Airspace buffer 3

22.03.2010

Submission:

The New Zealand perspective

The examples provided are talking about two quite different things. Controlled airspace containment designed for protection of aircraft against other uncontrolled aircraft is not the same as the separation from Special Use Airspace (SUA) which may be designated for many reasons, including non-safety reasons like conservation protection airspace.

Controlled Airspace Containment
A 300ft controlled airspace containment does not provide a 500ft separation from VFR operating outside controlled airspace. An IFR aircraft can be 200-300ft below an assigned altitude, depending on whether it is RVSM airspace or not. As far as controlled airspace containment goes, we use a minimum 500ft and 2 NM when operating within radar airspace or on an RNAV track, or 3 NM otherwise.

SUA Separation
What is being talked about is an ATC tactical separation standard when applying 500ft/1000ft to SUA. While it may be appropriate for ATC to use a generic separation standard as it is tactical decision-making and ATC may not be able to ascertain the internal buffers or the activity within SUA, procedure design is a strategic assessment. As such a designer can assess the sort of activity and with appropriate guidance, and apply a standard suitable to the safety risk. For example, a danger area containing a jet efflux or an explosives hazard is considered safe at the upper limit of the danger area. To apply a 500ft buffer on top of that would defy logic. On the other hand, a SUA containing flying activity will need a buffer unless there is already an internal buffer built into the airspace.

I cannot imagine why it is necessary to use 2000ft vertical and 5 NM lateral separation from SUA unless one was entirely uncertain as to the probability of containment with the SUA - which is why we use an extra 500ft on top of danger areas designed for rocketry and volcanic hazard zones. If it is acceptable to bring an IFR aircraft to 75 m (246ft) above terrain then it would appear to be somewhat conservative applying a multiple of this standard above a SUA, unless the containment within the SUA was not certain.

To prevent any confusion, we have decided as a State to confirm that each SUA either has an internal buffer, or has no buffer with the same result - the safety hazard of the activity contained at the upper limit is considered to be zero. As far as lateral separation is concerned, the same principle applies in that the lateral boundaries of the SUA are considered to contain the risk - hence a VFR aircraft can operate right up to the boundary or cross at the upper limit of the SUA. So as long as the primary area of the design does not overlap the SUA we do not require an extra lateral buffer.

It goes without saying that States that do not establish internal buffers within SUA will have to add an external buffer where necessary. The minimum internal buffer we use is 200ft and the upper limit is usually rounded up to the next VFR cruising level to obtain the upper limit of SUA.

Len Wicks – ATS, CAA New Zealand