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Malaysian Airlines MH370 contact lost

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Malaysian Airlines MH370 contact lost

Old 29th May 2014, 19:12
  #10841 (permalink)  
 
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Asking for clarification

From the JACC:
Yesterday afternoon, Bluefin-21 completed its last mission searching the remaining areas in the vicinity of the acoustic signals detected in early April by the Towed Pinger Locator deployed from ADV Ocean Shield, within its depth operating limits.

What it means?- that the Bluefin has only searched the areas within its operating limit?
or
- that all the area in the vicinity of pings was within its (upgraded) operating limit?
Sorry to ask something perhaps evident for all but not for me as a French speaking native
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Old 29th May 2014, 19:26
  #10842 (permalink)  
 
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In my experience aircraft can only fly TO an FMC fix
No, it can also fly using hdg-select, no FMC involved.

that requires no great imagination. Obviously the geographic South Pole.
Any other number would take 'no great imagination'.
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Old 29th May 2014, 19:40
  #10843 (permalink)  
 
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Blue-fin operations

Shadoko:What it means?- that the Bluefin has only searched the areas within its operating limit?
or
- that all the area in the vicinity of pings was within its (upgraded) operating limit?
It was reported some time ago that the bluefin-21 was unable to scan it's entire assignment despite it's "upgraded" limit.
Consequently there maybe smaller areas that were not scanned, but bluefin-21 had done the majority of the area.

Recall that the AF scanning "missed" the major debris field, it was after WHOI (as a private contractor) was engaged that they located the field close to where it was expected almost a year earlier (and in an area that had been previously scanned)
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Old 29th May 2014, 19:48
  #10844 (permalink)  
 
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Asking for clarification
From the JACC:
Yesterday afternoon, Bluefin-21 completed its last mission searching the remaining areas in the vicinity of the acoustic signals detected in early April by the Towed Pinger Locator deployed from ADV Ocean Shield, within its depth operating limits.
You are quite right, it could be understood as meaning that Bluefin only searched areas which were within its operating depth BUT if you read on to the 4th paragraph, it states:

The Australian Transport Safety Bureau (ATSB) has advised that the search in the vicinity of the acoustic detections can now be considered complete and in its professional judgement, the area can now be discounted as the final resting place of MH370.
The above leaves no doubt that Bluefin completed the search and did so within its operating limitations.

Well, that's how I understand it but could be corrected.
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Old 29th May 2014, 19:53
  #10845 (permalink)  
 
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porterhouse
Yes, heading select could be used but if you wanted to remove all human intervention from subsequent events you would use the FMC.

And something like 90S 90E has a certain attractive simplicity. The man we are working with has demonstrated that he was a planner and he was thinking ahead, he would not choose a random position.
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Old 29th May 2014, 21:31
  #10846 (permalink)  
 
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within its depth operating limits.

That is a ryder to the statement and to me causes confusion/doubt , why add it?

These pings, what were they? A fault in the ship or TPL electronics that caused a piece of circuitry (probably an amplifier) to go into oscillation not an unusual fault, BUT asking for it to be intermittent at a regular mark to space ratio of 1.1sec and 33.7kc , sorry I find that one difficult.

Be interesting to see where the next search starts, any bets on it being the failed bluefin search area.
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Old 29th May 2014, 23:19
  #10847 (permalink)  
 
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Not a pinger

The 1.1 second pulse rate and the frequency sound about like a hydrographic sonar system I worked on designing back in the late sixties. At 4800 feet per second in water and a two way path that is appropriate for depths of 2500 feet. The pulse width we used was in the 5 to 25 millisecond range depending in part on the bottom material which has varying reflectance qualities at 33 KHz.

But that range limitation is only if you only have one pulse in the water at a time. For the higher range sonar chart recorders we could have 8 or 10 pulses in the water at a time. The chart and some memory let us focus on the bottom profile so the multiple return echos were easy enough to identify... if you did a few 1 pulse soundings to get the bottom range. Something like the old Omega nav system: you had to know where you were to get started.

Our sonar output used a very large transducer to help focus the signal. But not too narrow a beam because of survey vessel roll. With 500 to 2000 watts into a good transducer the range to a sensitive receiver would be very long. Certainly many miles. The signals heard may have been an echo off the bottom.

The reported frequency of the pings sounded much too low and that deviation from spec was apparently considered a possible consequence of low battery voltage. But maybe the frequency did not go down further. I would be very surprised that the resonator could go more than 2-3 KHz off the centre frequency due to dropping battery voltage.

I would hope someone obtained an identical pinger and measured the output frequency with decreasing battery voltage.

Last edited by ve7pnl; 29th May 2014 at 23:20. Reason: typo: pulse width, not rate
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Old 29th May 2014, 23:51
  #10848 (permalink)  
 
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I would hope someone obtained an identical pinger and measured the output frequency with decreasing battery voltage.
And at a similar depth underwater.
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Old 30th May 2014, 00:01
  #10849 (permalink)  
 
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OK, I give up, if these pings came from the searching ship(s), why did they disappear, roughly at a time when the original locator batteries were expected to die?
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Old 30th May 2014, 00:05
  #10850 (permalink)  
 
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Quote:
In my experience aircraft can only fly TO an FMC fix


I think you will find a B777 can fly a bearing away from a waypoint that is in the nav database using LNAV
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Old 30th May 2014, 00:59
  #10851 (permalink)  
 
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Originally Posted by gonebutnotforgotten
... if these pings came from the searching ship(s), why did they disappear, roughly at a time when the original locator batteries were expected to die?
The #3 and #4 ping detections were dismissed some time ago as not being related.

#1 ping detection apparently occurred as the TPL was in the process of being lowered, I think around the 250 ~ 300m mark and while the vessel was moving slowly ~0.5 knots. The detection was lost after 2h 40m, and it is possible that if the source was on the Ocean Shield, that could be an explanation if the tow catenary had lengthened to beyond the detection range.

#2 ping detection was 7.16NM by 205T from the initial #1 ping and about 5 hours later as the vessel was returning on a reciprocal track, but only for a short duration. The timer on the ship's bar door had started! Think of any other explanation?

#2 ping location was the center of the 10km radius on which the Bluefin-21 search grid was based. JACC's reference to the search being centered on the 2nd ping detection of 8 April was not correct.

Last edited by mm43; 30th May 2014 at 02:40. Reason: added dist & brg info
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Old 30th May 2014, 05:33
  #10852 (permalink)  
 
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On the floor?

#1 ping detection apparently occurred as the TPL was in the process of being lowered, I think around the 250 ~ 300m mark and while the vessel was moving slowly ~0.5 knots. The detection was lost after 2h 40m, and it is possible that if the source was on the Ocean Shield, that could be an explanation if the tow catenary had lengthened to beyond the detection range.

#2 ping detection was 7.16NM by 205T from the initial #1 ping and about 5 hours later as the vessel was returning on a reciprocal track, but only for a short duration. The timer on the ship's bar door had started! Think of any other explanation?

I always thought the plane was floating at a great depth and drifting south at about 1 kt which accounted for the long first encounter.
Pings 3 and 4 killed that theory.
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Old 30th May 2014, 05:34
  #10853 (permalink)  
 
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Given it took a month to search 850 km2 (possibly with some deep areas missed), the proposal to search 60,000 km2 suggests a different methodology. Perhaps using multiple more capable AUVs.

Anyway the dramatic increased size of the proposed area suggests we are really back to the Inmarsat arcs.

I guess a ditching is an advantage here. We will presumably be looking for a large relatively intact fuselage rather than a debris field.
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Old 30th May 2014, 06:33
  #10854 (permalink)  
 
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Originally Posted by RayCee
I always thought the plane was floating at a great depth and drifting south
Anything on an aircraft that had the potential to provide some sort of buoyancy, is not designed to withstand the pressure differential it would meet as it sunk. Put into perspective, at a depth of 4500m the pressure imparted is the equivalent of just under 1 atmosphere per 10m - in this case 447.4 atm / 6575 psi.

The aircraft will be on the bottom - wherever that may be.
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Old 30th May 2014, 08:48
  #10855 (permalink)  
 
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Yeah the 777 landed perfectly without any damage. Then no doors or evacuation was commenced. It then sank to the bottom perfectly intact and therefore no debris.

What utter nonsense!
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Old 30th May 2014, 09:33
  #10856 (permalink)  
 
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Poor Design Validation DFDR CVR

Originally Posted by gonebutnotforgotten View Post
OK, I give up, if these pings came from the searching ship(s), why did they disappear, roughly at a time when the original locator batteries were expected to die?
There seems to be a common thread here.

The ULB, is at a frequency where its range is less than the ocean depths over which aircraft routinely fly
The ULB battery life is insufficient for a search and recovery operation in remote areas - such as over the ocean
The ULB is not encoded so a ping has to be assumed to come from a ULB based on its frequency and recurrence frequency
The CVR with the voice data is shorter than the oceanic flights routinely made and only records sounds not what is happening in the cockpit
The DFDR does not record the output to the pilots on the assumption that both sets of instruments are receiving and displaying the same data
etc etc

This discussion of pings by subject matter experts reminds me of similar discussions by other subject matter experts on 'what that noise was' on CVR recordings. Or the discussion on the data actually shown to the PF rather than the PNF

This is poor systems analysis. These 'black boxes' are literally not fit for their purpose in multiple ways. Not only have recording and data communication capabilities vastly increased but also the type of flying has changed with aircraft commonly flying 'thin routes' over sparsely populated areas including all oceans and the poles. Rather than a piecemeal approach to fixing shortcomings (or demanding that they are not fixed), it is time that the industry started a complete reappraisal of the areas such as recordings, emergency location, aircraft tracking, survivable recording devices; and generated a formal functional requirement that included all of these issues in one overarching specification. This is a job that ICAO, RTCA, EUROCAE and other standards bodies should take on urgently.
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Old 30th May 2014, 09:42
  #10857 (permalink)  
 
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Ian W
well said - good study

beggars belief with the latest technology now (and its cheap) that ETOPS is given out for 3 hours or more (5.5 hours max) with major safety recording instruments that record just for 30 mins and batteries that give up in 30 days plus the signal given off is poorly identifiable it seems.
its nonsense now...

considering these ETOPS aircraft now have been given that sanction which no doubt takes them further over very remote seas and land masses that technology has been not applied retrospectively -
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Old 30th May 2014, 09:56
  #10858 (permalink)  

Keeping Danny in Sandwiches
 
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Quote:
Originally Posted by BOING View Post
In my experience aircraft can only fly TO an FMC fix. Now, as a pilot in an aircraft west of Indonesia who wishes to fly the aircraft on an unlikely track for a long enough period of time to ensure it runs out of fuel what fix position would you enter into the FMC to meet these needs, a fix position that requires no great imagination. Obviously the geographic South Pole.
Or to an airfield near the south pole on the antarctic continent? You'd still flame out before you got there.
Quote:
Originally Posted by BOING View Post
If anyone is taking bets I would locate the aircraft on a track from its last known position to the geographic South Pole and a distance along track to a little beyond the last Inmarsat ping.
Looks like a decent bet.
See my post 8089 25th March

I do wonder whether the aircraft flew from close to MEKAR to SPOLE (South Pole) or to YWKS (Wilkins Runway) using LNAV thereby independent of further input.

Jeppesen should be able to provide a more accurate calculation of GS for the period rather than the 450kts GS estimate for the whole route south.
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Old 30th May 2014, 10:09
  #10859 (permalink)  
 
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To MM43 @00:59 today,

Thanks for the thoughtful reply, but any explanation of why the false positives occurred surely has to extend to why they stopped, given that the towing operations continued for some time. I remain puzzled. Though if the TPL results are indeed entirely false, it partly solves the problem of how the search area was successfully narrowed down so dramatically... it shouldn't have been.
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Old 30th May 2014, 12:03
  #10860 (permalink)  
 
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Reading between the lines, the govts and other authorities seem convinced this was a criminal act, so IMHO we can definitely expect some changes to the satellite tracking systems so they (a) transmit the position (i.e. the airlines will have to pay up the fairly trivial amounts involved) and (b) cannot be disabled from the cockpit or cabin.

None of that is technically hard. Maybe relocating some circuit breakers.

If this pilot really did what many think he did, it was a clear "go out in style" job, which some may want to copy. Let's face it, it is amazingly easy to do. Either pilot can do it if the other leaves the cockpit.
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