The original reports indicated that “a window” had blown out of the plane. But in reality, though that section of the skin did have a window in it, an entire unused, sealed doorway had blown out of the aircraft.
Even worse, as it turns out, the plane had already been placed on limited duty and was not allowed to fly over the ocean to Hawaii because a warning light related to potential pressurization problems had illuminated on three recent flights. Given that the blowout resulted in a massive depressurization event, shouldn’t the plane have already been grounded for further inspections? (AP)
Other possible defects were exposed during the explosive event. When the cabin depressurized, the cockpit door flew open, banging into a lavatory door. That door is supposed to be sealed to prevent external access by potential terrorists. Yet it was somehow unable to remain closed when the cabin lost pressure. It sounds as if that issue will require further attention as well.
We have further learned that the NTSB will not have the benefit of listening to the pilots’ conversations from the plane’s black box. The system on this model of Boeing aircraft overwrites all recordings after two hours, so those records were not preserved. What is the purpose of such a scrubbing regimen in the current era? Are we to understand that the black box doesn’t have enough storage space to hold recordings more than 120 minutes in length? What do they do about overseas flights that can last for ten hours or more?
As of this morning, nearly all of the Boeing 737 planes of this model used by both Alaskan Airlines and United remain grounded. They are awaiting a technical bulletin from Boeing that will provide specific instruction inspections for the rest of the fleet. From the sound of the details listed above, they will have plenty to inspect.
Yep. This whole thing about there have been warnings before makes me wonder why the row of seats at the bad panel 'happened' to be unused. Were they blocked because Alaska KNEW where the problem was?
ReplyDeleteThat two hour limit on the flight recorder may be a software issue, I've seen things like that. Reused program code from a time when one gig was a 'big' hard drive. But the installed drive was 500 gig.
ReplyDeleteLast week I was outside on trash day with a hammer smashing old drives I was throwing into the weekly pickup barrel. One 250 gig drive I had paid $300, new.
My company tests 4Tbit NAND Flash devices. They are smaller than a size of a quarter and could probably hold every movie I have ever seen, plus 100 more.
DeleteNot enough memory in the black box? Memory is cheap and small these days...
ReplyDeleteGoes to prove something I've known for years: Large corporations are like and are in bed with the government they both lie and peasants die.
ReplyDeleteThe FAA is in charge of regulating airline safety AND promoting commercial air travel. Obvious conflict of interest.
ReplyDeleteNo, dummy. If omly you knew what you're talking about.
DeleteAnyway, FAA bisected their charter long ago.
"limited duty"; In order to fly on (not really) long overwater flights, aircraft have to be ETOPS qualified. This is a long process of recurring inspections and data collection to establish probability of failures. Also, certain systems must have had no issues within time periods to assure they are resolved. These restrictions are FAA driven, not Alaska Airlines. Until more secret information is made public it actually looks like Alaska Airlines was doing the correct and prudent thing by suspending the planes ETOPS qual.
ReplyDeleteMany aircraft have pressure relief panels/latches in the cockpit door for just this event.
Lets be honest (!), the CVR is mostly, with respect to the public, a voyuer device. You all want to hear the last minutes. I dont see much value in this incident. Where do you think we could fault the crew? The data recorder is a different device and that is (curiously) being obfuscated. Just another political plea for power by ntsb. It has no bearing in this incident.
Folks, this story has alot of curious holes in it at this point. Stop being manipulated by them.
ETOPS - engines turn or people swim
DeletePush a few more sheet metal screws in them and send them back up!
ReplyDeleteAnd a bit of duct tape, and it'll be good to go. Just another reason why I do not fly, and have not since 2001.
DeleteAs far as limited recording time on the CVR it speaks directly to how difficult it is to introduce better and newer technology into new aircraft. As others have stated, tech has progressed far beyond any reasonable time limit on these things. The shear expense incurred to get anything certified is unbelievable. True, some “new stuff” should be held up until absolutely sure it has no unknown quirks or failures but this is. It one of them. Fancy new hydraulic fluid, hold up there bucko, new shape for the captains sunshade, let her rip. Flew learjets before moving to n airline job. A pencil thin cable used only to lift the lower clamshell door closed ran about $700 for 30 inches with a nice plastic knob on the end. You could have literally used a piece of clothes line if it broke but it has to have a PMA from the feds so there ya go. Before scrapping the last 747-200 models at my current job less than 15 years ago they were still using floppy disks to update navigation databases while the 75 and 767 sitting next to them were being uploaded from a tablet. The CVR met the fed requirement and it’s cheaper than a new design after all the red tape but, yeah, stupid.
ReplyDeleteLots of things can cause a depressurization, not just a door (or a door plug)....inflow valves, pressure switches, outflow valves, etc can cause that sort of issue.
ReplyDeleteOn my 340 it happened 3 times 3 years ago (and never since) and we have never found the issue. It holds 4.6 PSI all day long. Maybe a sticky outflow valve, but an intermittent is hard to find. Same on a 737. Lots of things can be at issue but if it won't stay broke then it's hard to find.
Also, the CVR wouldn't tell 'em much, this wasn't a pilot caused issue, but a mechanical or structural failure of the airframe, so no real loss as far as the investigation.
There’s a difference between a cockpit voice recorder and flight data recorder. CVR has to store 2 hours. The data recorder is usually start of flight to finish recording hundreds of parameters including cockpit switch/soft key selections usually at over 10Hz. Ten times per second.
ReplyDeleteWhen you get the download from one it’s gigabytes of CSV files. Get some coffee, you’re going to need it.
The CVR recording time is limited for two reasons. When they were made mandatory CVRs used a continuous loop tape that was limited in length due to the size of the reels that could fit inside the CVR. The second is the pilot's associations who argued it was a breach of privacy. How would you like to have everything you've ever said at work recorded? The recording during this flight emergency was overwritten through human error, the first thing to after arriving back at the ramp following an incident is pull the CVR breaker.
ReplyDeleteRegarding the FDR, only certain parameters are mandatory, I used to change stainless steel tapes on a '60s era FDR that had only 5 parameters, direction, altitude, airspeed, rpm1 and rpm2. In the early '90s 17 parameters became mandatory, my employer bought brand new aircraft which recorded 21 parameters including flight control position in the cockpit, flight control surface position on the wing, throttle position and fuel flow to each engine.
The current specification is a DFDR (Digital FDR) which survives better than a tape and records 88 parameters. I don't think there's anything in the standard about recording cabin pressure.
I used to deal with this bumpf but I'm retired now so here's a link, feel free to
look for yourselves
https://www.federalregister.gov/documents/2003/07/18/03-18269/digital-flight-data-recorder-requirements-changes-to-recording-specifications-and-additional
As pointed out by previous commenters, there are a few components that can cause pressurization problems without a leak in the pressure hull and troubleshooting intermittent snags can drive you insane. Trying to find a problem when the system is behaving is impossible, sometimes you have to throw parts at it until it's fixed. This will annoy the bean counters and schedulers.
Al_in_Ottawa
My comment here is more about the journalism than what happened here, but the airline in question here is "Alaska Airlines", not "AlaskaN Airlines".
ReplyDeleteIf you're going to write a story, the first thing to do is to spell the name of the story's subject correctly.
azlibertarian
on top of that, about month and a half ago an AK pilot flying ppassenger tried to take the plane down....don't remember if he's in jail or the hospital....they need to bring back mental institutions...
ReplyDeleteScary time for passengers and crew brings to mind personal experience in an aircraft that lost cabin pressure.
ReplyDeleteIn July ’66 I was a passenger on a C-130 traveling between Okinawa and Da Nang, RVN. with a replacement draft of personnel.
Less than halfway out the interior of the aircraft became foggy and we quickly descended to a lower altitude. Being less than hallway along, the pilot opted to return to Okinawa.
After an uneventful return to the air facility at Futenma, we bed down for the night in makeshift accommodations.
Bright and early the next morning we were off again. Then just before crossing that magical halfway point we lost an engine. Again we did a 180 and returned to Okinawa. This time with an occasional view of a propeller not propelling. And another night of roughing it.
Next day as we began boarding, we were directed to move away from the aircraft as it had a significant fuel leak. But reassured that this time we’d make it to RVN even if the crew had to flap their arms. After about an hour the aircraft was fixed and off we successfully went.
It was beyond a busy time for aircrews in RVN and no doubt that played into our experience.
Those three events were reported as “benign” occurrences by the airline, Homendy said. Further maintenance work to look into the light had been planned but not yet carried out by the time of the Jan. 5 incident. An E-TOPS restriction had been put in place preventing the aircraft being used on routes to Hawaii over the water so that it could return quickly to an airport if the light came on again.
ReplyDeleteGosh, the nasty old airline was actually following the procedures.
Airlines compare the costs of paying liability claims due to a crash versus the costs of upgrading their fleet. Low bid wins.
ReplyDeleteWasn't Boeing in the news a while back for hiring Indian programmers and getting rid of Americans? How diverse are the assembly and maintenance staff?
ReplyDeleteBut they had diversity and equity in every step on the production line!
ReplyDelete