Recommendation R19970083

Recommendation issued to: Civil Aviation Safety Authority

Recommendation details
Output No: R19970083
Date issued: 20 October 1997
Safety action status:

This recommendation resulted from a study carried out in to violations of controlled airspace.


When pilots were asked when to request a clearance, either in time or distance, answers ranged from 30 minutes down to 2 minutes or 1 NM. At 1 NM, the pilot of an aircraft travelling at 120 kts has only 30 seconds to request a clearance, be identified if in a radar environment, and receive the clearance. At 5 NM, the same pilot has only 2.5 minutes to request and receive a clearance. At anything less than 5 minutes, the call needs to be successful the first time. Any unanticipated problems with the radio can quickly lead to a situation where the pilot arrives at the boundary without a clearance.

AIP OPS 20.2.1 provides general guidance as to when a pilot should request an airways clearance. The section states in part:

In determining how far from the boundary to make the request, the pilot should allow for aircraft performance, and also the possibility of frequency congestion should the airspace be known to be busy.

The publication does not provide specific guidance or suggested distances or times at which to request a clearance.

The Bureau believes that pilots must allow sufficient time to obtain a clearance when approaching controlled airspace or be prepared to hold outside controlled airspace. The Civil Aviation Safety Authority should provide more specific guidance to pilots as to an appropriate time and/or distance at which to request a clearance when approaching controlled airspace.

Output text

The Bureau of Air Safety Investigation recommends that the Civil Aviation Safety Authority provide specific guidance to pilots as to an appropriate buffer when approaching controlled airspace and requesting a clearance.

Initial response
Date issued: 20 October 1997
Response from: Civil Aviation Safety Authority
Action status: Closed - Partially Accepted
Response text:

The following is in response to recommendations R970083 and R970084 contained in BASI Special Study 96254.


In the past, AIP OPS contained a specific distance by which pilots were to have initiated an airways clearance for entry into controlled airspace. With the continuing unacceptably high number of violations of controlled airspace (VCAs), the then Civil Aviation Authority (CAA) came to the view that the nominated distance was being used by a cross section of pilots as the point at which a clearance request should be initiated. With the wide range of aircraft performance involved and differing traffic situations, the CAA considered that the nomination of a distance was not the most appropriate means of identifying the requirement. The present wording at AIP OPS 21.1.6, which requires pilots to consider aircraft performance and possible frequency congestion when determining where the clearance request will be made, results from the Air Traffic Service/Flying Operations Branch review of that situation.

The Civil Aviation Safety Authority is still of the view that with the wide performance range of aircraft involved, it is inappropriate for a specific distance to be specified for the initiation of clearance request and that the present AI P OPS reference provides the best advice to pilots to determine an appropriate point at which to initiate a request. However, the issue is under review as part of the procedures associated with the proposed airspace model (Airspace 2000) which may require that a time be specified to satisfy Air Traffic Control requirement.

Last update 01 April 2011