Explanatory Statement
Civil Aviation Regulations 1988
Instructions — RNAV (GNSS) approaches by Qantas B747-400 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.
Instrument CASA 608/08, issued under subregulation 179A (1) of CAR 1988, provides instructions as to how a pilot in command of an aircraft operating under the I.F.R. may use the Global Positioning System (GPS). Among other things, the instrument details the procedures for using GPS for carrying out non‑precision approaches, now referred to as RNAV (GNSS) procedures. It specifies the navigational equipment that must be installed.
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 setting out minimum accuracy requirements, 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 0.3 accuracy, 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 aircraft assessed as RNP 0.3 capable.
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. With the change to the ICAO design rules, FMS-equipped aircraft are now approved to conduct RNAV (GNSS) approach procedures on the basis of their RNP capability. Qantas Airways Limited (Qantas) has applied for such approval for its Boeing 747-400 aircraft.
The instrument, therefore, contains procedures to allow for the conduct of RNAV (GNSS) approaches by Qantas in Boeing 747-400 aircraft capable of RNP 0.3 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, for runway‑aligned straight-in approaches, the use of automated flight systems and vertical navigation. This offers a significant safety benefit to those operations.
Conditions and procedures
The instrument sets out the conditions to be satisfied by Qantas and its specified aircraft for the approval to apply, and the procedures to be followed, during an RNAV (GNSS) approach.
For example, the aircraft FMS must be capable of meeting the RNP 0.3 standard of navigation. Qantas must use with its FMS an approved navigation data base as defined.
The flight crew must comply with the vertical limitations published in the chart for the approach. An approach must be discontinued if the RNP 0.3 capability cannot be maintained, if the vertical flight path cannot be maintained above the vertical limitations published in the approach chart or if the cross-track error is 0.2 nautical mile or more.
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. The instrument is similar to other instruments issued to operators. If in accordance with the ICAO standard, a similar instrument would be issued to any operator whose relevant aircraft can meet the required standard of navigation performance and are expressly endorsed as such by their manufacturer.
The instrument commences on the day after it is registered and stops having effect at the end of 31 December 2011.
The instrument has been made by a delegate of CASA under subregulation 7 (1) of CAR 1988.
[Instrument number CASA 577/09]