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Setting altimeters with no radio



 
 
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  #131  
Old November 13th 06, 08:57 PM posted to rec.aviation.piloting,rec.aviation.student
Mxsmanic
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Default Setting altimeters with no radio

Newps writes:

It's integral to the system.


It's completely separate.

You receive WAAS from a satellite.


Not a GPS satellite.

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  #132  
Old November 13th 06, 09:16 PM posted to rec.aviation.piloting,rec.aviation.student
Scott Post
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Posts: 30
Default Setting altimeters with no radio

In article ,
Mxsmanic wrote:

This is not a sandbox, and I don't
have time to play.


You've got to be kidding. Count your posts.

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Scott Post
  #133  
Old November 13th 06, 09:17 PM posted to rec.aviation.piloting,rec.aviation.student
Denny
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Posts: 562
Default Setting altimeters with no radio

I recently experimented with flying a GPS approach using the GPS
reported altitude as the "altimeter"... First, I flew the GPS approach
track making notes as to the altimeter reading versus the GPS reported
altitude on two GPS units in the cockpit...

Now, knowing the average local offset between the GPS datum circle and
the local ground altitude as reported by the local barometric pressure
altimeter the official pair of altimeters in the pilots lounge... I
wound up with 79 feet as my averaged offset between the GPS datum plane
and the local altimeter... Notice I am emphasizing the word 'local'
here... Your findings will differ with your area and with what they are
doing down inside that Colorado mountain at any given instant...... A
local WAAS transmitter and a WAAS receiver in my plane would, of
course, narrow that altitude difference... Also note the altitude
delta I found is almost within allowable altimeter error...

Anyway, the second trip around I concentrated on flying the altimeter
and IVSI on the
Garmins instead of the altimeter - jeez, are they twitchy; according to
them I never did establish level flight, they always showed either
climb or descent, albeit usually at a rate of ~10 or 20 fpm... Trying
to fly for real with an altitude instrument this twitchy would be
exhausting.. The descent phase on the various legs of the approach was
interesting but doable...

So, my little experiment shows that one can do a GPS approach - after a
fashion - using the GPS altitude reporting... Knowing in advance what
the local differential between the GPS and the cold hard ground would
be nice...

I intend to next fool around with using the GPS IVSI for flying an ILS
in place of the glide slope... I have done this with the barometric
IVSI and had the radar guys watch me... Two times out of three they
said they could not see any divergence... The one time they did see it
I was definitely off the glide slope as I got sloppy on speed control
and wound up too fast...

Fun stuff to do as opposed to droning around in circles...

denny

Newps wrote:
"Mxsmanic" wrote in message
...


No, it is not. It's especially dangerous for RVSM flight, but it's so
inaccurate that it should never be used for anything,


Your complete misunderstanding of the GPS system is showing. I have two
GPS's in the plane, one panel mount and one portable. It is rare that
either one is ever off by more than 100 feet in altitude. Using GPS for
your altitude for VFR flight would be perfectly fine.


  #134  
Old November 13th 06, 09:44 PM posted to rec.aviation.piloting,rec.aviation.student
Newps
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Default Setting altimeters with no radio



Mxsmanic wrote:

Newps writes:


Exactly, a system. WAAS is part of that system.



No, WAAS is a separate system.


Wrong, as usual. It's all part of the same system.
  #135  
Old November 13th 06, 09:45 PM posted to rec.aviation.piloting,rec.aviation.student
Newps
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Default Setting altimeters with no radio



Mxsmanic wrote:

Newps writes:


It's integral to the system.



It's completely separate.


You receive WAAS from a satellite.



Not a GPS satellite.


A satellite is a satellite. The information that spews forth from that
satellite is just information that my receiver makes use of.
  #136  
Old November 13th 06, 09:46 PM posted to rec.aviation.piloting,rec.aviation.student
Doug[_1_]
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Posts: 248
Default Setting altimeters with no radio

It's not something you need to know, in order to use the box.

  #137  
Old November 13th 06, 09:50 PM posted to rec.aviation.piloting,rec.aviation.student
Steven P. McNicoll[_1_]
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Posts: 660
Default Setting altimeters with no radio


"Barney Rubble" wrote in message
...

But it would be kind of weird to be above 10K where a Mode-C transponder
is required, but not have a radio or altimeter...


I've been above 10K without a transponder or radio, it didn't seem weird to
me at all.


  #138  
Old November 13th 06, 10:34 PM posted to rec.aviation.piloting,rec.aviation.student
mike regish
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Posts: 438
Default Setting altimeters with no radio

Thanks.

mike

"peter" wrote in message

You're thinking of height above the ellipsoid, which can be hundreds of
feet different from height above the geoid. But the geoid does
represent the mean sea level height - including in places that are far
from the sea. Internally GPS receivers generally initially calculate
height relative to the ellipsoid model of the earth's shape (using the
WGS-84 model parameters). However, recent models with which I'm
familiar then apply a correction term based on an internal lookup table
to convert the ellipsoid height to the geoid height (equivalent to
height above MSL) at that particular location. See:
http://www.esri.com/news/arcuser/0703/geoid1of3.html
The altitudes that end up being displayed by the GPS after its internal
correction are therefore based on elevation above MSL with some
measurement uncertainty that's dependent on the current satellite
geometry.



  #139  
Old November 13th 06, 10:36 PM posted to rec.aviation.piloting,rec.aviation.student
mike regish
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Posts: 438
Default Setting altimeters with no radio

Wow. That's news. What the hell are all these GPS companies trying to sell
us?

mike

"Mxsmanic" wrote in message
...
Neil Gould writes:

Ever hear of WAAS?


Yes. And it's not part of GPS.

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  #140  
Old November 13th 06, 10:41 PM posted to rec.aviation.piloting,rec.aviation.student
mike regish
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Posts: 438
Default Setting altimeters with no radio

No. Famous last words are usually "Oh ****."

mike

"Mxsmanic" wrote in message
...
Travis Marlatte writes:

The only ATC clearances for a pressure altitude would be in the flight
levels. Since the question was about setting a pressure altimeter, I
would
say that the flight levels are irrelevant. Below the flight levels, ATC
clearances are for pressure compensated altitude above MSL, so yes it is
based on pressure and not true altitude but close enough. My GPS gives me
a
calculated altitude above a theoretical sea level that's also close
enough.


"Close enough": famous last words.

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Transpose mxsmanic and gmail to reach me by e-mail.



 




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