A single-engined 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]

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 in landing configuration, and stalling speed with wing flaps retracted, respectively. These are the stalling speeds for the aircraft at its maximum weight.[3][4] The yellow band is the range in which the aircraft may be operated in smooth air, and then only with caution to avoid abrupt control movement. 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 designator Description
V1 The speed beyond which takeoff should no longer be aborted (see § V1 definitions below).[7][8][9]
V2 Takeoff safety speed. The speed at which the aircraft may safely climb with one engine inoperative.[7][8][9]
V2min Minimum takeoff safety speed.[7][8][9]
V3 Flap retraction speed.[8][9]
V4 Steady 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]
VA Design 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]
Vat Indicated 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]

Davies defines Vat and Vref as equivalent.[15]

VB Design speed for maximum gust intensity.[7][8][9]
VC Design cruise, also known as the optimum cruise speed, is the most efficient speed in terms of distance, speed and fuel usage.[16][17][18]
Vcef See 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.[19]
VD Design diving speed, the highest speed planned to be achieved in testing.[7][8][9]
VDF Demonstrated flight diving speed, the highest actual speed achieved in testing.[7][8][9]
VEF The speed at which the critical engine is assumed to fail during takeoff.[7]
VF Designed flap speed.[7][8][9]
VFC Maximum speed for stability characteristics.[7][9]
VFE Maximum flap extended speed.[7][8][9]
VFTO Final takeoff speed.[7]
VH Maximum speed in level flight at maximum continuous power.[7][8][9]
VLE Maximum 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][20]
VLO Maximum 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][20]
VLOF Lift-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[21] 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[21] while the aircraft is on the ground.
VMCL Minimum control speed in the landing configuration with one engine inoperative.[9][21]
VMO Maximum operating limit speed.[7][8][9] Exceeding VMO may trigger an overspeed alarm.[22]
VMU Minimum unstick speed.[7][8][9]
VNE Never exceed speed.[7][8][9][23] In a helicopter, this is chosen to prevent retreating blade stall and prevent the advancing blade from going supersonic.
VNO Maximum structural cruising speed or maximum speed for normal operations. Speed at which exceeding the limit load factor may cause permanent deformation of the aircraft structure.[7][8][9][24]
VO Maximum operating maneuvering speed.[25]
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.[7][26][Note 1]
Vrot Used instead of VR (in discussions of the takeoff performance of military aircraft) to denote rotation speed in conjunction with the term Vref (refusal speed).[19]
VRef Landing reference speed or threshold crossing speed.[7][8][9] Must be at least 1.3 VS0. Must be at least VMC for reciprocating-engine aircraft, or 1.05 VMC for commuter category aircraft.[28]

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.[19] Incorrectly, or as an abbreviation, some documentation refers to Vref and/or Vrot speeds as "Vr."[29]

VS Stall speed or minimum steady flight speed for which the aircraft is still controllable.[7][8][9]
VS0 Stall speed or minimum flight speed in landing configuration.[7][8][9]
VS1 Stall speed or minimum steady flight speed for which the aircraft is still controllable in a specific configuration.[7][8]
VSR Reference stall speed.[7]
VSR0 Reference stall speed in landing configuration.[7]
VSR1 Reference stall speed in a specific configuration.[7]
VSW Speed at which the stall warning will occur.[7]
VTOSS Category A rotorcraft takeoff safety speed.[7][23]
VX Speed that will allow for best angle of climb.[7][8]
VY Speed 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 designator Description
VAPP Approach speed. Speed used during final approach with landing flap set.[30] VREF plus safety increment,[31][32][33] typically minimum 5 knots,[34] and maximum 15 knots[30] to avoid exceeding flap limiting speeds. Typically it is calculated as half the headwind component plus the gust factor.[30] The purpose is to ensure that turbulence or gusts will not result in the airplane flying below VREF at any point on the approach.[30] Also known as VFLY.
VBE Best endurance speed – the speed that gives the greatest airborne time for fuel consumed.[citation needed]
VBG Best power-off glide speed – the speed that provides maximum lift-to-drag ratio and thus the greatest gliding distance available.
VBR Best range speed – the speed that gives the greatest range for fuel consumed – often identical to Vmd.[35]
VFS Final segment of a departure with one powerplant failed.[36]
Vimd Minimum drag[37]
Vimp Minimum power[37]
VLLO Maximum landing light operating speed – for aircraft with retractable landing lights.[9]
VLS Lowest selectable speed[38]
Vmbe Maximum brake energy speed[37][39]
Vmd Minimum drag (per lift) – often identical to VBE.[35][39] (alternatively same as Vimd[40])
Vmin Minimum speed for instrument flight (IFR) for helicopters[23]
Vmp Minimum power[39]
Vms Minimum 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.[41]
Vp Aquaplaning speed[39]
VPD Maximum speed at which whole-aircraft parachute deployment has been demonstrated[42]
Vra Rough air speed (turbulence penetration speed).[9]
VSL Stall speed in a specific configuration[9][39]
Vs1g Stall speed at 1g load factor[43]
Vsse Safe single-engine speed[44]
Vt Threshold speed[39]
VTD Touchdown speed[45]
VTGT Target speed[citation needed]
VTO Take-off speed. (see also VLOF)[46]
Vtocs Take-off climbout speed (helicopters)[23]
Vtos Minimum speed for a positive rate of climb with one engine inoperative[39]
Vtmax Max threshold speed[39][47]
Vwo Maximum window or canopy open operating speed[48]
VXSE Best 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.[44]
VYSE Best 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.[20][44]
VZF Minimum zero flaps speed[49]
VZRC Zero rate of climb speed. The aircraft is at sufficiently low speed on the "back of the drag curve" that it cannot climb, accelerate, or turn, so must reduce drag.[39] The aircraft cannot be recovered without loss of height.[15]: 144–145 

Mach numbers

Whenever a limiting speed is expressed by a Mach number, it is expressed relative to the local 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 may not be able to stop before the end of the runway, thus suffering a runway overrun.[50]

V1 is defined differently in different jurisdictions, and definitions change over time as aircraft regulations are amended.

See also

Notes

  1. ^ Most pilots often call out "rotate," instead of VR. The "rotate" callout has the same meaning of VR and Vrot.[27]

References

  1. ^ Love, Michael C. (2005). "2". Better Takeoffs & Landings. Mc-Graw Hill. pp. 13–15. ISBN 0-07-038805-9. Retrieved 7 May 2008.
  2. ^ Craig, Paul A. (2004). "1". Multiengine Flying (3rd ed.). McGraw Hill. pp. 3–6. ISBN 0-07-142139-4. Retrieved 7 May 2008.
  3. ^ FAA (July 2008). "Title 14: Aeronautics and Space PART 23—AIRWORTHINESS STANDARDS: NORMAL, UTILITY, ACROBATIC, AND COMMUTER CATEGORY AIRPLANES Subpart G—Operating Limitations and Information Markings And Placards, Part 23, §23.1545". Archived from the original on 29 September 2006. Retrieved 1 August 2008.
  4. ^ "Pilot's Handbook of Aeronautical Knowledge – Chapter 7" (PDF). FAA. Archived from the original (PDF) on 3 September 2013. Retrieved 29 January 2010.
  5. ^ "Pilot's Handbook of Aeronautical Knowledge – Chapter 8" (PDF). FAA. Archived from the original (PDF) on 3 September 2013. Retrieved 29 January 2010.
  6. ^ FAA (July 2008). "Title 14: Aeronautics and Space PART 25—AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY AIRPLANES Subpart G—Operating Limitations and Information Airplane Flight Manual, Part 25, §25.1583". Archived from the original on 29 September 2006. Retrieved 1 August 2008.
  7. ^ a b c d e f g h i j k l m n o p q r s t u v w x y z aa ab ac ad ae af ag ah ai aj "Title 14 – Aeronautics and Space; Chapter I – Federal Aviation Administration, Subchapter A – Definitions and General Requirements; Part 1 – Definitions and Abbreviations; § 1.2 Abbreviations and symbols". ecfr.gov. Federal Register. Retrieved 19 February 2023.
  8. ^ a b c d e f g h i j k l m n o p q r s t u v w x y Transport Canada (October 2012). "Aeronautical Information Manual GEN – 1.0 GENERAL INFORMATION" (PDF). Retrieved 1 January 2013.
  9. ^ a b c d e f g h i j k l m n o p q r s t u v w x y z aa Peppler, I.L.: From The Ground Up, page 327. Aviation Publishers Co. Limited, Ottawa Ontario, Twenty Seventh Revised Edition, 1996. ISBN 0-9690054-9-0
  10. ^ CAP 698: Civil Aviation Authority JAR-FCL Examinations: Aeroplane Performance Manual (PDF). Civil Aviation Authority (United Kingdom). 2006. pp. Section 4–MRJT1 Page 3. ISBN 0-11-790653-0. Archived from the original (PDF) on 14 November 2009. Retrieved 9 December 2009.
  11. ^ FAA Advisory Circular 23-19A Airframe Guide for Certification of Part 23 Airplanes, Section 48 (p.27) Archived 7 December 2016 at the Wayback Machine Retrieved 2012-01-06
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  17. ^ "] 14 CFR 1.2 Abbreviations and symbols "VC"".
  18. ^ "14 CFR 25.335(a) Design cruising speed VC".
  19. ^ a b c MIL-STD-3013A Department of Defense Standard Practice: Glossary of definitions, ground rules, and mission profiles to define air vehicle performance capability. 9 September 2008. Page 21.
  20. ^ a b c Pilot's Encyclopedia of Aeronautical Knowledge. Federal Aviation Administration. 2007. pp. G–16. ISBN 978-1-60239-034-8. Retrieved 12 May 2008.
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  28. ^ "Code of Federal Regulations 23.73" (PDF). Retrieved 27 June 2022.
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  33. ^ Gunston, Bill (1988). Airbus. Osprey. p. 60. ISBN 978-0-85045-820-6. Retrieved 26 October 2022.
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  40. ^ "Transportation Safety Board of Canada – A05W0109". 27 July 2006. Retrieved 26 March 2010.
  41. ^ "Wills Wing Hang Glider Mfg". 25 September 2014. Retrieved 31 May 2016.
  42. ^ "SR20 Pilot's Operating Handbook". Cirrus Design. 2004: 8. ((cite journal)): Cite journal requires |journal= (help)
  43. ^ "Performance. ATPL ground training series". CAE OXFORD AVIATION ACADEMY. 2016: 15. ((cite journal)): Cite journal requires |journal= (help)
  44. ^ a b c Flight Sim Aviation (2009). "Aviation Rules of Thumb – V-Speeds Abbreviations List". Retrieved 19 January 2009.
  45. ^ E.G. Tulapurkara, Chapter 10 Performance analysis VI – Take-off and landing, retrieved 18 November 2015
  46. ^ "C-130 Takeoff and Landing Data Card" (PDF). Elite Electronic Engineering, Inc. Archived (PDF) from the original on 19 August 2018. Retrieved 18 August 2018.
  47. ^ "VTMAX". The Free Dictionary. 2009. Retrieved 19 January 2009.
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  50. ^ "Takeoff Safety Training Aid" (PDF). Federal Aviation Administration. p. 3. Archived from the original (PDF) on 4 March 2016. Retrieved 18 June 2015. V1. [...](1) The maximum speed by which a rejected takeoff must be initiated to assure that a safe stop can be completed within the remaining runway, or runway and stopway;
  51. ^ "Code of Federal Regulations. Title 14 Chapter I Subchapter C Part 25 Subpart B Performance, Section 25.109 Accelerate-stop distance". ecfr.gov. Federal Register. Retrieved 12 October 2022.
  52. ^ Albright, James (November 2014). "Aircraft Performance: Certification versus the real world" (PDF). Business & Commercial Aviation: 46–52. Retrieved 12 October 2022.

Further reading

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