CNS-ATM Navigation frequently asked questions
- How is the airspace changing?
Under conventional navigation, aircraft flew from ground aid to ground aid using VORs or NDBs. With area navigation, a GNSS provides the aircraft with the location of where it is. In the database of the on-board navigation system are waypoints that, unlike the steel and concrete of ground aids, are virtual (only in numbers).
The aircraft flies between the waypoints and is freed from having to navigate between fixed points on the ground.
- If the satellites already exist and aircraft have GPS in them, what is changing?
PBN sets standards for safe satellite-based navigation, taking advantage of the accuracy satellite systems can provide. In PBN, the navigation specifications are navigation performance standards an aircraft must meet to operate on a specific route or in particular airspace. They are all GPS based, but differ in their accuracy and functional requirements.
For many operators, who have been doing GPS RNAV for years, there will be minimal change. Under PBN, the standard navigation specification for en route navigation will be RNP 2, for terminal procedures (SIDs and STARs) the standard will be RNP 1, and the standard non-precision approach will be RNP APCH – LNAV. These standards equate to the old GPS RNAV EN ROUTE, TERMINAL and NON-PRECISION APPROACH terminology.
- Do pilots' licences or instrument rating endorsements on pilots' licences need to change?
For pilots who are already authorised to use GNSS for primary navigation, there are no changes. Pilots wanting to plan to use GNSS for en route navigation for a flight conducted under the IFR must:
- complete the training specified in CASR Part 61
- have a pilot's licence with an instrument rating that is endorsed for the intended operations.
- I'm a private IFR pilot. Can't I just fly using VORs, NDBs and DME, as I've always done?
No. From 4 February 2016, GNSS is mandatory for all aircraft operating IFR and the Back-up Navigation Network (BNN) is established. On 26 May 2016, (the effective date for AIRAC cycle 1606) the BNN is implemented with 190 navigation aids (NDB, VOR and DME) being decommissioned. Many of the navigation aids being decommissioned are already at the end of their operational lives.
The purpose of the BNN is to provide an alternate means of navigation to enable an aircraft to navigate to an aerodrome where it can land in the unlikely event of its GNSS based system failing. From 26 May 2016, the standard PBN navigation specification to be used for Australian continental en route operations is RNP 2 and for terminal procedures (SIDs and STARs) the standard specification will be RNP 1.
Where a navigation aid is decommissioned and the aid was part of a route or procedure, it will be replaced by an ICAO 5-character waypoint designator. It is therefore important that aircraft operators ensure that they have the AIRAC cycle 1606 navigation database installed in their aircraft on 26 May 2016. Operators should also note that not including RNP 2 and RNP 1 in Item 18 of the flight plan is likely to cause it to be rejected.
- What are the impacts to aircraft operators of the navigation aids being turned off?
Aircraft equipped with TSO C145/146 GNSS will not need to carry a non-GNSS alternate means of navigation. In these aircraft, alternates can be planned for using GNSS. But aircraft equipped with TSO C129 GNSS when a designated alternate is required under the operating rules, the aircraft must carry an alternate means of navigation that is not GNSS. The designated alternate must have a non-GNSS approach available and the aircraft must be equipped to utilise that approach procedure.
For aircraft equipped with TSO C129 GNSS, this means that they will have to carry ADF or VOR equipment in addition to GNSS. With the decommissioning of the navigation aids and the formation of the back-up navigation network (BNN) in May 2016, aircraft equipped with TSO C129 GNSS may find that alternates with suitable non-GNSS approach procedures could impose significant fuel reserve penalties.
- Where are the official instructions and directions for performance-based navigation?
They can be found in CAO 20.91.
- Is CASA going to provide any other instructions or directions?
Yes. Advisory Circulars are now available online; operational information is provided in AC 91.U-01 and airworthiness information in AC 91U-04. These are accessible from the Advisory Circulars list on the CASA website.
- Australian RNAV routes have no PBN designations, so how is PBN being implemented?
From 26 May 2016 all RNAV routes will be designated RNP 2 and RNAV terminal procedures (SIDs and STARs) will be designated RNP 1.
- What are the differences between navigation authorisations for private operations and operations conducted under an Air Operator Certificate, for example RPT and charter operations?
There are no differences at all; the applicant must demonstrate compliance for all navigation specifications that authorisation has been applied for. The authorisation process is exactly the same, the only difference is that private (non-AOC holders) will have authorisations issued using a CASA Instrument whereas AOC holders will have authorisations issued in their Operations Specifications (Op Specs).
Note: CASA is in the process of installing new regulatory management software tools. Until the new systems are installed, charter and RPT operators may have navigation authorisations issued using CASA Instruments.
- What are the navigation authorisations requirements for ferry flights?
There are no differences in the requirements for the navigation authorisations for normal operations and ferry operations. Prior to commencing the ferry operation, the operator must have applied for and been issued with all the relevant navigation authorisations. For each navigation authorisation sought, the operator must demonstrate compliance with the relevant requirements.
CASA comment: AOC holders should conduct ferry operations under the provisions of their AOC to minimise time and costs. Carrying out ferry operations as private operations and then adding the aircraft to their AOC requires two applications and authorisations to be issued.
- What is the linkage between runway approaches, Baro-VNAV and GNSS TSO equipment?
A runway approach requires a published procedure; the lateral guidance is provided by a GNSS based navigation system that has a TSO approval for RNP APCH – LNAV. Aircraft equipped and approved for Baro-VNAV may carry out approach operations that are designated as RNP APCH – LNAV/VNAV.
- If I have ADS-B connected to TSO 129, will I have to update the box?
Unless the aircraft has a separate approval for ADS-B compliance, the GNSS will require upgrading to TSO C145/146 since TSO C129 systems do not output all the information required for ADS-B.
- I am currently flying an aircraft that is RNP 2 capable, what do I need to do between now and February 2017?
For IFR operations, the aircraft will meet the standard en route requirements. Terminal operations will require a system approved for RNP 1. If the aircraft is not already equipped with ADS-B, it will need to be equipped to comply with the relevant ADS-B and Mode S Transponder requirements in CAO 20.18. If the GNSS is not already TSO C145/146 it will need to be upgraded to this standard unless the aircraft has a separate approval for ADS-B compliance.
- Is there a date when an aircraft with a TSO 129 installed will be no good?
TSO C129 will become less useful from 2016: depending on the aircraft and the operation being conducted, IFR aircraft will require the installation of ADS-B no later than 2 February 2017. CAO 20.18 includes provisions for some aircraft requiring ADS-B prior to February 2017. From February 2016 GNSS is required but also the BNN is established at this time. This means that if a TSO C129 GNSS is used, the aircraft must be equipped with ADF and/or VOR and any required alternate must be based on a non-GNSS approach procedure. The combined effect of the BNN and a TSO C129 GNSS means that aircraft may be subject to fuel reserve penalties in order to meet alternate requirements. The move to TSO C145/C146 GNSS means that manufacturers are reducing support for older TSO C129 equipment; this equipment is expected to become obsolescent within the next few years.
- Is there going to be any restriction on access to airspace if you don't have ADS-B installed?
Yes. If the aircraft is not equipped with ADS-B in accordance with the CAO 20.18 requirements access to ADS-B airspace will be restricted. From 4 February 2016, aircraft operating in Class A, B, C or E airspace within the 500 NM quadrant north and east of Perth aerodrome require ADS-B. From 2 February 2017, all aircraft operating IFR need to be equipped with ADS-B.
- How is an operator 'deemed' under CAO 20.91?
- An operator is deemed to hold a navigation authorisation when the aircraft meets the airworthiness requirements for the GNSS installation applicable to the navigation authorisation and the flight crew meet the training and competency requirements. Currently the crew training requirements are defined in CASR Part 61.
- Are foreign operators covered by the deeming provisions?
No. Under the ICAO protocols for international operations, it is the operator's State of Registry or State of the Operator who is responsible for the oversight of the operations being conducted. Therefore, operators operating in foreign States must have authorisations from their home State regulator; these authorisations are accepted by the regulator in the State in which they are operating.
Some foreign operators may not be able to obtain RNP 2 and/or RNP 1 navigation authorisations from their National Aviation Authority because:
- The aircraft flight manual does not contain a statement that it complies with the airworthiness requirements of RNP 2 and/or RNP 1; or
- The National Aviation Authority does not have rules that enable them to issue RNP 2 and/or RNP 1 navigation authorisations.
Since RNP 2 is a relatively new navigation specification, Australia, under the provisions of CASA exemption EX01/16, has approved an acceptable means of compliance for operators holding a GNSS based RNAV 1 and RNAV 2 navigation authorisation. Such operators may operate on Australian continental RNP 2 routes and RNP 1 routes using GNSS based RNAV 1 and RNAV 2. Prior to exercising the privileges of the CASA exemption EX01/16, operators must complete and submit Form 667 to International_ops@casa.gov.au. For further information, refer to the CASA website CNS/ATM – Navigation.
- Some navigation specifications do not require a CASA written authorisation. What does this mean for operators?
The revision to CAO 20.91 on 11 December 2014 removed the requirement for operators to apply to CASA for a PBN navigation authorisation for each navigation specification they intended to use if the Aircraft Flight Manual (AFM) contained statements that the aircraft was approved for each. The specifications affected by this change are RNAV 5, RNAV 1 and RNAV 2, RNP 2, RNP 1 and RNP APCH – LNAV.
The removal of the requirement for the operator to apply to CASA for navigation authorisations means that each operator must assess their operation and each of their aircraft and determine that all the relevant requirements of CAO 20.91 are complied with. AC 91.U-01 provides guidance on the operational aspect of PBN, and AC 91.U-04 provides guidance on the continuing airworthiness aspects of PBN. The PBN Assessors Handbook and Worksheet are available to assist operators with this task. Note that the removal of the requirement for regulator issued navigation authorisations does not change any of the requirements; operators are now responsible for self-assessment.
In addition to the above, if the aircraft AFM contains statements that the aircraft is approved for Radius to Fix Path Terminators (RF Legs), Fixed Radius Transitions (FRT) or Baro-VNAV, these supplemental specifications are also included within the operator self-assessment provisions and may be used in accordance with the provisions of the respective CAO 20.91 Appendices.
- Will there be any changes in Class G airspace?
No, with the exception that aircraft operating above 10,000 feet have required an ADS-B capable Mode S Transponder since 6 February 2014.
- How do I know when I need an oceanic approval?
An oceanic approval is required if you are intending to operate in any Oceanic Control Area (OCTA), Oceanic Flight Information Region (FIR) or in RNP 10 or RNP 4 airspace.
- Under which regulation does the requirement for GNSS TSO C145/C146 come from?
CAO 20.18 Clause 9B (ADS-B requirements), Clause 9D (GNSS requirements) and Appendix XI.
- Do State aircraft have to meet the GNSS and ADS-B equipment mandates stipulated in CAO 20.18?
Legally, State aircraft do not have to meet the GNSS and ADS-B equipment mandates stipulated in CAO 20.18. However, if State aircraft are operating as General Air Traffic (GAT), if they are not compliant with the CAO 20.18 GNSS and ADS-B mandates, their presence in civil airspace could constitute a safety hazard. ATC may therefore limit their access to civil airspace. State operators often voluntarily comply with the civil requirements so that their aircraft are capable of operating as in civil airspace as GAT without restriction.
- I operate a GA aircraft with a stand-alone GNSS – do I fall under the deeming provisions of CAO 20.91?
Yes. The navigation specifications for which a navigation authorisation is deemed depends on the certification standard (TSO) of the installed equipment and compliance with the installation requirements specified in AC 21-36. An Aircraft Flight Manual (AFM) statement that the aircraft is compliant with the requirements for a navigation specification is also acceptable. In flight manuals that use the terms GPS RNAV En Route, Terminal and Non-Precision Approach, these approvals are the equivalent of RNP 2, RNP 1 and RNP APCH – LNAV respectively.
- What is the difference between GNSS only systems and multi-sensor navigation systems (FMS)?
A GNSS only system is one where the area navigation function used GNSS only for the purposes of determining the aircraft's position. For integrated avionics systems, such as the Garmin G1000, if it has multiple GNSS sensors providing input to the area navigation function, it is still a GNSS only system.
A multi-sensor navigation system is one in which multiple dissimilar sensors are connected to the system and their inputs used to determine the aircraft position. Typically sensors are inertial reference systems, DME or VOR. Multi-sensor systems are typically the Flight Management Computer Systems installed in the larger and more capable aircraft.
- Are helicopters subjected to the GNSS and ADS-B equipment mandates?
Yes, the GNSS and ADS-B equipment mandates apply equally to helicopters and other aircraft except where provided for in CAO 20.18 and CAO 20.91.