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(ADF) Finder Direction Automatic 7
Figure 7.11 shows an aircraft maintaining a relative bearing of 360°, with a crosswind from the left. As a result a curved track will be followed.
Figure 7.11 Homing Making no Allowance for Drift
Tracking Inbound
To achieve a required track inbound to an NDB, with a crosswind, the correct method is to allow for the anticipated drift therefore maintaining a constant track. In Figure 7.12, 20° Starboard drift is anticipated, so 20 is Subtracted from track. The aircraft is heading 060° with a relative bearing of 020°.
Figure 7.12
In Figure 7.13, 28° Port drift is anticipated, so this is added (Plus) to the track value. The aircraft is heading 108° with a relative bearing of 332°.
Figure 7.13
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Tracking Outbound
Figure 7.14 shows an aircraft maintaining the required track outbound from an NDB in zero wind (zero drift) conditions. The aircraft is heading 260° and has a relative bearing of 180°.
Figure 7.14
Figure 7.15 shows an aircraft maintaining a track of 100° in crosswind conditions where the drift is known. 23° of Starboard drift is anticipated, this is Subtracted from the track, therefore the heading is 077° with a relative bearing of 203° from the NDB.
Figure 7.15
In Figure 7.16 20° Port drift is anticipated, this is added (Plus) to track giving an aircraft heading of 110° with a relative bearing of 160°.
Figure 7.16
Automatic Direction Finder (ADF) 7
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7 Automatic Direction Finder (ADF)
Drift Assessment and Regaining Inbound Track
(ADF) Finder Direction Automatic 7
Figure 7.17 Assessing Drift Inbound
Initially, fly the aircraft on the required track with the beacon dead ahead (000° rel.).
Maintain the aircraft heading and watch the relative bearing indicator. If the relative bearing increases the aircraft is experiencing port drift.
Alter heading, say 30° starboard, to regain track. The relative bearing will become 330° when track is regained.
Assume a likely drift (say 10° port) and calculate a new heading to maintain track. When this heading has been taken up, the relative bearing will become 350°.
If the drift has been correctly assessed this relative bearing will be maintained until overhead the NDB. If the relative bearing changes however, further heading alterations and a new assessment of drift will be necessary.
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Drift Assessment and Outbound Track Maintenance
Automatic Direction Finder (ADF) 7
Figure 7.18 Drift Assessing Outbound
In Figure 7.18 it can be seen that with zero drift the RBI indicates 180° relative. With 10° starboard drift, the relative bearing increases to 190°, and with 10° port drift the relative bearing decreases to 170°. To assess drift by this means the aircraft must maintain a steady heading from directly overhead the beacon.
When the drift has been assessed, alter heading port or starboard, by say 30°, to regain track, until the correct relative bearing of 210° or 150° is obtained. The aircraft is now back on track. The heading must now be altered to take into account the original assessment of drift.
Figure 7.19 Determining Drift and Maintaining Track away from an NDB
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