V speeds

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A single-engine Cessna 150L's airspeed indicator indicating its V speeds in knots ASI01b.jpg
A single-engine Cessna 150L's airspeed indicator indicating its V speeds in knots

In aviation, V-speeds are standard terms used to define airspeeds important or useful to the operation of all aircraft. [1] 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. [2]

Contents

The actual speeds represented by these designators are specific to a particular model of aircraft. They are expressed by the aircraft's indicated airspeed (and not by, for example, the ground speed), 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 most safety-critical airspeeds are displayed as color-coded arcs and lines located on the face of an aircraft's airspeed indicator. The lower ends of the white arc and the green arc are the stalling speed with wing flaps fully extended, and stalling speed with wing flaps retracted, respectively. These are the stalling speeds for the aircraft at its maximum weight. [3] [4] The yellow range is the range in which the aircraft may be operated in smooth air, and then only with caution to avoid abrupt control movement, and the red line is the VNE, the never exceed speed.

Proper display of V-speeds is an airworthiness requirement for type-certificated aircraft in most countries. [5] [6]

Regulations

The most common V-speeds are often defined by a particular government's aviation regulations. In the United States, these are defined in title 14 of the United States Code of Federal Regulations, known as the Federal Aviation Regulations (FARs). [7] In Canada, the regulatory body, Transport Canada, defines 26 commonly used V-speeds in their Aeronautical Information Manual. [8] V-speed definitions in FAR 23, 25 and equivalent are for designing and certification of airplanes, not for their operational use. The descriptions below are for use by pilots.

Regulatory V-speeds

These V-speeds are defined by regulations. They are typically defined with constraints such as weight, configuration, or phases of flight. Some of these constraints have been omitted to simplify the description.

V-speed designatorDescription
V1The speed beyond which takeoff should no longer be aborted. (See V1 definitions below) [7] [8] [9]
V2Takeoff safety speed. The speed at which the aircraft may safely climb with one engine inoperative. [7] [8] [9]
V2minMinimum takeoff safety speed. [7] [8] [9]
V3Flap retraction speed. [8] [9]
V4Steady initial climb speed. The all engines operating take-off climb speed used to the point where acceleration to flap retraction speed is initiated. Should be attained by a gross height of 400 ft (120 m). [10]
VADesign maneuvering speed. This is the speed above which it is unwise to make full application of any single flight control (or "pull to the stops") as it may generate a force greater than the aircraft's structural limitations. [7] [8] [9] [11]
VatIndicated airspeed at threshold, which is usually equal to the stall speed VS0 multiplied by 1.3 or stall speed VS1g multiplied by 1.23 in the landing configuration at the maximum certificated landing mass, though some manufacturers apply different criteria. If both VS0 and VS1g are available, the higher resulting Vat shall be applied. [12] Also called "approach speed". Also known as Vth [13] [14]
VBDesign speed for maximum gust intensity. [7] [8] [9]
VCDesign cruise speed, used to show compliance with gust intensity loading. [15]
VcefSee V1; generally used in documentation of military aircraft performance. Denotes "critical engine failure" speed as the speed during takeoff where the same distance would be required to either continue the takeoff or abort to a stop. [16]
VDDesign diving speed, the highest speed planned to be achieved in testing. [7] [8] [9]
VDFDemonstrated flight diving speed, the highest actual speed achieved in testing. [7] [8] [9]
VEFThe speed at which the critical engine is assumed to fail during takeoff. [7]
VFDesigned flap speed. [7] [8] [9]
VFCMaximum speed for stability characteristics. [7] [9]
VFEMaximum flap extended speed. [7] [8] [9]
VFTOFinal takeoff speed. [7]
VHMaximum speed in level flight at maximum continuous power. [7] [8] [9]
VLEMaximum landing gear extended speed. This is the maximum speed at which a retractable gear aircraft should be flown with the landing gear extended. [7] [8] [9] [17]
VLOMaximum landing gear operating speed. This is the maximum speed at which the landing gear on a retractable gear aircraft should be extended or retracted. [7] [9] [17]
VLOFLift-off speed. [7] [9]
VMC Minimum control speed. The minimum speed at which the aircraft is still controllable with the critical engine inoperative. [7] Like the stall speed, there are several important variables that are used in this determination. Refer to the minimum control speed article for a thorough explanation. VMC is sometimes further refined into more discrete V-speeds e.g. VMCA,VMCG.
VMCA Minimum control speed air. The minimum speed that the aircraft is still controllable with the critical engine inoperative [18] while the aircraft is airborne. VMCA is sometimes simply referred to as VMC.
VMCG Minimum control speed ground. The minimum speed that the aircraft is still controllable with the critical engine inoperative [18] while the aircraft is on the ground.
VMCL Minimum control speed in the landing configuration with one engine inoperative. [9] [18]
VMOMaximum operating limit speed. [7] [8] [9] Exceeding VMO may trigger an overspeed alarm. [19]
VMUMinimum unstick speed. [7] [8] [9]
VNENever exceed speed. [7] [8] [9] [20]
VNOMaximum structural cruising speed or maximum speed for normal operations. [7] [8] [9]
VOMaximum operating maneuvering speed. [21]
VR Rotation speed. The speed at which the pilot begins to apply control inputs to cause the aircraft nose to pitch up, after which it will leave the ground. [Note 1]
VrotUsed instead of VR (in discussions of the takeoff performance of military aircraft) to denote rotation speed in conjunction with the term Vref (refusal speed). [16]
VRefLanding reference speed or threshold crossing speed. [7] [8] [9]

(In discussions of the takeoff performance of military aircraft, the term Vref stands for refusal speed. Refusal speed is the maximum speed during takeoff from which the air vehicle can stop within the available remaining runway length for a specified altitude, weight, and configuration. [16] ) Incorrectly, or as an abbreviation, some documentation refers to Vref and/or Vrot speeds as "Vr." [22]

VSStall speed or minimum steady flight speed for which the aircraft is still controllable. [7] [8] [9]
VS0Stall speed or minimum flight speed in landing configuration. [7] [8] [9]
VS1Stall speed or minimum steady flight speed for which the aircraft is still controllable in a specific configuration. [7] [8]
VSRReference stall speed. [7]
VSR0Reference stall speed in landing configuration. [7]
VSR1Reference stall speed in a specific configuration. [7]
VSWSpeed at which the stall warning will occur. [7]
VTOSSCategory A rotorcraft takeoff safety speed. [7] [20]
VXSpeed that will allow for best angle of climb. [7] [8]
VYSpeed that will allow for the best rate of climb. [7] [8]

Other V-speeds

Some of these V-speeds are specific to particular types of aircraft and are not defined by regulations.

V-speed designatorDescription
VBEBest endurance speed – the speed that gives the greatest airborne time for fuel consumed.[ citation needed ]
VBGBest power-off glide speed – the speed that provides maximum lift-to-drag ratio and thus the greatest gliding distance available.
VBRBest range speed – the speed that gives the greatest range for fuel consumed – often identical to Vmd. [23]
VFSFinal segment of a departure with one powerplant failed. [24]
VimdMinimum drag [25]
VimpMinimum power [25]
VLLOMaximum landing light operating speed – for aircraft with retractable landing lights. [9]
VLSLowest selectable speed [26]
VmbeMaximum brake energy speed [25] [27]
VmdMinimum drag (per lift) – often identical to VBR. [23] [27] (alternatively same as Vimd [28] )
VminMinimum speed for instrument flight (IFR) for helicopters [20]
VmpMinimum power [27]
VmsMinimum sink speed at median wing loading – the speed at which the minimum descent rate is obtained. In modern gliders, Vms and Vmc have evolved to the same value. [29]
VpAquaplaning speed [30]
VPDMaximum speed at which whole-aircraft parachute deployment has been demonstrated [31]
VraRough air speed (turbulence penetration speed). [9]
VSLStall speed in a specific configuration [9] [27]
Vs1gStall speed at 1g load factor [32]
Vsse Safe single-engine speed [33]
VtThreshold speed [27]
VTDTouchdown speed [34]
VTGTTarget speed[ citation needed ]
VTOTake-off speed. (see also VLOF) [35]
VtocsTake-off climbout speed (helicopters) [20]
VtosMinimum speed for a positive rate of climb with one engine inoperative [27]
VtmaxMax threshold speed [27] [36]
VwoMaximum window or canopy open operating speed [37]
VXSEBest angle of climb speed with a single operating engine in a light, twin-engine aircraft – the speed that provides the most altitude gain per unit of horizontal distance following an engine failure, while maintaining a small bank angle that should be presented with the engine-out climb performance data. [33]
VYSEBest rate of climb speed with a single operating engine in a light, twin-engine aircraft – the speed that provides the most altitude gain per unit of time following an engine failure, while maintaining a small bank angle that should be presented with the engine-out climb performance data. [17] [33]
VZFMinimum zero flaps speed [38]
VZRCZero rate of climb speed in a twin-engine aircraft [27]

Mach numbers

Whenever a limiting speed is expressed by a Mach number, it is expressed relative to the speed of sound, e.g. VMO: Maximum operating speed, MMO: Maximum operating Mach number. [7] [8]

V1 definitions

V1 is the critical engine failure recognition speed or takeoff decision speed. It is the speed above which the takeoff will continue even if an engine fails or another problem occurs, such as a blown tire. [9] The speed will vary among aircraft types and varies according to factors such as aircraft weight, runway length, wing flap setting, engine thrust used and runway surface contamination, thus it must be determined by the pilot before takeoff. Aborting a takeoff after V1 is strongly discouraged because the aircraft will by definition not be able to stop before the end of the runway, thus suffering a runway overrun. [39]

V1 is defined differently in different jurisdictions:

See also

Notes

  1. However most pilots often call out "rotate," instead of VR and Vrot. The "rotate" command has the same meaning of VR and Vrot.

Related Research Articles

Federal Aviation Administration United States Government agency dedicated to civil aviation matters

The Federal Aviation Administration (FAA) is the largest modern transportation agency and a governmental body of the United States with powers to regulate all aspects of civil aviation in that nation as well as over its surrounding international waters. Its powers include the construction and operation of airports, air traffic management, the certification of personnel and aircraft, and the protection of U.S. assets during the launch or re-entry of commercial space vehicles. Powers over neighboring international waters were delegated to the FAA by authority of the International Civil Aviation Organization.

The Federal Aviation Regulations (FARs) are rules prescribed by the Federal Aviation Administration (FAA) governing all aviation activities in the United States. The FARs are part of Title 14 of the Code of Federal Regulations (CFR). A wide variety of activities are regulated, such as aircraft design and maintenance, typical airline flights, pilot training activities, hot-air ballooning, lighter-than-air aircraft, man-made structure heights, obstruction lighting and marking, model rocket launches, model aircraft operations, Unmanned Aircraft Systems (UAS) and kite flying. The rules are designed to promote safe aviation, protecting pilots, flight attendants, passengers and the general public from unnecessary risk.

Ultralight aviation Aviation field involving lightweight aircraft

Ultralight aviation is the flying of lightweight, 1- or 2-seat fixed-wing aircraft. Some countries differentiate between weight-shift control and conventional 3-axis control aircraft with ailerons, elevator and rudder, calling the former "microlight" and the latter "ultralight".

Runway Area of surface used by aircraft to takeoff from and land on

According to the International Civil Aviation Organization (ICAO), a runway is a "defined rectangular area on a land aerodrome prepared for the landing and takeoff of aircraft". Runways may be a man-made surface or a natural surface. Runways, as well as taxiways and ramps, are sometimes referred to as "tarmac", though very few runways are built using tarmac. Runways made of water for seaplanes are generally referred to as waterways. Runway lengths are now commonly given in meters worldwide, except in North America where feet are commonly used.

STOL A class of airplanes that are designed to takeoff and land in a short distance

A short takeoff and landing (STOL) aircraft has short runway requirements for takeoff and landing. Many STOL-designed aircraft also feature various arrangements for use on runways with harsh conditions. STOL aircraft, including those used in scheduled passenger airline operations, have also been operated from STOLport airfields which feature short runways.

Landing Transition from being in flight to being on a surface

Landing is the last part of a flight, where a flying animal, aircraft, or spacecraft returns to the ground. When the flying object returns to water, the process is called alighting, although it is commonly called "landing", "touchdown" or "splashdown" as well. A normal aircraft flight would include several parts of flight including taxi, takeoff, climb, cruise, descent and landing.

An airfield traffic pattern is a standard path followed by aircraft when taking off or landing while maintaining visual contact with the airfield.

Airspeed indicator

The airspeed indicator (ASI) or airspeed gauge is a flight instrument indicating the airspeed of an aircraft in kilometers per hour (km/h), knots (kn), miles per hour (MPH) and/or meters per second (m/s). The recommendation by ICAO is to use km/h, however knots is currently the most used unit. The ASI measures the pressure differential between static pressure from the static port, and total pressure from the pitot tube. This difference in pressure is registered with the ASI pointer on the face of the instrument.

Pilot certification in the United States Pilot certification

Pilot certification in the United States is typically required for an individual to act as a pilot-in-command of an aircraft. It is regulated by the Federal Aviation Administration (FAA), a branch of the U.S. Department of Transportation (USDOT). A pilot may be certified under 14 Code of Federal Regulations (CFR) Part 61 or 14 CFR Part 141. Pilots may also be certified under 14 CFR Part 107 for commercial drone operations.

Light-sport aircraft category of lightweight aircraft that are simple to fly

A light-sport aircraft (LSA), or light sport aircraft, is a fairly new category of small, lightweight aircraft that are simple to fly. LSAs tend to be heavier and more sophisticated than ultralight aircraft, but LSA restrictions on weight and performance separates the category from established GA aircraft. There is no standard worldwide description of an LSA.

Ultralight aircraft (United States)

Ultralight aircraft in the United States are much smaller and lighter than ultralight aircraft as defined by all other countries.

Ultralight aircraft (Canada)

The Canadian Aviation Regulations define two types of ultralight aircraft: basic ultra-light aeroplane (BULA), and advanced ultra-light aeroplane (AULA).

TWA Flight 159 1967 aviation accident

Trans World Airlines (TWA) Flight 159 was a regularly scheduled passenger flight from New York City to Los Angeles, California, with a stopover in Cincinnati/Northern Kentucky International Airport, Kentucky, that crashed after an aborted takeoff from Cincinnati on 6 November 1967. The Boeing 707 attempted to abort takeoff when the copilot became concerned that the aircraft had collided with a disabled DC-9 on the runway. The aircraft overran the runway, struck an embankment and caught fire. One passenger died as a result of the accident.

Airworthiness

Airworthiness is the measure of an aircraft's suitability for safe flight. Certification of airworthiness is conferred by a certificate of airworthiness from the state of aircraft registry national aviation authority, and is maintained by performing the required maintenance actions.

Runway incursion Aviation incident in which an unauthorized aircraft enters an active runway

A runway incursion is an incident where an unauthorized aircraft, vehicle, or person is on a runway or runway protected area. Under some interpretations, a runway incursion also exists when an aircraft crosses into an ILS protected area or approach protected area when active. Any such incursion adversely affects runway safety, as it creates the risk that an airplane taking off or landing will collide with the object, distract the non-infringing flight crew, or interfere with navigational signals such as the glideslope or localizer. "Runway Incursion" is defined by the International Civil Aviation Organization (ICAO) on April 27, 2006, as:

Any occurrence at an aerodrome involving the incorrect presence of an aircraft, vehicle or person on the protected area of a surface designated for the landing and takeoff of aircraft.

Utility aircraft

A utility aircraft is a general-purpose light airplane or helicopter, usually used for transporting people, freight or other supplies, but is also used for other duties when more specialized aircraft are not required or available.

Engine failure on take-off (EFTO) is a situation, when flying an aircraft, where an engine has failed, or is not delivering sufficient power, at any time between brake release and the wheels leaving the ground / V2. The phases of flight are de-lineated to allow simplified standard procedures for different aircraft types to be developed. If an aircraft suffered engine failure on takeoff, the standard procedure for most aircraft would be to abort the takeoff.

The minimum control speed (VMC) of a multi-engine aircraft is a V-speed that specifies the calibrated airspeed below which directional or lateral control of the aircraft can no longer be maintained, after the failure of one or more engines. The VMC only applies if at least one engine is still operative, and will depend on the stage of flight. Indeed, multiple VMCs have to be calculated for landing, air travel, and ground travel, and there are more still for aircraft with four or more engines. These are all included in the aircraft flight manual of all multi-engine aircraft. When design engineers are sizing an airplane's vertical tail and flight control surfaces, they have to take into account the effect this will have on the airplane's minimum control speeds.

A power-off accuracy approach is an aviation exercise used to simulate a landing with an engine failure. The purpose of this training technique is to better develop one's ability to estimate distance and glide ratios. The variation in each angle refers to the degrees an aircraft must turn to be aligned with the runway. Consideration of the wind and use of flaps are important factors in executing power-off accuracy approaches.

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Further reading