It's the last leg of a four-day trip. Everything is ready for the arrival procedure at JFK. You update the passengers about the twenty minutes remaining in-flight and instruct the flight attendants to prepare the cabin.
Then, without warning, the air traffic controller asks: "are you ready to copy holding instructions?"
Sometimes there's a need to delay the aircraft while in flight temporarily. Since we can't just park the airplane in mid-air, holding patterns are used for this purpose.
Various reasons may require a hold, such as:
- Hazardous weather
- Traffic congestion
- Airport or runway closures
- Equipment outages, or
- for allowing more time when handling abnormal situations and emergencies
A holding pattern is a racetrack-shaped maneuver that keeps the aircraft around a specified fix until ATC and the pilot are ready to resume the flight to the destination or an alternate airport.
The maneuver consists of four legs:
- An inbound leg towards the holding fix
- an outbound leg, and
- two turns
The FARs require that all turns in the hold use the smallest bank angle out of these three options:
- 3º heading change per second (standard-rate turn), or
- a 30° bank angle, or
- a 25º bank angle when using a Flight Director system for navigation
ATC Holding clearance
The air traffic controller can issue either published or non-published holding clearances. You can find published holding procedures charted on low/high enroute, arrival, and area charts.
Issuing a published hold clearance reduces controller workload and radio chatter. For a published holding procedure, ATC only needs to include the following in the clearance:
- The holding fix
- The direction of the holding pattern relative to the fix (e.g., North, East, South West), and
- The Expect Further Clearance (EFC) time.
For non-published holds, the controller must include:
- The direction of the holding pattern from The fix (e.g., N, W, S, NE)
- The holding Fix
- The radial, course, airway, or route on which to hold.
- The leg length in miles (if DME or RNAV) or minutes otherwise.
- The direction of turns, if left, otherwise right turns are standard, and
- the Expect Further Clearance (EFC) time.
An example of an ATC holding clearance: "Hold West of KORRY on the 270º radial Expect Further Clearance at 18:55 Zulu". Since the controller did not mention turn direction, you know that right turns are required.
Once you have the holding clearance, you need to choose the best entry technique based on your position.
Holding pattern entries
The direct entry is the most straightforward holding pattern entry. Use this entry when approaching the holding fix from the 180º-sized sector in the image. After crossing the holding fix, turn to the outbound leg in the holding pattern direction to start your first hold.
Use this entry when approaching the holding fix from anywhere in the 110º-sized sector in the image. With this entry, upon crossing the fix, you would fly parallel to the outbound course for one minute, then turn into the hold, more than 180º, to intercept the inbound leg.
Note that you would have to make the first two turns in the "wrong" direction. For example, when flying a right-hand holding pattern, the turn after crossing the fix to the parallel leg and the turn to intercept the inbound are both left-hand turns. All subsequent turns would be right turns in the racetrack pattern.
Upon crossing the fix, turn 30º into the holding side. Follow this heading for 1 minute, then turn in the procedure's turn direction to intercept the inbound course.
Flying the holding pattern
Reduce speed within three minutes or less of arriving at the fix so that you cross it at or below the holding speed limit.
Choosing a holding pattern entry in the air could be tricky, especially if you receive the clearance at the last moment when close to the fix. For this purpose, I built a little app, Hold Trainer, that makes you better at quickly choosing the best holding entry with practice ATC holding instructions. The app also serves as a holding pattern entry calculator. Check it out here: Hold Trainer for Android and iOS.
Holding speeds restrictions
|Altitude (MSL)||Max airspeed (kts)|
|6000' or below||200 kts|
|14,001 and above||265 kts|
|Air Force fields||310 kts *|
|Navy fields||230 kts *|
* Unless published otherwise
Unless published or instructed otherwise by ATC, the inbound leg timing is: 1 minute below 14,000 ft MSL, and 1.5 minutes at 14,001 ft MSL and above.
The inbound timing begins when established wings-level on the inbound turn and ends at the fix.
To achieve this inbound timing, adjust the outbound leg. The outbound timing begins when the aircraft passes abeam or over the holding fix. If you can't resolve the abeam point, start the timer at the end of the turn outbound.
In the first holding round, fly outbound for 1 or 1.5 minutes, as dictated by the altitude. Then, measure the inbound length and adjust the next outbound turn as needed to get closer to the required timing.
The controller may also give the leg length as a distance instead of time.
To compensate for wind, find the wind correction angle required to stay on the inbound course. Then, triple it for the outbound leg. We do not try to compensate for wind during the turns, hence the massive correction on the outbound leg.
Arriving over the holding fix
A technique commonly used by pilots for remembering the required actions over and abeam the holding fix is the "Five T's" mnemonic:
- Turn: the aircraft to follow the desired entry technique.
- Time: note the time over the holding fix. Start the timer when wings are level or when abeam the point.
- Twist: set the OBS to the inbound course
- Throttle: adjust power to maintain holding speed
- Talk: advise ATC of the time and altitude at which the aircraft reached the holding fix. E.g.: "<callsign>, over VRB 8,000 ft at 1320 Zulu"
- Some add a 6th T to this acronym: "Think (ahead)"
A Flight Management system (FMS) provides excellent help for performing holds and reducing workload. You plug in the information from the holding clearance: fix, direction, radial, and the system will command the autopilot to fly a perfect hold for you.
With an FMS, you won't have to worry too much about choosing the correct entry or wind correction.
With this in mind, the number one rule of computing applies:
garbage in – garbage out.
Therefore, you must carefully ensure to input the correct information in the FMS and monitor the automation throughout the procedure.
You received the holding instruction with an EFC of 18:55 Zulu, about an hour away. You inquire ATC about the reason for the hold, and they reply its due to traffic congestion on arrival, a common scenario in the New York City area.
Once established in the hold, or when workload permits, it's time to start planning forward.
Ask yourself questions such as:
- How long can I stay in the hold with the available fuel?
- What is my alternate plan if ATC does not release me by that time?
- What is the current weather and availability of other airports in the area if I have to divert?
Knowing the answers to these questions early will help you avoid getting into a low-fuel situation and keep the flight safe.
After holding for about 30 minutes, ATC releases you earlier than expected and clears the flight to proceed to JFK. You continue the arrival and land safely at the airport.