Calcultion

[skyman48]

Would appreciate anyone to explain and the calculation for V.d.f.
for instrument approach.
tks.

[HEATHROW DIRECTOR]

VHF Direction Finding. Two types of approach: 1 where the pilot transmits for several seconds every 30 seconds or so and ATC provides him with QDMs to the station. By interpreting the bearings he receives he can follow an approach procedure to reach the airfield. 2. QGH.. where ATC asks the pilot to transmit about every 30 seconds... the controller obtains bearings on the aircraft and issues headings to fly to carry out an approach. A good QGH controller can be a Godsend.... but is it still used? It's 35 years since I last did one!

VDF can also be used by en route a/c calling a station for a bearing which may then be used for a nav plot.

[BOAC]

Skyman - if you mean a 'VHF Direction Finding Approach' (yes - I am old enough to have done them:eek: :eek: ) it relies on the sytem of using a CRT to display the bearing of a received radio signal (as used on 121.5 for 'triangulation').

The a/c is steered into the overhead by the controller who calls for transmissions by the a/c to establish a homing heading, and when the o/head is detected, steers the a/c onto the appropriate o/b track for the appropriate time before turning it i/b and steering it onto the correct i/b track - all done by calling for check transmissions which show the a/c's bearing from the station on his CRT.

It took a skilled controller and accurate flying and responses by the a/c. Typically DH's of around 6-800 feet could be achieved subject to terrain. It was used at airfields where no radar or ILS existed. Q code 'QGH'.

If you want 'calculations' for this, best wait until one of those 'skilled' ATC controllers comes along and gives away the secrets:D

EDIT: Whoops! There is that very man - we crossed:*