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{{Short description|Aeronautic procedure}}
{{Use mdy dates|date=October 2022}}
{{For|the novel|Holding Pattern (novel)}}
{{See Wiktionary|the flight maneuver|holding pattern|idiom}}
{{More citations needed|date=May 2011}}
[[Image:HoldDirectEntry.svg|thumb|200px|right|A standard holding pattern. Shown are the entry (green), the holding fix (red) and the holding pattern itself (blue)]]

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; i.e. "going in circles."<ref name="IFH-general">{{cite web |date=2001 |title=Instrument Flying Handbook (FAA-H-8083-15A), Chapter 10. |url=http://www.sheppardair.com/ACs/faa-h-8083-15.pdf |url-status=dead |archive-url=https://web.archive.org/web/20130411201142/http://www.sheppardair.com/ACs/faa-h-8083-15.pdf |archive-date=2013-04-11 |access-date=2014-08-15 |website=U.S. Department of Transportation}}</ref>

==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.<ref name=":0">{{Cite web |title=Holding Pattern |url=https://www.skybrary.aero/index.php/Holding_Pattern |access-date=2019-12-29 |website=SKYbrary Aviation Safety skybrary.aero}}</ref> 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).<ref name="IFH-general" /> 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)<ref name=":0" /> may be assigned patterns with legs defined in [[nautical mile]]s rather than minutes. Additionally, if there are wind, pilot is expected to adjust outbound timing so that the inbound leg can be flown in 1 minute, or 1.5 minutes if it is above 14,000ft.<ref>{{cite book |title=Instrument Flying Handbook |date=2012 |publisher=[[Federal Aviation Administration]] Flight Standards Service |edition=FAA-H-8083-15B |url=https://www.faa.gov/sites/faa.gov/files/regulations_policies/handbooks_manuals/aviation/FAA-H-8083-15B.pdf |chapter=Chapter 9. Navigation Systems |pages=38}}</ref>

==Usage==
[[File:Standard Holding Pattern.png|thumb|Standard holding pattern]]

The primary use of a holding pattern is to delay aircraft that have arrived at their destination but cannot land yet because of traffic congestion, poor weather, or runway unavailability (for instance, during [[snow removal]] or emergencies).<ref>{{cite web |last1=Martin |first1=Swayne |title=Aircraft Holding Procedures, Explained |url=https://www.boldmethod.com/learn-to-fly/maneuvers/what-you-should-know-about-holding-for-ifr-pilots/ |publisher=boldmethod |access-date=18 January 2025 |date=April 25, 2024}}</ref> Normally, when no delay is anticipated, ATC issues holding instructions at least 5 minutes before the estimated arrival at the fix. If an aircraft arrives at a clearance limit before receiving clearance beyond the fix, ATC expects the pilot to maintain the last assigned altitude and begin holding in accordance with the charted holding pattern.<ref name="IFH-2012">{{cite book |title=Instrument Flying Handbook |date=2012 |publisher=[[Federal Aviation Administration]] Flight Standards Service |edition=FAA-H-8083-15B |url=https://www.faa.gov/sites/faa.gov/files/regulations_policies/handbooks_manuals/aviation/FAA-H-8083-15B.pdf |chapter=Chapter 10. IFR Flight |pages=10}} {{PD-notice}}</ref>

=== Stacks ===

Several aircraft may fly the same holding pattern at the same time, separated vertically by {{cvt|1000|ft|m|order=flip}} 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, or because of vertical airspace limitations.

Since an aircraft with an emergency has priority over all other air traffic, it will always be allowed to bypass the holding pattern and go directly to the airport (if possible). This causes more delays for other aircraft already in the stack.<ref>{{Cite web |title=14 CFR 91.3 – Responsibility and authority of the pilot in command. |url=http://www.access.gpo.gov/nara/cfr/waisidx_01/14cfr91_01.html |url-status=dead |archive-url=https://web.archive.org/web/20080329151433/http://www.access.gpo.gov/nara/cfr/waisidx_01/14cfr91_01.html |archive-date=29 March 2008}} See ''[[Code of Federal Regulations]]''</ref>

=== In absence of charted holding pattern ===
If no holding pattern is charted and holding instructions have not been issued, pilots are expected to enter a standard holding pattern on the course on which the aircraft approached the fix and request further clearance as soon as possible. ATC will clear the aircraft with information including: direction of the hold in terms of the eight [[Cardinal direction|cardinal and ordinal directions]], holding fix, course, leg length, direction of turn, and time to expect further clearance.<ref name="IFH-2012" />

==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.<ref name="IFH-entry">''Instrument Flying Handbook'' (FAA-H-8083-15A), Standard Entry Procedures, page 10-12. {{cite web |url=https://www.faa.gov/regulations_policies/handbooks_manuals/aviation/ |title=Instrument Flying Handbook |access-date=2019-09-19 }}</ref>

* A ''direct'' entry is performed just as its name would suggest: 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, re-intercepting the inbound track, 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, proceeding to the fix and continuing from there.

<gallery caption="Standard holding entry diagrams">
File:HoldDirectEntry.svg|Direct entry (Sector 3)
File:HoldParallelEntry.svg|Parallel entry (Sector 1)
File:HoldTeardropEntry.svg|Teardrop entry (Sector 2)
</gallery>
The parallel and teardrop entry are mirrored in case of a left-hand holding pattern.

==Speed limits==
[[File:Kreisförmige Warteschleife.jpg|thumb|[[Contrails]] left by an aeroplane in holding pattern]]
Maximum holding airspeeds (MHA) are established to keep aircraft within the protected holding area during their one-minute (one-minute and a half above {{cvt|14000|ft|m|order=flip}} [[Mean sea level|MSL]]) inbound and outbound legs. For [[Civil aviation|civil aircraft]] (not [[Military aviation|military]]) in the United States and Canada, these airspeeds are:<ref name="IFH-general" /><ref>{{cite web |date=October 8, 2020 |title=Aeronautical Information Manual |url=https://tc.canada.ca/sites/default/files/2020-10/AIM-2020-2_ACCESS_E.pdf |access-date=29 November 2020 |publisher=Transport Canada}}</ref>
* Up to {{cvt|6000|ft|m|order=flip}} MSL: 200 [[indicated airspeed|KIAS]]
* From {{cvt|6001|to|14000|ft|m|order=flip}} MSL: 230 KIAS
** May be restricted to 210 KIAS in some situations<ref name="IFH-2012" />
* {{cvt|14001|ft|m|order=flip}} MSL and above: 265 KIAS

The ICAO Maximum holding speeds:<ref name="ICAO-Doc8168-1">ICAO Doc 8168 Vol. I, ''[http://dcaa.slv.dk:8000/icaodocs/Doc%208168%20-%20Aircraft%20Operations/Volume%201%20Flight%20Procedures,%205th%20ed..pdf Aircraft Operations]'', Volume I Flight Procedures, Part I — Section 6, Chapter 1. {{Webarchive|url=https://web.archive.org/web/20120131192221/http://dcaa.slv.dk:8000/icaodocs/Doc%208168%20-%20Aircraft%20Operations/Volume%201%20Flight%20Procedures,%205th%20ed..pdf|date=2012-01-31}}</ref>

* Up to {{cvt|14000|ft|m|order=flip}}: {{cvt|230|kn|km/h|order=flip}}
* {{cvt|14000|to|20000|ft|m|order=flip}}: {{cvt|240|kn|km/h|order=flip}}
* {{cvt|20000|to|34000|ft|m|order=flip}}: {{cvt|265|kn|km/h|order=flip}}
* Above {{cvt|34000|ft|m|order=flip}}: [[Mach number|M0.83]]

With their higher performance characteristics, military aircraft have higher holding speed limits. Pilots are expected to notify the ATC if they are unable to comply with the speed restrictions.<ref name="IFH-2012" />

==See also==

* [[Heathrow arrival stacks]]
* [[Flight planning]]
* [[Loiter (aeronautics)|Loiter]]

==References==
{{reflist}}
*Aeronautical Information Manual (AIM) paragraph 5-3-8 https://www.faa.gov/air_traffic/publications/atpubs/aim_html/
*(7) "A Treatise on the Holding Pattern: Expelling the Myths and Misconceptions of Timing and Wind Correction:, L. Glatt, PhD.
ATP, CFI-AI, (2016), https://www.holdingpattern.com/holding-patterns.html
*(8) "Holding Patterns 101: Finding the Holy Grail of Timing and Wind Correction", L. Glatt, PhD., ATP, CFI-AI (2018), https://www.holdingpattern.com/holding-patterns.html

==External links==
{{Commons category|Holding pattern}}
* [https://e6bx.com/holding-pattern/ E6BX Holding Entry Calculator and Trainer]
* [http://www.langleyflyingschool.com/Pages/IFR%20Groundschool--IFR%20Rules%20and%20Procedures--En%20Route%20and%20Holds.html Langley Flying School – IFR Rules and Procedures – En Route and Holds]
*[https://flightcrewguide.com/wiki/inflight/entry-holding/ Flight Crew Guide - Entry into the Holding]
*[https://flightcrewguide.com/wiki/inflight/flying-holding-pattern-wind-correction/ Flight Crew Guide - Flying the Holding pattern – Wind correction]
* [https://www.skybrary.aero/index.php/Holding_Pattern SKYbrary - Holding Pattern]
{{Flight phases}}

[[Category:Flight phases]]
[[Category:Air traffic control]]

Holding (aeronautics) - Revision history

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