Definition
A specific named RNAV (area navigation) Standard Instrument Departure (SID) procedure, used as an example in the Instrument Flying Handbook. The name follows the FAA convention for departure procedures: a fix or feature name (SHEAD), a revision number written as a word (TWO, meaning the second published version), the word DEPARTURE, and the equipment qualifier (RNAV) indicating it requires RNAV-capable avionics to fly.
Plain English
It is the name of a particular published departure route that pilots can fly out of an airport using GPS-based navigation equipment. The 'TWO' just means it is the second version of this departure that has been published; if it gets updated again it will become SHEAD THREE.
Context Anchor
Seen on IFR departure procedure charts and in FAA discussions of obstacle departure procedures.
Derivation
Departure procedures are named after a fix, waypoint, or geographic feature along the route -- in this case, a waypoint called SHEAD. The number (TWO) is the revision count, spelled as a word to avoid confusion with altitudes or headings on a radio call. RNAV stands for area navigation, meaning the route is defined by GPS waypoints rather than by ground-based navaids.
Why Pilots Care
Following the procedure guarantees safe obstacle clearance during low-visibility or night departures when visual references are unavailable.
Grounding Statement
Think of it as a protected published path from takeoff into the instrument system, provided the aircraft follows the chart and climbs as required.
Intuition Check
Do not read “SHEAD TWO DEPARTURE” as a general suggestion to depart toward SHEAD. It is the exact title of a published procedure; “TWO” is a version number, not a runway, altitude, or heading.
Example Sentence 1
After takeoff from runway 27, we were cleared to fly the SHEAD TWO DEPARTURE (RNAV) and climb to 5,000 feet.
Example Sentence 2
Reviewing the SHEAD TWO DEPARTURE (RNAV) chart confirmed the initial heading and altitude restrictions before engine start.