Definition
A gear with two sets of helical teeth cut at opposing angles on the same gear face, forming a V-shape pattern across the width of the gear. The opposing helix angles cancel out the axial (sideways) thrust that a single helical gear would otherwise produce, allowing the gear to transmit high loads smoothly without forcing the shaft sideways.
Plain English
A gear whose teeth are cut in a V-shape pattern, like rows of arrows pointing the same way. This shape lets the gear handle heavy loads quietly and smoothly without pushing its shaft sideways.
Context Anchor
Seen in aircraft engine, accessory drive, and mechanical power-transfer discussions, especially in maintenance or component descriptions.
Derivation
Named after the herringbone pattern in fabric weaving, which itself is named after the bone structure of a herring fish. The V-shaped teeth resemble the angled, alternating rows of that pattern.
Why Pilots Care
Allows high-power engines to drive propellers smoothly with minimal vibration and no need for extra thrust bearings.
Analogy
Think of two sets of diagonal tread marks meeting in the middle to make a repeating V pattern. Each side would tend to push one way, but together they balance each other.
Intuition Check
Do not confuse “gear” here with landing gear. Here it means a toothed wheel inside a mechanical drive system.
Example Sentence 1
The reduction gearbox uses a herringbone gear to transfer engine power to the propeller shaft smoothly.
Example Sentence 2
Herringbone gears in the reduction unit transmit crankshaft power to the propeller without creating axial loads.