Best-rate-of-climb speed is the airspeed, designated Vy, at which an aircraft gains the most altitude per minute. It gives pilots the fastest vertical progress from one altitude to another.
How It Works#
Every aircraft has two types of drag acting on it at all times. Induced drag (drag created by generating lift) is high at low airspeeds and drops as speed increases. Parasite drag (drag from the airframe, landing gear, and other surfaces) does the opposite: it rises with speed. Vy sits at the point where the power available most exceeds the power required to maintain level flight, producing the largest energy surplus for climbing.
This point falls close to L/D max, the airspeed where the lift-to-drag ratio peaks. At L/D max, the aircraft is flying most efficiently. Vy is slightly faster than L/D max in most piston aircraft, because maximum excess power (not maximum aerodynamic efficiency alone) determines the best climb rate.
Vy is published in the Pilot's Operating Handbook (POH) for a specific weight and pressure altitude. As weight decreases or altitude increases, Vy changes. At higher density altitudes, the speed for best power output shifts slightly lower. Many POHs provide a table showing how Vy changes with altitude.
Example in Aviation#
A Cessna 172 pilot departs a busy airport in a standard traffic pattern. After liftoff, she pitches to 74 knots indicated airspeed: the published Vy for that aircraft. She climbs straight ahead, gaining around 700 feet per minute. This gets her to pattern altitude quickly and clears terrain and obstacles in the shortest time.
Later, on a cross-country leg, she needs to climb from 3,500 feet to 9,500 feet. She holds Vy throughout the climb. Holding any other airspeed would either reduce her climb rate or force the engine to work harder for the same vertical progress.
Why It Matters#
Pilots use Vy whenever the priority is reaching a target altitude in the least amount of time. This matters most after takeoff, when obstacle clearance is critical, or during a cross-country climb where time and fuel both count.
Understanding Vy also teaches a broader lesson. Flying faster than Vy wastes excess power on overcoming parasite drag. Flying slower bleeds into the induced drag regime and reduces climb performance. Vy is the precise balance point, and knowing why it exists helps pilots make better speed decisions throughout a flight.
Key Takeaways#
- Vy is the airspeed that produces the greatest altitude gain per minute.
- It sits where excess power (available minus required) is at its maximum.
- Vy falls near L/D max but is typically slightly faster in piston aircraft.
- The published Vy assumes a specific weight and pressure altitude; it changes with conditions.
- Use Vy when climbing time matters most, such as immediately after takeoff.