Instrument Procedures - Departures — Page 159, Lesson 235

Let’s pick up with the departure procedure itself. We’ve already covered the general idea of instrument departures, so now I want to walk you through the specific rules that govern how these procedures are designed and flown. First, a key point about speed. The departure procedure is designed around a maximum speed at which it can be flown. Wherever limiting speeds other than those specified in the table are published, they must be complied with to remain within the appropriate protected areas. If an aeroplane operation requires a higher speed, then an alternative departure procedure must be requested. So the published speed limits are not suggestions — they are the boundaries of the protected airspace, and exceeding them means you may leave the protected area. Now, let’s look at the two basic types of departure route: straight, or turning. Departure routes are based on track guidance acquired within 20 km (10.8 NM) from the end of the runway — that’s the DER, the departure end of runway — for straight departures, and within 10 km (5.4 NM) after completion of turns for turning departures. When flying the route, the pilot is expected to correct for known wind and to remain within the protected airspace. So the pilot actively manages the track, compensating for wind, and stays inside the protected area. Let me define a straight departure. A straight departure is one in which the initial departure track is within 15° of the alignment of the runway. Track guidance may be provided by VOR, NDB, or RNAV. So if the track you need to fly is within 15 degrees of the runway heading, it’s a straight departure, and you can use a VOR, an NDB, or RNAV for guidance. Now, a turning departure. If the departure track requires a turn of more than 15°, a turning area is constructed, and the turn required is commenced upon reaching a specified altitude or height, or at a fix, or at a facility — such as a VOR or NDB. Straight flight is assumed until reaching an altitude not less than 120 m (394 ft) above the elevation of the DER. So you fly straight until you reach at least 120 metres above the departure end of runway elevation, and only then can the turn begin. Let’s also cover emergencies. It is the responsibility of the operator to establish procedures to cover the case of engine failure or an emergency in flight which occurs after V1. So the operator — the airline or operator — must have procedures in place for an engine failure or emergency after V1, the decision speed. Finally, let’s look at omni-directional departures. Where no track guidance is provided in the design of a departure procedure, the omni-directional method is used, which basically provides for initial departure tracks to be undefined. In other words, once off the end of the runway and at a safe height, the aircraft can be navigated in any direction required to achieve the initial en route point. It may be that some sectors of the departure area may contain obstacles which preclude departures in that direction, in which case the published procedures will be annotated to show the restricted sectors. The basic procedure is that the aircraft will climb on the extended runway centre line to 120 m (394 ft) above aerodrome elevation before turns can be specified, and at least 90 m (295 ft) of obstacle clearance will be provided before turns greater than 15° can be specified. Turns will not commence within 600 m of the beginning of the runway. Where obstacles do not permit the development of omni-directional procedures, it is necessary to fly a departure route — straight or turning — or ensure that ceiling and visibility will permit obstacles to be avoided by visual means. So to summarise the key numbers: straight departures are within 15° of runway alignment, turning departures require more than 15°, straight flight is assumed until 120 m (394 ft) above the DER, omni-directional departures climb on the extended centre line to 120 m (394 ft) above aerodrome elevation, with at least 90 m (295 ft) obstacle clearance before turns greater than 15°, and no turns within 600 m of the beginning of the runway. And remember, the pilot corrects for wind and stays within the protected airspace.