>-----Original Message-----
>From: [EMAIL PROTECTED]
>[mailto:[EMAIL PROTECTED]]On Behalf Of Paul Deppe
>Sent: Tuesday, July 09, 2002 4:31 PM
>To: FGFS-Devel
>Subject: RE: [Flightgear-devel] GS needle sensitivity.
>
>
>> I had someone recently comment that they thought the glide slope
>> needle was too sensitive in FG. Can anyone comment on this? What
>> sort of needle range relative to how many degrees off the target glide
>> slope should we be seeing? This person suggested 2 'dots' per degree
>> off the glide slope (but they aren't a pilot and haven't flown any
>> "real" instrument approaches.) I thought I had investigated this and
>> had done it correctly when I first wrote the code, but it would be
>> nice to verify that we are still doing this right since the question
>> has come up (and given that the 2d panel instrument can also scale the
>> values, there is more than one place an error could creep in.)
>
>Gents,
>
>Glideslope beams are designed to be 1.4 degrees "tall", that is, +/- 2 dots
>(full scale) deviation on the gauge is equal to +/- 0.7 degrees glidesope
>deviation, or 0.35 degrees per dot. This is the same for all standard
>ILS's.
This is correct.
>
>The localizer beam width is designed to produce +/- 2 dots deviation at +/-
>700 feet deviation from centerline at the runway threshold. The localizer
>scale sensitivity in degrees per dot is therefore a function of the
distance
>from the threshold to the localizer antenna.
This is worded weird. I would word it like this (this is from the diagram
in the FAA instrument rating written exam).
The glideslope is a beam 1.4 degrees thick. It is pointed 3 degrees up from
the horizon starting at the 1000' foot mark down the runway from the
threshold. At 1300' from the threshold you are at an altitude of 100' above
touchdown zone. If you are off the GS by 2 dots at the 1300' mark you are
off by 28' (so either 72' or 128' above the touchdown zone). If you are
5.6nm from the threshold (the Outer Marker) and you are off by 2 dots you
are off by 420' up or down. The target altitude at that point is 1500'
above the touchdown zone.
Here is a table of what 1 dot or 2 dots mean at different distances.
Distance from threshold Target Alt 1 Dot off 2 Dots off
Significance
1300' 100' 14' 28'
Inner Marker
2600' (1/2nm) 200' 28' 56'
Middle Marker
1.9nm 500' 70' 140'
5.6nm 1500' 210' 420'
Outer Marker
Ryan
_______________________________________________
Flightgear-devel mailing list
[EMAIL PROTECTED]
http://mail.flightgear.org/mailman/listinfo/flightgear-devel
