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.

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.

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.

And at a similar depth underwater. ;)

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?

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

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 205°T 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.

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 205°T 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.

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.

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.

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!

Poor Design Validation DFDR CVR
 

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.

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 -

See my post 8089 25th March

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.

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.

ULB range
 

My understanding, I think was from one of Angus Houston's briefings, is that the ULB is not intended to be detectable at such depths. It is for finding the flight recorders once you have already found the debris field.

Having said that it does lead one to the conclusion that when it was introduced possibly there was no expectation that debris would be recoverable from somewhere as deep and remote as the southern Indian ocean.

Every electrical system or circuit breaker removed from the control of the flight crew is an added fire risk.

Let's not be in such a rush to quick fixes for one in ten million risks that make more-likely risks worse.

I cling to the the perhaps naive view that there are not that many commercial pilots out there waiting to take out their aircraft and passengers - waiting only for suitable "inspiration".

If there is someone like that up-front who has decided that today is the day then basically we are pretty much stuffed. New tricks for finding the wreckage afterwards are not that much of a comfort.

This is absolutely correct the design was for cases such as when the debris was in a river - say the Potomac and the CVR/DFDR needed to be found. So what we have is a failure of systems analysis, what happens if an aircraft goes NORDO on the way to Hawaii and does not arrive? What about LAX - SYD? My suspicion is that the systems analysis was limited at the start by external inputs like funding, weight and the capabilities of the then systems. It is in urgent need of revisiting.

If its a criminal act...
 

....do the authorities/countries involved have to report what they know. How much information are they obliged to release?

....if it was a criminal act by a radical group - they would have let us know within hours that they were responsible to bask in their infamy.

....if it was the sad act of an individual who had the extensive knowledge and cunning to perpetrate this - surely that person would want the world to know that they were that clever/sick! They would have left some note, tweet, Facebook clue. I feel they could not have the self-control to leave no clue at all - unless the authorities have that clue and want to keep it to themselves.

....or it was an insurance job and had to be scrupulously covered up.