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Chapter 10 Visual flight rules operations
GNSS can be used under visual flight rules for:
- visual navigation
- night VFR RNAV.
VFR pilots may use GNSS to supplement map reading and other visual navigation techniques. This is not an approval to replace visual navigation techniques with GNSS.
Blind faith in GNSS has been blamed for a sharp rise in the number of violations of controlled and restricted airspace by VFR aircraft. You should also be aware of the human factors and technical standards issues associated with different types of receivers and installations.
As well as using GNSS to supplement visual navigation, you can train and obtain qualifications to use GNSS equipment for night VFR navigation in Australian domestic airspace.
If your GNSS performance degrades to the point at which an alert is raised, or you have any other cause to doubt GNSS information integrity, you should stop using GNSS and carry out appropriate navaid failure procedures.
178 seconds to live—VFR into IMC
Flights operating under VFR flying into IMC remains a prominent safety issue, with the Australian Transport Safety Bureau recording an average of 11 occurrences a year, including serious incidents and accidents.
In 1999, a pilot was conducting a VFR flight from Walgett to an airstrip near Merriwa. The Piper Archer had departed from Walgett earlier in the day, but returned a short time later when it was reported that weather at the destination was not suitable for VFR flight.
However, the pilot felt under pressure to complete the flight that day. He continued to monitor the weather by telephoning for weather reports from an automatic Bureau of Meteorology outlet and by contacting a friend near the destination airfield.
The aircraft departed again at 1415, but the pilot never reached Merriwa.
Read the full story and watch the ‘178 seconds to live’ safety video on the Flight Safety Australia.
VFR parallel offsets
International and Australian studies indicate there is some increased risk of head-to-head collision because of the increased navigation accuracy provided to aircraft using GNSS equipment. The following provides guidance to pilots using GNSS for VFR navigation in class E and class G airspace.
- Pilots should use known waypoints to determine tracks and, when broadcasting, give position information in relation to those waypoints to provide meaningful alerted ‘see and avoid’ positions to any possibly conflicting traffic.
- When operating clear of class C and class D, pilots flying VFR using a GNSS navigation source may offset 1.0 nm RIGHT of track. The offsets must not be used in proximity to controlled or restricted airspace because their use could infringe aircraft segregation.
- Prior to entering class C, class D or when changing to IFR, this offset must be cancelled. Offsets should not be included in default receiver settings and pilots should ensure that they are removed from the CDI settings after use.
- Pilots using the offset procedure while operating under VFR at night must ensure that LSALT calculations are based on the offset track.
GNSS as a supplement to visual navigation techniques
Continuing improvements to the accuracy, affordability and usability of GNSS and its flying-related applications have led to an increasing number of VFR pilots using it as a navigation aid. As with most new technologies, some safety issues have arisen and improper use of, or overreliance on, GNSS have been identified as contributing to a number of safety occurrences discussed in Chapter 8.
In addition to the use of GNSS to supplement visual navigation, pilots may undertake training and become qualified to use GNSS equipment as a night VFR navigation aid in Australian domestic airspace.
The following descriptions provide a general summary for educational purposes. Refer to AIP for full details of the approvals.
GNSS may be used under VFR at night as a navigation aid and RNAV system for the following purposes:
- position fixing
- operations on designated RNAV routes and application of RNAV-based LSALT
- deriving distance information for en route navigation, traffic information and ATC separation
- meeting the night VFR requirements for carriage of radio navigation systems and alternate aerodromes.
Lowest safe altitude
Night VFR LSALT can be determined by a number of different methods, including on the basis of GNSS RNAV capability.
Mandatory navigation equipment
GNSS systems used by appropriately qualified pilots may satisfy the night VFR requirements for serviceable radio navigation systems.
GNSS equipment may be used to satisfy the navigation aid aspects of night VFR alternate aerodrome requirements.
Day VFR operations
There are no GNSS qualifications issued for the use of GPS as a supplement to visual navigation. Pilots should review the competency requirements of the day VFR syllabus in regard to the use of navigation aids.
Night VFR operations
Pilots must be competent to use their GNSS unit and comply with a licensing requirements of CASR Part 61.
- GPS may be used in visual flight rules (VFR) operations for visual navigation and night VFR—you will just need to demonstrate competency in GNSS use in night VFR operations.
- Under VFR you cannot fly in cloud and must also stay a specified distance away from cloud, regardless of supplementary GNSS guidance available.
- ‘Blind’ faith in GNSS is often blamed for a sharp rise in the number of violations of controlled and restricted airspace by VFR aircraft.
CASA (2016). 178 seconds to live—VFR into IMC. Retrieved April 2017.
Airservices Australia (2016). Mode S transponders, ADS-B and VFR aircraft. Retrieved April 2017.
Australian National Airline College (2014). VFR Versus IFR Explained. Retrieved April 2017.
CASA (2006). Civil Aviation Advisory Publication 179A-1(1). Navigation using Global Navigation Satellite Systems (GNSS). Canberra.
Skybrary (2015). Using GNSS as a VFR Navigation Tool. Retrieved April 2017.