Mt Merapi, Java

Mt Merapi, Java
Mt Merapi, Java early one morning in May 2011

Saturday, May 2, 2009

VFR Navigation Considerations

AIP ENR 1.1 Para 19.2 - 19.5

As a VFR pilot you have two choices:-

1) You may navigate by VISUAL REFERENCE
or
2) You may navigate by the use of RADIO NAVIGATION AIDS

Navigating by visual reference you must:-

- Remain in VMC
- Obtain a positive fix at least every 30 minutes
- Within CTA advise ATC if you discover that the a/c had diverged more than 1 NM from the track given in your airways clearance.

Navigating by Radio Navigation Aids you must have one of the following qualifications:-

- Hold an IR endorsed on the aid/aids
- Hold a Night VFR Rating endorsed on the aid/aids
- Hold at least a PPL and have been instructed by a qualified flight instructor in the use of the aid/aids as the sole means of navigation and you have been assessed as competent to use those aids.

You must:-

- Remain VMC
- Use an approved GPS
- After allowing for 9 deg Track Error either side of FPT, come within the rated coverage of a navigation aid which can be used to fix your position, and you obtain a positive fix at least every two hours.
- When flying at or above BKN clouds consult forecast to ensure VMC can be maintained during the climb, cruise and descent.
- A/c's equipment as per Night VFR CAO 20.18 Appendix IV
- In CTA advise ATC if off track by more than 5 deg from assigned track given in your airways.
When tracking via a VOR, 5 deg is half scale deflection of the CDI. In the unlikely event that you you are tracking via a localizer you must also advise ATC if you have diverged more than half scale deflection on the localizer.

AIP ENR 1.1 Para 17.4.6 describes the approved methods of obtaining a fix based on radio navigation aids. They are:-

1) The intersection of 2 or more radio position lines at an angle not less than 45 deg

2) The passage of the a/c over the NDB, VOR or DME station (Station Passage)


If the aids are NDBs - if a positive fix is based on the intersection of 2 position lines from NDB alone, then both NDBs must be within 30 miles of the aircraft no matter what their rated coverages might be.


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