Standard holding entry diagrams

Holding.

In aviation, holding (or flying a hold) is a maneuver designed to delay an aircraft already in flight while keeping it within a specified airspace.

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). Deviations from this pattern can happen if long delays are expected.

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). Furthermore, in appropriately equipped aircraft, GPS waypoints may be used to define the holding pattern.

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.

Usage

The primary use of a holding pattern is delaying aircraft that have arrived at their destination but cannot land yet because of traffic congestion, poor weather, or runway unavailability. Several aircraft may fly the same holding pattern at the same time, separated vertically by 1,000 feet or more. This is generally described as a stack or holding stack. As a rule, new arrivals will be added at the top. The aircraft at the bottom of the stack will be taken out and allowed to make an approach first, after which all aircraft in the stack move down one level, and so on. Air traffic control (ATC) will control the whole process, in some cases using a dedicated controller (called a stack controller) for each individual pattern.

One airport may have several holding patterns; depending on where aircraft arrive from or which runway is in use.

Since an aircraft with an emergency has priority over all other air traffic, they will always be allowed to bypass the holding pattern and go directly to the airport. Obviously, this causes more delays for other aircraft already in the stack.

Flying a holding pattern

Many aircraft have a specific holding speed; this is a lower speed at which the aircraft uses less fuel per hour than normal cruise speeds. A typical holding speed for transport category aircraft is 210 to 265 knots (491 km/h). If possible, a holding pattern is flown with flaps and landing gear up to save fuel.

Modern autopilots, coupled with flight management systems, can enter and fly holding patterns automatically.

Entry procedures

The entry to a holding pattern is often the hardest part for a novice pilot to grasp, and determining and executing the proper entry while simultaneously controlling the aircraft, navigating and communicating with ATC requires practice. There are three standard types of entries: direct, parallel, and offset (teardrop). The proper entry procedure is determined by the angle difference between the direction the aircraft flies to arrive at the beacon and the direction of the inbound leg of the holding pattern.

A direct entry is performed exactly as it sounds: the aircraft flies directly to the holding fix, and immediately begins the first turn outbound.

In a parallel entry, the aircraft flies to the holding fix, parallels the inbound course for one minute outbound, and then turns back, flies directly to the fix, and continues in the hold from there.

In an offset or teardrop entry, the aircraft flies to the holding fix, turns into the protected area, flies for one minute, and then turns back inbound, proceeds to the fix and continues from there.

The parallel and teardrop entry are mirrored in case of a left-hand holding pattern.

Standard holding entry diagrams

Direct entry (Sector 3)

Parallel entry (Sector 1)

Teardrop entry (Sector 2)

Word List:

1. FIX: The "hub" of the holding pattern. Everything in the hold is based on the Fix- time, distance, and navigation. The Fix may be an intersection, a VOR/VORTAC, a Marker Beacon, or a DME (Distance Measuring Equipment) distance on an airway, among others.

2. FIX END: The end of the racetrack pattern that is near the Fix.

3. ABEAM: When the aircraft is at a ninety right angle to the Fix.

4. HOLDING SIDE: The outbound leg of the hold.

5. OUTBOUND END: The end of the racetrack pattern that is farthest from the Fix.

6. HOLDING COURSE: The course that the hold (along with the Fix) is predicated on. It may be a Localizer, an airway, or a VOR/VORTAC radial.

7. RECIPROCAL: The opposite (180 degrees) of the Holding Course. For example, if the Holding Course is 270 degrees the Reciprocal will be 90 degrees.

8. NON-HOLDING SIDE: The inbound leg of the hold.

Дата добавления: 2015-10-28