Conjecture on 737 crash?

[stevepaa]

Any pilots have any conjectures on how this can happen?
How can the pilot's O2 fail?
How fast does this happen?
They found a flight attendant in the cockpit, probably trying to wake up the co-pilot.
How many hand carry bottles of O2 are there on this plane?

thanks

[singpilot]

Can happen any number of ways. Time of USEFUL consciousness is measured in seconds. There are factors (shorter times) for health, surprise factor, suddenness of onset. Plane was at 34000. Outside (now inside) temp could be -20C to -50C.

We always discuss these scenarios on ocean crossings. Worst case scenario is some sort of a pressurization failure. Would have to take an (otherwise) perfect airplane (engines) down low enuf for pax to breathe, AND stay warm. Fuel flows double or more.

I'll usually mention to the lead FA as I walk aboard as a passenger that I am typed and / or current in the plane type if help is needed.

Intercept pilots said FO was slumped, Captain was not in his seat.

Sad, but this business keeps teaching some people that we don't get paid for the good days.

[oldE]

A web site for 737 plots mentions the report from the F16 pilots scrambled to check out the plane. They saw someone "slumped over" in the cockpit and two persons in the cockpit as well. It was also noted this aircraft had experienced loss of cabin pressure in the past.
Could be a combination of poor maintenance and too many cycles.
My condolences to the families.
Les

[singpilot]

All of Helios' 737's were NG's (Next Generation). Planes were reasonably new.

The passengers' oxygen comes from individual chemical generators. The pilot's oxygen comes from a tank, and there is a shutoff behind the copilot's seat (supposedly checked every first flight).

The Capt. could have been out of his seat for any number of reasons. I have flown with guys that could not sense a 1000 foot per minute cabin rate. I have always had sensitive ears, and can spot 100 foot per minute. Who knows, the Cockpit Voice Recorders have been recovered, but since they only record the last 30 minutes (endless loop), and the plane was holding at a fix over Athens for 90 minutes, and had not communicated since crossing the FIR at Rhodes 20 minutes prior to that, there won't be anything useful there.

Bad day, may they all RIP.

[JavaBrewer]

Why are the recording tapes only 30 minutes long and endless loop?

[speeder]

I read that the F-16s saw a person or persons in the cockpit trying to regain control of the plane, I wonder why they were not out cold(?) How could anyone still be awake and functioning if there was no oxygen and it is -50deg.?

[singpilot]

The SMS message "pilot is blue, freezing cold, and goodbye cousin' has been debunked. Never happened. Man arrested for sprading this rumor in Larnaca.

The CVR has always been a 30 minute duration. The technology exists to be more, but has never been implemented beyond what is required by law. In the 'old days' it was a continous loop tape. I believe nowadays, any installation after like 1995 is a chip.

[Dottore]

Singpilot:

What is your speculation on why the pilots did not immediately do a decompression dive?

Can you miss a catastrophic decompression like this? I mean can you just not notice it until you are starved of oxygen and freeze?

[singpilot]

We all practice the rapid decompression dive. But a not so rapid decompression (say 1000' per minute), might not have been noticed, believe it or not.

First sign of trouble to such a crew might have been the "LOW CABIN PRESSURE" EICAS message. Meaning 'high cabin altitude'. Book says 'Masks on, check 100% (oxygen), check A/C sources (packs and bleeds), use manual pressurization (usually closing the outflow valve), and check cabin rate'. If no joy, or at first sign of smoke or contamination, declare and descend.

Captain out of the seat says to me bad timing, or he was up troubleshooting. Or maybe removed by the FA or pax trying to get him revived with the walkaround bottle (if the pilots O2 valve was closed, for instance). The valve's location would not have been evident to anyone else, the FO being asleep too.

All of this is speculation (dangerous), but would explain the apparent circumstances.

Captains' body not identified yet. The cause will eventually be found. The Government of Cypress 'raided' the offices of the airline in Larnaca today. Is their way of getting maintenance records. Hopefuly they will keep them reasonably intact.

[singpilot]

More developments today. The Cockpit Voice Recorder CASE has been found. The innards have not been found. These things are designed for like 1000g's (crash). The pictures after the crash usually show these having been pried open, even after the crash.

The captains remains have not been found / identified. Granted, there can be a common area of several remains in one spot, but seems strange as well.

Climbing out of Larnaca, the flight requested a delay at 16000 feet to 'address a pressurization concern'. They were there for 3 minutes, then requested the rest of the climb.

The aircraft flew the entire route with no further communication after the Greek boundary, the normal arrival, transition, approach, ILS and missed approach to the miss holding fix, and entered the missed approach hold, all at 32000 feet. All at cruise speed. The entire aircraft route would have been preprogrammed by the crew either enroute or prior to takeoff. The aircraft would not have left cruise altitude unless the altitude command knob had been set to a lower altitude by the crew (who were asleep). The aircraft was in that hold just north of Athens for 90 minutes. Until they ran out of fuel, and at least one engine flamed out. The now single engine electric situation would have disconnected the autopilot, and according to the intercept pilots, it rolled off and spiralled in.

There's an unspoken situation here. From 32000 feet the guided (under control) gliding range of a powerless 737 is over 100 miles. The hold fix was 35 miles north of Athens, 25 miles northwest of the airport. The interceptors were there not to just investigate. The plane happened to flame out on a leg of the racetrack shaped hold pointed away from the city. The interceptors did not have to execute their probable second set of orders.

[likemystoppie?]

^^^^Meaning that the 2nd set of orders were to 'shoot' the plane out of the sky if this was a terrorist take over?

[singpilot]

More likely to destroy it if it was going to hit the city, terrorist or not. The initial intercept report indicating a pressurization problem (masks down, pilot slumped) is why even right after the crash terrorism was ruled out.

[Burnin' oil]

Sing,

I enjoy reading posts written by people who know what they are talking about (probably because they are so rare). Thanks.

[djmcmath]

So hang on, Sing, I'm not sure I'm following this. You're saying that the pilots had some pressurization problems, but continued the flight anyway. But the pressurization problems resulted in everyone passing out. The plane didn't know or care, it just kept flying and ended up in the pattern on it's own. Am I reading your posts correctly?

Thanks for the info, btw. Like Burnin' says, I like having people who know the details post useful information.

[singpilot]

Yep, that is the stink of it. Why would a competant crew take a plane with some sort of pressurization problem up to altitude. This is the typical foreign supplemental carrier. Experienced captain (usually from USA, or Common Market Country) from Germany, low time FO from flag of airline, Cypress in this case.

There are a couple of 'innocent' explanations as well. Technical, but relatively innocent. To enhance takeoff performance, there is a procedure to allow the APU to provide cabin pressurisation as well as heating and cooling in flight at low altitudes. So you take off using the APU to unload the engines, allowing them to have all available thrust for performance when needed. This was a short flight, long takeoff runway in Larnaca, sea level airport, not much fuel required (refuel planned in Athens for the continuing flight to Prague). I would have said it wasn't required that day, but then who knows what the captain wanted.

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.

Interesting note here. Regs require enough fuel to destination, alternate and 45 more minutes. Alternate was probably back to Larnaca (45 minutes), plus 45 minutes actual reserve. Hold at Athens was 90 minutes, then flameout.


Will be interesting to see how it turns out.

[Craig 930 RS]

Takes a combination of several factors to bring a plane down.
The 737 was only 7 yrs young.

[dhoward]

Originally posted by Craig911
Takes a combination of several factors to bring a plane down.
The 737 was only 7 yrs young.

...or 7 years OLD if poorly maintained...

[Craig 930 RS]

Theoretically yes. Practically, no.

[304065]

Egad.

So you're saying that the autopilot flew the approach and executed the published miss and entered the hold, all at FL 320? Makes sense if it had some kind of INS that would update off of DME's-- no need to tune the localizer in.

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.

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?

Would the lack of ice on the windows indicate that the depressurization was not rapid, but progressive? Or would the ice sublimate off after half an hour or so at altitude?

[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...