Talking about Heights above 3° GS Antenna:
At 300 ft you are, 300/TAN 3°= 5727 ft away from the antenna
At 200 ft you are, 200/TAN 3°= 3816 ft away from the antenna
At 100 ft you are, 100/TAN 3°= 1908 ft away from the antenna
1 Dot GS is 0,2° deviation.
For the 300 feet Point the deviation is 5724*TAN 0,2° = 19,9 Feet
For the 200 feet Point the deviation is 3816*TAN 0,2° = 13,3 Feet
For the 100 feet Point the deviation is 1908*TAN 0,2° = 6,6 Feet
TCH 78 ft is 78/TAN 3° = 1488 feet away from the antenna.
At TCH 50 ft the angle of the glidepath is 50/1488 = TAN 1,924°
So the difference between a 3° GS and the 1,9° GS for the assumed TCH of 50 feet is 3°-1,9°= 1,1 Degree.
A full deflection of the GS needle is 1 Degree. So crossing the threshold at 50 feet will give you more than a full deflection.
This stands for standard temperatures only.
Because with different temperatures the 50/78/100/200/300 feet points are moving.
Inbalance
edited for my bad english. I am ICAO level 4 only. :-(
Last edited by inbalance; 15th February 2009 at 02:10.