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V speeds

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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]

A single-engined Cessna 150L's airspeed indicator indicating its V-speeds in knots

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

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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

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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]

Davies defines Vat and Vref as equivalent.[15]

VBDesign speed for maximum gust intensity.[7][8][9]
VCDesign cruise, also known as the optimum cruise speed, is the most efficient speed in terms of distance, speed and fuel usage.[16][17][18]
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.[19]
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][20]
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][20]
VLOFLift-off speed.[7][9]
VMCMinimum 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.
VMCAMinimum 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.
VMCGMinimum 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.
VMCLMinimum control speed in the landing configuration with one engine inoperative.[9][21]
VMOMaximum operating limit speed.[7][8][9] Exceeding VMO may trigger an overspeed alarm.[22]
VMUMinimum unstick speed.[7][8][9]
VNENever 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.
VNOMaximum 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]
VOMaximum operating maneuvering speed.[25]
VRRotation 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]
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).[19]
VRefLanding 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]

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][23]
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

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

V-speed designatorDescription
VAPPApproach 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.
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.[35]
VFSFinal segment of a departure with one powerplant failed.[36]
VimdMinimum drag[37]
VimpMinimum power[37]
VLLOMaximum landing light operating speed – for aircraft with retractable landing lights.[9]
VLSLowest selectable speed[38]
VmbeMaximum brake energy speed[37][39]
VmdMinimum drag (per lift) – often identical to VBE.[35][39] (alternatively same as Vimd[40])
VminMinimum speed for instrument flight (IFR) for helicopters[23]
VmpMinimum power[39]
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.[41]
VpAquaplaning speed[39]
VPDMaximum speed at which whole-aircraft parachute deployment has been demonstrated[42]
VraRough air speed (turbulence penetration speed).[9]
VSLStall speed in a specific configuration[9][39]
Vs1gStall speed at 1g load factor[43]
VsseSafe single-engine speed[44]
VtThreshold speed[39]
VTDTouchdown speed[45]
VTGTTarget speed[citation needed]
VTOTake-off speed. (see also VLOF)[46]
VtocsTake-off climbout speed (helicopters)[23]
VtosMinimum speed for a positive rate of climb with one engine inoperative[39]
VtmaxMax threshold speed[39][47]
VwoMaximum window or canopy open operating speed[48]
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.[44]
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.[20][44]
VZFMinimum zero flaps speed[49]
VZRCZero 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

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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

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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.

  • The US Federal Aviation Administration and the European Union Aviation Safety Agency define it as: "the maximum speed in the takeoff at which the pilot must take the first action (e.g., apply brakes, reduce thrust, deploy speed brakes) to stop the airplane within the accelerate-stop distance. V1 also means the minimum speed in the takeoff, following a failure of the critical engine at VEF, at which the pilot can continue the takeoff and achieve the required height above the takeoff surface within the takeoff distance."[7] V1 thus includes reaction time.[26] In addition to this reaction time, a safety margin equivalent to 2 seconds at V1 is added to the accelerate-stop distance.[51][52]
  • Transport Canada defines it as: "Critical engine failure recognition speed" and adds: "This definition is not restrictive. An operator may adopt any other definition outlined in the aircraft flight manual (AFM) of TC type-approved aircraft as long as such definition does not compromise operational safety of the aircraft."[8]

See also

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Notes

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

References

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  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
  12. ^ PANS-OPS, Volume I, Part I, Section 4, Chapter 1, 1.3.3
  13. ^ Aircraft Noise Abatement: Hearings Before the Subcommittee on Aeronautics and Space Technology of the Committee on Science and Astronautics, U.S. House of Representatives, Ninety-third Congress, Second Session, July 24, 25, 1974, page 593.
  14. ^ Aerodrome Design Manual, Part 2, Taxiways, Aprons and Holding Bays. Fourth Edition, 2005. ICAO Doc 9157 AN/901. Page 1-34. https://skybrary.aero/bookshelf/books/3090.pdf
  15. ^ a b Davies, David P. (1971). Handling the Big Jets: An Explanation of the Significant Differences in Flying Qualities Between Jet Transport Aeroplanes and Piston Engined Transport Aeroplanes, Together with Some Other Aspects of Jet Transport Handling (3rd ed.). Air Registration Board. ISBN 0903083019.
  16. ^ MiMi. "Cruising speed". en.mimi.hu. Archived from the original on 5 March 2023. Retrieved 5 March 2023.
  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.
  21. ^ a b c Federal Aviation Administration. (February 2009). "Title 14: Aeronautics and Space PART 25—AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY AIRPLANES Subpart B—Flight Controllability and Maneuverability § 25.149 Minimum control speed". Archived from the original on 4 October 2010. Retrieved 16 February 2009.
  22. ^ Administration, Federal Aviation (2017). Airplane Flying Handbook: FAA-H-8083-3B. Skyhorse Publishing, Inc. pp. 15–9. ISBN 9781510712843. Retrieved 3 October 2017.
  23. ^ a b c d Bell Helicopter Textron: Bell Model 212 Rotorcraft Flight Manual, page II. Bell Helicopters Textron Publishers, Fort Worth, Texas, Revision 3, 1 May 1998. BHT-212IFR-FM-1
  24. ^ Pilot's Handbook of Aeronautical Knowledge: FAA-H-8083-25B. Federal Aviation Administration (FAA). 25 September 2016. Retrieved 6 June 2022.
  25. ^ USA 14 CFR §23.1507 Archived 12 February 2017 at the Wayback Machine Retrieved 2012-01-06
  26. ^ a b "Code of Federal Regulations. Title 14 Chapter I Subchapter C Part 25 Subpart B Performance, Section 25.107 Takeoff speeds". ecfr.gov. Federal Register. Retrieved 12 October 2022.
  27. ^ Cox, John (29 September 2013). "Ask the Captain: How do pilots decide when to take off?". USA Today. Retrieved 8 February 2023.
  28. ^ "Code of Federal Regulations 23.73" (PDF). Retrieved 27 June 2022.
  29. ^ TPUB INTERMEDIATE FLIGHT PREPARATION WORKBOOK APPENDIX A
  30. ^ a b c d Brenner, Thiago Lopes (15 May 2021). Aircraft Performance Weight and Balance. Thiago Lopes Brenner. p. 245. ISBN 979-8-5678-1522-9. Retrieved 26 October 2022.
  31. ^ Void, Joyce D. (1990). Aircraft Performance: Flying Training. Department of the Air Force, Headquarters US Air Force. p. 99. Retrieved 26 October 2022.
  32. ^ Flying Magazine. August 1985. p. 76. Retrieved 26 October 2022.
  33. ^ Gunston, Bill (1988). Airbus. Osprey. p. 60. ISBN 978-0-85045-820-6. Retrieved 26 October 2022.
  34. ^ Aircraft Accident Report: Runway Overrun During Landing. viii: U.S. Government. 12 April 2007. Retrieved 26 October 2022.
  35. ^ a b Brandon, John (October 2008). "Flight Theory: Airspeed and the properties of air". FlySafe.raa.asn.au. Archived from the original on 1 November 2008.
  36. ^ airplanedriver.net. "Cessna Citation". Retrieved 14 February 2009.
  37. ^ a b c Bristow, Gary (22 April 2002). Ace the Technical Pilot Interview. McGraw Hill Professional. ISBN 9780071396097. Retrieved 20 January 2009.
  38. ^ Castaigns, Philippe; De-Baudus, Lorraine (July 2017). "Procedures" (PDF). skybrary.aero. Archived from the original (PDF) on 24 August 2021. Retrieved 4 March 2022.
  39. ^ a b c d e f g h i Croucher, Phil (2007). Canadian Professional Pilot Studies. Lulu.com. ISBN 9780968192894. Retrieved 20 January 2009.
  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.
  48. ^ Blue Ridge Air Works (n.d.). "Cessna 152 – 4843H General Info". Archived from the original on 5 July 2008. Retrieved 13 February 2009.
  49. ^ "Speeds: Various Aviation Authorities" (PDF). sdmiramar.edu. Retrieved 4 March 2022.
  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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