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Where did you pick 20Ah? (Ah, not aH, amp/hour even less so).


Lithium is not lead.


22Wh / 50mW = 440h. 20% duty cycle make 2200h or 92 days.

Yes, I think I got a bit confused! Maybe it was the effect of liquid libation! Anyway, perhaps I should've looked at it as 20aH being 20 amps for one hour at 12 volts being 240 watts for one hour. Or 864000 joules. Assuming the thing operating at the same voltage, and if I've got it right this time, a 20aH car battery equates to 6000 hours at 40mW, which I think is just over 35 weeks. A bit different than my previous calculation!


But as we know a car battery is quite bulky and heavy, and the pinger I saw demonstrated on TV a while ago was quite small, to the point whereby it would fit into a clenched hand. And the battery appeared about the size of a D cell. So the 30 days duration of the present system seems a pretty efficient piece of engineering.


Anyway, hope if I've got it roughly right this time!

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That's an example of a (safe) 100Wh Li-MnO2 primary battery. It delivers 3V from one cell, compared with 6 cells for 12V at a car battery - and lithium is much better than lead.




22Wh would take some 8Ah, or 1/4 the drawn size. Alas, the pressure vessel around it triples the mass. A magnesium battery working in the open seawater would save this vessel.

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The 3kHz pinger works within a narrow resonance (Q=1000) which drifts more than the bandwidth: Ti-Al6V4 is 0.3% stiffer at +5°C than +20°C, and water pressure tilts the beams more, which raises the resonance by one half (tilting initially more would improve, as well as putting the extra elasticity elsewhere).

To drive the electromechanical aggregate at its resonance, the oscillator must include it in the loop. Here the coils have a few extra turns to provide a feedback voltage resulting from the speed gained by resonance.



The coils' inductance happens to make a voltage about as strong as the one resulting from the speed relative to the magnet. This helps the amplifier's output, which can saturate for efficiency. But to guarantee oscillation driven by the mechanical resonance, I suggest to have two feedback windings per voice coil, at two different positions, where the mutual inductance from the power winding differs. The induction by the magnet will differ as well, but by an other amount, so that some weighed difference between the voltages at both feedback windings results essentially from the speed and not from the mutual inductance. The adjustment can be made outside the mechanical resonance frequency.

Driving only one power winding still permits a decent degraded operation. If an open circuit is the more probable failure at these power and voltage, the windings from both sides can be paralleled. Separate amplifier outputs improve probably nothing.

Cycles of 0% to 100% power can make the start less easy. Keeping 1% power for permanent oscillation during the cycle can be done by a reduced voltage to feed the amplifier's output(s).

Marc Schaefer, aka Enthalpy

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Singapore Airlines, one of the type's largest customers,[1] ordered over half of its -200ERs with reduced engine thrust specifications (de-rated) for use on medium-length routes.[175][176] The de-rated engines lower MTOW, which reduces the aircraft's purchase price and landing fees, and can be re-rated to full -200ER standard for long-haul operations.

It's probably blowing chemtrails out there somewhere



800px-Boeing_777-200ER_Malaysia_AL_(MAS)Looks like it lands right at the bus terminal!


This one is waiting to pick someone up at the airport.


flight or246 Boeing 767-375(ER) Everyone has these new planes these days.


easyjet.com it blows



Maintenance photo shot from a helicopter. This is why I never fly on an airbus.



Do a barrel roll!


Dancing on the runway.


Tacky paint job.


Landing gear, landing gear, landing gear.

I take that back.

Say cheese :)

googled cheaptickets again

Edited by vampares
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I've checked the wiring cables on aeroplanes, and apparently they are still made often of copper, aluminium being the exception, for reasons I ignore and can't even guess. Very bizarre to me, since most high-power terrestrial cables are of aluminium. Houses had worries with alu cabling 50 years ago, but that's over, and plane manufacturer would easily afford to develop their own connectors for aluminium if it were any necessary.

I'd really prefer to wire aeroplanes with aluminium (Elec. Eng. was my first profession), and with the gained mass, have separate data networks on the 777 and Dreamliner to fly the plane and to carry passengers' data.


I'm not presuming MH370 was taken over by a malicious software: while this would fit what the public knows of this incident, there is no element to decide for or against it. Just to tell that a common network is foolish to my opinion, and that malicious software will take control some day if not at MH370.

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  • 11 months later...

More and more people realize that a data network common to flight control and to passengers, on the 787, A350, A380 is pure foolish.


Chris Roberts claims he could access data about the plane's health



Guess how the companies and the FBI reacted? Right.


The airline has banned Chris Roberts from its flights.

The FBI wants airlines to report suspicious activities.

I've heard about no single report imposing separate networks on airliners.


I would be about time to wake up. The common network is a huge blunder by the deisngers and all people who were supposed to supervise the plane design. This enormous error must be corrected, first for the future designs, then to retrofit all 787, A350, A380.


Software security does not exist. State terrorism does exist and is at work every day, it has all means to exploit the weaknesses. We cannot let the life of hundreds of people depend on a software firewall.

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  • 3 months later...

To better estimate MH370's crash location, a former seaman, François Vaudon, proposes to drop half a dozen of buoys near the present estimated location at the same season and follow them by radio. Comparing their arrival with La Réunion, where a flaperon landed, would narrow the zone of possible impact, as Mr. Vaudon claims currents reproduce accurately.


I have no opinion about changes in the Indian Ocean induced by El Niño that affects presently the Pacific. I do know that winds have a big influence on the drift of floating items, even if they're widely submerged. Anyway, here are my two cents proposal to avoid waiting for 17 months the arrival of the buoys:


Cut the supposed path in several segments. Drop more buoys, not just at the estimated crash site, but also further down on the path where the debris are supposed to be some months later. That way, one can observe simultaneously the drift over several segments of the estimated path, and get the data before the upstream buoys arrive in Africa.


In the simplest example, all buoys can be dropped at the same season as the crash happened. The downstream buoys group is dropped where the debris are estimated to be 12 months later. This reduces the waiting from 17 to 12 months.


The scheme can improve further. For instance, more buoys can be dropped about 6 months before the upstream groups (since presently we've past the season of the crash) at the estimated location 6 months downstream. The the two groups at 0 and 12 months locations need to drift for 6 months only, and we have a complete observation.

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Scenario for a shorter drift - two buoy groups must be the maximum:

  • The flaperon drifted from 201403 to 201507 (all months are inclusive), or 17 months.
  • The groups of buoys reproducing the end of the drift can arrive in 201607: it follows the flaperon 1 year later. If this group is immersed in 201510 (in 5 weeks), it reproduces 10 months of drift.
  • The other group must wait 201603 for immersion near the supposed crash site: it follows the flaperon 2 year later. The 7 months not covered by the other group end in 201609.

We get a result in 201609 (13 months from now) instead of 201707.

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  • 3 weeks later...

Hi Klaynos and everybody!

Neither do I know how good models are for Ocean currents. François Vaudon claims to be a specialist and tells currents aren't known well enough there, hence his proposal to measure them.

Dependency on depth must be a major worry, because winds drag shallow water mainly. Wind also uses to move floating items more than currents do, and I fear winds are less reproducible than currents. We don't even know for sure how much of the flaperon emerged. Well, it needs a specialist to tell.


I suggested on 05 May 2014 to use aluminium cables (which, by the way, are commercially available) on aeroplanes to afford with the saved mass separate networks for flight control and entertainment. Reports suggest that house fires that stopped the use of aluminium resulted from bad contacts on the too soft metal.

Alumnium cables exist that are coated with silver. These can be soldered to copper clips that fit in normal connectors. Nickel or palladium, instead of silver or over it, don't dissolve in solder.

Stranded cables can be spliced, here stranded aluminium with stranded copper cable. It's done over several metres for wire ropes to lose no strength. Once the aluminium cable has copper ends, it can be connected as usual.

The clear and proper way would be to develop connectors whose force, elasticity, or whatever needed, fits the properties of aluminium cables.

Marc Schaefer, aka Enthalpy

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  • 3 weeks later...

I suggested here on message #46 to build underwater drones, preferably cooperating as swarms with collective aperture synthesis, to obtain faster better maps of the Ocean floor. My suggested energy source was fuel cells.


An alternative is a magnesium battery that uses seawater as electrolyte. I believe to remember they have iron as the other electrode. Anyway, they provide a huge energy per mass unit because almost everything is the consumable electrode. They don't provide strong currents, and they self-discharge too, but for weak- or month-long operation at constant power they're excellent.


Just put the new electrode in place and let the drone operate. At constant modest power it's the most compact choice.

Edited by Enthalpy
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