To answer Pontius several pages back

It would depend on the system fitted, if chemical generators than only the masks in the units where one mask was pulled would flow. Therefore any units above unoccupied seats which were not activated would be available to the crew. I know on the 777 I trained on each unit lasts approximately 22mins. We know there were c50 empty seats on this flight...

However if it is a gaseous (bottled) systems as per 747, which one poster has suggested it was, duration would vary depending on altitude, number of masks in use and how many bottles are fitted to the system. Theoretically if only a couple of CC were quick enough they could long outlast the flight deck oxygen which is only designed for 2-4 people to use for as long as it takes to make an emergency descent. Of course if the pax are on it, it wouldn't last as long with 250+ using it...

Radar
 

Have I missed it somewhere? How do they Know :
A. The radar tracks WERE 370 without IFF
B. The origin of the "waypoints"

Does MAS subscribe to ADS-C?

Please do not de-bunk unless you KNOW and can give the evidence!

The pings are time distances from the satellite and translated to an arc subtended from the point immediately below the satellite.

By definition these lines do not provide positions from which to drive a strait (sic) line. The lines will be a measurable distance apart. Let us assume they are at one hour intervals and are 200 miles apart; this gives a velocity vector of 200 mile/hr towards the statellite sub-point. You can then use a ruler marked off with the max ground speed, say 450 kts, and use this to fit the 450 mile marks to the arc. If you subtend this from the last know position it will give to a track at a given angle to the North with a similar mirror image to the South.

If you now mark the rule with either the minimum speed you can get another track which will be closer to the direct line to the satellite ground position.

You now have two sectors, one to the north and one to the south. The line joining the two points at the end of the sector arcs will give a possible line of position. These lines can then be plotted further on if it is assumed that the aircraft flew one for a time after the last ping. Only if you assume the correct groundspeed would you have a discrete pair of tracks.

The closer together the ping arcs the greater the track angle would be to the north and south.

The logic only holds good if the aircraft made no course changes between pings and flew at a constant ground speed.

Deriving the course from the Inmarsat pings
 

Given a number of recent posts on the methods of interpreting the INMARSAT ‘ping’ data, here is my understanding of how this will have been done by the NTSB.

Each ping specifies a distance from the INMARSAT F1 sub-satellite point at 64degrees East on the equator. On the Earth’s surface this is a circle (but not a great circle). A model track can be specified from the last reported position of the aeroplane off the West coast of Malaysia to any point on the circle described by the last ping. The length of that track specifies the speed of the aeroplane (since the times are known) and hence where it would be when the intermediate (every hour) pings were exchanged. The distances of these ping positions from the sub-satellite point can be compared to the actual data (held by NTSB but not us). The point on the final ping circle (the arcs) can be moved until the model track matches the data. If there is no good match, change parameters like the final turning point, smooth changes in speed along the track etc. to get a good match to the data (there is a limit to how many things can be changed before the model can fit any data). Unless the aeroplane was performing extreme and random manoeuvres during its flight (in which case it would have crashed earlier) a course and speed of quite high accuracy can be obtained, I think.

The fuel exhaustion point is a different calculation and more uncertain IMHO.

A longer and even more boring post is at #5911 of this thread.

I will start by stating that I don't KNOW and no one except the relevant military air defence operations centre will be able to tell you how they KNOW.

What I can say is how they should have known.

The air defence centre is responsible for compiling a recognised air picture in its AOR. A civilian aircraft entering the AOR will be wearing a civil squawk which will display adjacent to the primary radar return on the military radars. Now assuming the squawk decode and its position in the airway structure correlate with a known civil flight it will be allocated a Friendly track number - this is an AD assignment and not exchanged with the civil ATC (unless they are co-located).

If the aircraft then 'strangles its parrot' (:)) this will not affect the allocated track number. As the aircraft leaves the airway structure it will continue to 'wear' the same track number.

Should this aircraft then depart the relevant AOA it can be handed off to the adjacent Air Defence Centre, in this case that would be Thai if a bilateral agreement existed but we have not heard of such bilateral liaison.

QUESTION RE PINGS:
Are the packets time stamped to enough accuracy for ranging or is INMARSAT timing the round trip or ?????
The error rate is around 186 miles (distance to satellite) per millisecond if I remember my math. You are deriving a sphere around the satellite and then plotting it against the surface of the planet which is another sphere.

The words are from a U.S. Senator, Saxby Chambliss, who was a lawyer before he entered politics 20 years ago. He threw out Boeing's name when he couldn't provide any direct support for his prior statement. This is standard behavior for US politicians.

The MH B777 have oxygen generators.
The BA B777 have a gaseous system, customer option.

Except that this aircraft didn't have the antennas that caused the cracks spawning the AD.

jmmilner

It should be noted that the words also perfectly fit the official position of the investigation (of which Boeing is a part of), and therefore could have very likely been said near exactly as Chambliss described them

The only reliable LKP available to the public is the last SSR position.

Note that it's a few degrees above the equator.

Moving West from the LKP would reduce the distance to IOR -- as would a course of 180 True until crossing the Equator, whereupon the distance would steadily increase.

The first ping arc after LKP coupled with a/c g/s might be useful to determine whether MH370 turned North or South. The second ping arc may also be helpful in determining the relative probability of which way the a/c turned.

That said, there remains the possibility the a/c assumed a closed course. In that case, we might see a steady oscillation in ping arc distances or a constant one depending on cycle times. For example if the a/c was tracking a wide circle n times an hour, the ping distance could remain constant.

To the first point, in addition to what Pontius Navigator posted earlier, the authorities will have the data from the Inmarsat "pings". Since it has been reported the plane they believe to be MH370 disappeared from military radar in the 2:15-2:40 time period, they can use the distance to MH370 at 2:11 based on the Inmarsat data. If the arc proscribed by this distance matches up with the radar returns at the same time, that will be additional information to support their conclusion.

Additionally, you will have significantly different Inmarsat distance data if the plane did a 180 and tried to return along its original heading as opposed to making a left turn to cross over the peninsula along the Malaysian/Thai border as described by the authorities.

I believe they have a very high degree of confidence that the plane they saw was MH370.

ELT
 

Does the 777 even carry an airframe ELT (the life rafts/slides have them but they are not automatic unless the slide is deployed)?

are you getting confused with the FDR sonar locating beacon (SLB)?

I have seen both quoted by posters claiming to know from experience is there a chance due to when they were ordered/delivered they could have either or is it a customer option.

Extremely unlikely for complex electronic systems to be damaged in such a way as to have such specific failures.

If I smash up a computer, what do you think the odds are that it'll (a) stop working / fail in many respects vs. (b) start doing something specific like sending an email every hour. I'm pretty sure you'd chose (a)....

Likewise having the flight systems damaged such that they change heading periodically but otherwise function perfectly, seems almost impossible.

Buttrick, air defence radars since their conception have been able to assess height. In very simple terms, there is a radar sweep in the vertical plane as well as the horizontal.

Some certainly do, can't speak for MH's fit.

and another poster (either RAAF or AMSA) stated categorically they can't only the americam P8 has that ability

Timing between satellite and transceiver
 

Some insight can be gained here:

Timing advance - Wikipedia, the free encyclopedia

GSM and Inmarsat C both use time division multiplex technique, the principle is the same.


Think of many a/c (transmissions) wanting to land at the same destination airport (satellite) with all a/c coming from different origination airports (airborne transceivers)
- Each a/c (transmission) has a time slot assigned when it's supposed to arrive.
- For obvious reasons those time slots may not overlap.
- Radio waves behave different than a/c : they can not fly holding patterns.
- So take off time of the radio transmissions (a/c) have to be timed, such that all transmissions (a/c) arrive at the satellite (destination airport) in their assigned time slots.
- ATC at destination (the satellite) has to measure the distance between origin and destination, so it can tell ATC at origin (airborn transceiver) when the a/c (transmission) has to take off.
- This distance measuring happens by measuring round trip times.

Excellent bit of insight into how difficult the task is going to be to find the aircraft. This thread has gone into over kill with suggestions and hypothesis of what actually happened. Either way we wont know for sure until the plane is found and and even then we may never find out. The time is well and truly over for any thoughts of working out what happened.

On a side note, I find it rather tedious now watching the day after day updates (or non updates) in the press conferences. It is doing nothing more than fueling speculation and adding to the tension of the families. I know they want answers, but if there isn't any, then there isn't any.