PDA

View Full Version : deflections on the ILS

atila_101
23rd Apr 2011, 16:21
Hi there guys,

After carefully trying to spot the answer, is there anyone out there that can get to know the answer to those questions?

If you are at 200 ft. DH and are 1 dot deflection on the localizer, how far in feet is it?
If you are at 200 ft. DH and are 1 dot deflection low on the GS, how many feet is that?

welliewanger
24th Apr 2011, 03:14
I'm not sure that the figures are published, but they can be derived using what we already know.

3 degree glideslope
At 200' that's 3822 feet away from the antenna (the length of the hypotenuse)

The glideslope is 1.4 degrees from full "Fly up" to full "Fly down"
That's 93.38 feet.
Half that gives you the hole you're allowed to fly through (1 dot up to 1 dot down deflection) i.e. 46.69 feet
Half that gives you what 1 dot deflection is: 23.345 feet.

The localizer is 5 degrees wide (2.5 left to 2.5 right)
That's 333.11 feet
Half that gives you the lateral hole you're allowed to fly through (1 dot left to 1 dot right) i.e. 166.55 feet
Half that gives you 1 dot deflection: 83.28 feet.

So 1 dot vertically is 23.345 feet
1 dot laterally is 83.328 feet