Flight MH370: Altitude issues, flight-recorder operation

trader_4 wrote:

I've monitored the flights I've been on using hand-held GPS, and I can tell you that flight altitudes rarely match up with what the pilots claim to be their cruise altitude or in-flight map display. Being off by 500 feet is common.
Altimeters based on air pressure are not as accurate as consumer GPS.
ATC or military ground radar also is not that good at measuring altitude.
But I'll tell you what is or has gotten little comment: The fact that the plane was carrying a load of batteries (lithium ion? lithium polymer?).
I'll tell you what happened: The cargo load was not secure, it shifted during takeoff causing damage, batteries were punctured, fire ensued, plane systems were damaged, smoke and fumes incapacitated passengers and crew, plane flew some random course until it ran out of fuel.
Fire damage could have disrupted power to black boxes, so there is a chance that they stopped recording much closer to the start of the flight and would therefore contain extremely relavent and useful information during the phase of the flight where humans were likely to be alive, concious, or otherwise in control of the plane.
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On Friday, April 4, 2014 10:12:55 AM UTC-4, Ho MeGu Y wrote:

It would be one hell of a magical fire to:
A - Occur so suddenly that there is no warning, no mayday issued by the crew for return to the nearest airport. They have smoke alarms, fire alarms, etc. Yet we're to believe that the fire conveniently took out all the things necessary to make the plane go missing, ie radio, ACARS, transponders, kill everyone on board, yet leave the plane perfectly capable of flying another 8 hours.
B - It apparently didn't fly a random course. There were numerous reports that it hit 3 waypoints in the Straits, leaving it aligned with flight paths to India/Middle East.
C - Said magical fire takes out everything to make the plane disappear in precisely the min or so window where it's ideal to deliberately make a plane go missing, ie just as it's been handed off by Malaysian ATC and where it would be contacting Vietnam ATC. The probability of that alone is .002% for a 6 hour flight.

Sure, fire can and has done a lot of damage to a plane. We know that from ValuJet, SwissAir, etc. But in every case, they have made mayday calls and requested a return to the nearest airport. They did that in both those incidents. And the fires resulted in the plane crashing. I'd like to see one example of a plane with a severe fire that continued flying for 8 hours. It would be one magical fire.
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everyone switches their altimeters (really a barometer) to standard pressure. That way, they don't have to keep finding out what the barometric pressure is where they happen to be. Remember, all this was in use long before GPS. So one date, flight level 370 (approx 37,000 feet) might be 36,500 while on another day, it might 37,500. Since everyone used the same system, it all works. When the plane gets near an airport, the air traffic controller tells them the local altimeter reading (a four digit number that matches the barometric pressure in inches of mercury without the decimal point). They dial that into their altimeter and can now read altitude in feet rather than "flight levels".
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Ho MeGu Y wrote:

I think you're wrong. Consumer GPS units are not designed to move at 500+ knots. Also, GPS altitude is inherently less accurate than its XY position. Also, there's the Flight Level factor already mentioned by Pat...
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John Weiss wrote:

You are wrong.
My Garmin Geko has no problems giving altitude, rate of ascent or descent and speed when moving at 500+ mph.
I've also had an older Garmin Nuvi (a mapping gps for use in cars) and I think the highest speed that it registered was 950 km/hr (almost 600 mph). Using a newer TomTop 1400 I remember flying into LAX last year and watching it continuously re-calculating the route based on the sparse roads in the desert southwest I was flying over.

GPS altitude is based on ellipsiodal model of the earth, so the exact verticle position of where sea level is on any given point on the planet will deviate from the elliptical model.
When you have a line-of-sight to a significant portion of the sky from the window of a plane that's 6 or 7 miles in the air, your hand-held consumer GPS can make contact with upwards of 12 gps satellites so the altitude accuracy will be, at worst, 50 to 75 feet. Lat/Long accuracy will be 8 to 10 feet - something my Geko can do from a small open field at ground level.
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On 04/04/2014 07:31 PM, H omeG uy wrote:

They should really have something that screams "DEAR GOD WHY WON'T YOU LISTEN TO ME?" if it has to recalculate more often than x per minute.
OTOH, my Garmin wanted to send me over a cliff on the edge of a mountain TWICE and the GPS in my phone clocked me skiing at 237.3 mph roughly a mile from any place I could actually have been. Definitely not trustworthy.    

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Cheers, Bev
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