Explanatory Statement
Civil Aviation Regulations 1988
Instructions — use of RNAV (GNSS) approaches by RNP-capable aircraft
Legislation
Section 98 of the Civil Aviation Act 1988 (the Act) provides that the Governor-General may make regulations for the Act and in relation to the safety of air navigation.
Under subregulation 179A (1) of the Civil Aviation Regulations 1988 (CAR 1988), CASA may issue instructions in relation to Instrument Flight Rules (I.F.R.) flights specifying the method by which an aircraft is to be navigated and how a positive position fix is to be obtained.
ICAO rule changes
It is Australian aviation policy that instrument flight procedures should conform to the International Civil Aviation Organization (ICAO) design rules (ICAO Document 8168, commonly referred to as PANS‑OPS). Approximately 450 RNAV (GNSS) approaches designed in accordance with PANS‑OPS have been commissioned at 260 aerodromes across Australia. Those procedures are designed to be flown by aircraft equipped with self-contained GPS receivers and operated in accordance with instrument CASA 608/08.
However, most modern Australian turbo-jet airline aircraft are equipped with computerised flight management systems (FMS) that are more sophisticated than the GNSS navigation equipment mentioned in instrument CASA 608/08. Such aircraft use GNSS positioning to update multiple inertial reference systems (IRS) employing self‑contained laser guided gyroscopes. These navigation systems are designed to comply with Required Navigation Performance (RNP) standards, and the operating procedures and cockpit displays are related to the RNP capability of the aircraft rather than to a specific GNSS receiver used by other less sophisticated aircraft.
On 25 November 2004, ICAO amended the criteria for RNP approach procedure design to reduce the obstacle clearance widths for RNP procedures. For aircraft capable of RNP 0.30, the new ICAO criteria require a lesser obstacle clearance area than is the case for aircraft using the “basic” GNSS receivers on which current RNAV (GNSS) approach procedures are based. Consequently, all existing RNAV (GNSS) approach procedures can now be flown by RNP 0.30 capable aircraft.
Although equipped with more sophisticated navigation systems, modern airline aircraft are not directly compatible with the relatively simple Australian airworthiness requirements that apply to the use of GNSS by general aviation aircraft. Consequently, special evaluation of each aircraft type has been necessary to approve FMS‑equipped airline aircraft with GNSS updating capability to conduct RNAV (GNSS) approach procedures. Approvals have been given to airlines on this basis, but the process of evaluation and approval is complex and resource intensive. With the change to the ICAO design rules, it is now possible to approve FMS‑equipped aircraft to conduct RNAV (GNSS) approach procedures on the basis of their RNP capability without the need for individual type approval. Virgin Blue International Airlines Pty Ltd, trading as V Australia (V Australia) has applied for such approval for the Boeing 777 aircraft.
The instrument, therefore, contains procedures to allow for the conduct of RNAV (GNSS) approaches by capable of RNP 0.30 performance (the specified aircraft). The RNP capability of an aircraft is specified in the aircraft’s flight manual (AFM) and displayed to the flight crew by the FMS.
RNAV (GNSS) approach procedures provide improvements in safety by allowing runway‑aligned straight-in approaches, the use of automated flight systems, and vertical navigation. The instrument allows the aircraft to use existing RNAV (GNSS) approach procedures, thereby, providing straight-in approach capability to many of the runways in Australia. This offers a significant safety benefit to those operations.
Conditions and procedures
The instrument sets out the conditions to be satisfied by V Australia and its specified aircraft for the approval to apply, and the procedures to be followed, during an RNAV (GNSS) approach.
For example, the AFM must expressly state that the aircraft is capable of meeting the requirements of RNP 0.30. RNAV (GNSS) must not be used to satisfy the requirements of alternate aerodrome planning.
Since these are relatively new procedures, V Australia must verify RNAV (GNSS) approach charts before use and must ensure that RNAV (GNSS) approaches are flown in accordance with authorised instrument approach procedures that have been validated by V Australia. An approach must be discontinued if the RNP 0.30 capability cannot be maintained or if the vertical flight path cannot be maintained above the vertical limitations published in the approach chart.
Legislative Instruments Act
Subregulation 179A (3A) of CAR 1988 declares instructions to be a disallowable instrument. Under subparagraph 6 (d) (i) of the Legislative Instruments Act 2003 (the LIA), an instrument is a legislative instrument for section 5 of the LIA if it is declared to be a disallowable instrument in legislation in force before the commencement of the LIA. The instructions are, therefore, a legislative instrument and are subject to tabling and disallowance in the Parliament under sections 38 and 42 of the LIA.
Consultation
Consultation under section 17 of the LIA has not been undertaken in this case. In accordance with the ICAO standard, similar instruments have been issued to other operators whose relevant aircraft can meet these exacting standards of navigation performance and are expressly endorsed as such by their manufacturer.
The instrument commences on the day after it is registered. It stops having effect at the end of July 2011.
The instrument has been made by a delegate of CASA under subregulation 7 (1) of CAR 1988.
[Instrument number CASA 371/09]