Wednesday, June 20, 2012

Is Your Life Going Around in Circles

Holding Patterns - IFR


If it is, you are probably in a Holding Pattern in a IFR Flight.

The holding pattern for aircraft on an IFR Flight Plan is like a car racing track. The track is based on a Holding Fix. The fix may be a Non Directional Radio Beacon (NDB) or a VOR. A plane will fly toward the Fix.

The fix is the start of a predefined racetrack pattern. This standard holding pattern uses standard rate right turns (3 degrees/second).

The pattern takes approximately four minutes to complete. (one minute for each 180 degree turn (two minutes) and two one minute straight ahead legs.

The ATC Center will advise the IFR Flight Pilot if extensions of the straight legs need to increase their length if  delays are required due to unusual length. (two or three minute legs).

If a plane has a DME the straight legs are defined in nautical miles rather than in minutes. If you have passengers they are more comfortable with less frequent turns over a period of time. (read longer hollding patterns).Some holding pattern turns are left turns if there is airspace restrictions nearby.

The fix is any fixed point in the air created by using two crossing VHF (VOR) radials. That fix is called an intersection.

If you have GPS capability, the waypoints define the holding pattern. This eliminates the need for ground based navigational aids.

For VFR Holding Patterns the racetrack pattern is smaller and a visible terrain below, like a lake, defines the fix.

Basically, a holding pattern delays the actual time of arrival because of traffic congestion, poor  weather or runway       unavailability (snow  removal).

Busy airports may stack holding pattern planes one above the other. New arrivals enter at the top of the stack. When the runway below clears the botom plane leaves the pattern and the ATC controller brings all the planes down to a lower level, one at a time, to continue emptying the holding pattern stack.

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