Definition
A specialized screw with a cylindrical head that has a hole bored through it perpendicular to the screw's axis. A rod or wire can be inserted through this hole to give the mechanic leverage for tightening or loosening the screw, allowing it to be turned by hand without a screwdriver.
Plain English
A screw with a small sideways hole through its head, so you can stick a thin rod through it and turn it like a little lever instead of using a screwdriver.
Context Anchor
Seen in aircraft maintenance manuals, parts catalogs, and hardware descriptions when identifying or adjusting certain aircraft fasteners.
Derivation
Named after the capstan, a vertical drum used on ships to wind ropes. Sailors pushed long bars (handspikes) inserted into holes in the drum to turn it. The screw works the same way in miniature: a rod through the head gives you the leverage to turn it.
Why Pilots Care
Correct cable tension ensures responsive flight controls without binding or slack that could affect handling or safety.
Intuition Check
Do not assume a capstan screw is defined by a special thread. The name mainly describes the head and how the screw is turned.
Example Sentence 1
The technician inserted a small pin through the capstan screw to make a fine adjustment to the instrument's calibration.
Example Sentence 2
After replacing the aileron cable, the technician used the capstan screws at each end to set proper tension.