As the Wikipedia link says, the rhumb line reaches the pole in a finite distance. It is relatively intuitive. When you are moving along the rhumb line, you have to travel fixed distance for every degree of latitude (60 nautical miles if you're going due north or due south, 60/|cos(bearing)| nm for other bearings). Therefore, to go from the equator to the end of the line, you go 60*90/|cos(bearing)| nm.

Down the plug hole
 

Right. I think that my tired old brain can visualise that now.


I'm not sure how much relevance there is in this to MH370, but an excellent reference can be found at Calculate distance and bearing between two Latitude/Longitude points using haversine formula in JavaScript

Search Update
 

http://www.jacc.gov.au/media/release...uly/mr054.aspx




Two ships, Zhu Kezhen and Fugro Equator, continue to work in the southern Indian Ocean, surveying the sea floor in preparation for the deep-sea search for missing Malaysia Airlines flight MH370.
In June, an expert satellite working group identified a search zone of up to 60,000 square kilometres, which represents the highest priority for future search efforts. As with previous search areas, it is located along the seventh arc—a thin but long line that includes all the possible points where the last known communication between the aircraft and a communications satellite could have taken place.
Before the deep-sea search can commence however, it is necessary to map the sea floor in this remote region of the Indian Ocean, which until now has been poorly charted. The aim is to identify significant features on the sea floor, which may present a hazard for the deep water vehicles that will be used for the search.
Since 24 May 2014, the Zhu Kezhen, a Chinese PLA-Navy vessel has been conducting survey operations. The bathymetric data it is collecting will assist in characterising the sea floor topography. As of 30 July 2014, it has sounded over 25,000 square kilometres along the seventh arc.
Fugro Equator, an Australian-contracted specialised survey vessel, has also been conducting bathymetric survey work. As of 30 July 2014, over 43,000 square kilometres have been sounded by Fugro Equator.
Analysis and mapping of this data is continuing.
On 6 July, the Government of Malaysia announced that its hydrographic survey vessel, the KD MUTIARA, would join the Zhu Kezhen and the Fugro Equator in August to continue the bathymetric survey work.
It is expected that the bathymetric survey work will be completed by September. The deep-water search is expected to commence in September following the appointment of a prime contractor through a request for tender process.
The JACC will provide updates on the activities of the bathymetric survey, which can be found at www.jacc.gov.au/media/maps/index.aspx

During the search for MH370, there was something sad about sailors on aboard RN ships, with binoculars, searching for wreckage by looking out to sea. How far can they see with any reliability? Is this next to futile?

A UK Freedom of Information request asked if the Royal Navy have any towed observation platforms, a device a bit like a parascender/hang glider, which, apparently, can reach almost to 1000 feet, and towed behind the ship. This seems gloriously low tech, very cheap and potentially useful. Having said that they did not, this is what they went on to say:


"UK Armed Forces rely on advanced sensors that provide a highly effective detection capability. For example, surveillance radar systems, such as the SCANTER 4100, which are currently in service with the Royal Navy, offer a combined surface and air surveillance capability to a range of 110 nautical miles from the ship. The radar is capable of detecting small objects in all weather conditions which gives it a clear advantage over the approach you propose. In addition, highly capable sonar systems, such as the 2087 used by the Royal Navy's Type 23 frigates provide an effective means of acoustically detecting submerged objects".

Can anyone comment on this, bearing in mind that nobody is talking of "either or", but rather of "all" useful ideas. Who knows when the world will be on another similar search?

latest from CNN
 

MH370: Australia to announce next phase of search - CNN.com

Wish them luck.

Transcript of press conference here

Joint Agency Coordination Centre

Dutch firm to conduct MH370 underwater search

A Dutch firm will conduct a deep-water search in the Indian Ocean for missing Malaysia Airlines Flight MH370 from September, Australia said on Wednesday, expressing "cautious optimism" that the plane will be found.

Fugro Survey will use its state-of-the-art vessel MV Fugro Equator and the Fugro Discovery to search a 60,000 square-kilometre (23,000 square-mile) zone in the southern Indian Ocean.

"The underwater search will aim to locate the aircraft and any evidence, such as debris and flight recorders, to assist the Malaysian investigation team on the disappearance of MH370," Australian Deputy Prime Minister Warren Truss said.

"The Malaysian government have also offered equipment which will participate in that search and of course, there's a Chinese vessel already operating in that area in relation to the survey."

A huge air and sea surface search has failed to find any sign of MH370, which went missing on March 8 with 239 people on board. Authorities believe the doomed airliner veered mysteriously from its Kuala Lumpur-Beijing route before crashing in the remote Indian Ocean.

The Fugro Equator is currently working with Chinese PLA-Navy ship Zhu Kezhen to map the seabed in the search area, based on the missing plane's last satellite communication around 1,800 kilometres (1,100 miles) west of Perth.

The Fugro Discovery is en route to Perth from Britain, with the deep-water search expected to take up to a year to complete.

Both vessels have towed deep-water vehicles and crew with search expertise, Australia's Joint Agency Coordination Centre said. The sea floor search will use sonar equipment and video cameras to locate and identify any debris.

Truss said he remained "cautiously optimistic that we will locate the missing aircraft within the priority search area". He added that the search "will obviously be a challenging one".

Martin Dolan, commissioner of the Australian Transport Safety Bureau, the agency leading the search, said the underwater mapping survey due to end in mid-September was discovering "some surprises".

"We haven't completed the mapping, so we are still discovering detailed features that we had no knowledge of -- underwater volcanos and various other things," Dolan said.

Truss said the discoveries "demonstrated why this mapping was so necessary".

"The ocean is not just simply flat and featureless," he said of the underwater terrain in the search zone, which is about half the size of peninsular Malaysia. About 60 percent of the area has been mapped so far.

"There's quite a lot of geological features there that will be a challenge in the search, that we needed to be identified to make it actually possible to undertake the sonar work that is going to occur from now on," Truss added.

The underwater search contract could cost Aus$52 million (US$48 million) if it stretches up to a year, he said.

by Usman SHARIFI © 2014 AFP

DL, I had 27 years carrying out SAR missions (airborne) and much of the time all those expensive sensors are useless, and you are reduced to visual search. Acoustics is useless unless there is an acoustic source, with a usable range.
Radio homers are useless if nothing is emitting. Radar is useless unless something detectable is sticking out the ocean.

Further problems abound (in all oceans and scenarios)...

The sea is full (and I mean full) of junk. All of which will have to be investigated if it is detected within the search area.

In deep ocean, range is massive issue (in terms of fuel and time on task for aircraft and reaction time for ships)

Surface wreckage drifts (50 miles plus a day), expanding the datum.

Sea state has a huge and very variable effect on the efficacy of visual search.

the list goes on but you get my point.

In the case of MH370 the deck was stacked against a quick find from the get go...no datum whatosever, long way from land, no sign of detectable sized wreckage or high visibility survival equipment, very short range and short life acoustic beacon...

So yeah, futile sums it up completely. Still have to try though, don't they?

Better sensors are not the answer (the sensors do what the taxpayer pays them to). The answer is better tracking in the sky and better beacons on the boxes.

Just documenting latitudes and distances for two key flight paths from the fan I generated last month in replicating & validating the ATSB’s original endurance line (SE border of S1/S2/S3, Fig.3, p.5, June 26 ATSB report):


(wide map: http://bit.ly/WIb2Ng close-up of search zone: http://bit.ly/1nI3V0Q)


Start point (NW tip of Sumatra):
18:36:03 5°59′ N


A 460 knot path would hit Inmarsat arcs 2-thru-6 at these SOUTH latitudes:
19:41:03 2°14′
20:41:05 9°50′
21:41:27 17°32′
22:41:22 25°11′
0:11:00 36°35′
…and end in the middle of the March 17-27 search zone
…with (according to the width of S2 at that point and heading) 329 nmi to spare
…for a total flight distance of 5.58hrs x 460 kts = 2,568 + 330 = 2,897 nmi



if new fuel analysis shortens range 11% = 319 nmi:
…still feasible (by March ATSB standards), with 10 nmi to spare


A 390 knot path would hit Inmarsat arcs 2-thru-6 at these SOUTH latitudes:
19:41:03 0°59′
20:41:05 7°30′
21:41:27 14°3′
22:41:22 20°27′
0:11:00 29°48′
…and end in the middle of the Mar.28-Apr.1 search zone
…with (according to the width of S3 at that point and heading) 248 nmi to spare
…for a total flight distance of 5.58hrs x 390 kts = 2,177 + 248 = 2,425 nmi



if new fuel analysis shortens range 11% = 267 nmi:
…NOT feasible (by March ATSB standards) by 19 nmi


If you drop fuel by less: original search location still feasible
If you drop fuel by more: new search location still infeasible




This simple, transparent demonstration proves mathematically – without a single parameter that does not come from the ATSB’s own reports – that their “drop in starting fuel” argument could not POSSIBLY have been a good reason to move the search 1,100km NE on March 28.


So why did they?

You have a government pleading poor yet they are paying for another countries expenses. Which will be huge as It will not be found.

So why did they?

IMHO, an erroneous detection by the HMS Tireless (remember the "self satisfied" statement when she returned to England?) and then, using the pinger locator of the Navy towed by Ocean Shield at the limits of its capabilities, a "false" signal from the black box pingers.
Anyway, it was (IMHO) the right thing to do if there was the smallest chance to find the plane there.
Perhaps this can't be told for "military" reasons (Tireless capacities) and thus the Australian can't tell that, nor show the "signal" acquisition charts (Navy capacities). Nothing abnormal from my point of view this is not made public. And they don't lie: the search zone was moved after "more study".

Shadoko: thanks for replying. If you agree with me that reduced available fuel could not possibly have been the reason the ATSB moved the search 1,100km NE on March 28, then wouldn't you also agree with me that the statement...


"On 27 March (D20), the JIT advised they now had more confidence in the increased speeds provided by primary radar near Malaysia. This increased the aircraft fuel burn and the most probable track moved north to the S3 area." (source: "MH370 - Definition of Underwater Search Areas", June 26, page 6)


...is deceitful?


P.S. I'm only pointing out the logical flaw in the FIRST humongous shift NE that occurred that week. Four days later, on April 1, they moved the search a FURTHER 1,500km (from yellow to red, on the chart I provided above) - up into 20s latitude - where the acoustic pings then pinned the search for eight weeks. Your quote may be referring to the rationale for that SECOND move (which is unrelated to my argument).

heading vs track
 

I expect T7, like FBW airbus, can be in heading or track. Assumptions about heading, but then describe track of the aircraft seems to indicate carelessness of a few posters.

In late April I commented it was rather odd that no identifiable wreckage had been found on shore. That the a/c could have found its way to the ocean floor completely intact, even in the unlikely event of a relatively successful ditching, seemed implausible. We're not talking about the Hudson River.

At risk of being a nuisance, did anyone come up with an explanation for that?

Chris Scott

There have been discussions about this elsewhere. The questions are about things like how rough the sea might have been - weather reports say calm. There are also questions about how much control the automatic flight envelope protection systems might have had over the final trajectory.

It is one thing to say that it is unlikely that the aircraft remained substantially intact but quite another to say it is impossible.

Subsequent to the touchdown there are questions about ocean winds and currents and locations where debris might eventually wash ashore. I have read suggestions by people who know more than I do that wreckage may drift for many months - even years - before washing up. The possible locations are affected by the range of possible impact points but may be as far apart as South Africa and Tasmania. Since the impact point is unknown and all of the searches to date may have been distant from it, I don't find it surprising that no wreckage has been identified. The Ocean is vast and the possibility remains that very little floating wreckage might be present.

The ATSB won't just pick search areas at random. Any area they pick will be based on advice from the groups studying satellite communications data and aircraft performance.

There is a difference between human behavior and what is likely and/or unlikely and purely technical things. Human behavior as we know from history of aviation can be so aberrant that anything however unlikely can't be discounted but on the other hand purely technical aspects - here what is likely and unlikely remains pretty much constant and I don't think this particular accident will surprise us a lot in technical aspects (if we ever solve it in its entirety) but human behavior can astonish us again.

I've just spent 3 weeks on Cocos-Keeling Islands and I was stunned at the absolutely vast amounts of flotsam and jetsam littering the shores of the islands.

I was always under the impression (now sadly corrected) that the Indian Ocean was one of the worlds cleanest oceans, and I was very pleased to live on the Eastern edge of it, and revel in its cleanliness.
The truth is, the Indian Ocean is a watery garbage pit, on a par with every other world ocean.

Much of the flotsam and jetsam has Asian origins, and much of it is reputed to be remnants of the Aceh and Fukushima tsunamis.
I believe a lot of it is even more recent and is a result of purely a lazy disposal attitude, on a large percentage of the population of the above nations.

Surviving MH370 wreckage (and there is bound to be some) would be buried in the overwhelming volume of general rubbish that populates the Indian Ocean.

AFAIC, the greatest failure on the authorities part is not immediately issuing a reward notice to the populace of every nation and every island and continent bordering the Indian Ocean, for a monetary reward for any possible aviation-related flotsam or jetsam found in these areas.

Even just one small wreckage item from MH370 would add to the tiny levels of available information and enable researchers to try and calculate the track of the wreckage.

I remember spending a day driving around Grand Cayman many years ago exploring all the little beaches and coves. One thing that struck me at the time was the extent to which the waves seem to sort the rubbish into objects of approximately equal size and density.

One small beach we found was obviously the place where lost shoes wash up. Large amounts of rubbish but almost all shoes. That leads me to believe that different components of any wreckage are likely to wash ashore eventually at different places or times depending on size.