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Malaysian Airlines MH370 contact lost

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Malaysian Airlines MH370 contact lost

Old 17th Jun 2014, 18:18
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Originally Posted by phil gollin
"It was by no means an unrealistic location but it was further to the north east than our area of highest probability," Chris Ashton at Inmarsat told Horizon.
and
"We can identify a path that matches exactly with all those frequency measurements and with the timing measurements and lands on the final arc at a particular location, which then gives us a sort of a hotspot area on the final arc where we believe the most likely area is," explained Ashton."
The good News I take from this is, there is a reasonable plan where to search next with a not too bad chance of finding it.

A bit similar to AF447 (and also similar to every day life) it simply sometimes takes a break and re- think in order to succeed.
Let's Keep our fingers crossed that the boffins got it right.
Here's carefully optimistic.
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Old 17th Jun 2014, 18:42
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henra:

A bit similar to AF447 (and also similar to every day life) it simply sometimes takes a break and re- think in order to succeed.
1. The knew with certainly AF447's track.

2. They quickly found proof of the crash, which was about where they expected to find floating parts.
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Old 17th Jun 2014, 20:12
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If they are looking at the 'Pings', then in free space the strength of the ping will attenuate as the cube of the distance... However if some form of layered ducting had taken place, then the attenuation would have been in the order of the square of the distance.


Also as anyone who has first-hand experience with radio wave propagation will testify, it is possible for enhanced ducting to have taken place, where the signal is beamed an even greater distance still, where the attenuation is just directly proportional to the distance involved.


Different temperature layers in the ocean could act as reflector of the sound waves. Much the same as a graded fibre optic strand keeps the light signal within the core of a fibre optic cable. Under some conditions the Pings could have travelled much further than first thought.
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Old 17th Jun 2014, 21:09
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Does anyone have access or a link to the actual winds aloft at that time, it could be an interesting line to follow?
I have access and have already examined this data. I know that Inmarsat also have this data and have already looked at it.

For the record, as far as I remember (not looked at the data in 2 months) the wind speeds were fairly low, around 30-40kts.
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Old 17th Jun 2014, 21:22
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The sighting by the lady on the yacht....is that consistent with the location that the company using that new type of data study has found (the one that uses the techniques used to find minerals and elements under the earth's surface)???

I would hope that the authorities would be checking on both of these leads...if they are ruled out, then no harm no foul. But, if they are right, we could be looking in the completely wrong location and will never find anything!!!
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Old 17th Jun 2014, 22:06
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The GFS data is not actual winds aloft values, they are forecasts that are modified by any local measurements that were taken. Unfortunately in the middle of the ocean there's not many measurements so for most of MH370's flightpath the GFS analysis is no better than the forecast (which, at least for Africa, is rubbish).
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Old 17th Jun 2014, 22:16
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BBC Documentary

In the BBC Horizon documentary this evening, it was stated that Inmarsat's 'hotspot' for the location of MH370 was at around latitude 28S on the 00:19 arc position. This corresponds to the best fit position using all four BFO values from 19:41 to 22:41UT. This is the analysis in section 7.7 of my document referenced above. The track I selected to plot the BFO data in figure 15 in that section terminates at 27.4S.

So it seems that Inmarsat believed the analysis using all four ping values, while others in the investigation preferred to omit the 19:41UT BFO value, presumably because they thought it an outlier, thus getting best fit locations to the North, in the red-zone of the ICAO report.
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Old 18th Jun 2014, 00:34
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Mach Numbers

For a standard atmosphere (1959 ARDC, 1962 ICAO, 1976 NOAA/NASA/USAF), temperature at sea level is 288.16 K, the tropopause is at 11 km altitude, and temperature decays linearly at 6.5 K/km to 216.66 K at the tropopause.

The speed of sound in knots is about 39 times the square root of the absolute temperature in degrees Kelvin.

Hence the speed of sound for a standard atmosphere is about 661 kts at sea level and about 573 kts at the tropopause (11 km, or about 36,000 ft).

Speeds of 323 kts to 350 kts are about 0.49 M to 0.53 M at sea level, and about 0.56 M to 0.61 M at high altitude.

These are all well below max range speed for a 777-200ER, and pretty far below max endurance speed.
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Old 18th Jun 2014, 01:09
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Aircraft Speed Assumptions

From an aircraft standpoint, the speeds shown in many recent trajectory hypotheses seem unreasonably low.

Aircraft tend to attain maximum cruise range over a rather small range of Mach numbers, typically not more than a few percent variation. Boeing provides a paltry amount of hard numbers here:

http://www.boeing.com/assets/pdf/com...f/777_perf.pdf

The 200-ER is on pgs. 4-6, with Rolls Royce engines on pg. 6. Note that they show data for only 2 engine types (Trent 884 and Trent 895), whereas 9M-MRO had Trent 892 engines ( ASN Aircraft accident Boeing 777-2H6ER 9M-MRO Indian Ocean ). But in either case, Boeing's recommended cruise speed is 0.84 M.

I haven't found the difference between the 895 and 892 engines, other than this brief press release:

ROLLS-ROYCE TO OFFER MORE POWERFUL TRENT ENGINE -- August 05,1998 /PR Newswire UK/

"Rolls-Royce plc announced today that it is to offer a more powerful derivative of the successful Trent engine family for the Boeing 777. The 95,000lb thrust Trent 895, which will be to the same production build as today's Trent 892, will be certificated in 1999, ready for entry into service in 2000."

This Boeing magazine article discusses cruise speed selection generically:

http://www.boeing.com/commercial/aer...7_article5.pdf

Fig. 1 is purely notional, i.e., not for a particular aircraft. However, the implication is that maximum range cruise occurs over a fairly small range of Mach numbers.

I can recall a flight manual from 40 years ago that had many graphs of specific range (nautical miles per pound of fuel), with the curves looking rather like parabolas, with Mach number on the horizontal axis, and specific range on the vertical axis. In other words, much like the notional Figure 1 in the Boeing magazine article.

Finding a similar graph on the web is another matter. Probably out there somewhere, but I haven't found it yet. Possibly in this file, or one of the recommendations at the right side of the page (I'm out of Scribd credits at the moment):

http://www.scribd.com/doc/55989739/B...raining-Manual

Here's a discussion from 2001 on best cruise speed of a B777-200ER with Trent 892:

B777-200ER Economical Cruise Speed Tech Ops Forum | Airliners.net

Roughly 0.82 to 0.85 Mach. A speed of 0.84 M is about 480 kts (assuming standard atmosphere, at or above tropopause). The range from 0.82 M to 0.85 M is roughly 470 to 490 kts. True airspeed, not groundspeed. The range of Mach numbers is likely due to winds input to the flight management computer, i.e., slow down with a tailwind, speed up with a headwind.

This simulator site shows a range chart on pg. 47 (pg. 11 indicates Trent 892 engines);

http://www.deltava.org/library/B777%20Manual.pdf

The chart is a bit hard to read, but the multiple curves account for various no fuel weights and fuel loads. It likely also includes takeoff, climb, descent, and landing, i.e., not purely cruise at altitude.

The Boeing performance table on pg. 6 of the first link above lists the 777-200ER operating empty weight as about 142,000 kg.

Reportedly, the aircraft had about 49,000 kg of fuel at departure ( https://twitter.com/jonostrower/stat...12316941299712 ).

It also carried 227 passengers and 12 crew members ( Investigation: AE-2014-054 - Technical assistance to the Department of Civil Aviation Malaysia in support of missing Malaysia Airlines flight MH370 on 7 March 2014 UTC ). Say 240 people total, and assume 100 kg each, including baggage, or 24,000 kg.

Then the no fuel weight would be about 166,000 kg, and the gross weight at takeoff would be about 215,000 kg. Probably a few thousand kg more for cargo.

The chart on pg. 47 of the simulator ("Virtual Delta") PDF has a gross weight of 217,700 kg in the 7th curve from the left. Follow that curve left and up to 166 (thousand kg) on the left hand scale, and you get on the order of 3,500 nm range.

Dividing that range by 7.6 hrs of flight time gives an average speed of about 460 kts, or about 0.80 M. Takeoff and climb are slower, so that's not inconsistent with cruise at 0.84 M.

However, we have no knowledge that the aircraft flew 3,500 nm. Suppose for example that it flew slower to attain max endurance rather than max range. But that would imply that it would have sufficient fuel to fly longer, perhaps as much as an hour.

There is no requirement for a max range or max endurance trajectory, and there are many possible explanations for a speed well below that. But it doesn't seem like the most likely scenario.

A few academic sources for aircraft performance:

40 year old RAF Cranfield document, "Range Performance In Cruising Flight", lists equations and criteria for max range cruise:

Range Performance in Cruising Flight

Charts from Arizona State University:

http://enpub.fulton.asu.edu/aero/mae...rmance%20I.pdf

Notes from Virginia Tech:

http://www.dept.aoe.vt.edu/~lutze/AO...&endurance.pdf

MIT lecture:

http://web.mit.edu/16.unified/www/FA...etNoteseps.pdf

From the RAF Cranfield paper, Peckham gives an example for which the maximum range speed is about 20% higher than the maximum endurance speed. He neither states nor implies that this is a general result. If it were, one might infer that the 777-200ER cruise speed of 0.84 M would imply a max endurance speed around 0.70 M. That's still a good deal higher than the speeds in the recent best estimates of trajectories.
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Old 18th Jun 2014, 02:41
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I see some considerations about Ground Earth Station in recent posts. In the published "raw data", there is this "remark":
"16:41 - Take-Off.Logged-On to Ground Earth Station (GES) 305/301, via the Indian Ocean Region (IOR) Inmarsat I-3 satellite"
And, the title line of each page shows that the GES numbers are octal.
There are only 4 lines with the code 301 on the main data pages (at 18:39:52,907), 2 in Appendix A (at 18:39:58,407 and 18:40:55,407) and none in Appendix B.
305 (197 decimal) is Perth and 301 (193 decimal) is Eik (in Norway) from the page 21 of this doc:
http://esupport.thrane.com/index.php...oaditemid=1411 (found reading Reddt post GES ID (octal) 305, what is 301? : MH370).
A note on the same page indicates that only Perth and Eik support the "Aero 1" services, but the document is from 2002.

About the (virtual) "nominal terminal": I don't understand why to use a virtual terminal which will ask for theoretical computation. I would understand the use of a physical one which could continuously give a "balance duration" by sending back some signal. Is it technically possible that a "special" signal from the GES is regularly sent and its very faint echo from the Earth surface (sea for instance!) below the satellite is detected and used? And by difference gives the BTO value?

Why the first "publications" from Inmarsat about the "pings" were angles? In the first days after, some people had thought those angles were from signal strength or from antenna number: this happens to be false (strength gives a too low accuracy, and 3F1 is not a multi-beam satellite). We know now that these arcs come from a duration. So, why to convert this value in angles rather than in distances?
If the BTO is computed like guessed above, the simplest geometry using the true distance of the satellite from the Earth center and the Earth radius gives an angle (from the arccosine of the relation between the sides of a triangle).
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Old 18th Jun 2014, 05:19
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Originally Posted by Shadoko
305 (197 decimal) is Perth and 301 (193 decimal) is Eik (in Norway) from the page 21 of this doc
I'm pretty sure Eik was decommissioned last year, and the 301 GES is now in Perth.
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Old 18th Jun 2014, 06:01
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Originally Posted by MG23
I'm pretty sure Eik was decommissioned last year, and the 301 GES is now in Perth.
My understanding is that 305 is Perth, W.A., and 301 was Eik, Norway, but is now Burum, near Groningen, Nederlands.

EDIT:: The following Inmarsat Aviation Safety Services -2013 Update PDF file outlines the current Aero setup.
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Old 18th Jun 2014, 07:48
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Originally Posted by Shadoko
Why the first "publications" from Inmarsat about the "pings" were angles?
I believe they were looking for the easiest media means of explaining the Doppler, as opposed to the "brain teaser" the BTO 'nominal terminal' is.
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Old 18th Jun 2014, 07:57
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Surely this was simply an attempt to make an 'easy' visualisation of the calculated range of the aircraft as an earth projection based on signal 'round-trip time' and had nothing to do with Doppler which I do not think had been looked at at the time by Inmarsat? It certainly did cause some confusion as to the satellite aerial technology.
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Old 18th Jun 2014, 08:32
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BOAC, MM43

I think BOAC is right. The elevation angles correspond to the ranges. In the Inmarsat promotional materials they show elevation angles across the geographical footprints of their antennae. I suspect that internally Inmarsat use elevation as a proxy (shorthand) for range from the subsatellite point. From the point of view of radio reception elevation is the key parameter.
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Old 18th Jun 2014, 08:33
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Some questions for the experts here. (I have looked at Richard's thorough paper):

1) Given that Inmarsat have produced a 'best fit' route for the aircraft, is this available to us? (It is a given that it will no doubt be a 'wide corridor' and not a precise track)

2) If so, can it be established what the approximate true and magnetic tracks were throughout the supposed southern flight? What is the projected path of a continued track as flown, ie is it possible to have guess at any waypoint that may have been active or be more certain that a fixed magnetic heading was in effect?
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Old 18th Jun 2014, 09:23
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1) Given that Inmarsat have produced a 'best fit' route for the aircraft, is this available to us? (It is a given that it will no doubt be a 'wide corridor' and not a precise track)
Not the Inmarsat version of course (no detail has been released), but I can derive the numbers from my model.

2) If so, can it be established what the approximate true and magnetic tracks were throughout the supposed southern flight? What is the projected path of a continued track as flown, ie is it possible to have guess at any waypoint that may have been active or be more certain that a fixed magnetic heading was in effect?
Others will have to speak about waypoints. Here is the data for the track from my model to the Inmarsat hotspot. As I said earlier, the track to the Inmarsat hot-spot is the best fit course from my modelling using all 4 BFO values, and a maximum speed of 500kt for the first leg as a limitation. If the allowed maximum speed on the first leg is higher, there are tracks to the South that fit better.

Interestingly, that model track has a quite smooth change of true heading of 14degrees per hour. Not all the tracks in the model set have that property.

The track data
https://www.dropbox.com/s/6jdz1srdc0...t_hot-spot.xls

and the track itself.
https://www.dropbox.com/s/8cfreiw89e...t_hot-spot.jpg
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Old 18th Jun 2014, 09:28
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change of true heading of 14degrees per hour.
- further to my PM, earth rate is 15 degrees per hour...................
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Old 18th Jun 2014, 11:30
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Last night's Horizon seemed well balanced ...no embarrassing claims about hijacks , crew mutiny , etc etc.

Nice to see Inmarsat explain their reasons for search locations , although still not convincing.

AAIBs man spoke with the voice of reason.....no theatrics.

When they go back to the right place , they might find the wreckage , but that depends on those in the know coming out of the woodwork.
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Old 18th Jun 2014, 12:37
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Nice to see Inmarsat explain their reasons for search locations , although still not convincing.
I thought that the 2 guys from Inmarsat were very honest in their explanations, although I admit I would like to have seen the chinagraph images the correct way round.

What more would you like to have for their conclusions to be convincing? Are you referring to the blog post here:

TMF Associates MSS blog MH370: analysis of where to look?

that gives another set of points that seem to be further south west of the Inmarsat estimate? It may be that Inmarsat used different values for the winds aloft, or indeed this group of analysts have used incorrect values from alternative sources. I don't know if there is any really solid wind information for the area in question but added to the IAS uncertainty (has this been resolved?) it might be responsible for these differences.
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