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-   -   Malaysian Airlines MH370 contact lost (https://www.pprune.org/rumours-news/535538-malaysian-airlines-mh370-contact-lost.html)

Propduffer 17th Jun 2014 05:39

@Shadoko
Thanks for the link.

The map also shows speeds in the low 300kt range.
Isn't maximum range speed higher than this for a 772?
Why would it be flying so slow?

p.j.m 17th Jun 2014 06:06


Originally Posted by SAMPUBLIUS (Post 8524749)
Inmarsat has told the BBC that the search for the missing Malaysia Airlines jet has yet to go to the area its scientists think is the plane's most likely crash site.

that's nice, but WHERE is the new "most likely" site?, none of the previous ones have been useful!

HeavyMetallist 17th Jun 2014 07:02

Good grief - they searched where they did because they (thought they had) detected ULB pings. Even if the pings didn't turn out to be from MH370, it would have been pretty stupid to have swanned off to the Inmarsat "most probable" location, while meanwhile the ULB batteries would have died in a "less probable" location.

This hindsight-enhanced armchair second-guessing of a very professional search team gets a bit ridiculous at times.

phil gollin 17th Jun 2014 07:40

This morning's Guardian has an article based tonight's BBC Horizon programme - it states that Inmarsat believe the "hot-spot" is further south and west from the area that was searched.

This is the article ;

MH370: searchers not looking in the best place, satellite experts say | World news | theguardian.com

This is the key bit ;

"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.

Experts from the satellite firm modelled the most likely flight path using the hourly pings and assuming a speed and heading consistent with the plane being flown by autopilot.

"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."

RichardC10 17th Jun 2014 08:47

A model for interpreting the BFO data
 
Over the last couple of weeks I have been developing an analysis of possible tracks for MH370. After adjustment for a very small cumulative frequency drift term during the flight (2Hz), the final results predict search areas very close to those published by the authorities.

I have written a paper on the analysis, posted here.

https://www.dropbox.com/s/ez4sxffxyl...14_issue_1.pdf

I have tried to be thorough but at the expense of being long. This was a lot of work – my wife thinks I am barmy!

The main progress on the system analysis that allows this level of analysis was on the nature of the mysterious D3 component. I have worked from the Inmarsat note with the data logs that stated it is related to the AFC system, plus some documents from Miteq that describe the Inmarsat AFC system. The conclusion is that D3 is related to the total Doppler shift on the pilot frequency used in the AFC system at Perth for the C-band downlink. This pilot frequency is generated (at L-band) at the TT+C ground station for Inmarsat 3F1 which is at Fucino, Italy (the so called primary ground station in the Miteq document). Because this is in the Northern hemisphere and Perth the Southern, the Doppler on the combined link is less than the C-band link to Perth alone. The combined Doppler can be calculated precisely. Details are in the paper.

The set of possible tracks used for the analysis is generated with two parameters, a) a speed for the leg from the turn-back point to the 18:29UT ping-ring, b) a different but constant speed for the rest of the legs. This is a parameterisation of the flight path, the speeds of the first part of the flight (before 19:41UT) can be adjusted without changing the conclusions, but the BFO and BTO data do not in themselves require that complication. This is again discussed in the document. I have not used any of the possible radar contacts with MH370 as a constraint on the model.

In general I have been trying to replicate and understand the analysis techniques that I believe the investigating authorities have used. The published work has always emphasised constant speeds, presumably on the basis of some analysis of the possible aircraft modes. I am not trying to second guess what the authorities have done.

I have used the chi-squared statistical test to judge whether models of the track can be excluded on the basis of the data. This is a quantitative test, rather than just picking the best fit. I don’t know what statistical tests the official analysis has used.

Comments are welcome of course.

sky9 17th Jun 2014 09:26


"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.
I presume that they were referring to Malaysian government publishes MH370 details from UK AAIB - Inmarsat

The interesting point of this is that it is based on constant groundspeed. Have they been though the aloft winds for the 8th March and integrated them into the constant TAS to obtain a groundspeed (the track would be the same if it was on LNAV)?
Does anyone have access or a link to the actual winds aloft at that time, it could be an interesting line to follow?

enjineerin 17th Jun 2014 12:30

A model for interpreting the BFO data
 
RichardC
Good work, and a great write-up... (I will have to finish reading it later.)

Comparing notes between different analysis might help each...

The rumor is that the Pilot signal is coming form an Earth station in Burum, Netherlands. (minor difference from Fucino, Italy)

The work Victor Iannello, Mike Exner, Duncan Steel, Don Thompson and others (as referenced: http://tmfassociates.com/MH370Jun8.pdf ) Is narrowing in on the rumor that the EAFC was incorrectly programmed as to the Lat/Lon location for the Perth ground station. A positive (Northern Lat) for Perth results in roughly 30% reduction in the sat-Perth correction.

In addition to the satellite data, there was reportedly (rumor 3?) an extensive analysis of the fuel range of the flight. The ACARS report at 17:07UT would have provided a fairly accurate fuel weight at that time. (Initial Fuel loads on the ground has been mentioned in the press, and some people done some analysis with those numbers. But, the later ACARS numbers would be more accurate.) The work presumed some truth to early reports that the plane flew erratic or evasive maneuvers West across the peninsula and NorthWest over the Straits {between the turnaround (just after 17:22UT) and the last radar blip (18:22UT)}. The working assumption was that fueld consumption was much higher than would have occurred for level cruise at FL350. {multiple extreme changes in altitude (>45000ft to <5000ft), terrain hugging, and avoiding Thai & Indonesian airspace...}
There was also a belief that the last radar blips established the speed and altitude of the plane at 8:22UT = low (2900ft) and slow (?)... But, my review of the radar blips indicates a much higher speed (~ 500kts ground speed) and altitude (over 35000ft to have been visible on radar at that distance). -- I believe (aka my opinion...) that the fuel exhaustion analysis based on the (overestimated) early flight fuel consumption and the (underestimated) low altitude & speed - pushed the most likely search zone far to the North and East along the 00:11UT arc ('ping ring').
Recent statements from Inmarsat and other participants in the official search effort seem to support the idea that the new search area will be along the same arc, but further South and West, closer to the initial Inmarsat projected paths.
One previously released image "Example Southern Tracks" shows a red line for a "Constant 400 Knts Track", and a yellow line for a "Constant 450 knts Track". With a little adjustment for other improvements they may have made to their BTO+BFO models (and possibly the addition of an even faster track) I am expecting the search area to be more in line with these early proposed tracks.


one person's 'rumor' may another persons 'fact'...

enjineerin 17th Jun 2014 12:48

BFO Graph midpoint line
 
Gysbreght,
The midpoint line would be heavily influenced by the satellite movement, and the relative direction of the plane from the satellite. The satellite movement is sinusoidal, and the impact of the plane's location is far from linear (also containing a at least two trig function dependencies).
The orange mid-track line should be drawn on top of the other lines up to the point where the two paths diverge (~18:28). As drawn, the section of the orange line 18:28-29:41 is too low. (although, correcting that gives the orange line two distinct turns...)
It is the satellite reversing direction around 19:41UT (as just one of the contributors to the BFO) that puts the turn in each of the possible tracks.
- If the plane is to the North of the satellite, the satellite changes from approaching to moving away.
- If the plane is South of the satellite, then the satellite changed from receding to approaching.
Combining in the other BFO contributions leads to the appearance that the North track turns at a different time (20:41) than the South track (19:41). But, the lines drawn between data points are NOT real... We only have discrete measurements, with no indication on the chart of the BFO values in between. If you model the intervening times and fill in the expected BFO values, the two lines show a better symmetry, with the line turning closer to the actual satellite reaching its Northernmost point. (quite close to 19:41UT).

enjineerin 17th Jun 2014 13:11

Shadoko,
(I have read many of your prior posts. Your understanding and explanations of what you understand have been very good.)

The 'are you still there' handshakes follow roughly an hour after the last contact, or contact attempt, from the ground to the plane. You are correct that the 17:07UT (probably the ACARS report to RR) would have set the 1 hour timer. Then the 18:03 and 18:05 attempts to send a text message to the flight crew would have reset the 1 hour timer. The SDU (satcom, satellite modem, ...) reset at 18:25 and the following activity through 18:28 would have rest the timer again. Then, the vice phone call attempt at 18:39 to 18:40:56.354 would have been the last timer reset leading up to the 19:41 handshake and the next three (20:41, 21:41, and 22:41).
Then, the next voice phone call attempt (23:13-23:15) reset the timer.
At 00:11 (00:10:58.000), the are-you-there handshake seems to be a little early. I have no explanation for that...

Just to complete the walk through the handshakes...
the SDU restarted (again) at 00:19. Only the initial log-in was completed.
The ground station then checks on the plane at 01:15:56.
(not exactly an hour... But, I have a theory on this one... Possibly the 00:11 log-in had not completed far enough to terminate the prior connection established at the prior log-in (18:25-28). The last contact from that communications session was the voice call attempt that ended at 23:15. ...and that would be an hour.
the ground station retries the are-you-there message few times (01:16:06 and 01:16:15), since the one at 01:15 was not answered.

BOAC 17th Jun 2014 14:00


Originally Posted by enjineerin
probably the ACARS report to RR

- has it now been confirmed that Malaysian did have this option? I thought it was declared not.

RichardC10 17th Jun 2014 18:11

enjineerin

The rumor is that the Pilot signal is coming form an Earth station in Burum, Netherlands. (minor difference from Fucino, Italy)
That's interesting, I will run the numbers on that.


The work Victor Iannello, Mike Exner, Duncan Steel, Don Thompson and others (as referenced: http://tmfassociates.com/MH370Jun8.pdf ) Is narrowing in on the rumor that the EAFC was incorrectly programmed as to the Lat/Lon location for the Perth ground station. A positive (Northern Lat) for Perth results in roughly 30% reduction in the sat-Perth correction.
I saw that idea but I don't think it is a starter. Inmarsat have been running this system for years - errors would have been sorted long since. The final output of the Ground station system has to correct for all the downlink Doppler before it gets to the Inmarsat control centre. Any error would cause the frequencies to float all over the place.


There was also a belief that the last radar blips established the speed and altitude of the plane at 8:22UT = low (2900ft) and slow (?)... But, my review of the radar blips indicates a much higher speed (~ 500kts ground speed) and altitude (over 35000ft to have been visible on radar at that distance). –
I am personally very dubious about any of the Malaysian radar data. The BFO analysis does not support it, that is, it does not show probable tracks that are consistent with it. The analysis is consistent with simple track solutions, not complex.


Recent statements from Inmarsat and other participants in the official search effort seem to support the idea that the new search area will be along the same arc, but further South and West, closer to the initial Inmarsat projected paths.
I await tonight’s BBC programme. However, the quotes so far seems to imply that Ocean Shield was starting its hydrophone search at the North end of the search area shown in the ICAO report, while we know the search by the Chinese Haixun 01 was at the South end of that area (in the green zone). If the Ocean shield was diverted, it was from carrying on its search South West along the ICAO report search areas, not even further South beyond those areas, I think. In the paper I speculate that the green zone is consistent with tracks that had a speed of 470kt on the first leg, that is the final reported speed for MH370, but this may be going too far.


One previously released image "Example Southern Tracks" shows a red line for a "Constant 400 Knts Track", and a yellow line for a "Constant 450 knts Track".
The early Inmarsat maps did not seem to use the detailed BFO data. The aim then was to demonstrate the aircraft flew South rather than North. I think the search areas moved North as the BFO data analysis matured and, frankly, was believed by the authorities.

The speeds in the BFO analysis in my paper are not directly constrained by the fuel usage. I have taken a maximum speed of 500kt for the first leg to the 18:29UT ping arc, if only because the original speed was 470kt, but the BFO data does not allow any faster speed that 330kt for later legs even for the fits to the four BFO values that take it much further South. Unless the BFO data has been changed a large amount by later analysis, the higher speed tracks are not consistent with the data.

The BFO data is a tough constraint on possible tracks, at least for simple track models.

henra 17th Jun 2014 18:18


Originally Posted by phil gollin (Post 8525063)
"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.

aterpster 17th Jun 2014 18:42

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.

phiggsbroadband 17th Jun 2014 20:12

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.

Nemrytter 17th Jun 2014 21:09


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.

atpcliff 17th Jun 2014 21:22

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!!!

Nemrytter 17th Jun 2014 22:06

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).

RichardC10 17th Jun 2014 22:16

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.

Vinnie Boombatz 18th Jun 2014 00:34

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.

Vinnie Boombatz 18th Jun 2014 01:09

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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