Holding (aviation) - Implementation

Implementation

A holding pattern for instrument flight rules (IFR) aircraft is usually a racetrack pattern based on a holding fix. This fix can be a radio beacon such as a non-directional beacon (NDB) or VHF omnidirectional range (VOR). The fix is the start of the first turn of the racetrack pattern. Aircraft will fly towards the fix, and once there will enter a predefined racetrack pattern. A standard holding pattern uses right-hand turns and takes approximately 4 minutes to complete (one minute for each 180 degree turn, and two one-minute straight ahead sections). Deviations from this pattern can happen if long delays are expected; longer legs (usually two or three minutes) may be used, or aircraft with distance measuring equipment (DME) may be assigned patterns with legs defined in nautical miles rather than minutes. Less frequent turns are more comfortable for passengers and crew. Additionally, left-hand turns may be assigned to some holding patterns if there are airspace restrictions nearby.

In the absence of a radio beacon, the holding fix can be any fixed point in the air, and can be created using two crossing VHF omnidirectional range radials (also called intersection), or it can be at a specific distance from a VOR using a coupled distance measuring equipment. When DME is used, the inbound turn of the racetrack may be permanently defined by distance limits rather than in minutes. Furthermore, in appropriately equipped aircraft, GPS waypoints may be used to define the holding pattern, eliminating the need for ground-based navigational aids entirely.

A hold for visual flight rules aircraft is usually a (smaller) racetrack pattern flown over something easily recognizable on the ground, such as a bridge, highway intersection or lake.