Holding Pattern Made Easy
"Golden Eagle 421CA proceed direct to the XYZ VOR and hold on the 057 radial. Time is now 1045. Expect further clearance at 1105."
Although a holding pattern is a fairly easy maneuver compared to other tasks in instrument flying, it is a source of confusion and apprehension to many instrument trainees and novice instrument pilots. A better understanding of holding patterns can help eliminate many of the psychological barriers.
A holding pattern is a predetermined maneuver designed to keep an aircraft within a specified airspace. Holding pattern procedures are designated to absorb any flight delays that may occur along an airway, during terminal arrival and on missed approach.
A realistic reserve of fuel should be carried aboard an aircraft on
an instrument flight. Although IFR regulations specify the minimum fuel
that is required for an IFR flight, including a reserve, the pilot in command
should consider carrying an additional reserve when delays are expected
along his route of flight. As soon as a delay becomes inevitable, the PIC
must take steps to conserve fuel. This is accomplished by adjusting the
power to the best economy cruise. Once a holding instruction was issued,
the aircraft speed should be adjusted not only to the maximum holding speed,
but to the best economy cruise speed.
A standard holding pattern is a race track shaped course. It incorporates two straight legs and two 180 degrees right turns. a non standard holding pattern, left turns are used.
A holding pattern provides a protected airspace for a safe operation during the hold. Pilots are expected to remain within the protected airspace (the holding side). One of the elements which causes unnecessary confusion and anxiety is the holding pattern entry. Holding pattern entry procedures are not mandatory, they are merely a recommendation (as long as the airplane remains within the protected airspace). The recommendation is based on three types of entries, depending on the sector from which the airplane arrives at the holding fix. These are the direct, parallel and tear-drop entries.
The sectors are divided by the holding course and a line which crosses the holding fix at a 70 degrees angle to the inbound leg as shown in the adjacent illustration. In a direct entry, a turn into the outbound leg is initiated upon crossing the holding fix. When a parallel entry is desired the airplane is turned into a flight path that is in a opposite but parallel direction to the inbound leg. After one minute the airplane is turned through the holding side to the holding fix. There are two methods of making the fix. One is by flying directly to the fix and the other is by intercepting the inbound leg at an angle of 45 degrees and proceeding to the fix thereafter. After passing the holding fix the airplane is turned to the outbound leg. In a tear-drop entry, the airplane is turned towards the holding side in an angle of 30 degrees from the inbound leg. After one minute it is turned towards the non holding side until the inbound leg is intercepted. When approaching the holding fix exactly on the holding course from the opposite side of the inbound leg, either a parallel or a tear-drop entry can be used.
Reality is that the recommended entry is also the easiest to execute. The problem is how to make a quick determination of the recommended entry without being distracted by it from performing other tasks. The quickest and most efficient way to make this determination is by super-imposing the hold onto the heading indicator. This results in visualization of the position in which the airplane approaches the holding fix and of the holding pattern itself.
This is accomplished by dividing the directional gyro card into three
sectors. For a standard holding pattern one sector is between the heading
of the airplane and 70 degrees to the right of it. This is the Tear-drop
sector. The Parallel sector is between the heading of the airplane and
110 degrees to the left of it. The remainder is the Direct sector. On a
non standard hold the 110 and 70 degrees are switched. The 70 degree sector
is to the left of the heading while the 110 degree sector is on the right.
Once a holding instruction is issued and the airplane is proceeding directly to the holding fix, an imaginary line is super-imposed in the direction of the outbound direction. The recommended entry is determined by the sector that includes this imaginary line. In the following three examples an aircraft is on a 180 degrees heading. In example A, the outbound leg of the hold is on a 230 degrees direction. Airplane B has a outbound direction of 310 degrees and airplane C is assigned a hold with an outbound direction of 160 degrees.
A. In this example the inbound and outbound legs are 050 and 230 respectively.
The airplane approaches the fix at a heading of 180 degrees. The outbound
course (red line) falls within 180 and 250 degrees zone which defines the
tear-drop sector. Upon crossing the holding fix the airplane should be
flown at a heading of 200 degrees for one minute before making a right
turn to intercept the inbound course.
B. In this example the inbound and outbound legs are 130 and 310 degrees respectively. The airplane approaches the fix at a heading of 180 degrees. The outbound course (red line) falls within 250 and 070 degrees zone which defines the direct sector. Upon crossing the holding fix the airplane should be turned right to a heading of 310 degrees which is the outbound course.
C. In this example the inbound and outbound legs are 340 and 160 degrees
respectively. The airplane approaches the fix at a heading of 180 degrees.
The outbound course (red line) falls within the 180 and 070 degrees zone
which defines the parallel sector. Upon crossing the holding fix the airplane
should be turned left to a heading of 160 degrees for one minute before
making a left turn of 225 degrees to intercept the inbound course (or direct
towards the fix if feasible).
When instructed to hold over a VOR or a NDB, the outbound course and the radial (or magnetic bearing on a NDB) share the same direction. That makes things even easier. For example if the fix in example B is a VOR station, the holding instruction would something like this: "...hold northwest on the 310 radial," the radial is super-imposed on the directional gyro to determine the hold. Obviously the result is the same as in B.
The holding timing procedures may vary from country to country. Generally, under no wind condition, the inbound and the outbound legs are flown for one minute ( a minute and one half when above 14,000 feet). Although both legs are timed, only one of the legs is used to determine the protected airspace. In the US the one minute inbound leg determines the airspace while most of the other countries use the recommendation of the International Civil Aviation Organization (ICAO). Under this recommendation the outbound leg is used to determine the protected airspace.
The inbound leg timing begins at the completion of outbound end turn
and it is complete upon crossing the fix. The timing of the outbound leg
should begin at or abeam the station whichever occurs later. If the abeam
position cannot be determined, timing should begin upon the completion
of the fix end turn. When holding over a VOR station the outbound timing
starts after the fix end turn is completed, and the TO/FROM indicator changes
back from TO to FROM. On a NDB hold, the outbound timing starts after the
fix end turn is completed, and the ADF needle is abeam. The abeam position
cannot be accurately determined when the holding fix is an intersection.
Therefore the outbound timing starts when the wings are level after completing
the fix end turn.
Distance Measuring Equipment (DME) holds are entered in the same manner as the timed holds. The difference is that DME distances are used to define the protected airspace. The length of the outbound leg is assigned by the controller.
The wind is a major factor during holding procedures. Not only the wind correction is required to remain within the geographic protected area, but also the ground speed affects the timing that is required to fly a uniform holding pattern. The most effective way to correct the wind effect is by determining the wind correction angle on the inbound leg. The wind correction angle should be doubled on the outbound leg as shown in the adjacent diagram.
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