Questions 8

8 Questions

Questions

1.Using the CDI shown, what is the aircraft’s QDR?

Figure 8.19

2.Using the CDI shown, what is the aircraft’s QDM?

Figure 8.20

3.Using the HSI shown, what is the aircraft’s QDR?

Figure 8.21

4.Using the HSI shown, what is the aircraft’s QDM?

Figure 8.22

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VHF Omni-directional Range (VOR) 8

In-flight Procedures

Typical uses of VOR by an aircraft equipped with both CDI-type deviation indicator and an RMI are illustrated in Figure 8.23.

	9		12
3			TO			12	15	18
					18
					9				21
0					21
					6				24
OBS	30		27					FR	27
					3
					OBS	0	33	30
									8
					N				(VOR)
					10° DRIFT				Omni-directional Range
				9	12				VHF
			3		TO
					18
									10° DRIFT
		0			21
			OBS	30	27
					Figure 8.23 In-flight Procedures

Radial Interceptions

In Figure 8.23 the aircraft is shown intercepting the 280° radial by flying a heading of about 045°(M), commencing the turn shortly before making good the radial so as not to over-shoot it.

A heading of 090°(M) is selected to allow for starboard drift inbound. So the turn is through 45° taking about 15 seconds. Arrival at the 277 radial should be announced by the Left/Right indicator showing about 1.5 dots ‘fly left’ and the RMI needle pointing a QDM of 097° at which point he would turn onto 090°(M).

InboundTrack-keeping

Having intercepted the inbound radial, the pilot maintains his heading (of 090°(M) in the Figure 8.23 example) and watches the Left/Right needle. Suppose the needle shows a progressively increasing displacement left; then the aircraft is moving to the right of the desired inbound track. The drift allowance is insufficient and a heading of 085° would perhaps be more suitable. The pilot would probably alter heading 30° port on to 060°(M) until the needle centred, indicating the aircraft to be back on track, before trying the new heading of 085°(M) and again watching the needle.

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8 VHF Omni-directional Range (VOR)

(VOR) Range directional-Omni VHF 8

Further alterations of heading may be necessary before the aircraft is settled down on a good inbound heading with the needle reasonably steady in the central position. It is worth visualizing how the RMI would behave during the homing just described.

After the interception, the heading of 090° would show against the heading index, the RMI needle indicating 100° (the required QDM to the VOR).

Station Passage

Overhead a VOR there is a ‘cone (or zone) of confusion’ with a vertical angle of about 60° to 80° (ICAO minimum is 40°). This leads to indeterminate indications over the beacon which at high level extend over a considerable area, for instance out to about 4 NM radius at 30 000 ft.

On the VOR/ILS indicator, the needle swings between hard left and hard right, the OFF flag may appear temporarily, and the TO/FROM indicator changes to FROM. The RMI needle fluctuates and then rotates through 180° to indicate the QDM back to the beacon. At low altitude these station passage indications are rapid; at high altitude they are slow.

Outbound Flight

The aircraft is shown outbound on the 150 radial on the right-hand side of Figure 8.23. The indications are ideal, the TO/FROM flag showing ‘FROM’, and the centralized L/R needle showing the aircraft to be on the selected track of 150°. The information on the deviation indicator is confirmed by the RMI needle showing a QDM of 330 back to the beacon.

If these indications were to change, showing a track error developing, the pilot would normally make a firm heading alteration (typically 30°) to regain track before steering a revised outbound heading appropriate to his revised assessment of drift.

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VHF Omni-directional Range (VOR) 8

Airfield Approach

VHF Omni-directional Range (VOR) 8

Figure 8.24 Example of a VOR DME approach pattern

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