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What If the Wheels Don't Come Down?

2 min read

The short answer

Landing gear has more than one way to come down. If the normal system has a problem, a backup lets the wheels drop and lock using gravity and the airflow. The rules require this backup on every airliner, and pilots practise using it in the simulator.

A Familiar Clunk

Before landing, you'll hear a rumble and a firm clunk beneath you. That's the landing gear — the wheels — lowering and locking into place. It's one of the most reassuring sounds on a flight.

How It Normally Works

The wheels are raised and lowered by hydraulics — powerful fluid systems that move heavy parts. Airliners have more than one hydraulic system, so one can stand in for another. Read backup systems.

The Backup: Gravity Does the Work

Aviation rules require every airliner to have an emergency way to lower the wheels if the normal system fails.

On most airliners, a switch or handle in the cockpit simply unlocks the gear. Gravity and the air rushing past then swing the wheels down until they lock in place. No hydraulics are needed at all.

Pilots practise this in the simulator, so it's familiar if they ever need it.

How Pilots Know the Wheels Are Down

Each set of wheels has its own indicator in the cockpit. Pilots look for three green lights — one for each landing gear leg — showing it's down and locked. If an indicator looks unusual, they have plenty of options:

  • run the checklist and try again
  • use the backup method
  • fly past the control tower so people on the ground can take a look

There's no rush. The plane carries spare fuel, so the pilots can take all the time they need. Read how much fuel a plane carries.

The Takeaway

The wheels coming down isn't left to chance. There's a normal system, a backup that relies on gravity, clear indicators, and pilots trained for every possibility.

Sources

Keep reading

Backup Systems: A Spare for Everything That Matters

How planes are designed so that no single fault can put a flight at risk — with backups for every important system.

The Landing Sequence Explained

Every sound and feeling as the plane comes down to land, explained in order — so you know exactly what to expect.

Common Flight Sounds Explained

A guide to every sound you'll hear during a flight — from boarding to landing — and what each one means.

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