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Recommendation issued to: Civil Aviation Safety Authority

Recommendation details
Output No: R20040015
Date issued: 13 January 2004
Safety action status:
Background:

Limitations of the See-and-Avoid Principle

The following recommendations were issued as part of the BASI Research Report - "Limitations of the See-and-Avoid Principle", 1991. At the time of the issue of that report the six recommendations were not assigned formal recommendation numbers. To facilitate publication of the recommendations and the responses to them, they have been entered into the OASIS database. As a result, the recommendation numbers assigned to them do not reflect the actual recommendation issue date, rather the date that they were entered.

Output text

Safety Recommendation

The CAA should take into account the limitations of see-and-avoid when planning and managing airspace and should ensure that unalerted see-and-avoid is never the sole means of separation for aircraft providing scheduled services.

Note: The Recommendation was issued to the [then] Civil Aviation Authority (CAA) in 1991 and in 2001 the ATSB and CASA agreed that the word 'never' had been overtaken by the Australian Risk Management Standard - See Background to Recommendation.

 

Initial response
Date issued: 29 April 2008
Response from: Civil Aviation Safety Authority
Action status: Open
Response text:

Firstly, we will be using our existing cost benefit formula (which is based on the proven FAA Formula) to mandate Class D airspace where traffic densities require.

CASA also proposes a complete package to address this important issue. Unfortunately, unalerted see and avoid can not be eliminated entirely, as even if primary and secondary radar, Class A airspace, mandatory radio, TCAS and transponders were deployed, there can always be a time, because of human factors or technical breakdown, that unalerted see and avoid becomes the primary means of separation.
The CASA proposal is to do everything we can, while still allocating the safety dollars effectively, to reduce the chance of unalerted see and avoid being the primary means of separation, whilst at the same time educating pilots on how they can improve their scan to improve the effectiveness of both alerted and unalerted see and avoid.

In relation to our package to improve the availability of alerted see and avoid, we have proposed to the airlines that in future, all airports serviced by scheduled services of over 10 passengers must have third party confirmation that the radio is on frequency. This will reduce the chance of an airline/aircraft being on the wrong frequency or the speaker is being deselected. We are also encouraging the fitment of Aerodrome Frequency Response Units which will operate 24 hours per day and reduce the chance of unalerted see and avoid. We are proposing to increase the number of recommended calls at non-tower aerodromes to seven, following the USA procedure. This will greatly assist alerted see and avoid.

In order to reduce the necessity to rely on see and avoid, we will be training VFR pilots to remain clear of areas of IFR traffic density, such as IFR air routes or IFR approach paths. These will be marked on maps in future. In relation to IFR aircraft, we will be training pilots to follow a recommendation to fly .1 nm to the right of track when flying on a marked air route between navigational aids or reporting points when the airway is used for two-way traffic.

In places where a tower is not cost effective and that have RPT services of over 10 passengers, we will have mandatory procedures in relation to alerting.

Further correspondence
Date issued: 12 November 2001
Response from: Civil Aviation Safety Authority
Response status: Closed - Accepted
Response text:

At our meeting on November 3, I undertook to follow up CASA's response to the outstanding recommendations contained in the 1991 BASI research report on the limitations of see and avoid. As you would be aware, most of the recommendations - including those concerning TCAS and the education initiatives - have been implemented and continue to provide positive safety outcomes for Australian aviation.

In respect of the remaining recommendations, CASA provides the following response.

"The CAA should take into account the limitations of see-and-avoid when planning and managing airspace...."

CASA agrees that the limitations of see-and-avoid should be taken into account when planning and managing airspace. Where traffic densities are such that see-and-avoid does not provide the required level of safety, CASA will require Class D or a higher level of airspace.

....and should ensure that unalerted see-an-avoid is never the sole means of separation for aircraft providing scheduled services."

CASA understands the intent of this recommendation but does not agree with its absolute form. The wording of the recommendation reflected its time and was prior to the 1995 Standards Australia AS/NZS4360 Risk Management Standard. CASA also understands that the use of the absolute "never" is not consistent with current ATSB practice.

To accept the absolute form of the recommendation would require the allocation of Class D or higher airspace wherever scheduled services operate. This would result in an allocation of resources that is not commensurate with risk.

ICAO Class E and G airspace specifically has no radio requirement for VFR aircraft. ICAO has introduced both of these classifications with the full knowledge of the limitations of see-and-avoid. ICAO makes no recommendation in relation to scheduled services not operating in these airspace classifications.

Overly discounting the effectiveness of see-and-avoid and devising unique procedures has itself led to unintended consequences that are unresolved. Pilots may scan significantly less and become over reliant on radio alerting through a concept known as diffusion of responsibility. The BASI report RP/93/01 (December 1993) and the continuing incident reports that are being filed listing near misses in mandatory radio Class E and G airspace may support this concern. CASA believes that radio alerting is only effective when the alerting area is small with readily identifiable reporting points so that the alert is specific.

Further correspondence
Response from: Civil Aviation Safety Authority
Response text:

At our meeting on November 3, 1 undertook to follow up CASA's response to the outstanding recommendations contained in the 1991 BASI research report on the limitations of see and avoid. As you would be aware, most of the recommendations - including those concerning TCAS and the education initiatives - have been implemented and continue to provide positive safety outcomes for Australian aviation.

In respect of the remaining recommendations, CASA provides the following response.

"The CAA should take into account the limitations of see-andavoid when planning and managing airspace...."

CASA agrees that the limitations of see-and-avoid should be taken into account when planning and managing airspace. Where traffic densities are such that see-and-avoid does not provide the required level of safety, CASA will require Class D or a higher level of airspace.

....and should ensure that unalerted see-an-avoid is never the sole means of separation for aircraft providing scheduled services."

CASA understands the intent of this recommendation but does not agree with its absolute form. The wording of the recommendation reflected its time and was prior to the 1995 Standards Australia AS/NZS4360 Risk Management Standard. CASA also understands that the use of the absolute "never" is not consistent with current ATSB practice.

To accept the absolute form of the recommendation would require the allocation of Class D or higher airspace wherever scheduled services operate. This would result in an allocation of resources that is not commensurate with risk.

ICAO Class E and G airspace specifically has no radio requirement for VFR aircraft. ICAO has introduced both of these classifications with the full knowledge of the limitations of see-and-avoid. ICAO makes no recommendation in relation to scheduled services not operating in these airspace classifications.

Overly discounting the effectiveness of see-and-avoid and devising unique procedures has itself led to unintended consequences that are unresolved. Pilots may scan significantly less and become over reliant on radio alerting through a concept known as diffusion of responsibility. The BASI report RP/93/01 (December 1993) and the continuing incident reports that are being filed listing near misses in mandatory radio Class E and G airspace may support this concern. CASA believes that radio alerting is only effective when the alerting area is small with readily identifiable reporting points so that the alert is specific.

Further correspondence
Response from: Civil Aviation Safety Authority
Response text:

At our meeting on November 3, 1 undertook to follow up CASA's response to the outstanding recommendations contained in the 1991 BASI research report on the limitations of see and avoid. As you would be aware, most of the recommendations - including those concerning TCAS and the education initiatives - have been implemented and continue to provide positive safety outcomes for Australian aviation.

In respect of the remaining recommendations, CASA provides the following response.

"The CAA should take into account the limitations of see-andavoid when planning and managing airspace...."

CASA agrees that the limitations of see-and-avoid should be taken into account when planning and managing airspace. Where traffic densities are such that see-and-avoid does not provide the required level of safety, CASA will require Class D or a higher level of airspace.

....and should ensure that unalerted see-an-avoid is never the sole means of separation for aircraft providing scheduled services."

CASA understands the intent of this recommendation but does not agree with its absolute form. The wording of the recommendation reflected its time and was prior to the 1995 Standards Australia AS/NZS4360 Risk Management Standard. CASA also understands that the use of the absolute "never" is not consistent with current ATSB practice.

To accept the absolute form of the recommendation would require the allocation of Class D or higher airspace wherever scheduled services operate. This would result in an allocation of resources that is not commensurate with risk.

ICAO Class E and G airspace specifically has no radio requirement for VFR aircraft. ICAO has introduced both of these classifications with the full knowledge of the limitations of see-and-avoid. ICAO makes no recommendation in relation to scheduled services not operating in these airspace classifications.

Overly discounting the effectiveness of see-and-avoid and devising unique procedures has itself led to unintended consequences that are unresolved. Pilots may scan significantly less and become over reliant on radio alerting through a concept known as diffusion of responsibility. The BASI report RP/93/01 (December 1993) and the continuing incident reports that are being filed listing near misses in mandatory radio Class E and G airspace may support this concern. CASA believes that radio alerting is only effective when the alerting area is small with readily identifiable reporting points so that the alert is specific.

 
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Last update 01 April 2011