Definition
Best-rate-of-climb (BROC) is the airspeed that produces the greatest gain in altitude per unit of time. In helicopters, it is the speed flown to reach a desired altitude in the shortest time, and is used during instrument departures and missed approaches when prompt altitude gain is required.
Plain English
BROC is the speed that gets the helicopter up to a given altitude as quickly as possible — the fastest way to gain height in terms of time.
Context Anchor
Seen on helicopter AFCS or flight director mode controls and displays during instrument departures and other climbs.
Derivation
The name describes exactly what it does: the airspeed that gives the best (highest) rate (feet per minute) of climb. 'Rate' here means change over time, so BROC is about climbing fast in time, not steeply over distance.
Why Pilots Care
Using BROC lets the crew clear terrain or weather layers quickly while staying within power and rotor limits.
Intuition Check
Best does not mean safest in every situation or steepest over the ground. In best-rate-of-climb, best means the most altitude gained in the least time for the conditions.
Example Sentence 1
After the missed approach, the pilot accelerated to BROC to reach the holding altitude as quickly as possible.
Example Sentence 2
During the missed approach the crew maintained BROC until clear of the cloud deck.