How Do Air Traffic Patterns Work?

Competent and professional contact with air traffic controllers is a weak area for even experienced pilots. Working in air traffic patterns is a basic part of life for student pilots, but it’s an important reality of aviation life that should be continually considered. While managing all the systems in the cockpit and making constant decisions about airspeed and altitude, it’s easy to think of the national air traffic control system as just a garbled voice in your ear. However, having a strong understanding of how air traffic patterns and ATC works, as well as why controllers make some of the decisions they do, can go a long way to establishing a better handle on how traffic flows. Especially when an airfield does not have a control tower, it’s vital to have a strong grasp of how to navigate when bearing down on the runway.

 

Working Together With Air Traffic Control and Other Pilots

Pilots and controllers must work together for the safety and effectiveness of everyone in the sky. When you are in the left seat, you can decrease frustration and potential misunderstandings by not only giving controllers space to do their job but by becoming familiar with air traffic control patterns and how they govern the ways in which the airways flow. Understanding this not only increases your knowledge base, it makes you a safer and better educated pilot. You will be more equipped to make decisions while flight planning and making final approaches. Once you understand air traffic patterns, as well as how controllers implement them, your workload in the cockpit will be processed more efficiently.

Air traffic patterns only work when they are thoroughly understood and well-deployed by the pilots in them. Being a strong member of the aviation community involves following these rules and conventions. Following is a discussion of a typical air traffic control pattern for general aviators.

 

Holding Patterns

Most general aviation holding patterns in America follow the same path. Practice and study will help new pilots to become familiar with them. They are in the shape of an oval, and standard distances over airfields help to keep aircraft separated within it and also out of the way of arriving and departing traffic.

If the airport at which you are attempting to land is busy, you may find yourself in a holding pattern. This will happen more often at larger, metropolitan airports to pilots who are flying commercial clients or an airliner. Sometimes the crew requires more time to complete a checklist and will request one. An aircraft may also be placed in a holding pattern if it misses an approach and needs to allow other planes to land before it takes another try. If the pilot is flying below 14,000 feet, the inbound timing is about one minute. Above 14,000 feet, the hold pattern takes ninety seconds.

 

Shape of a Holding Pattern

Air traffic control or a flight management system will provide the crew with a fix, which is either permanent or based on their position above the airfield. From the fix, the pilot will fly a standard holding pattern, which is usually flown to the right. Usually, the bank angle is at least twenty five degrees, or at a turn rate of three degrees per second, depending on which is less. The plot will then turn to the fix end and fly an outbound leg, then bank to an outbound end. This is the halfway point of the holding pattern. The pilot then turns to the holding side, arcing to the nonholding side. Another right turn brings the aircraft to the inbound side, then back to the fix.

Sometimes, a nonstandard holding pattern is issued. These usually turn to the left or have timing which is different than the usual sixty or ninety-second time frames. Entry sectors for a nonstandard holding pattern may be flexible within five degrees.

 

Distance Measuring Equipment and Holding Patterns

Distance Measuring Equipment is usually understood as the mix of aircraft and on-ground equipment. Using signals, it provides the pilot with an in idea of how far the aircraft is from a beacon.  Some DME systems can give an estimated time of arrival as well as current groundspeed.

When a pilot enters a DME holding pattern, entry is the same except that distance is measured by nautical miles instead of time. Air traffic control provides the DME distance in terms of the beacon. The position of the airplane and the beacon determine the length of the outbound and inbound legs. These patterns, while also in the shape of an oval once entered, have the form of a deep V at the entry point.

 

Speed Limitations Within Holding Patterns

You must prepare carefully to enter a holding pattern. Part of your responsibility includes knowing the speed at which to enter the pattern. Pilots can know what kind of holding speeds to expect at an airport simply by checking terminal, approach, or enroute charts. However, sometimes these speeds are not specified on the charts, and they can also change from area to area.

The International Civil Aviation Organization (ICAO) has established “speed limits” for holding patterns.  These vary by holding altitude, and familiarity with this chart can give a pilot a good rule of thumb to follow when preparing to enter a holding pattern. The higher an airplane is, the faster it may stay in the holding pattern. In altitudes below 14,000 feet, for example, aircraft must not exceed 230 KIAS (Knots Indicated Airspeed), but airplanes which in the pattern above 34,000 feet cannot go faster than Mach .83.

Sometimes, a pilot may find it necessary to exceed these maximum speeds. This can include attempts to avoid turbulence at lower altitudes. Particularly if an aircraft is carrying a large number of passengers who may be experiencing the bends in the pattern in addition to the turbulence, the crew may aim to ensure their comfort. In this event, they must alert ATC, then return to the top airspeed when returning.

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