omnidirectional departures

omnidirectional departures

When no track guidance is provided in the design of a departure procedure, the departure criteria are developed by using the omnidirectional method. The procedure commences at the departure end of the runway, which is the end of the area declared suitable for takeoff (i.e., the end of the runway or clearway as appropriate). Since the point of lift-off will vary, the departure procedure is based on the assumption that a turn at 400 ft (120 m) above the elevation of the airport will not be initiated sooner than 2000 ft (600 m) from the beginning of the runway. The basic procedure ensures that the aircraft will climb on the extended centerline to 400 ft (120 m) before turns can be specified, and that at least 300 ft (90 m) of obstacle clearance will be provided before turns greater than 15° can be specified. The omnidirectional departure procedure is designed using any one or a combination of the following:
i. Standard case. Where no obstacles penetrate the 2.5% obstacle identification surface and 300 ft (90 m) of obstacle clearance prevails, a 3.3% climb to 400 ft (120 m) will satisfy the obstacle clearance required for a turn in any direction (see Area 1).
ii. Specified turn altitude or height. Where obstacles preclude omnidirectional turns at 400 ft (120 m), the procedure will specify a 3.3% climb to an altitude or height where the omnidirectional turns can be made (see Area 2).
iii. Specified procedure design gradient. Where obstacles exist, the procedure may define a minimum gradient of more than 3.3% to a specified altitude or height before turns are permitted (Area 3).
iv. Sector departures. Where obstacles exist, the procedure may identify sectors for which either a minimum gradient or a minimum turn altitude or height is specified.