Conjecture on 737 crash?

[jyl]

Wow, this is a thread of which I understand not a single word.

[Joeaksa]

Originally posted by singpilot
Normally, the transition back to engines for pressurisation would be after cleanup, say 6 to 7 thousand feet. Takes throttles to low power for a sec, three buttons pressed, then shut down the APU and continue. Maybe a minute, two if your new at it, or reading the checklist while doing it.

Lets speculate again for a sec (dangerous). If you forgot to do this, the climbing APU will have to work progressively harder and harder to accomplish the requested tasks. It is rated for 15000 feet under this kind of load. If they forgot or realized late, or had a weak APU, all of this would have come to head about that altitude. Perhaps explains the requested pause in the climb. Would also explain why they requested the continued climb in spite of the obvious result (after transitioning back to engines for pressurisation). The FDR (Flight Data Recorder) will shed light on this.

Will be interesting to see how it turns out.

Michael,

Interesting idea here and I believe that you may have hit the nail on the head here. If there was a fresh copilot in the plane and he forgot to transfer the pressurization system over to engine bleed when he should have, then it would continue to work on the APU until it flamed out due to altitude. This would have left the plane with no heating and more important, no pressurization which keeps everyone alive in the plane. The masks would have come out at 10,000 or so and thats a good question why they did not descent at that time but who knows what happened inside the bird.

The APU normally does not have any "mixture control" and as the plane gets higher in altitude the APU will finally flame out (die) as there is too much fuel for the little oxygen available in the atmosphere. Some of the newer models will keep going up to 30,000 feet but ours is good only until 20,000.

Why the Captain was out of the cockpit is a good question but we may never know that with the short loop on the CVR. Our CVR is a newer version and is a 45 minute loop, but hear that they are working on newer models that are a 2 hour version.

Makes sense if we forget that the crew should have seen it. I am with you and can feel it when the climb or descent is off by as much as 100-200 fpm in the cabin. Got this way from too many years flying Learjets and forgetting once or twice to put the cabin air switch on!

JoeA

[singpilot]

Originally posted by john_cramer
Egad.

So you're saying that the autopilot flew the approach and executed the published miss and entered the hold, all at FL 320?

(Yes..... Exactly.)

Makes sense if it had some kind of INS that would update off of DME's-- no need to tune the localizer in.

(Actually, the FMS updates by GPS, then if none, by DME-DME, then if none, by VOR-VOR. We have the ability to fly an approach as a VNAV ILS 'blue needles' or, as you would, tuned to the ILS freq 'green needles'.)

I can understand that-- if they had 320 in the altitude preselect (whatever it's called on the 737) then it would have captured that and leveled off. Since you have to tell it when to start down (there's no VNAV program?) in the absence of a command to descend, it just did the whole thing at altitude. Frightening.

(The VNAV altitudes are programmed, but the Altitude command knob ALWAYS takes precedence.)

Ok, these are very interesting facts. Last check-in with ARTCC was level at FL 160. They reported the "pressuriziation concern" then requested, and were presumably cleared, for the climb to 320. So they set 320 on the altitude capture and then somewhere after that they experienced the decompression.

Don't the masks automatically drop at 9500 +/- 600 feet?

(YES)

Would the lack of ice on the windows indicate that the depressurization was not rapid, but progressive?

(Conventional wisdom says rapid D would fog, then ice the windows, but for a sick, funny reason. The rapid D forces the human body to expel any fluid whose container cannot be pressure equalized as rapidly as the decompress. The sudden humidity in the cabin would show on the windows.)

Or would the ice sublimate off after half an hour or so at altitude?

(Probably not, the lack of ice on the windows means that people were probably equalizing internal pressures as the cabin climbed at a rate less than 'rapid'.)

Yes!

[singpilot]

Originally posted by jyl
Wow, this is a thread of which I understand not a single word.

John;

Sorry, am trying to keep this as 'civilian' as possible, but the technical keeps getting in the way.

Michael.

[singpilot]

Originally posted by on-ramp
I've never had any formal flight training but my gut instinct tells me, any issue with pressurization during a flight is a red flag. Land the plane immediately and have it checked out. The people on board whose lives are in your hands might just thank you later.

btw, isn't this standard op. procedure to land a plane with any signs of pressure problems? it just seems like the "better safe than sorry" approach. Problems at 34,000 feet don't usually fix themselves, they get worse, so why risk it? that's common sense. could it be overconfidence...

This flight had all the makings of a simple easy day. A 45 minute leg from Larnaca to Athens. Larnaca is a great airport, long sea level runway, beautiful island setting. Is home base for the airline. Athens' new airport has long sea level runways, great service, quick turns, easy stop. Then a longer leg to Prague. Weather usually stacks up over Yugoslavian border with Europe, east side of the Alps. That leg will be the challenge today. The pilots might have been lulled by the easy first leg. Overconfidence? Who knows, I sure don't. Only the guys there know, and they cannot speak for themselves. Doubtful the Cockpit Voice Recorder will either.

Hopefully the Flight Data Recorder will shed some light on the cause of the decompress. I think the second most important part of the wreck will be that oxygen valve behind the FO's seat. Was it open or closed.

It was said earlier that it is never just one thing that causes crashes. So true...thank God. That the checklists we use are written in someone else's blood. So true.

Someone asked me in a PM why would Larnaca (the origination point) be the alternate for Athens? Funny reason again. An airline is responsible (with certain limitations listed in a Geneva Convention) for it's passengers from the moment of departure until the moment of arrival at the intended airport. Any diversion (especially to an airport that they don't normally serve) is a financial disaster. If they deliver the pax back to Larnaca for a divert, no prob, pax are on their own.

Read that fine print on the back of your ticket someday.

[Joeaksa]

Originally posted by singpilot
Hopefully the Flight Data Recorder will shed some light on the cause of the decompress. I think the second most important part of the wreck will be that oxygen valve behind the FO's seat. Was it open or closed.

Someone asked me in a PM why would Larnaca (the origination point) be the alternate for Athens? Funny reason again. An airline is responsible (with certain limitations listed in a Geneva Convention) for it's passengers from the moment of departure until the moment of arrival at the intended airport. Any diversion (especially to an airport that they don't normally serve) is a financial disaster. If they deliver the pax back to Larnaca for a divert, no prob, pax are on their own.

Read that fine print on the back of your ticket someday.

All the -737's that I flew did not have an O2 valve in the cockpit, only a QB fitting where you unplugged the mask. Were some of them equipped with a valve?

Regarding the alternate... Other thing is that the airline delivers the pax back to home base and many of them live there, so no hotel rooms to pay for. The transit pax who do not live there would stay in hotel rooms that the airline gets "brother in law" pricing for, and if they did this at any other city at the last minute, pricing would be a lot more expensive.

Lots of things working in the background here, and you are correct that reading the back of any ticket will have a lot of info.

JoeA

[Joeaksa]

Originally posted by john_cramer
Egad.

So you're saying that the autopilot flew the approach and executed the published miss and entered the hold, all at FL 320?

(Yes..... Exactly.)

Makes sense if it had some kind of INS that would update off of DME's-- no need to tune the localizer in.

(Actually, the FMS updates by GPS, then if none, by DME-DME, then if none, by VOR-VOR. We have the ability to fly an approach as a VNAV ILS 'blue needles' or, as you would, tuned to the ILS freq 'green needles'.)

I can understand that-- if they had 320 in the altitude preselect (whatever it's called on the 737) then it would have captured that and leveled off. Since you have to tell it when to start down (there's no VNAV program?) in the absence of a command to descend, it just did the whole thing at altitude. Frightening.

(The VNAV altitudes are programmed, but the Altitude command knob ALWAYS takes precedence.)

Ok, these are very interesting facts. Last check-in with ARTCC was level at FL 160. They reported the "pressuriziation concern" then requested, and were presumably cleared, for the climb to 320. So they set 320 on the altitude capture and then somewhere after that they experienced the decompression.

Don't the masks automatically drop at 9500 +/- 600 feet?

(YES)

Would the lack of ice on the windows indicate that the depressurization was not rapid, but progressive?

(Conventional wisdom says rapid D would fog, then ice the windows, but for a sick, funny reason. The rapid D forces the human body to expel any fluid whose container cannot be pressure equalized as rapidly as the decompress. The sudden humidity in the cabin would show on the windows.)

Or would the ice sublimate off after half an hour or so at altitude?

(Probably not, the lack of ice on the windows means that people were probably equalizing internal pressures as the cabin climbed at a rate less than 'rapid'.)

Originally posted by singpilot
Yes!

The FMS on our bird will do exactly the same thing as well. All we have to do is to plug into the route the expected runway at the destination point and when we get within 30 miles it brings up "blue needles" that shows that the ILS is within range and will be tuned.

When we intercept the inbound course it "goes green" (switches to the ILS for data) and shoots the approach. If we do not do anything it will then enter the hold, again totally auto and then continue in the holding pattern. It will not manage the altitude and thats why the -737 did all of the above but at altitude.

The automatic systems in todays airplanes are very nice to work with IF, and only if you know how to "massage" them into doing what you want when there is a glitch.

JoeA

[tcar]

So the plane 'flew' the normal flight pattern, but at 30 some thousand feet?

...and it crashed because it ran out of fuel? What would have caused the huge fire?

or maybe whoever was in the cockpit trying to fly the plane switched off the autopilot and it came down out of control?

[singpilot]

The fire that was seen in the post crash videos was a brush fire, no fuel was evident in the crash. Is why all the rescue and fire trucks were parked so close. This was scrub brush burning, could have been started by the crash impact itself.

It appeared that the efforts to 'regain control' were after the engine flameout and roll. That whoever it was in the cockpit was not even experienced enough to be able to talk on the radio.

[djmcmath]

Originally posted by singpilot
...whoever it was in the cockpit was not even experienced enough to be able to talk on the radio.

Hey, go easy, killer. I've heard the way you pilots talk on the radio, and that's not the same language normal people use. It seems to me that the mechanics of recovering a rolled or spinning plane would be a lot simpler than learning all that ratchet-jaw you folks use on-air.

[singpilot]

I issued a memo to the pilots and flight attendants at my company a couple of days ago. I wanted the flight attendants to be shown how the pilot's oxygen masks work (in detail), how they are stored, and deployed. To assume the pilots was unconscious, and how to get the mask to flow 100% pressure breathing to get the pilot awake again hopefully.

Not that surprised that none of the FA's had ever been shown this.

[304065]

I am a big fan of "pinch-hitter" courses and videos for every nonpilot who might ever have the occasion to take the controls. Heaven forbid a big hunk of Peter Luger's steak breaks off and goes to my brain, I would want the passenger to know how to navigate to the nearest airport and land AND call for help on guard.

Certainly the technology exists for a "panic button" to be installed somewhere in the cockpit-- upon actuation, it could;

1) Check the nav database and locate the nearest suitable airport;
2) Check the fuel status and determine whether fuel remaining would be sufficient to make it to that airport and land; or whether the aircraft would be overweight;
3) Navigate to the final approach fix and land, applying auto-reverse and the brakes, coming to a stop on the runway centerline;
4) All the while squawking a special emergency code, broadcasting on 121.5 and sending ACARS messages to everybody and their dog that things had gone horribly awry and that the airplane was in "limp-home mode."

Now obviously, there's no guarantee that the weather would allow this to happen, but it would be a decent shot.

Seems to me that the cost of such a programming change and a minimal amount of hardware wouldn't be that great, although certification could be tough. If it saves one flight every few years, might it be worth it?

[singpilot]

John, along the lines of your post.....

More news from the German press (Der Spiegel) today. The captain was German, and the press there has taken a special interest in this crash.

The intercept pilots report of 'someone trying to regain control' has been amplified.

It now appears that someone (presumed to be one of the FA's who had a Private Pilot's License), had taken the captains' seat, and was flying the plane. The intercept pilots reported that the plane left the hold fix, descended out over the sea down to 800 meters, then turned back towards the airport. As it approached the coast, it had to climb to clear a low set of hills between them and the airport. The flight ran out of fuel as the engines spooled up to cross the ridgeline.

[dhoward]

Wouldn't that pi$$ you off...

[304065]

Wow, Michael. That's very interesting data.

I was initially very incredulous about the intercept pilots' report. The combination of thin air and cold temps would seem to preclude the idea that anyone would be able to take control. But if she had her mask on, and was able to enter the cockpit. . .

[Joeaksa]

Originally posted by singpilot
I issued a memo to the pilots and flight attendants at my company a couple of days ago. I wanted the flight attendants to be shown how the pilot's oxygen masks work (in detail), how they are stored, and deployed. To assume the pilots was unconscious, and how to get the mask to flow 100% pressure breathing to get the pilot awake again hopefully.

Not that surprised that none of the FA's had ever been shown this.

Our FA is ex-Kiwi and Eastern and we practiced it a few months ago. Also did the AED and actually did our medical training on OUR airplane. Went so far as to practice using the AED on the pilots, after getting them out of the cockpit.

Better safe and trained now than needing it in a time of crisis.

JoeA

[singpilot]

Even more info now. The FA that sat in the pilot's seat was a male, and his significant other, a woman was also a FA, was working aboard.

[Joeaksa]

Michael,

The more info that comes out, the worse it sounds. No one wants to see a bird go down but this strikes home... a lot.

Will say another prayer for them tonight. Hope that they had a good and safe flight West...

JoeA

[304065]

Amen to that.

"To fly west is a flight we all must take for a final check."

How would the FA get through the locked cockpit door?