The Anatomy Of The Pushback

A forward journey starts by moving in reverse.

The pushback is an ironic part of flying—an aircraft capable of flying many hundreds of miles per hour needs help to move backward at an almost immeasurably slow speed. Nearly every flight starts in this same way. The captain releases the parking brake, and the aircraft is pushed back from its parking stand. Except in rare instances when a plane can "power out" from its parking location, a tug is needed to move the plane away from the terminal. A choreography of triggers and responses is used during every pushback. Here's a step-by-step account of how an airline pushback is achieved.

Before anyone can start thinking about the pushback, the boarding door(s) need to be closed and the jetbridge removed from the aircraft. In order to close the door, flight attendants are required to conduct a passenger count that matches the number of tickets scanned by the gate agent. Additionally, passengers need to be seated in the "zone" of the aircraft they were ticketed in for weight and balance purposes.

A miscount or discrepancy requires resolution before the boarding door can be closed. This is why flight attendants often request passengers to take their seats as quickly as possible in their assigned seats. When gate agents for flight attendants query if a passenger is onboard and to ring their call button, it's usually not because there's uncertainty if they're on the plane. Rather, that passenger has taken a seat other than the one they were ticketed for, resulting in a weight and balance discrepancy.

The boarding door is closed after the captain confirms that the flight attendants' passenger count matches the total generated by the gate agent. At this point, the pilots are interested in the status of the cargo doors and the other service doors. Last-minute bags frequently arrive after all the passengers have boarded, and airline procedures usually don't allow pilots to bring the hydraulic systems to life until every door has been closed. After all the doors have been secured shut, the pilots run the before-start checklist.

Pilots activate the plane's red beacon as part of the before-start sequence. This, along with the removal of the jetbridge, is a cue to the ground staff that the pilots are ready to get into contact with them for the pushback. Ground crews normally connect a headset jack near the plane's nosewheel. Most commercial aircraft have an indicator light in this same area that shows when the pilots have disengaged their ability to steer the plane and have released the parking brake. Both of these are requisite items for a ground crew to push a plane. If the crew tried pushing a plane back without the steering disengaged or the parking brake set, there would almost certainly be damage to the nosewheel assembly.

With the headset having been connected, the tug driver now has direct communication between him or herself and the pilots. Large airports have ramp controllers that issue push and start clearances to pilots. After the captain and tug driver have confirmed each other is ready, the first officer calls the ramp tower for clearance. This is usually phrased something like, "Push approved, tail east, call back for taxi." This information is then relayed by the pilots to the tug driver. In the event that headset communications aren't available, there are a series of standard hand signals that pilots and ground crew use to rudimentarily communicate this same information.

Engines are started during most (but not all) pushbacks. Some airports and airlines have policies that forbid engine starts during pushback for safety reasons. If the engines are allowed to be started during the push, the go-ahead is always given by ground staff. Pilots are trained to never start an engine before being told it's safe to do so by the tug driver. During most pushbacks, wing walkers with orange batons are present at both wingtips to ensure clearance. One arm raised and one arm parallel to the ground means it's clear to push, while crossed batons in the shape of an "x" are an indication to stop the push immediately.

The tug driver will request the captain to set the parking brake after the push is complete. The captain does so and then clears the ground crew to disconnect and remove the tug. Policies differ by airline, but most ground crews stand in the pilot's field of vision while disconnecting the ground equipment. Before walking away, the person who disconnected the headset and towbar (if used) holds a pin or strap above their head for the pilots to view. A pin is used to override steering on some aircraft, while a strap is used to hold other planes in position on lift-type tugs. Regardless of the method, this indicates that every external item used to push the aircraft has been removed and that it is safe for the pilots to taxi. Pilots now move the flaps and slats into the takeoff position, as well as check the flight controls.

Some planes are capable of a "power back" maneuver. All but lost to a previous era of flying, it was once common to see McDonnell Douglas MD-80 variants powering back from gates without needing a pushback tug. The thrust reversers, known commonly as "buckets" or "clamshells," deploy as shields against backward thrust produced by the engines. Thanks to their design, as well as their higher mounting points on the aft fuselage of the aircraft, MD-80s, and similar planes, could reverse off the gate if need be. If you haven't seen this maneuver, do a quick internet search for "MD-80 power back," and you'll find a few great examples.

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Every pushback is a choreography. So many things have to go right to push a plane back safely. Redundancies are built into every element of a commercial flight for this reason. As evidence, pushbacks at large airports usually require at least six people (one controller, two pilots, and three ground staff) to be in agreement with the operation. For passengers, the pushback is the genesis of a journey. Planes need to move a few meters backward before they can speed thousands of kilometers forwards.

Jack is an airline pilot in the United States. He previously worked as a flight instructor, where he discovered a passion for teaching about every topic related to flight, as well as mentoring prospective pilots. With a degree in Political Science, Ethnic Studies, and Philosophy from Santa Clara University, Jack is delighted to share his passion through writing with Simple Flying.