reviewing....cant find...

[Airpiraterob]

gotta review, the most obscure things are the easily forgotten but also the most easily remembered <cliff claven>

trying to find the separation between aircraft on the ILS, problem is i cant find the info. dosent it have to do with type of aircarft? (ie: light medium heavy therefore certin distances for each) or is it just 3 miles?

next question:
-computing the VDP? only information i can find is the definition of the VDP being a point on the final approach course that you can descend from and land once the airport is visually in contact. however the answers i keep getting are about descents from altitude to another altitude. (ie X-speed and X miles and X distance=X descent per minute....etc) whats the best answer?

 

[Andy Neill]

For the VDP question, take a look at this thread:

http://forums.flightinfo.com/showthread.php?s=&threadid=16766&highlight=vdp

 

[Airpiraterob]

thanks, for some reason the use is illuding me. i understand the calculations now however how am i to use it in lieu of the usual ILS and VOR and NDB minimums printed on the chart? am i right in guessing that theyre used to move your decision POINT of going around or missed to a distance that you can land from "by normal safe methods and control inputs" ? cause the chop and drop cargo approach dosent go well with passengers.


anything on the separation question?

 

[Andy Neill]

From the ATC Handbook:
References for general separation criteria in radar environment and wake turbulence considerations:
http://www2.faa.gov/atpubs/ATC/Chp5/atc0505.html#5-5-4

References for separation between departing aricraft and between departing and arriving aircraft on the same runway:
http://www2.faa.gov/atpubs/ATC/Chp3/atc0309.html#3-9-6

For VDP:
Lets say you have a non-precision approach you are doing that has a HAT of 600' and your approach speed is 120 kts. The MAP which is over the end of the runway is given as 4.6 DME beyond the FAF. You would adjust from the MAP to establish a VDP at 4.6 - (600/300) miles DME = 2.6 DME. If you don't see the runway at 2.6 DME, yoou will not be able to make a 3 degree descent to the runway. Some might use a last call VDP by dividing the HAT by 400 to let you get a half mile further on the approach (and giving you about a 4 degree descent path to the runway). As a purist (or by company policy) you would say "If I don't see the runway by 2.6 DME (or 3.1 DME for a 4 degree approach), I'll not attempt a straight in. I'll either go around or, if I break out before the MAP, I'll consider doing a circling apporach (MDA permitting)."

The other poster on the VDP thread had some credible thoughts about adjusting the VDP relative to 50' above the threshhold, but I think the alteration of the approach in the roundout is sufficient.