally..... NOTHING.
The door is a plug that's installed at the factory in case the aircraft operator later wants to convert to high-density seating. If they do, the additional seats are added, the plug is popped out and another emergency exit is added.
You literally (there's that word again) can not access any part of the plug from inside the airplane without depanelling it. The plug is supposed to be permanently installed, so there's nothing to check-- at least not until a heavy maintenance visit when they pull the interior of the airplane apart, and these jets were too new for that to have happened yet.
The pressurization system does give warning if a door is open or not indicating closed-- but that's only for the two doors in front, the two or four (depending on model) over the wings, and the two in the rear (there are some other doors like the avionics service door, but we'll ignore them since they're not in the passenger cabin).
But none of that matters here. The light that the NTSB is talking about is the the auto-pressurization controller light. It's COMPLETELY unrelated to the door lights mentioned above. The auto-press light comes on when the pressurization computer decides that the system isn't working properly to pressurize the plane-- so it shifts to a backup computerized system. The usual fix is to replace the pressurization control box, which is located over the First Officer's head-- it's a simple job-- four screws, a couple cannon plugs and you're done...... IF you have a spare auto-press controller handy.
Airlines don't want to randomly replace parts-- the fact that it came on more than once (and you electronically write up anything that goes wrong on the flight so MX can look at it) may mean that it was an intermittent fault in the controller and that the mechanics weren't completely sure that was the problem-- but as the controller was shifting to the backup, it was a non-event (there's a manual backup as well where the First Officer will manually control pressurization-- it's a triple redundancy system). I don't know if the auto-press light came on for flights in a row or within the space of a bunch of flights. It could also have been a fault somewhere in the system, so MX may have wanted the jet to be programmed for a long layover somewhere in Alaska's system (i.e. have the jet layover somewhere where they have the proper mechanics) so they could have a lengthy amount of time to troubleshoot it. It's not unsafe and is a very common thing to fly with (especially if the system resets with no faults staying active)-- it's called a "deferral" and is done in accordance to FAA-blessed maintenance procedures.
To Alaska's credit, they went a step farther and restricted the jet from ETOPS operations (either Extended Twin-engine Overwater Operations or Engines Turn Or Passengers Swim, depending on who you ask)-- basically, they restricted the jet from flying to Hawaii (and realistically, any Captain would refuse the jet for ETOPS if it had a wonky auto-press controller, so it wouldn't matter if they'd restricted it from ETOPS or not).
So there's no conspiracy or anything nefarious here. The bottom line is that Boeing's subcontractor who did the fuselage plug install screwed the pooch on a whole bunch of Max9's.
There will be fallout there. But the flight crew, Alaska and their maintainers appear to have by and large followed the proper procedures with the exception of not pulling the cockpit voice recorder circuit breaker to save the cockpit audio tapes (and that's on MX).
R.