A clearance at a busy airport could, in principle, be a long recital of headings, altitudes and fixes. Instead it is often a single name: a SID on the way out, a STAR on the way in. These published procedures do a lot of quiet work, turning a tangle of departing and arriving traffic into tidy, repeatable streams, and reading them well is a core instrument skill.
This is general educational information, not operational, legal, or regulatory advice. Rules differ by authority and change over time. Always verify against current official sources and follow your operator's approved procedures.
What they are
A SID, a standard instrument departure, is a pre-published route from a runway out to the en-route airway structure. A STAR, a standard terminal arrival route, is a pre-published route from the en-route structure in toward the initial approach. As the FAA AIM and SKYbrary put it, the point of both is to let a controller and a crew agree on a whole sequence of tracks and altitudes by naming it, rather than reading it out heading by heading.
Why they exist
Three things at once:
- Reduced radio workload. "Cleared via the MID 2F departure" replaces a paragraph of instructions and readback.
- Orderly, predictable flows. Streams of departing and arriving aircraft follow known paths, which keeps them separated and lets controllers plan ahead.
- Obstacle clearance (on a SID). A SID is designed, under the rules in ICAO Doc 8168 Volume II, to keep you clear of terrain and obstacles as you climb, provided you meet its published climb gradient.
The climb gradient that matters
The default minimum climb gradient used in procedure design is 3.3 per cent, which works out to about 200 feet per nautical mile. Where terrain or obstacles demand, a SID publishes a steeper required gradient, often expressed both as a percentage and as a feet-per-nautical-mile figure, and sometimes as a required rate of climb at a given groundspeed. The rule is firm: if your aircraft, at the day's weight and conditions, cannot meet the published gradient, that SID is not available to you, and you need an alternative departure or different conditions.
A worked example
You are assigned a SID that requires a minimum climb gradient of 5 per cent to a crossing altitude, because of high ground off the end of the runway. Five per cent is about 300 feet per nautical mile. At a groundspeed of 120 knots, which is 2 nautical miles per minute, that is a required rate of climb of about 600 feet per minute (300 feet per mile times 2 miles per minute). Check that figure against your aircraft's climb performance for the day; if you cannot sustain it, you do not fly that SID.
On the arrival, a STAR might include a crossing restriction such as "cross WAYPT at or above FL080 and at 250 knots." That is the STAR doing its job: sequencing you down and slowing you into the terminal area at a known point, so the controller can fit you into the arriving stream without a string of individual instructions. You meet the restriction the same way you meet a SID gradient: by planning the descent and speed to arrive at the fix within the limits.
Common pitfalls
- A SID's obstacle protection is conditional. It assumes you make the published climb gradient; if you cannot, the protection does not apply.
- Percentages and feet-per-mile are two faces of one number. Convert deliberately and turn it into a rate of climb for your groundspeed before you accept the procedure.
- Crossing restrictions are not optional. "At or above," "at or below" and speed limits on a STAR are clearance items; plan the descent so you meet them.
In Pilot EFB
Pilot EFB is a study and planning companion for reading departures and arrivals and for the route planning around them, alongside your weather, NOTAMs and flight time in one offline-first place. It does not issue clearances or replace your charts and avionics, so fly the published procedure from your official source of record. Pilot EFB is not a certified Electronic Flight Bag, so treat it as a study and planning aid and brief from your official source of record.