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Flight MH370: Malaysian radar, passenger phone contact, high-altitudehypoxia



 
 
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  #11  
Old April 4th, 2014, 05:16 PM posted to alt.home.repair,rec.travel.air,misc.consumers
Pat[_20_]
external usenet poster
 
Posts: 1
Default Flight MH370: Altitude issues, flight-recorder operation

On Fri, 04 Apr 2014 10:12:55 -0400, Ho MeGu Y "Ho wrote:

trader_4 wrote:

Another thing no one has mentioned. Malaysian military said they had
it on radar somewhere over the Straits at 29,500 ft. No one AFAIK
has commented on that. That's not a standard altitude.


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.

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".


  #12  
Old April 4th, 2014, 07:54 PM posted to rec.travel.air
nam sak
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Posts: 29
Default Flight MH370: Altitude issues, flight-recorder operation

doesn't really factor in the Malaysian Government lying it's ass off.







On Fri, 04 Apr 2014 12:16:39 -0400, Pat wrote:

On Fri, 04 Apr 2014 10:12:55 -0400, Ho MeGu Y "Ho wrote:

trader_4 wrote:

Another thing no one has mentioned. Malaysian military said they had
it on radar somewhere over the Straits at 29,500 ft. No one AFAIK
has commented on that. That's not a standard altitude.


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.

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".

  #13  
Old April 4th, 2014, 07:58 PM posted to alt.home.repair,rec.travel.air,misc.consumers
John Weiss[_3_]
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Posts: 1
Default Flight MH370: Altitude issues, flight-recorder operation

Ho MeGu Y 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.


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...
  #14  
Old April 5th, 2014, 03:31 AM posted to alt.home.repair,rec.travel.air,misc.consumers
H omeG uy
external usenet poster
 
Posts: 1
Default Flight MH370: Altitude issues, flight-recorder operation

John Weiss wrote:

I've monitored the flights I've been on using hand-held GPS


I think you're wrong. Consumer GPS units are not designed to
move at 500+ knots.


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.

Also, GPS altitude is inherently less accurate than its XY position.


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.
  #15  
Old April 6th, 2014, 05:34 AM posted to alt.home.repair,rec.travel.air,misc.consumers
The Real Bev[_2_]
external usenet poster
 
Posts: 2
Default Flight MH370: Altitude issues, flight-recorder operation

On 04/04/2014 07:31 PM, H omeG uy wrote:

John Weiss wrote:

I've monitored the flights I've been on using hand-held GPS


I think you're wrong. Consumer GPS units are not designed to
move at 500+ knots.


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.


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.

Also, GPS altitude is inherently less accurate than its XY position.


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.


--
Cheers, Bev
" While in high school, we were encouraged to keep a daily journal.
I never liked it, especially when early on I realized that anybody
could find it and read it. Fortunately, the jury never saw it."
-- Anonymous, for obvious reasons
 




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