Around 5,000 ft or so. You don't fly much, I guess? :rolleyes:

NEVER at 5000' or so. Do not try to belittle people when you have no clue yourself. This is a website for Professional Aircrew.
In quite a few companies, seatbelt signs are only put off when cruising altitude is reached, sometimes after up to 30 minutes.

That means nothing!!

If you call a cell phone that's been destroyed or out of service you'll still hear a ring from your end.

Facts and Conclusions
 

As I mentioned, this conclusion reflects what is *publicly* known at present. Later information could (most likely) change this conclusion.


Cell phones are only off during takeoff, people use them during flight for all kinds of activities (except calling off course).


Fire is highly likely in a crash into jungle but if sufficient attention has not been paid to remote areas, it could easily escape focus of scrutiny.

Chronus,

I call overseas cell phones often and this happens to me many times a year. I redial and this time the person I called pick up and confirm his cell was in his hands and never rang/vibrated. Cell phone technology is still far from perfect.

Bono,

They can only be turned 'on' in airplane mode, meaning their radio is switched off. For the network, that phone is off the grid.

"If true, seems a bit coincidental if comms were lost just as cruise was reached. When would the seatbelt signs have come off and people started to move around the cabin?"

Depends on the airline's SOPs : I've seen it 10'000ft, at cruise altitude, and I suppose there are many variations. Maybe someone from MH or who recently flew with MH may provide a better answer.

In terms of probabilities I would say pilot's suicide is more probable than a "massive electrical" failure on something like 777 which is full of redundancies specially in terms of electricity.

Seat Belt Sign off ...
 

10,000 feet is sometimes more typical (a) to have climbed well out of the local terminal manoevering area's arrival and departure routes, (b) to avoid turbulent low cloud if any, (c) to coincide with the 10,000 foot checklist items like landing lights off, end of <250 kt speed limit. I'm a pilot but not 777 so others may know differently.

I now see why the pilots and aircraft engineers get uppity when people post garbage about their area of expertise.

If the phone is detached from the network, as recorded by the Home Location Register (or its successors, for the pedantic), the caller will not hear ringing. They will either get a message to say the phone is out of service, and/or redirected to voicemail.

If the phone is in service so far as the network is concerned, it will be paged in the last known group of cells ("Location Area"). If Colour Ring Back Tones are subscribed to, then you'll hear music while the phone is paged. If not, you will probably not hear anything until the phone responds to the page. It will then ring, and the caller will also get a ring tone.

Sound propagation in the oceans is a complex process. If you want the details along with some math to back that up, there was a thesis link a few hundred posts back. The short of it is that the ocean's surface and bottom both reflect sound waves in a complex manner, resulting in channeling of the acoustic energy in what amount to a wave guide. Further complications include wave bending due to differences in water temperture and salinity. Signal loss in the channels is inversely proportional to distance, not the square of the distance as in line of sight, so signals can and do travel very long distances.

The hydrophone networks (e.g. the USN's SOSUS) were initially placed at choke points like the GIUK Gap to detect transit of Soviet submarines but proved able to track submarines as far away as the US continental shelf and low-flying Soviet patrol aircraft, all back in the 1960s. The capabilities of current systems are not publically available but I'd assume that the massive improvements in sensors, underwater cables, and computing power have produced near-realtime knowledge that might be applicable to the current search. The problem is that providing such data provides a lower bound on what the system is capable of.

The issue of propagation in shallow water interacting with surrounding land masses is complex but of critical interest to both civilian and military sectors due to the hunt for natural resources and the focus on littorial warfare. Lack of public disclosure for the supporting evidence behind the current search areas is hardly surprising.

TOC at 17:01 UTC
 

@HeathrowAirport
MAS370 reached 35,000 feet (which I assume was its TOC that day) at 17:01 UTC, well 20 minutes before the last blip reported by FR24 (17:21 UTC).

I assume that 35,000 feet was TOC for that flight because the altitude did not change for 20 minutes. However, having tracked the same flight on FR24 the day after and yesterday, I noticed that TOC was 37,000 feet.

I guess only the airline may provide further information about this.

Cellphones
 

I don't think we can put too much credence on the cellphone stories. I believe the process goes something like this: When you physically turn off your cellphone part of the shut down sequence is that it tells your carrier "I am no longer here - send all calls to voicemail. Goodbye." On the other hand if you simply go out of range the carrier will spend a few seconds trying to find you, and while it's doing that it plays the ringing signal to the caller. If it can't find you it then diverts to voicemail.

I can't state for a fact that's the way it works, but empirical data would lead me to believe it to be accurate. My wife is cabin crew on a major airline in the US and there have been occasions when she has accidentally left her cellphone on during take off. Naturally she turns it off if she remembers, but on those occasions, despite the phone being off when she lands, it rings 2 or 3 times before switching to VM. Conversely when it's turned off while still in range the call goes straight to VM regardless of where in the country she is, until she turns it on again.

I can also confirm that, in the US at least, the seat belt sign and the portable electronic devices sign remain on below 10,000.

There are several nations keen to lend humanitarian assistance. Also unless the Chinese are getting more facts than we are on the fate of their citizens they are going to lose patience with the reports and results so far very soon

For the last time the Mobile operators have a LOT more data on phone location and switch-off vs. out of range etc. than can be inferred from customer observed behaviour.


Whoever the mobile operator is has either not been contacted (!) or the results are being withheld for some reason (e.g. customer or phone not actually on the flight)

"FACTS"
 

Can we please stop referring to "facts".

99.9% of us are getting our "facts" from the media. This is the same media that was still reporting a 777 door spotted in the SCS 12 hours after commercial pilots & engineers on this very forum (and others), were pointing out that no such door of the "type" shown could have come from a 777. We are now told by the same media that this never was a door.....

What is most distressing is that the media need to supply "copy" - or they get sacked. Idiots on this forum, who know no more about aviation than my dog, then "dissect" it, offering up their views.

Guess where the media come looking for some insight to what is going on, eagerly ready to provide more copy? This and other forums, hence the deeply flawed process is perpetuated.

There is one undeniable fact at the moment surround MH370. It is missing.

Telecom guy here...if they had ANY cell signal, it would be easy to triangulate which tower was lit up. That's a five minute job to figure out.

My guess is, the phone never un-registered from the network hence why its ringing.

The "ringing" sound, so many rings etc is a complete red herring.

What the caller hears and what the phone does are two very separate things. When a call is sent to voicemail, the signaling message from the voicemail system that acknowledges the call causes the ring tone to be played. Once the VM system has allocated the resources to answer the call, it sends the answer message, and the call sequence continues. Most of the time, the call is acknowledged and answered simultaneously, hence no "ring" before the VM system answers. Sometimes, it doesn't. So you hear a short ring before it answers.

The handset itself does not generate a ringing tone that is heard by the caller. Network equipment does this, usually the main switch (MSC).

As has been said, this is a vein of information that the authorities will have been looking into. Whether they wish to share their findings is another matter.

It's been sunrise in Vietnam for about half an hour now. I strongly suspect they'll find the crash site in the next couple of hours looking at the Aviation Herald reports....

"Vietnam's Headquarters for the Search and Rescue operation of MH-370 confirmed receiving the report by Hong Kong's Air Traffic Control Center stating that a Hong Kong based airliner reported a large field of debris while enroute on airway L642. A Thai cargo ship in the area was asked for assistance and has set course to the area but did not find anything unusual so far. A second vessel asked for assistance did find some debris. Following this finding Vietnam's Maritime Search and Rescue Services (MRCC) dispatched a ship to the debris field.

Hong Kong's Civil Aviation Department confirmed a Cathay Pacific flight from Hong Kong to Kuala Lumpur spotted large amount of debris while enroute off the coast of South East Vietnam."

The question is, how did it end so far away from it's last reported position without any contact? A bomb would have scattered debris all over the place far further back towards Malaysia no? Either a technical problem so severe it took out all communications or a hijacking/pilot suicide look most likely but suspect someone would have raised the alarm if a hijacking. After all, if it is in this crash site then they were only 50 miles from the Vietnamese coast (probably in range for mobile signal?).

Cause is still a long way off knowing but does look odds on it's around that area 80NM SE of HCMC.

At that local time there is no reason to think any military radar will have been operating with vigilance in that part of the world ( let alone recording track formations)

Mr Optimistic


Yet we are told that primary radar saw a turn back . .
Who uses primary radar ?
Operator has very good memory ?