V-speeds are standard terms used in aviation to define airspeeds that are important or useful to the operation of all aircraft. These speeds are derived from data gathered by aircraft designers and manufacturers during flight testing for aircraft type-certification testing. Adhering to V-speeds is considered a best practice to maximize aviation safety, aircraft performance, or both. The speeds represented by these standards are specific to a particular model of aircraft and are expressed by the aircraft's indicated airspeed, rather than ground speed or other speeds, so that pilots may use them directly without having to apply correction factors, as aircraft instruments also show indicated airspeed.
In general aviation aircraft, the most commonly used and safety-critical airspeeds are displayed as color-coded arcs and lines on the face of the airspeed indicator. The lower ends of the green and white arcs are the stalling speed with wing flaps retracted, and stalling speed with wing flaps extended, respectively, when at maximum weight. The yellow range is the range in which the aircraft can be operated in smooth air, and the red line is the VNE, or the never exceed speed. Proper display of V-speeds is a requirement for airworthiness in most countries, though most common V-speeds are defined by a particular government’s aviation regulations. For instance, V-speeds in the United States may be different from those in Canada.
The “V” in V-speeds comes from the word vitesse, the French word for speed. There are dozens of standardized V-speeds, some more complex than others. This blog will list the most common ones and provide a brief explanation of each.
V1 is the maximum speed during a takeoff at which the pilot must decide to abort or carry-out a takeoff. It also refers to the minimum speed, following the failure of a critical aircraft engine, at which the pilot can continue a takeoff and achieve the required height about the surface within the takeoff distance.
This is the takeoff safety speed for aircraft in the jet, turboprop, or transport category. V2 is the best climb gradient speed, meaning this speed will bring the best altitude increase per mile. Twin-engine aircraft are guaranteed a 2.4 percent climb gradient.
This is the minimum speed at which an aircraft can take off safely. V2MIN is generally 1.2 times the stall speed when the aircraft is configured for takeoff.
VA, the design maneuvering speed, is the highest safe airspeed for abrupt control deflection or operation in turbulence and severe wind. VA does not allow for multiple large control inputs. If only one VA speed is denoted, it refers to speed at maximum landing weight. This speed will decrease as weight decreases.
VABE is the maximum speed for air brake extension. VABO is the maximum speed for air brake operation.
This is the target speed for aircraft on approach. This speed is determined by combining the landing reference speed with the wind factor.
VB is the design speed for maximum gust intensity for transport-category aircraft and other aircraft certified under Part 25 airworthiness standards.
VC, or design cruising speed, is the speed at which a given aircraft was designed to cruise. A completed aircraft may actually cruise slower or faster than VC, as VC is simply the speed at which an aircraft must be able to withstand a standard 50 feet per second (fps) gust.
Similar to VC, VD, or design diving speed, is the speed at which an aircraft is designed to be capable of diving in smooth air without control reversal or buffeting. Control surfaces have natural vibration, but if they begin to flutter, it can cause serious problems. VD is an important speed to monitor for the safety of an aircraft.
VDF and MDF both represent demonstrated flight diving speed, but are displayed differently. VDF is represented in knots, while MDF is a percentage of a Mach number. Certain aircraft are not capable of reaching design diving speed, in which case the pilot dives to the maximum speed possible, the demonstrated flight diving speed.
These refer to the maximum speed in undesirable flight conditions. This speed must be respected, as instability could develop beyond the pilot’s ability to recover. VFC and MFC are the same speed, but VFC is expressed in knots, while MFC is expressed in percentage of Mach.
VFTO is the final takeoff speed, or the speed an aircraft must reach at the end of a takeoff path.
VLO refers to the maximum landing gear operating speed, the highest speed at which the landing gear can be safely extended or retracted. This is usually limited by maximum loads on the wheel-well doors. On certain aircraft, these doors close after extension of the landing gear, allowing for acceleration to VLE, the maximum speed with landing gear extended.
This is the liftoff speed, or speed at which an aircraft becomes airborne.
The VNE is the never-exceed speed, also known as red line speed. This applies only to piston-powered aircraft. VNE is never more than 90 percent of VDF. it is critical to not the VNE as G loads at this speed can easily overstress and damage aircraft.
VNO is similar to the never-exceed speed, but refers to the maximum structural cruising speed. In theory, a new aircraft can withstand 50 fps gusts at this speed, though the pilot has no means of accurately measuring the intensity of wind.
Lastly, VS is the stall speed or minimum steady flight speed at which the aircraft is controllable. VS is a broad term and does not usually refer to a specific airspeed.
Hopefully this has shed some light on what V-speeds are and how important they are. For a wealth of resources and purchasing options pertaining to the aerospace, civil aviation, defense, electronic, and industrial markets, look no further than Just NSN Parts. Owned and operated by ASAP Semiconductor, we can help you find a broad range of unique parts for all types of applications. We’re always available and ready to help you find all the parts and equipment you need, 24/7-365. For a quick and competitive quote, call us at 1-714-705-4780 or email us at email@example.com.