Originally Posted by
JackReacher
I generally agree with you with one caveat. A ground based glide path (ie ILS GS) is completely different from a GPS based glide path (without WAAS) and will not give you the same thing every time since it’s not baro compensated. As another poster said, you follow the VD path provided by the GPS approach and then adjust accordingly when within the PAPI usable distance, which is 3.4 NM from the threshold, which is about 1000’ on a 3 degree GP. So if the GPS glide path is giving me three white and one red on the PAPI, simply adjust to two red/two white. Be careful of blindly following the GPS based VD pointer.
As long as you don’t exceed or go under the temp limits on the chart, you are still given obstacle clearance if you stay on the magenta glidepath. But I agree you should try and get on the papi. No way these crew was close to being on the magenta glide path. Regardless of the temperature.