CAP 413, Manual

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CAP 413 Radiotelephony Manual
Chapter 6 Page 12
1.7 Direction Finding (DF)
1.7.1 The aeronautical stations that offer a VHF Direction Finding (VDF) service are listed in
the UK AIP AD. Some VDF stations stipulate that the service is not available for en-
route navigation purposes (except in emergency). VDF bearing information will only
be given when conditions are satisfactory and radio bearings fall within calibrated
limits of the station. If the provision of a radio bearing is not possible the pilot will be
told of the reason.
A pilot may request a bearing or heading using the appropriate phrase or Q code to
specify the service required. Each aircraft transmission shall be ended by the aircraft
call sign. A VDF station will provide the following as requested:
a) QDR – Magnetic bearing of the aircraft from the station (i.e. ..... Approach G-ABCD
request QDR G-ABCD).
b) QDM – Magnetic heading to be steered by the aircraft (assuming no wind) to reach
the VDF station (i.e. ..... Approach G-ABCD request QDM G-ABCD).
c) QTE – True bearing of the aircraft from the station (i.e. ...... True bearing, True
bearing ..... Approach G-ABCD request True bearing (or QTE) G-ABCD).
The direction-finding station will reply in the following manner:
a) The appropriate phrase or Q code.
b) The bearing or heading in degrees in relation to the direction finding station.
c) The class of bearing (Class may be omitted after passing the initial bearing).
d) The time of observation, if necessary.
1.7.2 Controllers may request a pilot to make a transmission so that the DF bearing
associated with the transmission may be observed.
1.7.3 The accuracy of the observation is classified as follows:
Class A – Accurate within plus or minus 2 degrees
Class B – Accurate within plus or minus 5 degrees
Class C – Accurate within plus or minus 10 degrees
Class D – Accuracy less than Class C
NOTE: Normally no better than Class B bearing will be available.
Kennington Approach, G-ABCD,
request QDM G-ABCD
G-ABCD, Kennington Approach,
QDM 090 degrees class Bravo
QDM 090 degrees class Bravo,
G-ABCD
True bearing, true bearing,
Kennington Approach, G-ABCD,
request true bearing, G-ABCD
G-ABCD, Kennington Approach, true
bearing 276 degrees true, I say
again, 276 degrees true class bravo
True bearing 276 degrees class
Bravo, G-ABCD
G-ABCD Kennington Approach,
transmit for DF
Transmit for DF, G-ABCD
31 March 2011