Search crews in the remote southern Indian Ocean have completed a task so vast and technically ambitious that it once seemed impossible: to scan a three-mile-deep, 120,000 sq km swathe of seabed using a side-scan sonar “towfish” in hopes of finding the wreckage of missing Malayia Airlines 777 MH370. After considerable delay due to mechanical problems and bad weather, the final square miles were scanned on October 11 by the research vessel Fugro Equator. The $180 million project turned up no trace of the missing plane, though searchers did find several long-sunken sailing ships.
The Fugro Equator will next use an AUV, or autonomous sub, to scan selected areas where the rugged seabed topography was too rough for adequate imaging by the towfish. “The total combined area of the spots that will be surveyed with the AUV is very limited, but still required to ensure that no area has been missed,” says Fugro spokesman Rob Luijneburg.
The Australian National Transport Board (ATSB), which is overseeing the search, expects this fill-in work to be completed by the end of February.
The fact that that the Pennsylvania-sized towfish scan had been completed was first noticed by Richard Cole, a space scientist at University College London who has been meticulously logging the search ships’ movements via online tracking services and then posting charts of their progress on Twitter. “At the completion of Equator’s last swing in mid-October the target of 120,000 square kilometers had been achieved, at least as far as my calculations show,” Cole wrote me last week. Both Fugro and the ATSB subsequently confirmed Cole’s observation.
The 120,000 sq km area has special significance in the effort to find MH370, because ministers from the four countries responsible for the search have made it clear that if nothing turns up within it, the search will be suspended. Unless new evidence emerges, the mystery will be left unsolved.
Plans to search the seabed were first mooted during the summer of 2014, after officials realized that metadata recorded by satellite-communications provider Inmarsat contained clues indicating roughly where the plane had gone. At first, investigators were confident that the wreckage would be found within a 60,000 sq km area stretching along the 7th ping arc from which the plane is known to have sent its final automatic transmission. When nothing was found, ministers from the four governments responsible for the search declared that the search zone would be doubled in size.
In December, 2015, officials declared that the search would be completed by June, 2016. In July of 2016, Malaysia’s transport minister indicated that it would be finished by October; weeks later, a meeting of the four ministers pushed the completion back to December. Last week, the Australian Safety Transport Board announded that “searching the entire 120,000 square kilometre search area will be completed by around January/February 2017.”
In an email to me, ATSB communications officer Dan O’Malley said his organization will issue a report on the seabed search once the full scan is completed. Under ICAO guidelines, Malaysia will only be obligated to release a comprehensive final report on the investigation once it has been formally terminated; so far, Malaysia has only talked of suspending the search, not ending it.
The bulk of the work has been carried out by ships pulling a sidescan sonar device on a long cable. This so-called “towfish” uses reflected sound waves to create an image of the sea floor. By sweeping up and down the search zone in much the same way that a lawnmower goes back and forth across a lawn, searchers have been able to build up a comprehensive image of the search area’s bottom.
But, just as a landscaper might have to use a weedwhacker to clean up areas around rocks or stumps, searchers will have to fill in gaps in the scan where underwater mountains, volanoes and escarpments have prevented the towfish from getting a close enough look.
“A total area for search by the AUV is difficult to give because it concerns a number of relatively small spots that all are relatively difficult to reach and in difficult terrain,” Luijnenburg says.
The fill-in work will be carried out by an Autonomous Underwater Vehicle deployed from the Fugro Equator. The Kongsberg Hugin 100 is capable of diving to depths of up to 15,000 feet and can maintain a speed of 4 knots for up to 24 hours before being retrieved by the mothership. Whereas the side-scan sonar of the towfish has a resolution of 70 cm, the AUV’s sonar has a resolution of 10 cm, and so can image the seabed in much greater detail, as well as taking photographs when necessary.
Meanwhile, as the AUV work progresses, a Chinese vessel will deploy an Remotely Operated Vehicle (ROV) to take photographs of targets previously identified as being of interest. The ATSB has stated that none of these targets are “category one” targets, namely those likely to have come from MH370, however. Says Cole, “In the absence of category one targets there must be a list of targets from the sonar search that look the most interesting, so the question is how far down that list they are going to go.”
While the fill-in work must be carried out in order for the work to be declared 100 percent done, little prospect remains that the missing plane will be found in the southern Indian Ocean.
NOTE: This story was updated 10/26/2016 to include comments from Fugro spokesman Rob Luijnenburg.
@TBill
I questioned the O2 filling-up just before the flight also some time ago.
I wondered if this would be done on special request of the captain.
One of the pilots on this blog assured me the O2 was checked before every flight.
If it is also topped-up before every flight was not clear to me from his anwser.
A special request to top-up the pilots O2 before the flight could be suspicious IMO.
Especially if it was well above it’s minimum pressuse of 350psi with 1120psi. There was no need to top-up.
Maybe one of the pilotos here can give a conclusive anwser?
@DennisW
I presume you are referring to the ‘Lido’ radar image – yes, the labelling was seen to be wrong a long time ago. The factual information states 10nm after MEKAR as the final position (which is also what the Lido image shows, at the resolution available), which is what I was using. DSTG don’t use that due to doubts about accuracy at that range, but they are working at high levels of precision.
@David
I don’t know what you exactly mean with TRU regarding AC or DC current to the SDU.
I assume you mean the SDU has no battery connection if the AC fails?
I think this is the case, for the SDU will get cut-off if the left IDG is not working anymore or left main bus is isolated.
Load-shedding will prevent it and also the AC back-up generators won’t supply AC-current to the SDU.
The batteries are only meant for essential flight-instruments which the SDU is not.
So I would not be supprised if the SDU has no back-up battery (TRU?) connection but only AC via the left main bus (and IDG).
And a breaker opening if a diode is failing seems logical for those diodes are used to rectify the AC to DC used by the SDU.
The electronics in the SDU would probably get damaged if this was not protected this way.
@dennisW – re: ” I come up very short of the 18:25 ring.” and “adding 7800us to the BTO bias is still short”
What kind of scenarios are you thinking may cause this and would it change the direction mh370 flew?
@Ge Rijn
If I read the FI correctly (and maybe not) the last O2 top-off was January. But as low as 1120 psig would suggest quiet a few flights from 1800 psig, I would think. Otherwise I might be worried about a leak if it went 1800 to 1120 psig in just one flight.
I think the pilots can request service after a flight so I’d ask who requested it and when and why. Does not just have to be Z, if there is a larger plan.
@Ge Rijn
P.S.- I would also ask which exact aircraft No. Z flew in his prior flights (9M-MRO?).
@TBill
Gilbert’s paper states there were repaires on 9M-MRO before the flight which required the removal of the FO seat under time-stress.
He suggested maybe the drop in pressure in such a short time was caused by damaging a O2 hose (or something like that) which was not accounted for.
If Z. flew that plane (9M-MRO) before is not relevant IMO. There was sufficient pressure and no need to top-up it seems.
Still they did.
Relevant could be if he requested to top-up the pilots O2 to the max. just before this flight IMO.
@DennisW
Thanks for your patience with me. I’m merely trying to make sure I understand the BTO fully.
I also agree with your remark that having fixed Tchannel for the entire flight might be an assumption that needs to be re-considered. Good find! You’re obviously well ahead of me!
I have the feeling that the BTO has not been studied (by the blogo-sphere at least) carefully enough. In fact the BTO logging was relatively new to Inmarsat them-selves :
JON pg 2 “The BTO was only a relatively recent addition to the ground stations’ data set, being added following the Air France 447 accident in 2009 to assist in geo-locating an aircraft.”
To the mass media however, the BTO was simply (and wrongly) explained as the time it takes for the signal to do a round trip. The BFO on the other hand was quite difficult to explain to the public. But to Inmarsat (and to any person having a little knowledge about Doppler effect) this was straight forward.
Remember in the early days, Inmarsat took a long time to publish their data. At first we only got the elevation angles, and from that the derived ping rings.
I’ve seen a few people asking why did Inmarsat first publish elevation angles and not the BTOs or the round-trip times?
My guess is that at first, Inmarsat had no clue how to interpret the BTOs.
But they knew that it was correlated to the distance between GES and AES.
So by calibrating the BTOs with known positions, they could by simple trigonometry extrapolate the elevation angles of BTOs of unknown position.
In fact when Inmarsat published in the JON they still don’t give the definition of BTO! Maybe they want to keep it as a trade secret, or maybe they are still not fully sure about what that value represents. Please compare what they say about BFO and BTO :
-BFO : “The BFO is the recorded value of the difference between the received signal frequency and the nominal frequency at the GES.”
-BTO : “The BTO is a measure of how long from the start of that time slot the transmission is received. This is essentially the delay between when the transmission was expected (given a nominal position of the aircraft) and when it actually arrives.”
Notice the use of “a measure” instead of “the measure” ?
Then they give an example of what BTO is “essentialy”.
That example is used as the definition of BTO in Gordon’s paper :
“The BTO is thus the difference between the round trip message delay and the nominal delay used for scheduling.”
Then they give the 5.3 formula which is :
BTO = round_trip_time – nominal_round_trip_time + channel_bias – anomaly
The fact that they have to add the anomaly to me is an other sign they don’t understand the BTO fully.
As you said it’s fudge factor!
Wikipedia – fudge factor : “To suggest that other calculations may include a “fudge factor” may suggest that the calculation has been somehow tampered with to make results give a misleadingly good match to experimental data.”
They need Tanomaly because Tnom is non-sense! It’s an invention to give the impression of a good match with the data.
The fact that the BTO calculation works is only due to the lucky fact that the “nominal round trip time” is close to 500ms. That’s the same time as a frame time length!
If you haven’t yet please see the excellent document provided by @ventus45 in a earlier post – 4.4.2 :
“All P channel frames shall be either 500 ms, or a multiple of 500 ms to provide simple derivation of an 8-second superframe which shall be used for R channel and T channel slot allocation.”
This is what the BTO is about!
Sinux, you write:
“My guess is that at first, Inmarsat had no clue how to interpret the BTOs.”
Not supported by the evidence. From the JON article:
“3.1. Initial BTO Analysis. The initial analysis related BTO measurement to the elevation angle from the aircraft to the satellite, BASED ON WORK performed following the Air France 447 investigation.”
One imagines that Inmarsat knew exactly how to interpret the BTOs.
—————-
“The fact that they have to add the anomaly to me is an other sign they don’t understand the BTO fully.”
The anomalous BTOs are explained in detail in the DSTG book, p.24. They are only a subset of all BTOs. You are correct that they are not fully understood: “The origin of these anomalous BTO measurements has not been fully determined …” but rather than throw them out, the DSTG derived an empirical correction formula.
“The fact that the BTO calculation works is only due to the lucky fact that the “nominal round trip time” is close to 500ms. That’s the same time as a frame time length!”
Not at all. All that matters is that the slot length time (not the frame length time) be large compared to the variation in start times for all possible aircraft positions, which is about 40 millisec. Slot length time depends on the transmission rate of a particular packet and can range from 125 msec to 1 sec (deduced from description in AMSS manual, p. 15).
Frankly, the BTO is dirt-simple to understand.
@Richard Cole
Yes, I was referring to the labeling in the Lido image – 200nm range and 295 azimuth. Those values are clearly not compatible with the 18:25 range ring.
And yes, i know the labeling was deemed by the cognoscenti as suspicious/incorrect a long time ago. I am simply revisiting it from a due diligence perspective. At the time (a long time ago) I had some pause relative to tossing out the labeling too quickly since it likely was derived from data output by the radar itself (azimuth and range), and probably not derived by estimating values from a screen display. I could certainly be wrong about that. In any case, just playing what-if games at the moment.
To my knowledge the incorrect labeling has never been revisited or acknowledged by anyone in authority.
Jeff – I’d say you are right in asserting Shah was not an radical Muslim. He wasn’t, but I think you overlook something. It wasn’t radical Muslim’s alone that propelled a bunch of Shiite Ayatollahs to power in Iran. There were a lot of ordinary folk in that push, from students to professionals, and they gravitated to religious clergy to move an obstacle – The Shah of Iran. A similar situation is developing in Malaysia around Anwar Ibrahim. And he isn’t a screaming radical either by any means. He is a calculating one. If Shah did something crazy, or something stupid that just ended badly, it was never for Allah, it was for his quest for change. Most of Anwar’s supporters are anti government, and who else do they have?
@Matty-Perth, Good post. My thoughts are along the same lines.
@ Ge Rijn. “I don’t know what you exactly mean with TRU regarding AC or DC current to the SDU.“
This refers to my response to your earlier, “Btw, I don’t think the SDU works on AC but only on DC.
The higher AC gets transformed and rectified to the lower DC.”
The SDU is powered by 115Vac and it would run on low voltage DC internally only with its own TRU (transformer rectifier unit), which I had in mind it would not have. I added that only to accommodate your thought that they work on DC.
In any case it is powered by the left ac bus and only that, whether that receives its power for the left engine IDG or other (in the air, right engine, APU).
“. ..diode is failing seems logical for those diodes are used to rectify the AC to DC used by the SDU.” As above it doesn’t rely on a DC external supply. Aside from being for rectification for some purpose, I do not know what the IDG diodes are for.
@TBill, Ge Rijn. The oxygen bottle was charged after an entry was made in the Technical Log. FI Appendix 1.6A p1. “S/N 4918752 – 07 March 2014 Night Stop. Crew oxygen system pressure reads 1120 psi (EICAS)… then…. 07 March 2014 Crew oxygen system replenished to 1800 psi – EICAS. AMM 12-15-08 refers”. Note, FI p27, that when it comes to whether a bottle exploded or not this one was not fully charged, which being to 1850psi. I do not have access to AMM Chap 12. I would expect that if that does not do so, MAS would specify at what pressure replenishment is required. At 1120 it is well beneath full. I expect the second oxygen bottle was added to the 777 Extended Range version and there would be a ‘standard’ minimum top-up pressure well above 350, based on possible usage plus reserves. Otherwise the specification of two bottles would be unnecessary: simply double minimum pressure or thereabouts. ‘Possible usage’ to me would include that which pilots are expected to consume routinely, which includes continuous use of the masks above some altitudes, by at least one of them. Apparently this is not common practice but that is not what Boeing/MAS would be planning for. They would specify a recharge well above what ‘should do’. It would be too complicated for this to vary depending on the length of the forthcoming flight.
As to who required a top up, it might be the previous crew, noticing that pressure had got beneath that the specified: they have a cockpit read out. Otherwise it would have been the maintenance personnel in post-flight checking. In short I see no grounds for concern.
Also, see FI p28 about the top up, “The servicing was normal and nothing unusual was noticed. There was no leak in the oxygen system and the decay in pressure from the nominal value of 1850 psi was not unusual”. Mick Gilbert thinks there was a leak, as he relates owing to recent consumption being above what he would expect. He may not have taken into account the possibility that flight crew had been using masks for some flights, when a member was under training, this then lifting consumption and sidelining his leakage theory.
Aside from being for rectification for some purpose, (then) or as electrical check valves……
@sinux:
The SDU, HPA, HSU primary power is supplied to either +28 V dc (pins 2 and 3) or 115 V as (pins 1 and 7).
Unit dual power supply use 28 V dc or 115 V ac.
The complete system description, installation, and maintenance maual PDF of Honeywell MCS-4200/7200 Multi-Channel SATCOM System is available here:
https://docs.google.com/file/d/0Bxl9Zw66ZRDmUWJoOUVfbEI1RjQ/edit?pref=2&pli=1
For some assistance please with the SDU, ACARS, logs-on.
What follows is my interpretation of FI pages 43-56.
The aircraft prior to flight logged on via the Low Gain Antenna, data capable, at 1250:19, establishing an ACARS data link at 1554:41. One minute 16 secs later it renewed the log-on but added Flight ID, viz.“MAS370”. A minute 11 secs later the crew “keyed in” Flight Information, viz. “MH0370, 9M-MRO”. (This last is under the heading ‘ACARS Traffic Log’ on page 43. Fig 1.9D on that page describes this keying in, “ACARS data link established SATCOM transmission”. Page 54 continues with a Class 3 log-on a minute and a half later, voice and data using the High Gain Antenna, quoting the ID. 2 mins 8secs later the SATCOM shifted from the Pacific Ocean satellite to that for the Indian Ocean, again with ID.
At take- off and during climb there were routine ACARS messages relaying engine data, then the one combined message, the last, at 1707 that relayed aircraft data accumulated at five minute intervals since take off.
This is rather detailed and the main point I would like to bring forward is that there seems to have been a separate method of providing aircraft identity, the FI, for ACARS SATCOM transmission, to Flight ID for voice and data generally.
So a question is, what would be the outcome if that Flight Information were unavailable or deleted. What happened subsequently was that because there was no ACARS transmission, the SDU appeared down. Could it be that loss of the ACARS transmission link would make it appear the SDU had failed? I have little knowledge of the SDU and suppose with all the study which has gone before there is an easy explanation and would appreciate learning of it if so. But nothing ventured….
In extending this, if for example the ACARS FI became unavailable at say 1725, would the SDU software incline it to reboot an hour later, logging on (IFE etc) once more but without its ID, as happened, because it had lost ACARS. Would this account for both the 1825 log on and the lack of ACARS transmissions subsequently?
Footnote: At p43 FI notes, “……A ping response indicates a healthy ACARS communication.” I do not follow this. Weren’t there five ping responses without ACARS communication between the two aircraft initiated logs-on?
Incidentally for those troubled about the effect of cabin temperature on the oscillator frequency (as was I) and hence BTO/BFO interpretation, I notice from the Honeywell brochure that the temperature limits of the -7000 version (MH370 had the MCS-6000) the temperature limits for operation extend to -55˚C. That does not mean I suppose that the oscillator will be stable down to that but there has been mention it has a heater, which I had not heard before.
I see Marc has posted a Manual ID while I wrote this and that might tell. I have to go so for me that is later.
@Keffertje: “He was very senior and a midnight boring flight to beijing could have been handled by many other, younger captains”
By virtue of being senior, Z was a 777 captain. While there are exceptions, most 777s are used for mid- and long-haul services. Very few 777 captains do not fly overnight flights.
Typically, longer flights are taken by more senior crew…so that they meet their monthly flying requirement with as few days actually working as possible. Many longer flights are red-eyes, at least in one direction.
Nothing about Z serving as captain of an overnight flight unto itself would be considered unusual.
@ Ge Rijn: “The first airliner who would implement a third crew member into the cockpit again would certainly have an advantage above others IMO.”
Nearly all airlines as a longstanding practice do not advertise safety records. (I cannot think of one that does.)
With that in mind, certainly no carrier is going to market having a third pilot I the cockpit at all times for a “reduced risk of pilot suicide crashes.” I do not believe that would be an effective marketing pitch.
FWIW< my understanding is that the crew enters the Flight ID in the FMS during the pre-flight set-up of the FMS. The Flight ID is then available to ACARS, IFE and SDU via AIMS.
"What happened subsequently" was that at 18:03 the ground station attempted to send an ACARS message to the aircraft via SATCOM and there was no response from the SDU to the GES attempt to open a SATCOM link. That doesn't tell us anything about the status of the aircraft ACARS system at 18:03.
That quote is from the description of the ACARS system: “Pre-set time interval for MAS B777 is 30 minutes. When the aircraft ACARS is silent for more than 30 minutes, MAS Operation Control Centre (OCC) will send a text message via ACARS to the cockpit or will call the cockpit via SATCOM.”
@David
Thanks explaining. So ‘TRU’ can be translated as ‘transformator rectifier unit’ I understand.
As @Marc explains the SDU has connections for both 28V DC and 115V AC. So I concluded the SDU has it’s own ‘TRU’ and can be powered both ways DC or AC.
A description from the internet about the IDG:
‘At the risk of being overly simplified and wordy here’s a basic description of the differences and advantages of IDG vs. GEN/CSD systems.
The 737 NG’s and 757’s in my company use a 115/200VAC – 90KVA IDG. The generator section speed is maintained at 24,00rpm. It’s all in one package and replaced as a unit. (Troubleshooting time is reduced because it doesn’t matter what caused the output problem. You replace the package.) It weighs approximately 117lbs. The IDG is an assembly that has a hydromechanical constant speed drive (CSD) section and an oil-cooled brushless AC generator section. The IDG also includes a permanent magnet generator (PMG) for control and excitation power to the main generator section. The generator rotation speed allows for very little fluctuation in power or frequency output.’
Question was possible small voltage/power fluctuations could cause the SDU to swith off and on.
From this information this seems unlikely to me.
Still unclear to me is if the SDU is also backed-up with DC battery power for @Marc states it also has connections for direct 28V DC. I suppose those are only there to give a choice of AC or DC but not both at the same time.
@SK999
Thanks for your positive criticism!
First let me say that I have the utmost respect for the work Inmarsat has done. Just re-reading the JON paper increased my appreciation for the outstanding level of accuracy in this report.
I may have been a bit harsh when I said that at first they “had no clue”. They certainly had a few clues. Thus my next sentence where I said they knew it was correlated to the distance.
You quote 3.1 from JON. But please don’t forget 3.2. Refined BTO Analysis. If they had a perfect understanding of the BTO from start there wouldn’t be a need for refinement later.
Interestingly in the Mark Dickinson interview, he says a lot of times “essentially” it seems to be his pet word 😉 either that or he’s been briefed by the legal team before the interview.
http://www.youtube.com/watch?v=rEr8BDD9q14
He also says they needed external experts to help them make sense of the data.
Inmarsat didn’t build the satellites they operate, they didn’t build the electronic equipment they use to log the data, and very likely they didn’t program that equipment.
Also Classic Aero system is old technology… 1990… The engineers who built it are very likely retired now if not under ground.
Please also have a look at the Chris McLaughlin interview
http://www.youtube.com/watch?v=dv9bRnThNls
where he offers the following definition of BTOs :
“the time differences between signals to and from our satellite and our network”
You said :
“Slot length time depends on the transmission rate of a particular packet and can range from 125 msec to 1 sec”
please state which paragraph you are referring to. I can’t find this information on page 15. Note that what ever the slot length, they would still be synchronized to the P channel.
My concern is not regarding Tanomaly (sorry if I didn’t expressed myself right). It is the Tnom that’s the problem – the fudge factor. Tanomaly is not related, thanks for pointing it out!
Gordon defines Tnom as “the nominal round trip delay”.
This notion is not linked to anything physical. It’s a construct of mathematics to make the model work, based on misunderstanding the JON paper.
Here is how the BTO is measured to my understanding (please note that maybe the slot time is different from what I’m using at this stage) – This is also simplified (Tanomaly and Tchannel not taken into account at this stage) :
1. GES sends P frame to AES
2. During the travel time from GES to AES the signal accumulates some delays (Transmission delay + processing delays).
3. AES receives the P frame and synchronizes itself with it (note it is now synchronized to a delayed frame)
4. AES processes the signal, computes the reply, and thus accumulate an other processing delay.
5. AES waits for the next slot available to transmit, calculated from 3 (slotted aloa – note that this masks the processing delay in 4)
6. AES sends the reply back to GES. Between 3 and 6 there was N1 P frames.
7. During the travel time from AES to GES the signal accumulates some more delays (Transmission delay + processing delays)
8. GES receives the reply and logs the time offset between the P channel frame it last sent and the reply. Between 1 and 8 there was N2 frames.
A. Round trip time :
Round_trip_time = Transmission_delay + Processing_delays + ( P_channel_time_length x N1 )
B. Round trip time is also :
Round_trip_time = (N2 x P_channel_time_length ) + BTO
C. BTO is then :
BTO = Transmission_delays + Processing_delays + P_channel_time_length x (N1-N2)
With numerical values :
At 16:00:13.906 P frame is sent
At 16:00:17.430 reply is received on R channel with BTO 14740
Measured Round trip time : 3524 ms = 3524000us (time difference of above)
From JON – Transmission delay at that time is : 510478us
From B :
3524000us = N2 x P_channel_time_length + 14740
P_channel_time_length = 501322us (N2=7)
From C :
14740=510478 + processing_delays + 501322 x (N1-N2)
processing_delays = 5584us (N1-N2=-1 N1=6)
Just realized from the above that BTO bias as defined in JON is then :
BTO_bias=processing_delays – P_channel_time_length
At 16:00:17 5584 – 501322 = -495738 us
@sinux
What’s the conclusion, in lay person’s terms? Are we still on track (if you pardon the pun)? Or is there still a chance some nasty, previously unanticipated gremlin is going to jump out of the woodwork an shout “GOTCHA!, due to your compounded errors, you are now a thousand miles off track”?
Would just like to know.
@NYBanker
No offcourse no airliner is going to market a third pilot that way (as suicide-flight prevention).
But I, and I assume a lot more people, would regard it as a reassuring safety messure in more ways than only the possibility of a suicidal/terrorist pilot.
F.i. also on longer flights it would have benefits IMO.
Pilots could rotate more often during flight leaving always two alert, fresh pilots in the cockpit.
Sudden illnesses (stroke, heartattack happened before to name some critical ones) could be dealt with immediatally.
A third pilot while in the cockpit or outside the cockpit could monitor different tasks especially when there are problems to solve.
And offcourse a pilot with suicidal/terrorist intentions would have much less opportunity.
Like the good old flight engineer.
In those days accidents like pilot suicides were hardly possible.
And maybe in the case of MH370 if mechanical/electrical failure played a role a third pilot could have made the difference too.
If an airliner would announce they will bring in a third pilot into the cockpit, to me it would certainly be a concideration to choose that airliner.
I wouldn’t mind to spent maybe 10 euro’s extra on a ticket to pay for his salary.
@ROB
I’m not too sure about what conclusions we can draw from that at the moment.
At this stage, the math looks fine. So nothing new should magically popup… But who knows?!
Inmarsat has it right. But the way they explain the BTO is obscure. They merge the processing delays in the BTO bias. That’s not wrong. But then you loose some information.
Gordon has the math right but he explains it wrong… does he understand what he is talking about? Or did he just accept what Inmarsat gave him without asking questions; just like the radar points?
After doing a few calculations, something that strikes me is that the P_channel_time_length is not constant.
I was expecting it to be as it’s a slotted Aloa communication protocol. It might be normal though but I just don’t know enough on the subject.
An other thing that strikes me, is that the processing delay varies considerably, so far between 887us and 5584us. Here again it might be normal, someone else might be able to shed some light on the subject.
@sinux
What you say is encouraging. I always had confidence in the INMARSAT guys, and nothing has really given me cause to have any doubts in that direction, and that’s not just because I’m British (ie being patriotic) but it was more a 6th sense. I’m also a little less confident when it comes to Gordon. He’s a little to close to the ATSB camp for my liking to be impartial.
Thanks
Rob
sinux,
Slot timing is shown in Figure 4-5, p. 185, of the AMSS manual.
If I remember correctly, P-channel timing information is transmitted continuously. The AES needs to be synchronized even before it sends a logon message. AES transmissions (whether in response to a message from the ground or generated spontaneously) are synchronized to slot time boundaries. All that the GES needs to determine is which slot a message was sent in, and provided everything is working properly, it can do that unambiguously. The GES knows the start time for each slot in any particular P channel superframe sent to the AES for synchronization, and it knows the nominal return time for whatever R channel bursts are sent back from the AES in any particular slot. The BTO is then the difference between the actual return time and the nominal value for that slot.
@Ge Rijn:
Judging from MH370 the third cockpit crew member might have to be a telegraphist.
An airline company will probably be able to sell in a third “pilot” in positive terms if they had to. I am more worried that they will at the same time sell you a green salad you dare not eat, mixed peanuts you don’t want and soft french fries from the grill and raise the ticket €59,95 instead.
@sk999
That is my understanding also. The AES clock is synced to the P Channel transmissions from the GES, so is ‘slow’ by the light travel time from GES to the AES. The transmissions by the AES are synced to this clock (within +/-300 μs as prescribed by the AMSS standard) and take the same travel time (or that corresonding to the aircraft’s position a few seconds later) to get to the GES, which measures the total lateness with reference to its pre-defined bias – the BTO. The effective processing time in the calculation is thus small (and could be negative) but that is lost in the wash of calibrating the bias at the airport gate. Thus the qualified terms used in defining BTO, as no single signal actually goes from GES to AES and back.
I guess in the case of the transmissions at 18:25:27 and 00:19:37 with anomalous BTOs, the AES did not comply to the +/-300 μs standard.
@Richard Cole
I’m guessing you mean anomalous BFOs at the log-ons, not BFOs? Interpreting the BFOs at 00:19 might be crucial to the end of flight scenario and finding the plane. If the BFOs at 00:19 are due to transmission errors, then all options are back on the table IMO.
@Richard Cole
In meant BFOs not BTOs.
Richard Cole,
The basis for the +/-300 μs requirement has always been a bit of a mystery, since the GES can (and indeed, must) handle offsets many tens of milliseconds in length. My guess is that it doesn’t have a basis, it’s just that some number was needed, and 300 μs is big enough that any self-respect AES should meet it with ease while it is small enough that it is not a problem for the GES.
@ROB
There were two anomalous start-up BTO measurements as discussed in section 3.3 of the Inmarsat paper.
@SK999
The system wants the traffic related to one P channel sync pulse to be bounded by some fixed times, 46 milliseconds in width minimum given the orbit geometry. If the sync requirement was plus/minus a few milliseconds then that width would increase similarly, which I suppose starts being a significant difference, perhaps with impact on the higher speed modes?
@sk999
Thanks for the figure reference! Very informative. So as long as we are talking about R1200 channels, the slots should always be 500ms.
You say :
“The GES knows the start time for each slot in any particular P channel superframe sent to the AES for synchronization, and it knows the nominal return time for whatever R channel bursts are sent back from the AES in any particular slot.”
Could you please detail :
How does the GES know the nominal return time? How is it measured?
“The GES knows the start time for each slot” Agreed!
” All that the GES needs to determine is which slot a message was sent in, and provided everything is working properly, it can do that unambiguously.” Agreed!
The slot no is encoded in the message.
But! I don’t think the BTO is calculated this way at GES!
If it were true, Imagine the huge database of start time slots that needs to be kept up to date? The AES can reply 2 minutes after a P channel message (see timing between 18:25 and 18:28)
Also if it were calculated the way you say, Inmarsat would readily have the round trip time to log. No need for a BTO!
I also agree with you regarding the 300us. It’s very likely that this value is close to 0 in normal cases.
@ Richard Cole
You say :
“measures the total lateness with reference to its pre-defined bias”.
How is this pre-defined bias computed at GES?
If it’s known to the GES, why do we have to struggle to back-calculate it and then average it?
If it were known to Inmarsat, things would be much different! The accuracy of BTO would also be greatly improved.
@all
Some BTO considerations – a draft subject to modification.
http://tmex1.blogspot.com
@all
Put the draft out there before I normally would due to the fact that we are getting deluged at our beach house, and I did not want to run my Mac on generator power (inevitable as soon as a tree blows down). So forgive grammar and typos.
I drove all the way to the ranch yesterday to retrieve the Mac. I only brought the Chromebook with me to the beach, and Chromebooks do not support Google Earth (go figure).
@Richard Cole
Re the anomalous BTO. Yes thank you for reminding me. I remember now reading about them. This has been going on for so long now, I would benefit from a revision exercise.
@DennisW said;
“what if the LIDO Hotel graphic note of 200nm @295 degrees is accurate?
The default opinion is that this is a “mislabel””…”comments”..”welcome”.
_________
There is another interpretation of the text box on the Lido graphic that
you (nor anyone else apparently) has considered. This;
TIME 02:22H
295Reciprocal 200nm {,}
from Butterworth AB {that is, HQIADS, Headquarters Integrated Area Defence
System}
Therefore, the reference ‘from Butterworth Airforce Base’ can be seen as
not a locational reference, but rather as an attributation as to
the source of the preceding data.
Regarding the IADS, Nihonmama posted this;
http://jeffwise.net/2014/10/29/mh370-where-is-the-debris/comment-page-2/#comment-54971
A “journalist named Peter La Franchi commented”… “that Australia,
Malaysia, Singapore and the United Kingdom jointly operate the Five Power
Defence Arrangement (FPDA) integrated air defence centre” (which enables
an) “”air picture” of all of Southeast Asian airspace using feeds from both
civil and military radars.”
Consider, it was a Malaysian delegation that presented the graphic to the NOK,
and probably the graphic was produced by Malaysians who think in the
Malay language, not the English language, so it is not so unlikely that they
would drop an English punctuation mark here or there, such as a comma.
Now the interesting result of this interpretation, is that 295 degrees
from the indicated (arrowed) point on the Lido graphic, to a distance of
200 nautical Miles, gives you a location about or over Katchal Island –
(to see, in SkyVector, input flightplan, 063810N0962333E 080013N0931958E)-
additionally, it locates to on N571, or offset to the right of the
centreline of the air corridor for an aircraft flying eastward along N571
(which, if you remember my previous post regarding offsets on N571, is
where the Malaysian eAIP allows an aircraft flying along N571 to be offset.)
You may also be aware of the wording in an ATSB report (26th June 2014,
updated 13/15/18th August) that has puzzled posters on this forum in the
past, regarding “known radar sources (mainly Singapore)” in the area.
Given that the Indian military would have been unlikely to allow a
Singaporean warship to be in close proximity to that area, if there was
a Singaporean military radar source operating in that area, it was likely
to be a Singaporean AWACS aircraft,(Note;EL/W-2085 radar to “a range of
200nm”, https://en.wikipedia.org/wiki/IAI_EL/W-2085 ), or a Singaporean
KC-135R (maximal radar model/range unknown). A non-Indian military aircraft
could be in that location (which is Indian airspace) without incident, if
it were following an international air corridor such as N571.
Cheers
(N.B. You spoke too soon when you said, about MH370, “Nothing new has come
up in any regard“).
sinux,
“How does the GES know the nominal return time? How is it measured?”
It’s the sum of the time that the outbound P channel superframe (or more precisely, the “unique word” within the superframe) was sent, plus the time offset from the unique word for each slot defined in Figure 4.5 plus about 0.5 seconds – the round trip travel time. The latter is determined by calculation.
“If it were true, Imagine the huge database of start time slots that needs to be kept up to date? The AES can reply 2 minutes after a P channel message”
No. It is only the current outbound P-channel superframe that the that the R-channel burst is synchronized to that matters. These superframes are being sent continuously. The fact that the R-channel burst is a reply to a message sent 2 minutes earlier is irrelevant. What if the AES is sending a logon request? Or a request to open a T-channel? Those messages are not replying to any P-channel message, yet it is still possible to measure a BTO.
@DennisW
small typo at end
3> the fact THAT no trace…(persumably because your 7th arc is different – oh pls show us the new 7th arc)
@dennisw – have you found any possible path to the north from your recent re-analysis of BTO since it was not specifically stated yet.
@Sinux
“measures the total lateness with reference to its pre-defined bias”.
I refer just to the calculation of the round-trip time to the ‘nominal terminal’ at the surface (or close to it) under the satellite. This time defines the start of the 50ms slot (with respect to the frame start) for receipt of responses at the GES from all the AES units, and is the reference for measurement of the BTOs. As you pointed out earlier, this bias is calculated by the GES. However, any BTO measured by the GES cannot quantify additional delays in the loop due to non-travel time effects so a calibration against a known position (at the airport gate) is needed if the BTOs are to be used to define the arcs to best accuracy.
@TBill
I don’t use the 00:19 values. However the 00:11 arc would be about 50km greater in radius.
@dennisW – with the 00:11 arc greater in radius that might bring it closer to Sarawak than when we last spoke of this idea??
@MH
Yes, that is true, but it is a relatively minor tweak at the final arcs. Plus that, I have not looked at Sarawak since I abandoned my agnostic path propagator which was hopelessly flawed. I was drinking at the time.
TBill. Thanks for the response to my query about Malacca Strait flight opportunities. “.. it is perhaps interesting to note that Fariq’s last flight was to Europe I believe”. The only reasons I can think of why Shah would not have elected such, IF of nefarious mind, would be that he was intent on a 8th March flight (as per Keffertje) and there was none that way, or he could not inveigle himself onto it without undoing his cover.
@David
We would need to look at flight schedules in that time frame, but the MH370 had the moon setting at KLIA exactly at take off time 12:40AM on March 8. He would need a March 8 flight to Europe about the same take-off time, assuming moonless night was intentional (to be invisible to planes and satellites).
@buyerninety
at Post October 30, 2016 at 4:12 PM you said:
“There is another interpretation of the text box on the Lido graphic that you (nor anyone else apparently) has considered.
This; TIME 02:22H 295Reciprocal 200nm {,} from Butterworth AB {that is, HQIADS, Headquarters Integrated Area Defence System}”
and
“Now the interesting result of this interpretation, is that 295 degrees from the indicated (arrowed) point on the Lido graphic, to a distance of 200 nautical Miles, gives you a location about or over Katchal Island – (to see, in SkyVector, input flightplan, 063810N0962333E 080013N0931958E)- additionally, it locates to on N571, or offset to the right of the centreline of the air corridor for an aircraft flying eastward along N571 (which, if you remember my previous post regarding offsets on N571, is where the Malaysian eAIP allows an aircraft flying along N571 to be offset.)”
I have been trying to “visualise” what you mean in Skyvector, and came up with this graphic.
https://www.dropbox.com/s/yw6npsgffk6fjat/Geometry-Buyerninety-Points.gif?dl=0
Is it correct, ie, have I interpreted what you are saying correctly ?
Points Q and W are your points
Q = 063810N0962333E
W = 080013N0931958E
Point L = 064755N0971218E and is 49.5 Nm from Q and is 200 Nm 295 Radial (115 towards) to the Western Hill Radar on Penang Island Point P = 052530N1001511E
Point B = 052833N1002351E is Butterworth.
The obvious problem with point W is that it is about 448 Nm from Butterworth on the 290 Radial, which is way beyond the maximum radar range of either the Butteworth or Western Hill Primary Search Radars (PSR’s), which, under ideal conditions, is about 250 Mn at FL400 (red range ring).
Therefore, would I be correct in assuming that what you are essentially saying, is that the only way, that point W could be “known”, is that there was “another radar sensor” feeding data into IADS, and the only (known) plausible “source” for that data would be the Singapore AWACS ?
@Ge Rijn. Yes fair question. “As @Marc explains the SDU has connections for both 28V DC and 115V AC. So I concluded the SDU has its own ‘TRU’ and can be powered both ways DC or AC”…..and…..“Still unclear to me is if the SDU is also backed-up with DC battery power for @Marc states it also has connections for direct 28V DC. I suppose those are only there to give a choice of AC or DC but not both at the same time.”
I have been unable to locate a manual for the MCS 6000 fitted to 9M-MRO and the technology/characteristics possibly because its technology is out of date. Marc’s manual is of different models as you will have seen. At his manual’s 23-20-35 p1-27 the SDU pictured is of a different external configuration to the -6000’s depicted in the FI at p50. Likewise the High Power Amp at p1-35 differs from FI p50 also.
Whether the -6000 can or cannot accept DC I cannot say just from this. The -4200 and -7200 might have TRUs to convert from the 115V inside or inverters to do produce the 115: I have not read into that (or for that matter into an oscillator heater. It took a while just finding the pages I mention!)
The 115Vac supply I quoted comes from the 2005 AMM. I doubt it would have changed since then or been supplemented by back up DC. If it was considered important enough, it could have been supplied backup ac from the standby ac bus, displacing lower priority requirements, though it is hardly a last ditch capability. The FI quotes the 115Vac also and description of failure of that make clear there is no back up.
As before if the -6000 in 9M-MRO were to operate on DC with just the 115ac to it, it would need an inverter I think.
Again I have not read enough into Marc’s manual to get clear whether the intention of the ‘either DC or AC’ in those models is to allow for ‘either’ as the main supply or whether the duality is for a back up requirement.
A -6000 manual would help if the issue is to be pursued.
@David
For what it’s worth I was able to find the Malaysia Airlines March 2014 Timetable including MH370:
http://www.malaysiaairlines.com/content/dam/malaysia-airlines/mas/PDF/MH%20November%202013.pdf
There do appear to be flights going to Europe at 2359hr (MH16). OK but if moonless-ness is important for stealth, the Moon would still be up at KLIA at 2359 and flying West the plane would be “catching up” to the Moon and also the altitude of the plane comes into play.