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-   -   Malaysian Airlines MH370 contact lost (https://www.pprune.org/rumours-news/535538-malaysian-airlines-mh370-contact-lost.html)

simon43 14th Mar 2014 00:27

How do MAS pilots get weather, etc. enroute when over oceans? Wait for VHF? I find that hard to believe- it's a global airline. If true, it says a lot about the operation in general.
They would use HF ACARS (link to a list of HF ACARS ground stations is here:


As posted earlier, the nearest F ground station is at Hat Yai (south Thailand).

They would also use HF voice comms for weather reports etc.

A link to a list of HF aeronautical stations is here:


For the region of interest, there are HF ground stations at KL, Singapore, Bangkok etc.

flt001 14th Mar 2014 00:27

Strange to who?
My understanding on satellite technology is that anything you do is incredibly expensive. You don't do anything unless there is a reason for it.

Pinging a satellite which then logs and downlinks this data (again x1000's planes 100's times a day). A satellite which will not respond under any circumstances has no point. A simple off switch in the software onboard would be the most logical way to perform this rather than a credential check via satellite using up bandwidth from the plane to the ground base to the satellite back to a ground base and then onto IT HQ and back again.

Now maybe this pinging leads to results but that isn't by design.

FIRESYSOK 14th Mar 2014 00:33


Thanks. Had no idea HF ACARS would be used by an airline such as this.

PilotsResearch 14th Mar 2014 00:35

Costs of Satellite Data (e.g., the pings)
Your understanding has gone out of date. Smartphone plans over satellite now have costs similar to what we paid for cellphones a decade ago.

I'm told by a friend in the business that the satellite industry has surplus capacity, and companies are out beating the bushes to find new users.

Evey_Hammond 14th Mar 2014 00:44

Even more to the already-long tale. The question is: deliberate or not?

"KUALA LUMPUR, Malaysia -- Two communications systems on board the missing Malaysian Airlines plane were shut down separately, CBS News confirmed Thursday, a development that suggests the systems were deliberately turned off.

CBS News correspondent Bob Orr reported the two systems used to track Flight 370 were shut down sequentially, just before the Boeing 777 apparently changed course and turned west.

While that could suggest a deliberate act, CBS News aviation and safety expert Capt. Chesley "Sully" Sullenberger cautioned that it is "conceivable" that the communications systems could shut down sequentially on their own in the event of a catastrophic electrical failure. He said the systems in a plane are so compartmentalized that things could shut down in a cascading, domino fashion instead of all at once."

Full story here

Ollie Onion 14th Mar 2014 00:45

I was just reading a report on CNN that states that MAL 'DOES NOT' subscribe to the ACARS aircraft monitoring so no data was uploaded during the 4 hour period. But it did also say that even if the airline does not subscribe to the ACAR's Satcom service the aircraft will still ping the satellites and establish contact because that is how the 777 system is designed, the fact that MAS doesn't subscribe does not effect that. It is these 'pings' that they have now found to have carried on for 4 hours after last contact and they apparently will only happen whilst the aircraft is powered with engines running. The report also said that the aircraft could be airborne on land or indeed just flying around in circles.

Communicator 14th Mar 2014 00:46

ACARS Access
There seem to be three separate issues in connection with ACARS that MAS senior management has been unclear about:

1. Human Messaging through ACARS

When MAS talks about ACARS, they are probably viewing it from a layperson's perspective: No HUMAN OPERATOR received/sent any messages through ACARS.

2. Automatic Messaging through ACARS

It seems that some system status information was successfully sent to Rolls Royce and to Boeing, presumably through ACARS. These transmissions occur only when triggered by specific conditions (e.g. engine start/take off). It is not clear when the last transmission from MH370 was received.

3. ACARS Link Establishment

Apparently, the ACARS Satcom "pings" a satellite at regular intervals (hourly?) to establish contact and download incoming messages (if any). Unless messages are actually sent or received, this link establishment or "ping" information would only be available to the ACARS system operator, NOT to MAS, Rolls Royce or Boeing.

Ollie Onion's post above indicates that Satcom "pinging" would occur even though MAS may not have subscribed to the Satcom options for ACARS.

It seems that U.S. Government statements were referring to these Satcom pings, NOT to full messages. (Of course, anyone familiar with the detailed workings of the system would have tried to ascertain the ping log on Day 1.)

NOTE: Similarly, there has been no official recognition of the potential that cell phones left active established contact with ground-based cell towers if/when the plane crossed peninsular Malaysia (and Sumatra). Also, ADS-B messages may have been received by ground-based stations in those areas beyond those evaluated by FR24. All this would be of a piece with the apparent failure to check primary radar recordings at an early stage.

TheShadow 14th Mar 2014 00:46

No inflight Internet Access for Pax?
If there had been, you might conclude that a well thought out cockpit-driven "total disappearance event" may have given a disabling of that non-essential bus feeding the rear areas a high priority. They'd not want the pax emailing their concerns to anybody (such as a locked cockpit door). But if MAS were too cheap to maintain a satellite ACARS contract, they'd likely also not offer their pax inflight internet access. Organic IFE is much cheaper.

Why would a "total disappearance" be a priority to someone? You have to conclude that the eventual lessons of Silkair and Egyptair's MS990 was that any relocatable wreckage would always give up the facts of the accident. A solution to that would be to place the aircraft beyond the search parameters and in water too deep for recovery of DFDR/CVR. That's the Indian Ocean, not the South China Sea/Gulf of Thailand.

But the additional puzzle might be that there should be no in-cockpit or avionics bay methodology for disabling an Emergency Locator Transmitter (E.L.T.) or stop it transmitting to a SAR satellite on 406MHZ. This jigsaw is missing a few pieces.

grumpyoldgeek 14th Mar 2014 00:57

"There is probably a significant likelihood" that Malaysia Airlines Flight 370 is on the bottom of the Indian Ocean, a senior U.S. official told CNN's Barbara Starr Thursday, citing information Malaysia has shared with the United States."
And I submit that there is a significant likelihood that US subs or subhunters have picked up the underwater ping from the emergency locator transmitter.

If so, expect a breakthrough in the next 12-24 hours.

slats11 14th Mar 2014 00:58

Many posts ago somebody stated that their cell phone had received three texts welcoming them to a country that the aircraft they were in had transited at FL330

If this occurred it would have required a “handshake” signal exchange between the phone and mobile network operator.

I can’t help wondering if those coordinating the SAR effort have considered cross referencing the mobile phone numbers of all on board with every cellular network that flight MH370 could conceivably have over flown?
I wil guarantee you this has been checked very early on.

If we find this plane, more than likely it is due to some device that has been detected pinging away. Could be passenger mobile phones. Could be ACARS. Could be engine telemetry. These signals may have been received by various means other than the intended network.

Note that RR aren't saying there was no transmission. Just that they didn't receive any transmission. That seems to tie in with the WSJ clarification.

White House: Hunt for missing airliner may extend to Indian Ocean - The Washington Post

One senior administration official said the data showing the plane engines running hours after contact was lost came from the Aircraft Communications Addressing and Reporting System, or ACARS, a way that planes maintain contact with ground stations through radio or satellite signals. The official said Malaysian authorities shared the flight data with the administration.
Interestingly, this doesn't state in which direction the information was shared. Words can be chosen very carefully and used very specifically at times.

mickjoebill 14th Mar 2014 00:58

Damage caused by a bomb, missile, un-contained engine failure or mid air collision does not necessarily mean a catastrophic in flight disintegration, with a significant amount of wreckage that would float.

So those who theorise since no wreckage has been found at sea level around the point of loss of contact that none of the above could have happened, should be more equivocal.:ok:

Nor do we know that any of the above events could have been reliably picked up by a surveillance satellite tuned to monitor "flashes", especially a brief flash from a small bomb that could be shadowed by the body of the fuselage.

The US say they have monitored some faint electrical/RF activity on the plane which they say was connected with engines running.
We do not know why contact with this signal was lost, the plane may either have crashed, landed and shut down or travelled out of reception range and so it could have continued on its way for a further hour or more.

They say they couldn't derive the heading of the plane from this signal so it may have turned again.

Evey_Hammond 14th Mar 2014 01:01

Just found this link, unsure of how accurate it is but if there is truth to it then it's very interesting as it shows where satellites are being focused.

If you hover your mouse pointer over a coloured area it tells you the date the satellite was looking. It's interesting to see how many satellites have taken a look at Malacca (which has a runway) since MH370 disappeared.


Feathered 14th Mar 2014 01:05

Breaking news from WSJ suggesting that new ACARS data shows the aircraft may have flown up to 5 hours toward the Indian Ocean at cruising altitude.

Meanwhile other reports state that the United States Navy is now relocating a Destroyer to the Indian Ocean for the search.

Originally Posted by Wall Street Journal
Updated March 13, 2014 8:43 p.m. ET

Communication satellites received intermittent data "pings" from a missing Malaysia Airlines jet, giving the plane's location, speed and altitude for at least five hours after it disappeared from civilian radar screens, people briefed on the investigation said Thursday.

The final satellite ping was sent from over water, at what one of these people called a "normal" cruising altitude. The people declined to say where specifically the transmission originated, adding that it was unclear why the transmissions stopped. One possibility one person cited was that the system sending them had been disabled by someone on board.

The automatic pings, or attempts to link up with satellites operated by Inmarsat PLC, occurred a number of times after Malaysia Airlines Flight 370's last verified position, these people said, indicating that at least through those hours, the Boeing Co. 777 carrying 239 people remained intact and hadn't been destroyed in a crash, act of sabotage or explosion.

Malaysian Airlines said it hadn't received any such data.

If the plane remained airborne for that entire period it could have flown more than 2,200 nautical miles from its last confirmed position over the Gulf of Thailand, these people said.

Satellites Received 'Pings' on Location, Altitude From Malaysia Airlines Flight 370 for Hours After Jet Fell Off Radar - WSJ.com

onetrack 14th Mar 2014 01:07

Would the "mumbled" communication between the MH370 crew and the Japan-bound B777, as the last reported contact, possibly indicate slow hypoxia?

Slow decompression leading to stealthy hypoxia seems by far, to me, the most likely event. Confused crew, gradually slipping into unconsciousness, make cockpit errors, turn off transponder accidentally, try to set return course, select wrong heading, along with incorrect reduced height setting - aircraft sets off flying steadily into the Indian Ocean until fuel exhaustion.
Many aviation people with extensive knowledge are emphatic that the transponder must have been turned off by a deliberate action.

It just happens by pure coincidence that the course the disoriented crew set, is into an area not covered by any radar, and their flight over the Malay peninsula isn't picked up by the Malaysian military, or dismissed as a radar return of no consequence.

The denials by the Malaysians are in line with what they do actually know - but the Americans know vast amounts that the Malaysians (or Chinese) don't know - and the Americans are not about to tell anyone what they do know.
One must keep in mind, it takes days to sort through logs, and decipher the right info from the vast amount of electronic noise.

Uncontrolled decompression - Wikipedia, the free encyclopedia

dmba 14th Mar 2014 01:16

Evey Hammond link

slats11 14th Mar 2014 01:17

Single point of failure
We spend a lot of time trying to eliminate single points of failure. We do this because many years of hard won and at times bitter experience have shown that single points of failure are weaknesses, and that redundancy intrinsically makes systems much less likely to fail.

When I fly in a helicopter, I sometimes think about the various single points of failure.

There is an enormous amount of redundancy built into modern airliners, and I applaud the efforts of engineers over the years.

There is still a major single point of failure. However unpleasant, we do need to consider this. Especially with several (widely accepted) precedents involving over recent years (and not counting 9/11 here).

Clearly we are all interested in this incident. To this discussion, we all bring our past experience, professional background, and personal biases and prejudices. A balanced discussion that attempts to integrate our differences and cancel out bias is most likely to lead to the answer.

I find some of the theories with 100's of posts a bit to hard too accept, and there is no single point of failure and too many things have to line up just right. We have some event which simultaneously destroyed all forms of communication and incapacitated the pilots, but left the autopilot fine. Or we have hypoxia (either sudden or gradual onset) which also knocked out the transponder. Or we have a fireball across the sky seen from a oil rig far away, but no debris you would expect to find at the end of such an event. While some things may be conceivably possible, that does not make them plausible.

As more information slowly comes out, these theories are starting to fall down.

Against this background, I can't help wondering why the few posters speculating about a single point of failure are repeatedly deleted.

Turkey Brain 14th Mar 2014 01:21

View from an average 777 line pilot
Notes from an average B777 pilot. I feel deeply sorry for family and friends affected by this terrible situation. I have read most posts, 2000+.

1: Depressurisation without the necessary descent.

Leading to pilot incapacition sounds very plausible. Putting your mask on then checking your mate has his or hers on wastes time, maybe 5 to 10 secs. If you then find that the oxygen is not working game over, too late to descend the aircraft, your unconscious.

I have heard aviation doctors suggest that one pilot should use his useful conscious time, maybe only 5 secs to start the plane down to min safe altitude. The other puts on his oxygen straight away. If all goes wrong with donning the oxygen mask or supply at least the plane is going down and you might regain consciousness later at a lower level and hence regain control.

If the plane did depressurise and the crew were incapacitated why did it stay at a high altitude? Possibly the autopilot was working, because it flew at a high altitude and on a relatively steady westerly heading for maybe hours, using the best guess from primary radar and ACARS 30min radio pings! This suggest that the electrics were working in some way, but no transponder signals.

Seems too much of a coincidence, autopilot ok, transponder not, aircraft depressurisation and pilots not OK. Aircraft heading about west.

2: unlawful interference.

Timing perfect, just out of normal radio range, miles from land near a change of airspace. Transponder switched off, radio silence apart from some garbled messages. Military radar think they saw an aircraft flying west at FL295. ( Can't remember but I think all the 911 aircraft turned back with transponders switched off. So it's happened before. ) Plane eventually disappears. Did the pilots fool the hijackers or were the hijackers on their own and lost. Unfortunately I can't see a successful ditching being the outcome, because of the lack of ELT's etc.

Big problem with this theory, why didn't the few passenger phones that were almost certainly on, not get a signal over Malaysia or anywhere else. Not sure anyone would plan to bring jammers on board or confiscate every phone.

3: Note on transponder use.

We don't touch the transponder when busy.

When we do select a new code we just type in the new code,
NO switching to stby. When practicing Rapid depressurisation in the SIM it's very rare to see anyone select 7700, were just too busy. We turn of the airway or away from traffic, most pilots keep an eye on nearby traffic using TCAS. Some use look down on TCAS during emergency descent, it's force of habit from normal descents.

simon43 14th Mar 2014 01:25

Thanks. Had no idea HF ACARS would be used by an airline such as this.
I don't know whether or not they would use it - but the HF ACARS system exists in that region.....

HF voice comms is (AFAIK), commonplace for aircraft flying over ocean routes where VHF comms coverage is not available - I have listened in many times to the HF traffic for south-east Asia.

Feathered 14th Mar 2014 01:29

HF ACARS is most often used near the poles, due to poor satellite geometry.

cynar 14th Mar 2014 01:29

Because the CVR only captures 2? hours, we will never know what exactly happened in that cockpit at 1:30 am. Barring the remote landing-strip, all safe scenario, at least.

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