Definition
Altitudes published on a Standard Instrument Departure (SID) or other instrument procedure that the pilot must comply with as charted. They appear in three forms: a mandatory altitude (a single value the aircraft must cross at), a minimum altitude (cross at or above), and a maximum altitude (cross at or below). The form is shown on the chart by where the line is drawn relative to the altitude figure.
Plain English
Altitudes printed on a departure or instrument chart that you have to fly to in a specific way. Some say 'be exactly at this altitude,' some say 'be at or above this,' and some say 'be at or below this.' How the number is drawn on the chart tells you which kind it is.
Context Anchor
Seen on Standard Instrument Departure charts and in departure clearance review, especially when checking whether the aircraft can climb fast enough to meet the procedure.
Derivation
Required comes from a Latin word meaning “to need or demand.” Altitude comes from Latin altus, meaning “high.” Together, the phrase points to heights that are not optional; the procedure needs the aircraft to meet them.
Why Pilots Care
Meeting these altitudes guarantees terrain clearance and keeps the flight within the protected airspace of the procedure.
Intuition Check
“Required” does not mean recommended or approximate here. It means the altitude is part of the procedure or clearance and must be met unless ATC changes it.
Example Sentence 1
Briefing the SID, the captain pointed out the required altitudes at each fix and noted that the crossing at WILMA was a mandatory 5,000 feet, not a minimum.
Example Sentence 2
The crew leveled at the required altitude until ATC issued a higher clearance.