Notice of Proposed Rule Making -
Proposed Amendment to Civil Aviation Orders 100.5, 108.56, AD/RAD/43, AD/INST/8 Amdt 4 and AD/INST/9 Amdt 6
The primary method used by pilots to monitor and maintain a desired altitude is with a barometric altimeter. It works by measuring ambient air pressure (static) and providing a display to the pilot in units of height. These instruments, whether they are aneroid based or solid state, need to be checked on a regular basis to ensure that what is being presented to the pilot is accurate. This is particularly critical during approach and departures that have terrain obstacles in close proximity and in ensuring adequate separation between aircraft during flight.
The Civil Aviation Regulations 1988 (CAR), Division 2 details the obligations that the holder of the certificate of registration has regarding maintenance. In particular, CAR 39 refers to Class A aircraft and CAR 41 to Class B aircraft. These regulations require (at sub-paragraph (2)), that the aircraft must not be used unless there is provision for the maintenance of all aircraft components included on or fitted to the aircraft. The ADs, identified above, were introduced to ensure that certain systems fitted to the aircraft were maintained to a known standard.
AD/INST/8 Amdt 4 and AD/INST/9 Amdt 6 currently require either:
- the pressure altimeter/s fitted to an aircraft to be tested every two years in accordance with the nominated altimeter maintenance standard; or
- all aircraft instruments and instrument systems to be tested in accordance with specified requirements every three years.
Following correspondence from industry regarding current altimeter setting procedures, a review of those procedures exposed an indirectly related anomaly in published material regarding altimeter maintenance standards.
Conflicting maintenance standards that are defined for aircraft operating under the Visual Flight Rules (VFR) and Instrument Flight Rules (IFR) effectively allow aircraft with altimeters maintained to different standards to operate in the same airspace, which in the worst case scenario, could result in a loss of separation between the two aircraft.
With the introduction of Wide Area Multilateration (WAM) systems into the Sydney (SYDWAM) area as well as Tasmania (TASWAM) accurate altitude information, broadcast via the Mode C transponder, is essential for Air Traffic Control. This would apply to aircraft transmitting Mode C information regardless of operation under either the VFR or IFR.
An unintended consequence of allowing a choice of actions within the ADs has been identified. Opting to do the pressure altimeter check has been interpreted that the other aircraft instruments and instrument systems do not have to be checked for accuracy. This interpretation may result in the degradation of the accuracy of critical aircraft instruments and does not comply with the intent of CAR 39 or 41 (as applicable).
How to respond
Comment period now closed
Contact: Charles Lenarcic, Project Officer
- Addendum to NPRM 1101CS - Proposed Amendment to CAOs 100.5, 108.56, AD/RAD/43, AD/INST/8 Amdt 4 and AD/INST/9 Amdt 6
- NPRM 1101CS - Proposed Amendment to Civil Aviation Orders 100.5, 108.56, AD/RAD/43, AD/INST/8 Amdt 4 and AD/INST/9 Amdt 6
- Annex A - Proposed Amendments to Civil Aviation Order - CAO 100.5 - Additional maintenance requirements - pitot-static systems, pressure altimeters, airspeed indicators and fuel quantity gauges