Definition
A reversible direct-current series motor whose field winding is divided into two separate sections wound in opposite directions on the same field poles. Energizing one section turns the motor in one direction; energizing the other section reverses the magnetic field and turns the motor in the opposite direction. Only one field section is energized at a time, and the armature current path is the same in both cases.
Plain English
A small DC motor with two field windings instead of one. Power up the first winding and the motor turns one way. Power up the second winding and it turns the other way. You pick the direction by choosing which winding gets the current.
Context Anchor
Seen in aircraft electrical system descriptions for parts that must move in two directions, such as some flap, trim, or landing gear mechanisms.
Derivation
Called split-field because the single field winding of an ordinary series motor is split into two halves wound in opposite directions, giving the motor two selectable directions of rotation from one shared armature.
Why Pilots Care
Provides reliable bidirectional motion for critical actuators while keeping the control circuit simple and fail-safe.
Analogy
Think of it like a reversible fan with two separate buttons: one button makes it turn one way, and the other button makes it turn the other way.
Intuition Check
“Field” here does not mean an airport or an open area. It means the magnetic part of the motor that helps control rotation.
Example Sentence 1
The flap motor in this trainer is a split-field motor, so the same motor drives the flaps both up and down depending on which field winding the switch energizes.
Example Sentence 2
During preflight the mechanic applied voltage to each field winding separately and confirmed the split-field motor turned in both directions.