Please note this is an html version of a draft CASA Advisory Circular AC 91-220(0) initially circulated September 2001; all the CASR 91 series regulations referred to are still not enabled, thus this document has not progessed beyond draft status and furthermore, at July 2014, the CASR 91 series regulations are not applicable to RA-Aus aircraft operations.
However, the Civil Aviation Safety Authority have produced two civil aviation advisory publications applicable to RA-Aus aircraft operations that recommend particular procedures and provide guidance on a code of conduct to allow greater flexibility for pilots when flying at, or in the vicinity of, non-controlled aerodromes. These Civil Aviation Advisory Publications (available on this website) are: CAAP 166-1 'Operations in the vicinity of non-controlled aerodromes' (August 2014) and CAAP 166-2 'Pilots responsibility for collision avoidance in the vicinity of non-controlled aerodromes using 'see and avoid' (December 2013).
This Advisory Circular (AC) provides information to enhance the safety of flight at aerodromes and landing places which do not have an aerodrome traffic control (tower) service in operation. It is intended to give an overview of pilot responsibilities and highlight principles applicable to all pilots who operate at non-controlled aerodromes.
This AC is the first that has been issued on this subject. Advisory Circulars are intended to provide recommendations and guidance to illustrate a means but not necessarily the only means of complying with the Regulations, or to explain certain regulatory requirements by providing interpretative and explanatory material. Where an AC is referred to in a `Note' below the regulation, the AC remains as guidance material. ACs should always be read in conjunction with the referenced regulations.
Non-controlled aerodrome means an aerodrome where there is no aerodrome control facility in operation at the time of a particular take-off or landing.
5.1 CASR 91.220 states the minimum legal requirements for operation of an aircraft at an aerodrome which does not have an aerodrome traffic control service. The regulation requires all pilots to conduct their operations in accordance with standard procedures. The objective is to ensure that each pilot in the vicinity of an aerodrome is aware of any other traffic at the aerodrome, knows the position and intentions of other pilots and can participate in an orderly flow of traffic.
- CASR 91.185 Basic rule "see and avoid"
- CASR 91.190 Operating near other aircraft
- CASR 91.195 Giving right of way
- CASR 91.200 Who has right of way
- CASR 91.205 How to give right of way
- CASR 91.210 How to overtake in flight
- CASR 91.215 Right of way rules aircraft on the ground or water
- CASR 91.220 Operating on or in vicinity of non-controlled aerodromes
- CASR 91.225 Safety during take-off and landing
5.2 Safe operations have been conducted at non-controlled aerodromes for the best part of 100 years, but the basic requirements have always been the same. Non-controlled aerodrome operations work well up to moderate levels of traffic if pilots know the characteristics of the aerodrome, inform themselves well, say what they are doing, keep a good look out and use standard procedures.
5.3 CASR 91.220 imposes a series of common-sense obligations on pilots, the aim of which is to ensure that any hazard associated with non-controlled operations is reduced to the minimum, consistent with the way operations at non-controlled aerodromes are actually conducted by sound pilots.
5.4 ATC may be placed into operation at an aerodrome without a tower for special purposes such as an air display, disaster relief or other significant event. Times of operation of a tower facility are promulgated in ERSA, and imposition of tower-type aerodrome control at other places will be notified by NOTAM.
6.1 Factors. The principal factors or elements relating to operations in VMC are:
6.2 Operational needs and manoeuvres.There can be varied operational needs and manoeuvres conducted at a non-controlled aerodrome:
- the type of operation, i.e., agricultural, pilot training, air transport etc;
- type of aircraft;
- wind speed and direction;
- number of runways;
- obstructions and topography in the vicinity of the aerodrome;
- built up areas and local noise sensitivity;
- number of aircraft;
- other activities, i.e., parachuting, glider flying, flight training;
- whether all aircraft are radio-equipped; and
- proximity of controlled airspace and low-level operations;
- non-communicating traffic; and
- non-compliant traffic.
6.3 Safety rules permitting, the pilots of each type of aircraft will want to fly the circuit pattern most suited to the aircraft and the type of operation. Pilots have to give and take relevant information and exercise tolerance and consideration if varied circuit flight paths and experience levels are to be accommodated safely.
- skilled pilots will often want to make smaller circuits than pilots under training or with low recency;
- larger air transport aircraft are expensive to run, and minutes saved make straight-in approaches an attractive proposition;
- helicopters are not restricted to normal circuit patterns and generally operate to stay clear of fix-wing circuit patterns;
- pilots doing actual or practice instrument approaches will often make straight-in or abbreviated approaches to a landing or to a missed approach point on an instrument runway, or will elect to join the circuit from overhead a navigation aid via the most convenient turn to the runway in use;
- agricultural pilots conducting local deliveries may prefer to do a contra or a low-level circuit, or make straight-in approaches on a cross runway (expect any legitimate manoeuvre that will speed up delivery rates);
- parachuting and glider tug aircraft may make steep descents into the circuit area;
- ultralight pilots generally prefer to make low, small circuits, and to overfly terrain with potential for a safe forced landing;
- gliders require winching or towing, often use parallel runways and/or contra circuits, and are committed to land from the time they enter the circuit; and
- trainee pilots require relatively large circuits, don't have reserve capacity to cope with unusual manoeuvres by other aircraft , and can easily be forced to abandon their preferred flight path by other aircraft, including those on normal manoeuvres.
6.4 Wind, and pattern conflicts. Wind direction is generally more critical to smaller aircraft, hence the common provision of a small secondary runway.
6.5 Obstructions, topography, local noise sensitivity and adjacent CTA. Topography and obstructions (transmitting towers, smokestacks and so forth) may restrict circling in some parts of the circuit area, and built-up areas, hospitals, noise sensitive livestock or the like may require modification of normal traffic patterns or dictate close or wide circuits. Adjacent CTA must be avoided unless clearance to enter is obtained. Pilots must make themselves aware of any pattern variations peculiar to an aerodrome prior to operating at that aerodrome.
- If a strong wind favours a short runway the circuit pattern may be complicated because small aircraft will use the short runway while larger aircraft may be forced to use a longer, out-of-wind runway.
- Light winds can make for a difficult traffic situation because pilots are not provided with a cue to use a particular runway, and will prefer to use the runway which is most suited to their operation.
- Where wind direction is not available from other sources, incoming aircraft may have to overfly the aerodrome to see a windsock, and may enter the traffic pattern in conflict with preceding aircraft.
- A difficult situation can arise when an aircraft is established on final leg in conflict with another aircraft taking off in the opposite direction.
6.6 Number of aircraft, activities and communications. The greater the number of aircraft and the more varied the activities the harder it is for pilots to keep track of other traffic. Each pilot must be on the lookout for no-radio aircraft, ultralight aircraft, helicopters, aircraft on crosswind training, aircraft on straight-in approaches and aircraft operating contrary to the recommended circuit direction. Ready communication with other aircraft is vital, but if the traffic level is too high for self-arranged separation each pilot may have to resort to "unalerted see and avoid" techniques. In this situation each pilot should self-announce and try to keep track of other traffic by listening to other broadcasts of aircraft type, position and intention, simultaneously looking out for unannounced traffic. If there is too much traffic for a satisfactory level of safety, comply with the recommended circuit direction, announce your position and intentions, adopt alerted see-and-avoid practices and either land or vacate the circuit as soon as possible.
6.7 Gathering information. Before operating at any aerodrome, listen out, if possible, on the relevant CTAF or UNICOM frequency. Establish that the correct frequency is selected and use UNICOM, ATIS, AWS and/or other traffic to establish the pressure and wind direction, traffic numbers, traffic type and the runway in use. Maintain a good lookout while using radio to arrange self-separation; bearing in mind that excessive RT will decrease safety. Announcements made shortly before committing to particular manoeuvres such as entering a runway, taking off, entering downwind, or turning base give other pilots at the aerodrome a chance to adjust or arrange separation.
6.8 Circuit protocols. All pilots should develop the following habits:
- carry radio, and use it appropriately;
- make turns in the direction recommended for the aerodrome unless there is good reason to do otherwise, bearing in mind that there may be a left-hand pattern when landing in one direction and a right-hand pattern when landing in the opposite direction;
- comply with CASR 91.220 (2) if making a turn contrary to the normal direction for the runway;
- observe the right-of way rules (CASR 91.195, 91.200, 91.205, 91.210 and 91.215 );
- turn at a safe height and speed after take-off, (ideally, not less than 500ft AGL);
- aim to line up above 500ft AGL for landing, and at least 1000m before the threshold; (g) where it is reasonable to do so, follow the approximate flight path of preceding aircraft (beware wake turbulence - never approach below the flight path of any large aircraft). If unable to follow, maintain your position in the sequence and broadcast your intentions if this will require an unusual shape or size to the circuit;
- if possible follow the convention that most fixed-wing aircraft fly the circuit at 1000ft AGL, helicopters at 800ft AGL and jet aircraft at 1500ft AGL;
- if overflying to review the windsock and signal square, do so at 1500ft AGL, (bearing in mind the possibility of jet or instrument practise aircraft at that height).
- be proactive, do not remain silent because other aircraft are broadcasting. Let them know you are there.
In 2010 CASA produced two advisory publications to support CTAF procedures and provide guidance on a code of conduct to allow greater flexibility for pilots when flying at, or in the vicinity of, non-towered aerodromes. These Civil Aviation Advisory Publications (available on this website) are: CAAP 166-1 'Operations in the vicinity of non-towered (non-controlled) aerodromes' and CAAP 166-2 'Pilots responsibility in collision avoidance in the vicinity of non-towered (non-controlled) aerodromes by 'see and avoid'.
7.1 IMC. If the weather is below VMC all aircraft must carry radio and proceed on the basis of a professional level of broadcasting, although the possibility of a pilot operating full broadcast but on the wrong frequencyremains. Visual circuit practice should not be done in weather below VMC, even if the ceiling is above the circling minima. In reduced visibility it is especially important that pilots display anti-collision lights and navigation lights in compliance with CASR 91.590.
Note that the 'ultralight' term used in the CAAPs when recommending a 500 feet circuit height, refers only to those RA-Aus aircraft which have a normal cruising speed below 55 knots, or thereabouts.
There are some variations in the advice given in the CAAPs and in this document. The CAAPs are the superior publications.
CASA has produced an online interactive learning tool titled 'Operations at, or in the vicinity of, non-controlled aerodromes' which is now available at CASA online learning.
7.2 Marginal conditions.There is a possibility that the pilot of an IFR aircraft may assume there will be no VMC traffic, and there a possibility that a VFR pilot may be airborne in conditions too demanding for his or her skills. A saving grace is that traffic numbers are usually fairly low, but there is a need to know what other IFR and VFR aircraft (the latter possibly without radio) are doing and to remain alert. Full use of radio, sight and lights is needed. A pilot should avoid doing repetitive circuits in marginal conditions, and should not fly as PIC if his or her skill levels are not enough to be comfortable in the prevailing conditions.
8.1 In an endeavour to align expectations and lookout with what often happens in real life regardless of rules, the regulation for operations at non-controlled aerodromes does not limit straight-in approaches to certain classes of aircraft. Pilots must be on the lookout for aircraft on straight-in approaches, and any pilot who does a straight-in approach must exercise sound airmanship and observe the relevant rules
8.2 CASR 91.200 requires that, in the event of conflict between a powered aircraft on base leg and a similar aircraft on finals, the lower of the two aeroplanes has the right of way, subject to the courtesy expressed in the rule.
The regulations permit turns contrary to the recommended circuit direction subject to supplementary safety procedures. Left-hand circuits should be performed unless right-hand circuits are recommended for the particular runway, but the pilot may use a contrary direction if it is safe to do so (CASR 91.220 (2)). In assessing the safety of a contrary turn the pilot should take into account, among other things, the prevailing visibility, the probable expectations of other pilots, and the possibility of a missed broadcast.
10.1 Parachuting. Parachuting operations are conducted at many non-controlled aerodromes used by a variety of traffic. Protocols developed by CASA and parachuting organisations are expressed in the AIP. Some of the main elements are:
10.2 Gliding operations.Gliding operations are also conducted at many non-controlled aerodromes used by a variety of traffic. Gliders may also overfly or land at aerodromes where no gliding operation is established. Again, protocols developed by CASA and the gliding movement are expressed in the AIP. Some of the main elements of this are:
- Parachutists are not authorised to drop through cloud, but are not subject to the rules of VMC and may drop through gaps in cloud.
- The dropping pilot must broadcast intentions to drop 2 minutes prior to the planned exit, and must not drop if there is evidence of conflicting traffic.
- All aircraft except balloons must give way to descending parachutists.
- Parachutists will not exit within 15 minutes of the ETA of a scheduled passenger transport flight unless the drop pilot can be sure that all parachutists will have landed before the passenger aircraft has entered the circling area. Similarly, parachutists will not be dropped until a departing scheduled passenger aircraft is clear of the circling area.
- Parachutists' pilots will listen out on both the CTAF and area frequency, and will give an additional call 4 minutes prior to the planned exit.
- Parachutists will avoid conflicting with traffic on the live side of a licensed aerodrome (assuming a live side is defined by aerodrome traffic), nor will they intentionally land on any runway, taxiway or apron.
- Parachutists will not be dropped if another aircraft is conducting an instrument approach, or is expected to commence an instrument approach within 5 minutes after the planned drop.
- If the drop zone is on the aerodrome, the drop aircraft will usually proceed to a drop point upwind from the aerodrome, the distance being proportional to the wind strength and the release height. The exit point can be up to 4 miles upwind, which may at first appear to be clear of the circuit area.
Refer to the AIP or the VFR Flight Guide for further advice about circuit operations, particularly operations at aerodromes and landing places that have special characteristics or which support parachuting, gliding, military, aerobatics or various training operations.
- Gliders may be launched by aerotow, ground-based winch or car tow, or may be self-launching.
- Aerotow and wire launches may involve releases up to 4000 feet AGL.
- Overflying an active wire-launching site below 2000 feet AGL is not advisable.
- Pilots must be aware that if a launch cable breaks during a launch it may lie across a runway until cleared.
- Tug aeroplanes, winches and tow-cars will normally be radio-equipped.
- Gliders must monitor and broadcast on the CTAF if there is a scheduled service at the aerodrome. Elsewhere they must monitor the CTAF if they are fitted with radio capable of using the appropriate frequency.
- At locations where contra-circuits are notified in AIP ERSA there is no dead side to the circuit and all operations below 1500 feet AGL should remain on their own side of the runway. Traffic should join circuit on either an upwind leg over the runway, or a downwind leg.
- Any glider which thermals within 2nm/below 1500 feet AGL of the downwind end of the runway in use must be fitted with VHF and must monitor the CTAF, and are not permitted to interfere with other circuit traffic.
- Powered aircraft must give way to gliders, as gliders are committed to landing once established in the circuit, and may need to return to land if a launch is aborted or if sinking air is encountered after launch.
- Gliders, more so than powered aircraft, may need to vary their circuit patterns and fly a non-standard pattern during landing manoeuvres.
- AIP ERSA contains the details of specific aerodromes and landing places.
- AIP AD contains technical information about aerodrome construction, marking and facilities.
- AIP NOTAMs are used to provide notice of events and changes.
- AIP Supplements and Aeronautical Information Circulars (AIC) are used respectively to convey details about special operations and procedure updates prior to their appearance in the AIP proper.
The need for sound airmanship is at its greatest at a busy non-controlled aerodrome, where all pilots must obtain and use all relevant information, observe the rules, use radio and lights where possible, maintain the best of lookouts, and practice patience and courtesy.
Assistant Director Aviation Safety Standards