Instrument Procedures - Departures — Page 159, Lesson 231

Let’s start with the document that governs all of this. The ICAO document that specifies the recommendations for instrument procedures is called PANS-OPS. That term is shorthand for the content of ICAO Doc 8168. The full, correct title is “Procedures for Air Navigation Services – Aircraft Operations.” Now, this document is printed in two volumes. Volume 1 – Flight Procedures describes the operational procedures recommended for the guidance of flight operations personnel — that’s you, the pilot. We’re going to limit our study of instrument procedures to the content of Volume 1. Volume 2 – Construction of Visual and Instrument Flight Procedures is intended for the guidance of procedures specialists — the people who design the procedures — and it describes the essential areas and obstacle clearance requirements needed to achieve safe, regular instrument flight operations. Here’s the key relationship: Volume 1 outlines the various parameters on which the criteria of Volume 2 are based. So the pilot’s operational procedures are built on the designer’s criteria. Both volumes cover operational practices that go beyond the scope of Standards and Recommended Practices, which we call SARPs, but where a measure of international uniformity is desirable. PANS-OPS expands the SARPs of Annex 6, and it considers both departure and arrival procedures, and to a lesser extent, en-route procedures where obstacle clearance criteria should be taken into consideration. Now let’s move into the actual departures. The General Criteria for instrument departure procedures assume that all engines are operating. That’s a fundamental assumption — the procedure is designed for a fully functioning aircraft. The design of an instrument departure procedure is, in general, dictated by the terrain surrounding the aerodrome, but it may also be required to cater for ATC requirements — things like adjacent ATS routes, restricted, prohibited or danger areas, and the proximity of other aerodromes. These factors in turn influence the type and position of navigation aids required to provide track guidance for the departure route. Airspace restrictions may also affect the position of those navigation aids. From the pilot and operator point of view, you also need to take into account the use of automatic take-off thrust control systems, which we call ATTCS, and noise abatement procedures. Now, here’s the decision logic. Where no suitable navigation aid is available to provide specific track guidance, the criteria for omni-directional departures are applied — that means any direction. Wherever possible, a straight departure will be specified, which is aligned with the runway. But where a departure route requires a turn of more than 15° to avoid an obstacle, a turning departure is constructed. So the threshold to remember is 15 degrees — anything beyond that turn becomes a turning departure rather than a straight one. Let me show you what these look like.