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
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
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.
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.
Don't confuse altitude with "flight level". Above 18,000 feet,
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".
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
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.
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
" While in high school, we were encouraged to keep a daily journal.
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