Summary

  • Pilots use in-cockpit technology like moving map displays to navigate taxiways, especially in low-visibility conditions.
  • Communication between pilots and air traffic control is crucial, and reading back hold-short instructions is essential for safety.
  • Ground controllers use ASDE-X equipment to track aircraft and vehicles on runways and taxiways, preventing potential conflicts.

At busy airports, it is common for commercial aircraft to pass through long and congested taxiways to and from the runway. It can take anywhere between 10 and 30 minutes to reach the runway after departing from the gate. The same can be the case after landing at a large airport. Have you ever wondered how pilots navigate through complex and crowded taxiways? From a passenger’s perspective, taxiing may be a set of random movements, but pilots follow specific instructions while using advanced equipment and other cockpit resources.

Large airports, such as London Heathrow (LHR) and Chicago O’Hare Airport (ORD), are especially challenging. Pilots navigate around these airports based on moving map displays and specialized taxi diagrams. This article focuses on a set of resources pilots use to navigate complex airport taxiways, as Aerotime Hub highlighted.

Cockpit resources

Flight crews operating commercial aircraft often benefit from using all in-cockpit technology. This includes panel-mounted, moving map displays that allow them to follow their aircraft movement on the airport diagram page. The benefit is exponential when operating at night or in low-visibility conditions.

An IndiGo aircraft on the apron at Mumbai Airport.
Photo: Harsh – S | Shutterstock

Those aircraft that do not have electronic displays require the crew to have tablet computers with similar taxi diagrams or even paper taxi charts. Regardless of what equipment is used, communication is vital between pilots since the pilot taxiing the aircraft will follow guidance from the pilot not flying, who constantly refers to the airport diagram and communicates with air traffic control. Situational awareness is critical.

A paper diagram of Dallas Fort Worth airport.

Photo: FAA

Construction notice diagrams are also beneficial since many big airports are constantly under some ongoing expansion, revamping, or construction. This can significantly impact potential taxi routes when on the ground. Looking at these can help crews determine potential limitations to taxi routes during the flight planning process.

Communication is the best resource

Signs and markings

  • Pilots confirm their current position and further directions using signs and markings.
  • Signs with yellow text on a black background indicate the current location [of the aircraft]
  • Signs with black text on a yellow background indicate a directional information sign, generally accompanied by an arrow.
  • Mandatory instruction signs are white text on a red background, indicating a must-not-enter-without-clearance location.
  • Runway numbers are two digits and correspond to the magnetic compass direction of that runway to the nearest 10º, 15 being 150º and 36 being 360º.
  • Parallel runways are given L for left, C for center, or R for right.
Taxiway

In-cockpit communication is crucial, and following air traffic control instructions is vital. There are some ATC instructions to keep in mind. Hold-short instructions must be read back every time they are issued. These can pertain to holding short of a taxiway or runway environment. Land And Hold Short Operations (LAHSO) are used at many airports with intersecting runways.

Pilots are asked to confirm a hold-short instruction even before they land on a runway that intersects another runway further down the landing surface. If a crew cannot accept such an instruction, they must advise ATC, which would then coordinate traffic on the other runway.

Related

How Pilots Master the Precise Art Of Taxiing An Aircraft

The taxi regime of a flight involves the ground movement of the aircraft on its power.

LAHSO clearances are not mandatory, but once on the ground, all hold-short instructions must be adhered to. This applies to inbound and outbound traffic. Many complex airports have signage and specific taxiways for aircraft taxing for departure and another set of the same for arrivals. This comes in handy but certainly adds to the likelihood of confusion.

United and American Airlines aircraft on an airport apron.

Photo: Daniel Martínez Garbuno | Simple Flying

It is possible that an experienced captain would ask for progressive taxi instruction if they were not familiar with the airport, especially during inclement weather or at night. When requested, a progressive taxi instruction is used upon clearing the landing runway and asking for a progressive taxi. ATC can provide a complete set of turns and routes right there before the start of the taxi.

The other option is the step-by-step instructions, provided in stages, while the aircraft taxis. Progressive taxiing is provided when the pilot requests or when necessary by the air traffic controller (e.g., due to construction works, closed taxiways, etc.).

A United Airlines Boeing 737 MAX 9 on the apron at Los Angeles International Airport.
Photo: Lukas Souza | Simple Flying

ATC equipment

Ground controllers can use their equipment to aid pilots when giving taxi instructions. The Airport Surface Detection System — Model X (ASDE-X) is a surveillance system using radar and satellite technology that allows air traffic controllers to track the surface movement of aircraft and vehicles.

The ASDE-X alerts air traffic controllers of potential runway conflicts by providing detailed movement coverage on runways and taxiways. By collecting data from various sensors, ASDE-X can track non-transponder-equipped and transponder-equipped vehicles and aircraft in the airport movement area.

Regardless of the equipment pilots or controllers use, the best way to prevent a runway incursion or accident is to say the magic words “Say Again.” This will ensure the transmitting party knows the receiver has not fully understood the message. Opening the door for a clear repeat of the intended message will go a long way to making sure flight crews safely navigate complex airport ground environments.

What are your thoughts on the instructions and resources pilots use to navigate through taxiways? Share your opinion in the comments section.

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