Get a plain-English read of (c) Advisory Circulars (ACs).
Turn the raw legal text into a practical explanation grounded in Manual of Standards Part 173—Standards Applicable to Instrument Flight Procedure Design.
1.1.1 Authority for this Part and CASA’s Commitment to ICAO
1.1.1.1 The Civil Aviation Safety Regulations Part 173 – Instrument Flight Procedure Design establishes the standards pertaining to the design of Instrument Flight Procedures.
1.1.1.2 For the design of:
(a) Instrument Flight Procedures, other than the design of Required Navigation Performance Authorization Required Approach (RNP AR APCH) procedures, the design standards are contained in:
(i) International Civil Aviation Organization (ICAO) Publication Doc 8168-OPS/611, Volumes I and II, also referred to as the Procedures for Air Navigation Services – Aircraft Operations (PANS‑OPS); and
(ii) this Manual of Standards (MOS) which comprises:
(A) additional design standards not included in PANS-OPS; and
(B) differences which are adopted by Australia; and
(C) new or developing standards; and
(b) RNP AR APCH procedures, the design standards are contained in:
(i) PANS OPS; and
(ii) this MOS which comprise:
(A) additional design standards not included in PANS-OPS; and
(B) differences which are adopted by Australia; and
(C) new or developing standards; and
(iii) ICAO Publication Doc 9905-AN/471, also referred to as the Required Navigation Performance Authorization Required Procedure Design Manual (ICAO Doc 9905).
1.1.2 Differences between ICAO documents and standards in the MOS
1.1.2.1 Notwithstanding the above, where there is a difference between a standard prescribed in ICAO documents and the MOS, the MOS standard shall prevail.
1.1.3.2 The regulatory documents establish, for service providers, a comprehensive description of system requirements and the means of meeting them.
1.1.3.3 CASRs establish the regulatory framework (Regulations) within which all service providers must operate.
1.1.3.4 The MOS comprises specifications (Standards) prescribed by CASA, of uniform application, determined to be necessary for the safety of air navigation. In those parts of the MOS where it is necessary to establish the context of standards to assist in their comprehension, the sense of parent regulations has been reiterated.
1.1.3.5 Readers should understand that in the circumstance of any perceived disparity of meaning between MOS and CASRs, primacy of intent rests with the regulations.
1.1.3.6 Service providers must document internal practices (Rules) in their own operational manuals, to ensure the maintenance of and compliance with standards.
1.1.3.7 ACs are intended to provide recommendations and guidance to illustrate a means, but are not necessarily the only means of complying with the Regulations. ACs may explain certain regulatory requirements by providing interpretive and explanatory material. It is expected that service providers will document internal actions in their own operational manuals, to put into effect those, or similarly adequate, practices.
1.1.4 MOS Documentation Change Management
1.1.4.1 Responsibility for the approval of the publication and amendment of the MOS resides with the Branch Head, Airways, Air Traffic and Aerodrome Standards Branch, of the Aviation Safety Standards Division, Civil Aviation Safety Authority (CASA).
1.1.4.2 This document is issued and amended under the authority of the Branch Head, Airways, Air Traffic and Aerodrome Standards Branch.
1.1.4.3 Requests for any change to the content of this MOS may be initiated by:
(a) technical specialist areas within CASA;
(b) instrument approach procedure designers;
(c) ATS service providers;
(d) pilots and ATC staff;
(e) other aviation industry service providers.
1.1.4.4 The need to change standards in the MOS may be generated by a number of causes. These may be to:
(a) ensure safety;
(b) ensure standardisation;
(c) respond to changed CASA standards;
(d) respond to ICAO prescription;
(e) accommodate new initiatives or technologies.
1.1.5 Related Documents
1.1.5.1 These standards should be read in conjunction with:
(a) ICAO Procedures for Air Navigation — Air Operations, Doc 8168‑OPS/611, Volume II — Construction of Visual and Instrument Flight Procedures; and
(b) ICAO Instrument Flight Procedures Construction Manual, Doc 9368‑AN/911; and
(c) ICAO Template Manual for Holding, Reversal and Racetrack Procedures, Doc 9371‑AN/912/2; and
ALS, in relation to a runway, means an approach lighting system for the runway.
AMSL means above mean sea level.
BALS (short for basic ALS), in relation to a runway, means an ALS for the runway that is at least 210 m, and less than 420 m, long.
CASR 1998 means the Civil Aviation Safety Regulations 1998.
CAT I lighting system has the same meaning as in section 9.41 of the Part 139 (Aerodromes) Manual of Standards 2019.
CAT II and CAT III lighting system has the same meaning as in section 9.42 of the Part 139 (Aerodromes) Manual of Standards 2019.
DH means decision height.
FALS (short for full ALS), in relation to a runway, means an ALS for the runway, consisting of a CAT I lighting system, or CAT II and CAT III lighting system, which is at least 720 m long.
GNSS means Global Navigation Satellite System.
IALS (short for intermediate ALS), in relation to a runway, means an ALS for the runway that is at least 420 m, and less than 720 m, long.
kt means knots.
MAPt means missed approach point.
MDA means minimum descent altitude.
MDA/H means minimum descent altitude or height.
MSA means minimum sector altitude.
NALS (short for no ALS), in relation to a runway, means:
(a) no ALS in relation to the runway; or
(b) an ALS, in relation to the runway, which is less than 210 m long.
NM means nautical miles.
RVR means runway visual range.
TIFP means terminal instrument flight procedure.
visibility means the ability, as determined by atmospheric conditions and expressed in units of distance, to see and identify prominent unlighted objects by day and prominent lighted objects by night.