How do airport passenger bridges connect to airplanes?

1. A plane follows the yellow line to its gate and stops at a mark on the ground. The door is higher than a room is tall. The bridge is waiting, tucked out of the way.
2. The bridge is fixed to the building by a round joint called the rotunda. It works like a hinge. Wheels at the far end drive sideways, and the whole tunnel swings toward the plane's door.
3. The tunnel is made of two or three tubes, one inside the other, like a telescope. The wheels drive forward and the tubes slide out, so the bridge grows longer until it nearly touches the plane.
4. Two strong lift columns stand on the wheels. They push the end of the bridge up or pull it down, until its floor is exactly level with the plane's doorstep.
5. The little room at the end, the cab, turns to face the plane. A soft folding hood stretches out and presses gently around the door. A small wheel rests on the plane to feel if it moves up or down.
6. The doors open and the passengers walk straight from the building onto the plane, warm and dry. When a bigger or smaller plane comes next, the bridge simply swings, stretches and lifts to a new spot.

Tap each part. You see the bridge from above in the top picture, and from the side in the bottom one.

• Rotunda. The rotunda is the round room where the bridge joins the building. It stands on a strong pillar and works as a hinge, so the tunnel can swing left and right.
• Telescoping tunnels. The walkway is made of two or three tunnels that fit inside each other. They roll in and out like the tubes of a telescope, so the bridge can be short or long.
• Lift columns. The lift columns are two strong legs near the far end. They push up or pull down to set the floor at the height of the plane's door.
• Drive wheels. Under the lift columns is a pair of big wheels with electric motors. They can roll forward, backward and sideways, and that is what swings and stretches the bridge.
• Cab. The cab is the room at the end that meets the plane. The operator stands here and steers the bridge with a joystick, watching the door through a window.
• Canopy. The canopy is a soft hood that folds like an accordion. It reaches out and presses gently around the plane's door to close the gap.
• Auto-leveler. As people and bags go on, the plane sinks a little on its wheels. A small wheel resting on the plane feels this and tells the bridge to move down with it.

Drag the cab to the plane's door in the top picture, then set the height in the side picture. Then press Next plane and dock again.

Experiment: A small jet parks at the gate after a big one. What must the bridge do to meet its door?

1. Dock the bridge with the plane at the gate. Notice the swing, the reach and the height.
2. Press Next plane. A plane of a different size rolls in.
3. Dock again. Which of the three settings had to change?

What we found: Each kind of plane has its door at a different height and a different distance from the building. So the bridge has to change all three things: where it points, how far it reaches and how high its end is. That is why it is built to turn, stretch and lift.

Turn on JavaScript to try it yourself.

Three planes are coming, one after another: small, medium and big. Dock the bridge with each one, without bumping any of them.

Before jet bridges, passengers walked across the open ground and climbed a staircase to the plane, whatever the weather. A jet bridge is a covered walkway from the airport building straight to the plane's door. It keeps people warm, dry and safely away from the trucks and engines below.

The tricky part is that planes are not all alike. A small jet has its door near the ground, and a jumbo's door is as high as the roof of a house. The doors are at different distances from the building too. So the bridge has to be able to move in three ways.

It swings around a round joint called the rotunda, where it joins the building. It stretches, because its tunnels slide inside each other like a telescope. And it lifts, because strong columns raise or lower its far end. Big motor-driven wheels do the swinging and stretching by rolling across the ground.

At the end is the cab, where the operator steers with a joystick. A soft folding canopy closes the last gap, and a little sensing wheel keeps the floor level with the plane as it sinks under the weight of people and bags. A desk lamp's arm moves in similar ways, with one difference: a lamp bends at an elbow, while a jet bridge slides straight in and out.

Key words

Jet bridge

A covered, movable walkway that connects an airport building to an aircraft door.

Rotunda

The round joint at the building end, around which the bridge swings.

Telescoping

Getting longer or shorter by sliding tubes inside one another.

Cab

The room at the far end of the bridge that meets the aircraft.

Door sill

The doorstep of the plane's door.

Slope

How steep a floor is.

Check your thinking

1. How does a jet bridge change its length?

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   Its tunnels slide inside each other, like a telescope. The tunnel sections are nested, and the wheels drive them in or out.

2. Why must a jet bridge be able to move up and down?

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   Different planes have doors at different heights. A small jet's door is low and a jumbo's is high. The lift columns set the floor to match.

3. What is the rotunda for?

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   It is the hinge that lets the bridge swing left and right. The rotunda is the turning joint where the bridge is fixed to the building.

4. Why is the canopy at the end soft and folding?

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   So it can press gently around the plane's curved side without hurting it. A plane's skin is thin. A soft hood closes the gap and keeps the weather out without pushing hard.

5. The terminal floor is 4 meters high and a plane's door sill is 2 meters high. What is the shortest bridge that keeps the slope to 1 in 12?

   Show the answer

   24 meters. The height difference is 2 meters, and 2 times 12 is 24 meters of length.

6. A plane sinks a little as people get on. How does the bridge know?

   Show the answer

   A small wheel resting on the plane feels it move. That wheel is the auto-leveler. When the plane moves, it tells the lift columns to follow.