News and theories about the missing Malaysian plane

Alan:

Aha. I hadn't realised the timing of signal arrival was that precise - almost seems they planned to do something like this during the satellite design: I thought it was an ad-hoc thing. Haven't read all the attachments yet but thank you.

RHP:

they always leave the best until last . . .

 

MH-370 Position

I apologize for inadvertently misleading you. The transceiver in the aircraft does NOT have a very good or consistent ‘handshake’ circuit, BUT;

Originally the Inmarsat people were trying to calculate position using doppler only. A tough job.

During this, the Inmarsat people, who are generally very secretive and hardly speak to anyone, made an obscure inquiry of one the English universities, who promptly suggested contacting Boeing direct. Sheffield, particularly (AMRC), but also Nottingham and Cambridge all have fairly close ties to Boeing, and would have technical contacts there. Iv’e lectured at all three universities whilst a ‘fellow’ at Boeing. No, not all scientists in Boeing know each other, but we know off each other, so a specialist in satellite communications could easily be found. The transceiver equipment was built by a third party, but Boeing has to be expert in all the equipment installed on its aircraft for certification reasons, if no other. Hence we often know as much, occasionally much more than the manufacturer of such equipment.

In this case, when the transceiver was 'idle', and ACARS "off" i.e. not doing anything at all, they processed the handshake immediately, using the same logic each time, hence the same ‘pass through’ time. After a lot of ‘blind’ testing, both parties were confident enough to assume/accept a constant ‘pass through’ time. I suspect, but do not know, that some ‘handshakes’ might have been suspect, hence the disparity over how many there were, i.e. there were 8, but not all were ‘clean’.

Once this ‘pass through’ time was established, they tested every single possible combination. I have not seen their results, but talked to some of the participants. The first web reference i gave you was a pretty fair representation of what was involved. He certainly used the same method, and class of software.

I hope this helps.

 

MH-370 Glider

I have a question for you boat designers.

Originally i though in terms of the plane sinking slowly due to trapped air, but was corrected in this.

When i see a movie purporting to show a ship sinking, they show it as sinking quite slowly. Knowing the relative density of steel, and the possibility of trapped air, is this correct, or a figment of the film makers imagination?

Aluminum, being quite light compared to steel, even given little or no compressed trapped air, would it sink still slower?

Equally, the wing of a 777 is very large, and designed to lift at a minimum of, say, 200kts. Water being ~800 times denser, would this wing ‘fly’ in water at 200/800kt, i.e. 1/4kt? or perhaps faster? Best gliding speed for a 777 is about 300kt i think, and it glides at like 20:1. All this assumes a relatively ‘level’ sinking, but such things are possible.

Some of you may know, but a few years ago, an unmanned, automatic ‘submarine’ glided across the atlantic using the ‘weight’ of sucked in water ballast to fly forward on the way down, and the ‘lift’ of buoyancy as that same water was pumped out to ‘fly’ forward on the way back up. It made the trip successfully i think, but i cannot now remember the power, perhaps just a battery.

Could our 777 have ‘glided’ some distance underwater after landing intact?

 

The Titannic took several hours to sink, but I doubt that was due to trapped air, more likely a measure of how fast the water was entering. The decks of a large ship that is going down while upright may not resist the pressure of the air bubble indefinitely and the air will escape with some energy, but an upright ship of considerable length usually breaks its back and hull pieces go down separately. The pieces of the Titannic nosed down and gained considerable speed as they sank, striking the bottom with great force.

Some ships become unstable and roll, this seems to be happening in recent passenger boat sinkings where the hull seems to stay together. Recent sunken ferries and the Costa Concordia rolled for example, perhaps due to top-heavy design.

The hulls of heavily loaded ships like bulk carriers seem to break up but that typically happens due to heavy seas, and in many cases the hull parts remain afloat. What can be achieved presumably depends on condition and construction quality: salvaged hull parts of broken-backed warshipd for example have been welded back together and sent back to sea.

The plane that landed in the Hudson River stayed afloat for some hours, despite the full wing tanks, failure to close the rear fuselage air vent and open doors. It was towed to shallow water, broken and removed. Once below the surface a plane that landed on water intact would sink slower than a ship and smaller planes are sometimes found more-or-less intact on the bottom; the . Obviously that is not the case if it augers in at a high speed and steep angle.

Speaking of submarines gliding, I believe the Ben Franklin mission to explore the Gulf Stream used depth variation to navigate in the currents; not strictly gliding: technically soaring perhaps?

 

You were one of the 777 designers Alan ? I could not be trusted to design a paper plane to throw out the window, but that looks like schoolboy maths to me, the kind that gets marked with a cross !

 

Sailor Alan

If you take the compressed air out of the equation, aluminium sinks at the same rate as steel. What sinks boats is gravity and gravity acts on all objects the same, regardless of weight.

Poida

 

http://en.wikipedia.org/wiki/Galileo's_Leaning_Tower_of_Pisa_experiment

 

Last time I was on the Tower of Pisa there was a sign "do not drop objects from tower" or words to that effect is several languages, and they rang the bells just as I was leaning against one. almost deafened me! I doubt you can go up there now: it was a bit hairy, steps were way out of whack . . .

 

Why take the compressed air out of the picture? It, too, is a sinking object, subject to gravitational forces just like the aluminum or steel.

Your statement is true only if both the steel and aluminum objects were falling in a vacuum, which they are not. Hoyt's reference to Galileo's famous Pisa experiment mentions that the heavier of the two dropped balls did in fact arrive at the ground before the lighter one.

 

Unmanned submarines glide across the ocean, putting Rutgers at leading edge of exploration

Underwater glider | WIKIPEDIA

 

Why the Official Explanation of MH370’s Demise Doesn’t Hold Up | THE ATLANTIC

 

MH370: ‘Pings’ Detected came from Marine Animals, The Questionable Australian-led Search | INTERNATIONAL BUSINESS TIMES

 

Mr Imaginary

The question was asked what would be the rate of sinking if the compressed air was taken out of the factor.

I was stating and I probably should have been clearer to some people that the rate of decent is the same taking all other factors out of the equation.

For example, the surface area, as well as trapped air would change the rate of decent.

Your example of the dropped objects, air resistance is the factor there.

Poida

 

So the pings could have come from fishing nets ? What a shambles !

 

If the plane sank with the doors closed I think the hydrostatic pressure at depth would have quickly crushed it, I doubt the rear cabin vent would have admitted water fast enough to prevent that. The empty fuel tanks in wings at least would have been flattened.