More on Inmarsat tracking

http://t.co/5FWaYp6T1a This will link you to an SBS visual on how Inmarsat tracked MH370.

Advertisements

What’s all this mean?

This morning, both news.com.au and ABC News (Australia) are reporting that the Malaysian Government has announced that revised data has the last known position of MH370 in the hypothesised ‘southern flight corridor’ – pretty much the middle of the Indian Ocean, west of Perth.

According to ABC News Radio this morning (Australian time) the reviewed data came from Inmarsat who have been auditing their own records.

Inmarsat is a satellite telecommunications company that host data for transmissions aircraft tracking as well as satellite voice communications. according to GMA News, investigators relied on tracking hourly ‘pings’ received from the aircraft along with when the satellite started receiving these ‘pings’, to find a position. This is how they determined the two flight corridors for the aircraft, and ultimately, it seems, the southern flight corridor.

All this indicates that the search under way in the southern Indian Ocean is the likely crash site.

Image

Image credit AMSA.

What theory are we up to?

The more I think about it now, given that the aircraft continued on so far without a change in heading it is my belief that Scenario 2 occurred from my post on March 17, that is:

  • Aircraft flies toward destination for an hour
  • Flight crew make standard report at IGARI reporting point
  • A rapid, intense fire breaks out, affecting multiple electrical systems (transponders go offline)
  • Whilst one flight crew member is fighting the fire, the other programs the autopilot to turn back toward Malaysia
  • The fire continues until the flight crew are overwhelmed but then the fire goes out
  • Aircraft continues on the current heading until running out of fuel, probably over the Indian Ocean

What Next?

The search is going to continue. Various items that cannot yet be linked to the missing aircraft are beginning to turn up which may indicate that either the ocean is full of floating, large scale rubbish or that the aircraft (or things the aircraft was carrying) are beginning to surface. 2.5 weeks is a long time though. The pieces being found may be well separated from the bulk of any wreckage and the all important ‘black boxes’ or flight data recorders (FDR).

Assuming the recorders are functioning normally, they are required by regulation to transmit for 30 days, though some recorders will transmit for longer.

There is a history of flight data recorders being recovered despite heavy odds. These articles on Air France 447 and South African Airways 295 accidents have good information on search areas and techniques used to locate wreckage and FDRs. Both had large search areas and deep ocean floors.

The ever changing sequence of events

According to the ABC (Australia) the sequence of events around the time time MH370 blinked off radar screens has been clarified by the investigation team. This new series of events would rule out theory two in my post from yesterday.

Apparently it goes like this:

  1. ACARS is disabled
  2. 12 minutes transpire
  3. Air traffic control (ATC) initiate hand over to the next controller
  4. MH370  replies with just a “All right, good night”
  5. MH370 does not make contact with the next assigned controller
  6. 2 minutes transpire
  7. Transponders are disabled
  8. A short time later, the aircraft makes a turn toward land, flies for several more hours and is not seen or heard from again

The Handover process

To help control ATC workload (and factors affecting radio wave propagation) , the world’s airspace is segmented into various ‘sectors’ with an ATC responsible for one or more sectors at a time. As an aircraft approaches the boundary of a sector, the ATC instructs the aircraft to contact the next center by stating the new controller’s callsign (how they are to be addressed) and the radio frequency. The aircraft is required to respond by reading back the frequency. The process is designed so that if the aircraft reads back an incorrect frequency, the error may be detected by the ATC and the aircraft is less likely to have communication trouble finding the next controller. The handover conversation typically goes as follows:

ATC:              Generic 456, contact Melbourne Centre, 132.0
Aircraft:       132.0, Generic 456

It is also common for both ATC and flight crews to add greetings and goodbyes as to these handovers but from a technical stand point that is not required and the most important information is the new frequency. In my experience the absence of a read-back is not always a priority from ATC as generally, the crew know the next frequency and are expecting the handover and ATC also know that if they call the wrong frequency they’ll usually come back to the first one and sort any problems out. The trouble with MH370 is that they subsequently disappeared.

What does it mean?

From this latest version of events, if I were the investigation team assigned to investigating the mindset of the crew, I would be focusing on the First Officer at this stage. I say this because systems were being turned off and his voice was heard on the radio (with presumably no struggle in the background) prior to it going missing.

Has anyone done this before?

Yes. There have been many cases (a list can be found here) where aircraft have been used as vessels for suicide. From my recent research, lead causes seem to be trouble with spouses, finance and insurance fraud.

So…What did happen to MH370?

The following is an expression of my opinion only and dealing with purely the hypothetical – and I don’t even answer my question!

As I see it, and based on the information at hand (reported by Australian media) these are 3 possible explanations that have the least flaws:

1. Unlawful Interference

It is reported that the aircraft transponders were turned off approximately 1 hour after departure. This is not something any crew member would consciously do whilst in flight. In is usually selected on as the aircraft lines up on the runway for departure and remains on until the aircraft lands and reduces to taxi speed. Indeed, this Boeing 777 likely selected its transponder on automatically. Even if the transponder failed in flight, there is a second transponder readily available to takeover.

Air traffic control (ATC) would ordinarily notice such an event and notify the flight crew. This is a routine but critical function of ATC since, if the controller can’t see the aircraft on screen, then they must establish verbal communication immediately to ensure that all is as it should be.

It is my position that one or both of the flight crew, or someone (originally) outside the flight deck turned of all communication systems that they had access to.

It seems strange that the crew did not communicate anyone forcing entry into the cockpit which would implicate either one or more of the cabin crew or passengers that had been invited into the cockpit.

Then what?

Well exactly. This model is mysterious since there have been no demands made and no willful damage to anything outside the aircraft. No threats. Nothing “terrifying” in the context of terrorism. – other than the fear of the doubt and the unknown.

So that brings me to the idea that perhaps someone has some kind of insurance scheme available. However stealing and crashing a B777 is a pretty elaborate way of taking yourself out…seemingly effective though so far.

2. Major Failure

The only scenario I can think of that doesn’t rely on unlawful interference is a complicated one. This was originally my lead idea, however the information as it stand is consistent with the aircraft turning around which does not match the model of something instantly catastrophic such as in-flight breakup or explosion. So the only thing I can come up with is something like this:

  • Aircraft flies toward destination for an hour
  • Flight crew make standard report at IGARI reporting point
  • A rapid, intense fire breaks out, affecting multiple electrical systems (transponders go offline)
  • Whilst one flight crew member is fighting the fire, the other programs the autopilot to turn back toward Malaysia
  • The fire continues until the flight crew are overwhelmed but then the fire goes out
  • Aircraft continues on the current heading until running out of fuel, probably over the Indian Ocean

This model does not fit precisely either. One would think that such a fire would have had bells going off that would have appeared on ACARS messages that get sent back to the airline’s maintenance facilities. Additionally such a fire would likely have been smelt by cabin crew, and they would have then been able to follow procedures for disabled flight crew. Again, this model is not a perfect fit.

3. Combination Theory

  • The problem with stating that there was simply a major failure is that, according to the latest reports (http://www.abc.net.au/news/2014-03-17/missing-flight-mh370-good-night-issued-from-plane-after-shutdown/5325816) the aircraft almost certainly turned around and headed back toward land for several hours before finally disappearing, probably into the Indian Ocean. This, after the transponders being deactivated.The only way I can account for this sequence of events is that there was unlawful interference and then some kind of failure. Scenarios that play in my mind go like this:
    • Aircraft flies toward destination for an hour
    • Flight crew make standard report at IGARI reporting point
    • Unknown person(s) disables communications (transponders)
    • Unknown person(s) programs some destination or heading into the autopilot then;
      • Accidentally disengages altitude hold function
      • Aircraft makes slow decent into the ocean and this goes unnoticed by unknown person(s) in the black of the night, or;
    • Aircraft flies toward destination for an hour
    • Flight crew make standard report at IGARI reporting point
    • Unknown person(s) disables communications (transponders)
    • Unknown person(s) programs some destination or heading into the autopilot then;
      • Inadvertently (perhaps during struggle for authority over aircraft) the cabin is depressurised
      • Aircraft continues on straight and level until running out of fuel, probably over the Indian Ocean

This scenario needs a lot of holes in the Swiss cheese to line up. However it seems to me just crazy enough to be possible and is thus my leading theory.

Edited: I couldn’t count!

How does an aircraft just disappear?!?

This is the question I have heard most from the public in relation to the disappearance of MH370. It is an embarrassing situation but not all that uncommon during normal operations. I will attempt to answer the question in terms that the media has somewhat confused.

Primary Radar

Most people are aware of the basic principle of radar. The first generation of radar involves the emission of radio waves that are sent out by a radar dish (typically on the ground), are reflected of an aircraft or object and ‘bounced’ back to the same radar dish. The electronics translates this radar return as a distance and bearing from the radar and can also calculate speed based on that information. This is displayed pictorially on Air Traffic Control radar screens.

The main short fall of this technology is that it is truly raw positional data and cannot depict additional data such as the flight number (callsign), and altitude (military radars can depict altitude). Additionally it is limited in range.

Secondary Radar

Also known as Secondary Surveillance Radar (SSR) is second generation tracking technology is aptly referred to as secondary radar. This technique builds on the idea of primary radar. A second radio wave leaves the radar station and ‘interrogates’ a transponder located on the aircraft. The aircraft, in turn, replies and transmits it’s altitude and a code which is assigned to it by air traffic control. The ground station uses the time taken for the radio wave to bounce and the aircraft’s reply to determine the position and speed of the aircraft and also receives the altitude information and code. The radar electronics uses the code to correlate the aircraft data to the flight plan filed by the flight crew. So now the air traffic controller can now see the position, speed, altitude, flight plan details and other information about the flight.

Additional advantages include increased reliability (fewer false radar returns) and better reliability. Also, aircraft can select emergency transponder codes to communicate non-verbally to air traffic control during radio failures or other events, including unlawful interference.

The useful operating range of both primary and secondary radar varies with the height of the radar station above sea level and the aircraft’s altitude since both systems require line of sight. This means at cruising altitude of large passenger transport aircraft, a range of around 150 nautical miles.

OK, so what’s this ADS-B thing I’ve heard about?

Radar installations are expensive to set up and maintain and, as I’ve mentioned, have some limitations in range and use.

ADS-B is a relatively new technology and is considered state-of-the-art for tracking aircraft. The information is wholly derived on board the aircraft using GPS. That is to say; the aircraft knows it’s own GPS position, altitude, heading and flight number. It transmits this information twice per second via the transponder (a modern type that is also compatible with secondary radar) to a ground station.

The cost of installing an ADS-B receiver is minimal when compared to radar installations. This means that you could place a receiver either side of a mountain range and monitor aircraft on both sides of the mountain that would ordinarily be blind to one or both of an equivalent radar station.

So there are fewer errors associated and it’s cheaper to install ADS-B compared with radar.

Is that the same as ACARS?

In short, no.

Primary and secondary radar along with ADS-B are what Air Traffic Control use to track aircraft. ACARS is used for the airline to communicate with aircraft in flight and vice versa.

ACARS is essentially a text and information service. Flight crew use it to retrieve up-to-date weather information, pre-flight information and other uses.

The aircraft uses the information to regularly transmit aircraft engineering parameters to maintenance controller so that fixes/parts to problems in flight can be addressed while the aircraft is still inflight and the flight crew are doing other things.

Got it! But how did air traffic control lose them?

All of the data from the systems above that I have mentioned is combined into various air traffic controllers screens as a target, with flight telemetry along side it. The flight appears on different radar (surveillance) screens during it’s journey. Various countries administer their own airspace. Some of the raw data is shared, some is not.

The raw data is turned into a situation display which is what the air traffic controller ultimately sees.

There are times when aircraft fly outside of the range of the ground equipment that detect them. In such cases, flights are procedurally separated. This means that the flight is tracked by the methods above until it is out of range. Up until that point, a highly accurate position is known to the controller. Once out of range, the aircraft will call the controller on the radio at regular, published intervals with the name of their position, the time at that point, their altitude and their estimated time of arrival at the next reporting point.

The controller will then enter this information, and their situation display will update with a ‘calculated’ position. This sound less exact than it is, and the required separation standard for aircraft in flight is increased to account for margins of error.

Ok. But what about MH370?

Good question.

From media reports, it sounds as though everything was going well until the crew reported their position at IGARI. From here it ‘disappeared’ from the controllers’ screens.

Such occurrences are not infrequent. Transponders fail, GPS may be unavailable to the aircraft for some minutes, atmospheric anomalies interfere. However the reason so much speculation has gone straight to fowl play is because B777 sized aircraft carry two transponders, just in case one fails.

For the aircraft to stop transmitting, and the crew not respond to calls by radio to verify any problem is where things start to get strange.

There are three logical explanations for everything going quietly so quickly:

  1. A total, rapid electrical failure. This would need to be a profound failure as there are four sources of elctical power on the B777 and this is distributed to provide redundancy for navigation and communication radios. In other words, a fire or explosion would need to occur.
  2. An in-flight break up. A rapid destruction of the aircraft from some kind of massive, rapid structual failure. These are very rare in smooth air and this type of aircraft. Also the theory that the aircraft continued flying discredits this idea – but I’m just looking at why it went of the radar in this post
  3. Deliberately turning off the transponder. Usually one transponder operates at a time but both can be selected to Standby/OFF from the flight deck and this is a very simple process. I will go on to say only that if this is what happened, whoever was in the cockpit at the time DID NOT WANT TO BE TRACKED.

 What’s all this about the aircraft turning back toward KL?

My interpretation from media reports is that the air traffic controllers at the time of the disappearance did not have ready access to military radars and the aircraft was outside the range of any civilian primary radar facility.

When an aircraft fail communication checks, it may take hours to inform the people that need to be informed and for the correct questions to be answered. In this case, it took many hours to either start or to complete, the playback of all the recorded radar information for the hour before and the multiple hours after the aircraft went missing.

Depending on various factors, any primary radar information that is now available, may not allow for positive identification (it’s basically just a dot on a screen) and various black spots on its tracking further hamper efforts to track it successfully to a crash site.

It is not my intention, in this post, to speculate on the various theories behind the disappearance. Merely to try and clear up how it is that air traffic control could ‘lose it’.

Welcome!

Alrighty.

Welcome to my blog. This is my first time so please be patient and gentle.

I’ve been meaning to start a blog for some time now but have only had intermittent inspiration. However in monitoring the media coverage of MH370 lately I have had my inspiration return with a fury.

Not it that I think it’s the medias’ fault. Aviation is a highly specialised field, as is journalism. So it is unsurprising that a professional pilot would find of the reporting inaccurate and sometimes misleading.

It is my intention in my next post to expand upon the various theories around the community that exist around the disappearance of Malaysian 370/China Southern 748.