Definition
A type of static air vent used on some aircraft fuel tanks in which a curved or scoop-shaped tube is mounted so that it can rotate or be positioned to face into the relative airflow. As the aircraft moves through the air, the vent admits outside air into the fuel tank to replace the volume of fuel being consumed, keeping tank pressure near ambient and preventing a vacuum from forming as fuel is drawn from the tank.
Plain English
A small air inlet on a fuel tank, shaped and angled so that air from the slipstream can flow in and replace the fuel as it is used up. Without this incoming air, the tank would form a partial vacuum and fuel would stop flowing properly.
Context Anchor
Seen during aircraft battery inspection, servicing, or maintenance manual procedures.
Derivation
From Latin 'rotare', to turn, plus 'vent' from Latin 'ventus', wind. The name reflects that this style of vent can be turned or oriented so its opening faces into the airflow, using the wind to keep the tank vented.
Why Pilots Care
Maintains proper tank pressure to prevent fuel flow interruptions or collapse of the tank structure.
Intuition Check
Do not read rotator vent as a cabin air vent or an engine part. Here it is a battery vent cap that helps prevent spillage while still letting gas escape.
Example Sentence 1
During preflight, the pilot checked that the rotator vent on the fuel tank was clear of insects and debris.
Example Sentence 2
A clogged rotator vent can cause the fuel tank to develop a vacuum and restrict fuel delivery to the engine.