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Malaysian Airlines MH370 contact lost

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Malaysian Airlines MH370 contact lost

Old 9th Mar 2014, 22:38
  #1041 (permalink)  
 
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I don't see any provision for air resistance in that equation...
True - but it's still probably closer than the 3 minute figure.

For comparison, it took just under 50 seconds between the PA103 explosion (at FL310) and the wing impacting the ground at Lockerbie.
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Old 9th Mar 2014, 22:42
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On the freefall time, the 3+ minute estimate is a bit off.

s=ut + 0.5at^2, assuming an initial vertical velocity of 0, and initial height s=8000m (I can't be bothered to convert 35,000' to m), t would be around 40s.
Based on the assumption the aircraft continued to accelerate in a uniform manner all the way down. That equation (better expressed as v^2=u^2 + 2as) gives a velocity after 8000 metres descent of 396 metres/sec or approx 900mph. Is it reasonable to assume that kind of velocity could have been achieved?
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Old 9th Mar 2014, 22:44
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"Yes, 40s is about right for an object released with no initial velocity.

If an aircraft pitches down, however, some part of the horizontal velocity becomes the initial velocity (100% if it goes vertical) so it will take less time even if it breaks up."

Please stop using a formula for motion under gravity in a vacuum in relation to the descent of aircraft falling through the air.

Air resistance is the dominant factor, downward velocity will stop increasing once air resistance equals weight. Erratic of course if tumbling, but far far slower than in a vacuum, where speed keeps increasing until impact.
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Old 9th Mar 2014, 22:44
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Originally Posted by surfcat
On the freefall time, the 3+ minute estimate is a bit off.

s=ut + 0.5at^2, assuming an initial vertical velocity of 0, and initial height s=8000m (I can't be bothered to convert 35,000' to m), t would be around 40s.
Oops Yes that logic you've used (with a=g=10m/s/s) also requires that the falling object hits the deck at 400m/s which ... er ... I fancy is a bit off for the reasons Messrs Gruntpuddock, dude, Cheer Up and 32 have gently reminded!

Terminal velocity.
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Old 9th Mar 2014, 22:46
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Lakedude: indeed no air resistance- this is the lower limit to freefall. But another alternative in the post I tried to quote was nose down. In that case, a>g, so t<40s.
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Old 9th Mar 2014, 22:51
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Yes, 40s is about right for an object released with no initial velocity.

If an aircraft pitches down, however, some part of the horizontal velocity becomes the initial velocity (100% if it goes vertical) so it will take less time even if it breaks up.
That's not right - but the point highlights that if the aircraft is pitched down and assuming the motors are still running the thrust is added to the gravitational acceleration so a is going to be > 9.81 m/sec squared.

What's the terminal velocity of a 777 pointed towards the centre of gravitational attraction?
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Old 9th Mar 2014, 22:54
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Look up the 447 dynamics for the timeline of one trajectory from 35000.
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Old 9th Mar 2014, 22:59
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On the freefall time, the 3+ minute estimate is a bit off.

s=ut + 0.5at^2, assuming an initial vertical velocity of 0, and initial height s=8000m (I can't be bothered to convert 35,000' to m), t would be around 40s.
It's been awhile since I took physics, but I came up with 46 seconds doing the conversion. Problem is, that particular equation does not take into account air resistance and terminal velocity (around 60 m/s). I'd say 3 minutes is probably closer the real answer. I found an equation that does take air resistance into account, but I don't feel like doing calculus today.
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Old 9th Mar 2014, 23:00
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@WillowRun6-3

ICAO/civil aviation des not deal with passports of passengers excepting that all international passengers must comply with immigration requirements of destination state to be permitted to board. The PIC has authority over all souls on board, irrespective of nationality. What is currently under some review is how to handle any possible conflicts between the law under which the PIC exercises authority (the law of the state of registry) and the law of the destination where anyone ordered to be restrained by the PIC is taken over by local law enforcement.
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Old 9th Mar 2014, 23:01
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Searchers Report Spotting Plane Debris - WSJ.com

Report by Wall Street Journal, includes vid showing locations of last known position, reported oil slick and parts discovered.
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Old 9th Mar 2014, 23:01
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447 hit the water at 10.912 ft/min = 124 mph. It went in almost flat pitched up about 16 degrees. The discussion here was about a nose-first trajectory to come up with a time of 40 seconds and a final speed in excess of 800 kt
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Old 9th Mar 2014, 23:07
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This is all desperately sad for everyone involved. It just seems so very similar to BOAC Flight 781 - the De Havilland Comet 1 crash off Elba. In that instance there was no apparent surface wreckage from the airframe but unfortunately the bodies of some of the passengers did stay on the surface. I don't envy the SAR teams their job one little bit.
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Old 9th Mar 2014, 23:12
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Since speculation in some of the last few posts has included mention of speeds in the supersonic neighborhood, I'll ask a question that's been on my mind--Has there been any mention anywhere of reports of a sonic boom? How far across open water might one be audible?
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Old 9th Mar 2014, 23:16
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For what it's worth, the two passengers travelling on the stolen passports were booked to fly out of Beijing and on to Amsterdam later that day.

Missing Malaysia Airlines plane: What happened to MH370?
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Old 9th Mar 2014, 23:18
  #1055 (permalink)  
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Have read through the previous posts - both informed and speculative.
All very puzzling.
The following questions meant in no way to distress, or cast aspersions on MH.
Fair to say that modern airliners usually only vanish during the cruise for one reason.
If there was an explosive device, then why no sign of a flash from IMINT satellites? I assume that thousands of pounds of Jet-A1 vapourising, even at that altitude would create some kind of instantaneous flash - or is a breakup in the cruise possible with no accompanying fire - I suppose it is?
And as yet, no revelations of primary radar trace of large parts of structure falling?
IIRC, one positive comment often made about the 777 is that it's a very strong air-frame. Even at circa 0.84 mach, air loads that might induce a catastrophic structural failure would surely still see large pieces left as part of the break-up sequence?
And no debris field yet.
Very strange.
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Old 9th Mar 2014, 23:22
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ACARS?

ACARS is not mandatory equipment. Aircraft can dispatch under the MEL with inop ACARS.

The information posted here so far does not categorically state that the ACARS was working prior to the event. The information I can see indicates that 'no failure messages were received' etc...

Was the ACARS operating normally prior to the event?
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Old 9th Mar 2014, 23:28
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Submarines to search? sure, the sonar may yield something but it's got to be a WTF moment here!
Modern submarines are the best mobile platforms available for detecting sounds in the ocean. The whole front of a sub is a giant array of microphones coupled with major computing power all riding on a platform that itself is designed to be ultra-quite. AF447 included a French nuclear submarine in the initial search for the black boxes.
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Old 9th Mar 2014, 23:28
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Why no flash detection?

Probably because none of the three operational birds are looking for missile launches or nuke detonations in Malaysia.
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Old 9th Mar 2014, 23:30
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Tokyo's (Rosy) Convention

@andrasz

Thank you; Sir. I understand that the legal scheme you described is what exists.

But the present legal system is set up from the inside looking out. That is, each nation state has its own system of identity controls and verification. And of dealing with all the fine-point particulars noted alluded to or otherwise mentioned on-thread. And from this, sort of like the UN, set of each nation taking its own approach (no pun intended), the international system is constructed. It looks from the inside (each nation) out (to the international, world-wide, global order of civil aviation).

That's why we have a "conflict" between the state of registry and the situs (legal word for, "place", one that is "formally identified by or with a juridical structure") where PIC's inherent legal authority is exerted in fact. In my legal opinion the ICAO governance system not only should be changed, but it MUST be changed so that the situs law yields to the authority of the PIC as articulated by such Captain's "rank" in the overall global civil aeronautics sector. It's a concept of "the legal right of way". The system needs to be re-done, looking from the outside (the global system perspective) in (into each country).

And as with collaring a stinking drunk, ordering my brother the rabbi to finish his prayers later and get in his seat (and belted) and so on and so forth - the civil aeronautics system globally has to impose some order on the apparent Swiss cheese paradise of passport laxity.

I was a student radical in the era of the SDS. Posters need not waste their fingers telling me 'things can't be changed'. I'm on the ORD perimeter - happy to chat over a brew with any and all four-stripers, oh and surely yes, I'm buying.
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Old 9th Mar 2014, 23:32
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You understand that shallow water is a very difficult acoustic environment for a submarine, right?
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