What are V-speeds
V-speeds are the airspeeds defined for specific maneuvers, they are specific for that aircraft in a specific configuration. For example Vso is the speed for a stall with full flaps, landing gear down, power-off. The actual speeds are usually expressed as indicated airspeeds (IAS), which allows you the pilot to read them directly from the airspeed indicator. To assist the pilot in this task, the airspeed indicator in most general aviation aircraft has color-coded arcs and lines that demarcate some (but not all) of the most commonly used and most safety-critical airspeeds.
How are V-speeds determined?
Aircraft designers and manufacturers perform flight tests to help determine aircraft performance and limitations. They use the resulting flight test data to help determine specific best speeds for safe operation of the aircraft. Once the designers and manufacturers have done their part, government flight inspectors verify the data during type-certification testing.
The V-speeds can be broken down into two different categories: performance and limitations.
Performance
Vr – Rotation speed – Recommended speed to start applying back pressure to the yoke.
Vg – Best glide speed – Speed used in emergency situations to stay airborne as long as possible. This speed decreases as weight decreases.
Vy – Best rate of climb speed – The speed at which the airplane will obtain the greatest altitude over time. The best rate-of-climb speed will normally decrease with altitude.
This is the speed that you want to use to get to your altitude over time.
Vx – Best angle of climb speed – The airspeed at which the airplane will obtain the highest altitude in a given distance. The best angle of climb speed normally increases with altitude.
This is the speed you would use to get to your altitude quickly, in case you were trying to clear an obstacle at the end of a runway.
Test tip: To remember best angle vs best rate. The letter X has more angles than the letter y. So VX is the Best angle of climb speed.
Limitations
Vso – The minimum steady flight or the stalling speed in the landing configuration.
In small airplanes this is the power-off stall speed at the maximum landing weight in the landing configuration (gear and flaps down).
On the airspeed indicator, it is indicated as the lower limit (the lowest speed on the airspeed indicator, not the lower side) of the white arc.
Vs1 – The minimum steady flight or the stalling speed obtained in a specified configuration.
For small airplanes, this is the power-off stall speed at the maximum takeoff weight in the clean configuration (gear up, if retractable, and flaps up) Make sure to check your plane’s POH for specific information.
On the airspeed indicator, it is indicated as the lower limit the lowest speed) of the green arc.
Vfe – The maximum speed the aircraft should be operated with the flaps extended.
On the airspeed indicator, it is indicated as the higher (the fastest speed) of the white arc.
Vno – The Normal operating speed. The maximum speed for normal operation or the maximum structural cruise speed.
On the airspeed indicator, this is indicated as the beginning of the yellow arc.
Vne (Red Line) – The never exceed speed. Operating above this speed is prohibited because it can result in damage or structural damage.
Va – Maneuvering speed – The design maneuvering speed. This is the maximum speed at which the limit load can be imposed either by gusts or full deflection of the control surfaces without causing structural damage.
Vle – Maximum landing gear extension speed. The maximum airspeed at which the airplane can be safely flown with the landing gear extended. Faster speeds can have issues with stability and controllability of the airplane.
Vlo – Maximum landing gear operating speed. The maximum speed at which the landing gear can be safely extended or retracted. Faster speeds can have airflow/airload problems imposed on the mechanisms of the gear.
NOTE: These are the speeds at which your aircraft has been tested, if you decide to operate the plane outside these speeds with the specified configurations, you are now a test pilot.
Final Thoughts
These speeds are derived from data obtained by aircraft designers and manufacturers during flight testing for aircraft type-certification. Using them is considered a best practice to maximize aviation safety, aircraft performance, or both. You should know these numbers for your airplane or have them in a place where you can easily access them if needed like on your knee board.