Aerodrome Obstacle and Approach Minima Conflict
An operator plans a new scheduled service into a regional aerodrome. The published RNAV (GNSS) approach to Runway 27 has LNAV minima of 480 ft and a missed approach climbing to 3,000 ft. A new 45 m mast has been erected 2.1 NM before the threshold, 180 m left of the extended centreline, penetrating the published obstacle limitation surfaces. The AIP has not yet been amended and the approach chart still shows the old obstacle data. The aerodrome operator says the mast is 'outside the runway strip' and therefore irrelevant. The operator's dispatch office intends to use the existing LNAV minima unchanged.
1. Assess the regulatory and operational implications of the un-amended obstacle.
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The mast matters. Under Annex 14 and the national aerodrome rules, obstacle limitation surfaces (approach, transitional, take-off climb, etc.) protect the approach and departure paths. A 45 m mast at 2.1 NM, 180 m off-centreline, penetrating the OLS, is an obstacle that must be:
- Assessed for effect on the published procedure, minima, and missed-approach gradient.
- Promulgated - the AIP/charts must be amended and a NOTAM issued until then; using stale charts is not acceptable.
- Reflected in the operator's route/airport analysis and, if necessary, in revised minima or a procedure change.
The aerodrome operator's 'outside the strip' argument is wrong: the runway strip is a different concept from the OLS. The operator cannot dispatch to unchanged minima based on superseded data; it must obtain the current obstacle assessment and, until the procedure is validated, treat the approach as unavailable or apply higher minima/visibility.
2. What should the operator do before starting the service?
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Before dispatch:
- Obtain the aerodrome operator's/ANSP's obstacle survey and the procedure-design assessment of the mast.
- Confirm whether a NOTAM and revised chart/minima are in force; do not rely on the old AIP.
- Re-run the operator's airport/route suitability analysis and, if needed, set company minima above the published ones or select an alternative procedure.
- Brief crews on the obstacle, the missed-approach gradient, and any restriction.
- Verify the aerodrome's rescue and firefighting category and other services remain adequate for the planned operation.
Only once the obstacle is properly assessed and promulgated, and the operator's analysis is complete, should the service begin.