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Chapter 5 Aircraft equipment

Receiver standards

Aircraft equipment certified for different operations is measured against a technical standard. These standards are developed by regulators across the globe including:

US Federal Aviation Administration as a technical standard order (TSO)
European Aviation Safety Agency as a European technical standard order (ETSO)
CASA as an Australian technical standard order (ATSO).

Pilots can identify the TSO status of GPS equipment by referring to the compliance stamp on the receiver, or by referring to the operating handbook in the aircraft. Reference to a manufacturer’s model number is not a guarantee of TSO certification.

Non-TSO

Non-TSO GPS receivers do not have to meet any regulatory standards for power supply, installation, lighting, database, integrity monitoring or performance. For example, many hand-held units not identified as suitable for aviation purposes are unable to operate when the aircraft groundspeed exceeds 99 knots.

Navigation information from non-TSO equipment should be treated with extra care until verified by another source.

Day VFR

CASA does not prescribe any required equipment standards and both panel-mount and hand-held equipment may be used for day VFR operations. Non-TSO equipment can be used to supplement visual navigation under VFR.

Night VFR

For night VFR operations you can also use a non-TSO receiver to supplement visual navigation, but such equipment cannot be used to meet alternate aerodrome, mandatory aircraft equipment, or flight crew qualification requirements.

IFR

A non-TSO receiver does not meet any of the requirements for IFR navigation.

Safety first with avionics

To ensure safety, pilots must use GNSS properly. Here are some safety tips:

This table contains safety tips with avionics
Advice	Risk
✓ Use appropriate standard avionics equipment	Hand-held and panel-mount VFR equipment does not ensure the integrity and reliability needed for IFR and some night VFR applications.
✓ Use a database valid for the operation	Many non-aviation databases lack accuracy, and currency is critical for operations relying on GNSS for navigation clear of terrain, obstacles and airspace boundaries.
✓ Check that all procedures that could be required are present in the database	Data storage limitations have resulted in some manufacturers omitting certain data, such as small aerodromes, from the receiver database.
✓ Always carry and use current VFR charts, as they are the primary reference for navigation	VFR receivers can be used to supplement map reading in visual conditions. Some VFR units show airspace boundaries and terrain, but there is no standard for this data and no guarantee that the depiction is correct.
✓ Portable receivers and related cables should be positioned carefully in the cockpit	Avoid the potential for electromagnetic interference (EMI), and to avoid interfering with aircraft controls.
✗ Don’t rest the GPS on the glareshield near the magnetic compass	This can create electromagnetic interference. Be aware also of the potential for EMI from mobile phones and other personal electronic devices.
✗ Do not be tempted to design your own approach	Approach designers receive special training and use specific tools. There are many levels of validation before an approach is commissioned.
✗ Never fly below published minimum altitudes while in instrument conditions	Accidents have resulted from pilots placing too much reliance on the accuracy and integrity of GNSS.
✗ Don’t rely on a backup battery to give a navigation solution following an electrical failure	The backup battery may also fail, so additional redundancies should be employed. Pilots should continue to use and practise navigation skills by running a basic plot at all times.
✗ Resist the urge to fly into marginal weather when navigating VFR	The risk of becoming lost is small when using GNSS, but the risk of controlled flight into terrain or obstacles increases in low visibility.

Directions for GNSS use

There are various requirements for the use of GNSS in an aircraft. Details are in CAO 20.91 but in summary:

If a GNSS database contains details of waypoints and navigation aids that are published in maps and charts required to be carried in the aircraft, those details must not be capable of modification by the aircraft operator or flight crew. This does not prevent the storage of ‘user-defined data’ within the equipment.
The database must also be current and provided by an approved supplier.
The manufacturer’s operating instructions for the GNSS receiver must be carried in the aircraft, in a place easily accessible to the pilot.
If the aircraft is engaged in commercial operations, the operating instructions must be incorporated in the aircraft’s operations manual.
GNSS equipment must be operated in accordance with its operating instructions.
Additional requirements relating to the operation of GNSS equipment may be incorporated in an aircraft’s flight manual, if they are consistent with the operating instructions.
Manually-entered data must be cross-checked by at least two flight crew members for accuracy.
In the case of a single-pilot operation, manually entered data must be checked against other aeronautical information, such as current maps and charts.

Navigational data

Data integrity

A significant number of data errors in general applications occur as a result of human error during manual data entry. Whenever possible, navaid and waypoint positions should be derived from a commercially prepared aviation database which cannot be modified by the operator or crew.

In some situations, it may be necessary to create ‘user’ waypoints by manual entry. In this situation, pilots are responsible for the integrity of the data and must follow CASA’s directions for cross-checking. Manually entered data must not be used for navigation below the lowest safe altitude (LSALT) or minimum sector altitude (MSA), unless specifically authorised by CASA.

Stored user waypoints and stored flight plans are considered manually entered data and must be checked prior to use.

Database currency

Many VFR databases do not have an expiry date, as the VFR equipment is intended only to supplement visual navigation using current charts and documents.

All IFR databases have an expiry date, as data currency (integrity) is critical to safe navigation without visual reference.

The principal requirements relating to GNSS navigation data are:

GNSS navigation requires a current database appropriate to the operation
only data from a current database should be used for IFR flight.

GNSS navigation database maintenance

Quality control of the navigation database includes the maintenance required to update it. Some equipment may require a maintenance authority from CASA. They can also provide advice for particular GNSS units.

WGS84 coordinate system

Waypoint coordinates, particularly those used for approach and landing, must be based on the same geodetic reference system used by satellite positioning systems. ICAO and Australia have adopted the coordinate system known as the World Geodetic System of 1984 (WGS84) as the common geodetic reference datum for civil aviation.

Pilots and operators should ensure that WGS84 is selected as the default geodetic reference in their GPS receivers.

Equipment failures

Potential operating failures for GNSS units

Although very unlikely to occur, potential errors include:

GNSS constellation failure—pilots can revert to use of ground-based navaids
single satellite failure within a constellation failure—if FDE is functioning, the GNSS unit should locate a new satellite. If no FDE is operating, revert to ground-based navaids
electrical failure or distortion in screen display—reboot device. Commercial operators will have a second GNSS unit fitted, which will likely still be operational.

Common installation problems for ADS-B transponders

Over the past years the following installation faults have repeatedly occurred. It is strongly recommended that the LAME use an ADS-B capable transponder test set.

This table contains common installation problems for ADS-B transponder
Fault	Advice
Incorrect setting of ‘SIL’ value for DO260A/B transponders	Needs to be 2 (10E-5) or 3 (10E-7).
Incorrect 24-bit address	Ensure ICAO 24-bit address matches the CASA-assigned code.
Incorrect Flight ID	Domestic aircraft should not include ‘VH’ unless on international flight leg. Not ‘N’ as can easily be entered for a common GA transponder.
Incorrect software version in GPS or transponder	Regularly update software and navigation database.
NUC or NIC set to 0	NUC or NIC should not be 0, because it indicates the data has no integrity.
Non-compliant ADS-B transponder installed	It MUST be disabled.

Pre-flight requirements checklist

All pilots (VFR and IFR) must have checked and completed the following:

Battery power supply
Database must be current
Pilot operating handbook (POH)
NOTAMs check RAIM and planned outages
Flight review check if current
EFB, maps and charts packed and accessible in cockpit
SARTIME lodged
Personal administration up-to-date licences, medicals and required memberships

IFR requirements in addition to those for all pilots include:

Approach appropriate instrument rating
Currency 90 days
Receiver must be correct TSO for the type of operations
Installation IFR with baro-aiding if available
Manual must be on the aircraft
RPS RAIM prediction service (RPS) must be used for planning
Report any GNSS interference or database errors

Key points

For day VFR operations, CASA does not prescribe any required equipment standards and both ‘panel-mount’ and ‘hand-held’ equipment may be used. Non-TSO equipment can be used to supplement visual navigation under VFR.
For night VFR operations you can also use a non-TSO receiver to supplement visual navigation, but such equipment cannot be used to meet alternate aerodrome, mandatory aircraft equipment or flight crew qualification requirements.
Portable receivers and related cables should be positioned carefully in the cockpit to avoid the potential for electromagnetic interference (EMI), and to avoid interfering with aircraft controls.
For IFR operations, GNSS navigation data must be drawn from a current database appropriate to the operation and only data from a current validated database may be used for navigation below the LSALT or MSA.

Resources

References

CASA (2006). Civil Aviation Advisory Publication 179A-1(1). Navigation using Global Navigation Satellite Systems (GNSS) Canberra.

CASA (2014). GPS guides to distraction. Flight Safety Australia, November–December. Retrieved April 2017.

CASA (2014). Performance-Based Navigation. Canberra.

CASA (2015). Advisory Circular 91.U-01 Navigation authorisations. Retrieved April 2017.

The navigational component of CNS/ATM is performance-based navigation or PBN, which is becoming more common worldwide. For more than 15 years, Australian aviation has been adopting GNSS-based area navigation in place of ground-based navigation aids such as non-directional beacons (NDB) and VHF omni-range (VOR) for the en route, terminal and approach phases of flight.

This chapter will introduce PBN, discuss PBN-based approach designs and look at deeming provisions for GNSS-equipped aircraft.

Airspace