V speeds

{{Short description|Standard terms to define airspeeds}} {{Use dmy dates|date=March 2023}} {{Use American English|date=March 2023}} [[File:ASI01b.jpg|thumb|upright=1.35|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.<ref name="btal">{{cite book |last=Love |first=Michael C. |title=Better Takeoffs & Landings |chapter-url=https://books.google.com/books?id=p9XT6aHBrGAC&q=definition+of+v-speed&pg=PA13 |access-date=2008-05-07 |year=2005 |publisher=Mc-Graw Hill |isbn=0-07-038805-9 |pages=13–15 |chapter=2}}</ref> 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.<ref name="multiengineflying">{{cite book |last=Craig |first=Paul A. |title=Multiengine Flying|chapter-url=https://books.google.com/books?id=Tu0zmyyCkwwC&q=aviation+%2B+v-speed&pg=PA3 |access-date=2008-05-07 |edition=3rd |year=2004 |publisher=McGraw Hill |isbn=0-07-142139-4 |pages=3–6 |chapter=1}}</ref>

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.<ref name="FAR23.1545">{{cite web|url = http://ecfr.gpoaccess.gov/cgi/t/text/text-idx?c=ecfr&sid=9b06546343b9c534cd8cbe093366e8a1&rgn=div8&view=text&node=14:1.0.1.3.10.7.105.16&idno=14|title = 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|access-date = 2008-08-01|last = FAA |date = July 2008|archive-url = https://web.archive.org/web/20060929161342/http://ecfr.gpoaccess.gov/cgi/t/text/text-idx?c=ecfr&sid=4f889c54de122f84f222f4139ad72995&rgn=div8&view=text&node=14:1.0.1.3.10.7.105.16&idno=14|archive-date = 29 September 2006|url-status = dead}}</ref><ref name="faa-phak-7">{{cite web|url=http://www.faa.gov/regulations_policies/handbooks_manuals/aviation/pilot_handbook/media/PHAK%20-%20Chapter%2007.pdf|title=Pilot's Handbook of Aeronautical Knowledge – Chapter 7|publisher= FAA |access-date=2010-01-29|archive-url=https://web.archive.org/web/20130903044211/http://www.faa.gov/regulations_policies/handbooks_manuals/aviation/pilot_handbook/media/PHAK%20-%20Chapter%2007.pdf|archive-date=3 September 2013|url-status=dead}}</ref> 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 V_NE, the never-exceed speed.

Proper display of V-speeds is an airworthiness requirement for type-certificated aircraft in most countries.<ref name="faa-phak-8">{{cite web|url=http://www.faa.gov/regulations_policies/handbooks_manuals/aviation/pilot_handbook/media/PHAK%20-%20Chapter%2008.pdf|title=Pilot's Handbook of Aeronautical Knowledge – Chapter 8|publisher= FAA |access-date=2010-01-29|url-status=dead|archive-url=https://web.archive.org/web/20130903055247/http://www.faa.gov/regulations_policies/handbooks_manuals/aviation/pilot_handbook/media/PHAK%20-%20Chapter%2008.pdf|archive-date=3 September 2013}}</ref><ref name="FAR25.1583">{{cite web|url = http://ecfr.gpoaccess.gov/cgi/t/text/text-idx?c=ecfr&sid=9b06546343b9c534cd8cbe093366e8a1&rgn=div8&view=text&node=14:1.0.1.3.11.7.200.32&idno=14|title = 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|access-date = 2008-08-01|last = FAA |date = July 2008|archive-url = https://web.archive.org/web/20060929171930/http://ecfr.gpoaccess.gov/cgi/t/text/text-idx?c=ecfr&sid=eded54e7a564dbd6b114da05773f31a0&rgn=div8&view=text&node=14:1.0.1.3.11.7.200.32&idno=14|archive-date = 29 September 2006|url-status = dead}}</ref>

==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).<ref name="faacfr">{{cite web |title=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 |url=https://www.ecfr.gov/current/title-14/chapter-I/subchapter-A/part-1/section-1.2 |website=ecfr.gov |publisher=Federal Register |access-date=19 February 2023}}</ref> In Canada, the regulatory body, Transport Canada, defines 26 commonly used V-speeds in their Aeronautical Information Manual.<ref name="TCAIM">{{cite web|url = http://www.tc.gc.ca/publications/en/tp14371/pdf/hr/tp14371e.pdf#34|title = Aeronautical Information Manual GEN – 1.0 GENERAL INFORMATION |access-date = 2013-01-01|last = Transport Canada |date=October 2012}}</ref> 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. {| class="wikitable" |- ! style="width:7%;"| V-speed designator ! Description |- id="V1" | style="text-align:center;"| V₁ | The speed beyond which takeoff should no longer be aborted (or "the point of no return") {{xref|(see §{{nbs}}V₁ definitions below)}}.<ref name="faacfr"/><ref name="TCAIM"/><ref name="Peppler">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}}</ref> |- id="V2" | style="vertical-align:top; text-align:center;"| V₂ | Takeoff safety speed. The speed at which the aircraft may safely climb with one engine inoperative.<ref name="faacfr"/><ref name="TCAIM"/><ref name="Peppler" /> |- id="V2min" | style="vertical-align:top; text-align:center;"| V_{2_min} | Minimum takeoff safety speed.<ref name="faacfr"/><ref name="TCAIM"/><ref name="Peppler" /> |- id="V3" | style="vertical-align:top; text-align:center;"| V₃ | Flap retraction speed.<ref name="TCAIM"/><ref name="Peppler" /> |- id="V4" | style="vertical-align:top; text-align:center;"| 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 {{convert|400|ft|m|abbr=on}}.<ref name="CAP698">{{cite book|title=CAP 698: Civil Aviation Authority JAR-FCL Examinations: Aeroplane Performance Manual|url=http://www.caa.co.uk/docs/33/CAP698.pdf|access-date=2009-12-09|year=2006|publisher=Civil Aviation Authority (United Kingdom)|isbn=0-11-790653-0|pages=Section 4–MRJT1 Page 3|archive-url=https://web.archive.org/web/20091114115235/http://www.caa.co.uk/docs/33/CAP698.pdf|archive-date=14 November 2009|url-status=dead}}</ref> |- id="VA" | style="vertical-align:top; text-align:center;"| V_A | 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.<ref name="faacfr"/><ref name="TCAIM"/><ref name="Peppler" /><ref>[http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgAdvisoryCircular.nsf/0/d1a4060f22939f36862572eb0061ca3f/$FILE/AC%2023-19A.pdf FAA Advisory Circular 23-19A ''Airframe Guide for Certification of Part 23 Airplanes'', Section 48 (p.27)] {{Webarchive|url=https://web.archive.org/web/20161207154456/http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgAdvisoryCircular.nsf/0/d1a4060f22939f36862572eb0061ca3f/$FILE/AC%2023-19A.pdf |date=7 December 2016 }} Retrieved 2012-01-06</ref> |- id="Vat" | style="vertical-align:top; text-align:center;"| V_at | Indicated airspeed at threshold, which is usually equal to the stall speed V_S0 multiplied by 1.3 or stall speed V_S1g multiplied by 1.23 in the landing configuration at the maximum certificated landing mass, though some manufacturers apply different criteria. If both V_S0 and V_S1g are available, the higher resulting V_at shall be applied.<ref>PANS-OPS, Volume I, Part I, Section 4, Chapter 1, 1.3.3</ref> Also called "approach speed". Also known as V_th<ref>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.</ref><ref>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</ref> Davies defines V_at and V_ref as equivalent.<ref name="Davies">{{cite book |last1=Davies |first1=David P. |title=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 |date=1971 |publisher=Air Registration Board |url=https://books.google.com/books?id=TKZTAAAAMAAJ |language=en |isbn=0903083019 |edition=3rd}}</ref> |- id="VB" | style="text-align:center;"| V_B | Design speed for maximum gust intensity.<ref name="faacfr"/><ref name="TCAIM"/><ref name="Peppler" /> |- id="VC" | style="text-align:center;"| V_C | Design cruise, also known as the optimum cruise speed, is the most efficient speed in terms of distance, speed and fuel usage.<ref>{{cite web|url= https://en.mimi.hu/aviation/cruising_speed.html|title= Cruising speed|access-date= 5 March 2023|author= MiMi|work= en.mimi.hu|url-status= live}}</ref><ref>{{cite web |url=https://www.ecfr.gov/current/title-14/chapter-I/subchapter-A/part-1/section-1.2#p-1.2(VC) |title=] 14 CFR 1.2 Abbreviations and symbols "VC"}}</ref><ref>{{cite web|url=https://www.ecfr.gov/current/title-14/chapter-I/subchapter-C/part-25/subpart-C/subject-group-ECFR3e855ea22ea15d0/section-25.335#p-25.335(a) |title= 14 CFR 25.335(a) Design cruising speed V_C}}</ref> |- id="Vcef" | style="text-align:center;"| V_cef | 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.<ref name="Milstda">[http://everyspec.com/MIL-STD/MIL-STD-3000-9999/MIL-STD-3013A_22905/ 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.</ref> |- id="VD" | style="text-align:center;"| V_D | Design diving speed, the highest speed planned to be achieved in testing.<ref name="faacfr"/><ref name="TCAIM"/><ref name="Peppler" /> |- id="VDF" | style="text-align:center;"| V_DF | Demonstrated flight diving speed, the highest actual speed achieved in testing.<ref name="faacfr"/><ref name="TCAIM"/><ref name="Peppler" /> |- id="VEF" | style="text-align:center;"| V_EF | The speed at which the critical engine is assumed to fail during takeoff.<ref name="faacfr"/> |- id="VF" | style="text-align:center;"| V_F | Designed flap speed.<ref name="faacfr"/><ref name="TCAIM"/><ref name="Peppler" /> |- id="VFC" | style="text-align:center;"| V_FC | Maximum speed for stability characteristics.<ref name="faacfr"/><ref name="Peppler" /> |- id="VFE" | style="text-align:center;"| V_FE | Maximum flap extended speed.<ref name="faacfr"/><ref name="TCAIM"/><ref name="Peppler" /> |- id="VFTO" | style="text-align:center;"| V_FTO | Final takeoff speed.<ref name="faacfr"/> |- id="VH" | style="text-align:center;"| V_H | Maximum speed in level flight at maximum continuous power.<ref name="faacfr"/><ref name="TCAIM"/><ref name="Peppler" /> |- id="VLE" | style="vertical-align:top; text-align:center;"| V_LE | Maximum landing gear extended speed. This is the maximum speed at which a retractable gear aircraft should be flown with the landing gear extended.<ref name="faacfr"/><ref name="TCAIM"/><ref name="Peppler" /><ref name="PEAK">{{cite book|title=Pilot's Encyclopedia of Aeronautical Knowledge |url=https://books.google.com/books?id=m5V04SXE4zQC&q=v+speeds+%2B+Vyse&pg=PT333|access-date=2008-05-12|year=2007|publisher=Federal Aviation Administration|isbn=978-1-60239-034-8|pages=G–16}}</ref> |- id="VLO" | style="vertical-align:top; text-align:center;"| V_LO | 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.<ref name="faacfr"/><ref name="Peppler" /><ref name="PEAK"/> |- id="VLOF" | style="text-align:center;"| V_LOF | Lift-off speed.<ref name="faacfr"/><ref name="Peppler" /> |- id="VMC" | style="vertical-align:top; text-align:center;"| V_MC | Minimum control speed. The minimum speed at which the aircraft is still controllable with the critical engine inoperative.<ref name="faacfr"/> 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. V_MC is sometimes further refined into more discrete V-speeds e.g. V_MCA,V_MCG. |- id="Vmca" | style="vertical-align:top; text-align:center;"|V_MCA | Minimum control speed air. The minimum speed that the aircraft is still controllable with the critical engine inoperative<ref name="FAR 25.149">{{cite web|url = http://ecfr.gpoaccess.gov/cgi/t/text/text-idx?c=ecfr&sid=c884df43e59bd72bc094f5e164c7ec8b&rgn=div8&view=text&node=14:1.0.1.3.11.2.156.24&idno=14|title = Title 14: Aeronautics and Space PART 25—AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY AIRPLANES Subpart B—Flight Controllability and Maneuverability § 25.149 Minimum control speed.|access-date = 2009-02-16|last = Federal Aviation Administration.|date = February 2009|archive-url = https://web.archive.org/web/20101004170519/http://ecfr.gpoaccess.gov/cgi/t/text/text-idx?c=ecfr&sid=f843d8e5eee070d245ba39cd21c739d0&rgn=div8&view=text&node=14:1.0.1.3.11.2.156.24&idno=14|archive-date = 4 October 2010|url-status = dead}}</ref> while the aircraft is airborne. V_MCA is sometimes simply referred to as V_MC. |- id="Vmcg" | style="vertical-align:top; text-align:center;"|V_MCG |Minimum control speed ground. The minimum speed that the aircraft is still controllable with the critical engine inoperative<ref name="FAR 25.149"/> while the aircraft is on the ground. |- id="Vmcl" | style="text-align:center;"|V_MCL |Minimum control speed in the landing configuration with one engine inoperative.<ref name="Peppler" /><ref name="FAR 25.149" /> |- id="VMO" | style="text-align:center;"| V_MO | Maximum operating limit speed.<ref name="faacfr"/><ref name="TCAIM"/><ref name="Peppler" /> Exceeding V_MO may trigger an overspeed alarm.<ref name="FAA2017">{{cite book|last1=Administration|first1=Federal Aviation|title=Airplane Flying Handbook: FAA-H-8083-3B|date=2017|publisher=Skyhorse Publishing, Inc.|isbn=9781510712843|pages=15–9|url=https://books.google.com/books?id=CpTfDQAAQBAJ&q=vmo+overspeed&pg=PT530|access-date=3 October 2017|language=en}}</ref> |- id="VMU" | style="text-align:center;"| V_MU | Minimum unstick speed.<ref name="faacfr"/><ref name="TCAIM"/><ref name="Peppler" /> |- id="VNE" | style="text-align:center;"| V_NE | Never exceed speed.<ref name="faacfr"/><ref name="TCAIM"/><ref name="Peppler" /><ref name="Bell212">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</ref> In a helicopter, this is chosen to prevent retreating blade stall and prevent the advancing blade from going supersonic. |- id="VNO" | style="text-align:center;"| V_NO | 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.<ref name="faacfr"/><ref name="TCAIM"/><ref name="Peppler" /><ref>{{cite book |title=Pilot's Handbook of Aeronautical Knowledge: FAA-H-8083-25B |date=25 September 2016 |publisher=Federal Aviation Administration (FAA) |url=https://books.google.com/books?id=C99DDQAAQBAJ |access-date=6 June 2022 |language=en}}</ref> |- id="VO" | style="text-align:center;"| V_O | Maximum operating maneuvering speed.<ref>[http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgFAR.nsf/0/2A0AA756267EFE8F85256687007232CC?OpenDocument USA 14 CFR §23.1507] {{Webarchive|url=https://web.archive.org/web/20170212174633/http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgFAR.nsf/0/2A0AA756267EFE8F85256687007232CC?OpenDocument |date=12 February 2017 }} Retrieved 2012-01-06</ref> |- id="VR" | style="text-align:center;"| V_R | 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.<ref name="faacfr"/><ref name="CFR 25.107"/>{{#tag:ref|Most pilots often call out "rotate," instead of V_R. The "rotate" callout has the same meaning of V_R and V_rot.<ref>{{Cite news |last=Cox |first=John |date=2013-09-29 |title=Ask the Captain: How do pilots decide when to take off? |url=https://www.usatoday.com/story/travel/columnist/cox/2013/09/29/takeoff-speed-v1-v2-rotate/2885565/ |access-date=2023-02-08 |work=USA Today}}</ref>|group="Note"}} |- id="Vrot" | style="vertical-align:top; text-align:center;"| V_rot | Used instead of V_R (in discussions of the takeoff performance of military aircraft) to denote '''rotation speed''' in conjunction with the term ''V_ref (refusal speed).''<ref name="Milstda" /> |- id="VRef" | style="vertical-align:top; text-align:center;"| V_Ref | Landing reference speed or threshold crossing speed.<ref name="faacfr"/><ref name="TCAIM"/><ref name="Peppler" /> Must be at least 1.3 V_S₀. Must be at least V_MC for reciprocating-engine aircraft, or 1.05 V_MC for commuter category aircraft.<ref>{{cite web |title=Code of Federal Regulations 23.73 |url=https://www.govinfo.gov/content/pkg/CFR-2011-title14-vol1/pdf/CFR-2011-title14-vol1-sec23-69.pdf |access-date=27 June 2022}}</ref> In discussions of the '''takeoff''' performance of military aircraft, the term V_ref 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.<ref name="Milstda" /> Incorrectly, or as an abbreviation, some documentation refers to V_ref and/or V_rot speeds as "V_r."<ref>[https://archive.today/20130204203513/http://www.tpub.com/content/aviation2/P-862/P-8620053.htm TPUB INTERMEDIATE FLIGHT PREPARATION WORKBOOK APPENDIX A]</ref> |- id="VS" | style="text-align:center;"| V_S | Stall speed or minimum steady flight speed for which the aircraft is still controllable.<ref name="faacfr"/><ref name="TCAIM"/><ref name="Peppler" /> |- id="VS0" | style="text-align:center;"|V_S₀ | Stall speed or minimum flight speed in landing configuration.<ref name="faacfr"/><ref name="TCAIM"/><ref name="Peppler" /> |- id="VS1" | style="text-align:center;"| V_S₁ | Stall speed or minimum steady flight speed for which the aircraft is still controllable in a specific configuration.<ref name="faacfr"/><ref name="TCAIM"/> |- id="VSR" | style="text-align:center;"| V_{S_R} | Reference stall speed.<ref name="faacfr"/> |- id="VSR0" | style="text-align:center;"| V_{S_R₀} | Reference stall speed in landing configuration.<ref name="faacfr"/> |- id="VSR1" | style="text-align:center;"| V_{S_R₁} | Reference stall speed in a specific configuration.<ref name="faacfr"/> |- id="VSW" | style="text-align:center;"| V_SW | Speed at which the stall warning will occur.<ref name="faacfr"/> |- id="VTOSS" | style="text-align:center;"| V_TOSS | Category A rotorcraft takeoff safety speed.<ref name="faacfr"/><ref name="Bell212" /> |- id="VX" | style="text-align:center;"| V_X | Speed that will allow for best angle of climb.<ref name="faacfr"/><ref name="TCAIM"/> |- id="VY" | style="text-align:center;"| V_Y | Speed that will allow for the best rate of climb.<ref name="faacfr"/><ref name="TCAIM"/> |}

==Other V-speeds== Some of these V-speeds are specific to particular types of aircraft and are not defined by regulations. {| class="wikitable" |- ! style="width:7%;"| V-speed designator ! Description |- id="VAPP" | style="text-align:center;"| V<sub id="vbe">APP</sub> | Approach speed. Speed used during final approach with landing flap set.<ref name="Brenner">{{cite book |last1=Brenner |first1=Thiago Lopes |title=Aircraft Performance Weight and Balance |date=15 May 2021 |publisher=Thiago Lopes Brenner |isbn=979-8-5678-1522-9 |page=245 |url=https://books.google.com/books?id=lY-BEAAAQBAJ |access-date=26 October 2022 |language=en}}</ref> V_REF plus safety increment,<ref>{{cite book |last1=Void |first1=Joyce D. |title=Aircraft Performance: Flying Training |date=1990 |publisher=Department of the Air Force, Headquarters US Air Force |page=99 |url=https://books.google.com/books?id=G-zvu2CYZjQC |access-date=26 October 2022 |language=en}}</ref><ref name="Flying VAPP">{{cite book |title=Flying Magazine |date=August 1985 |page=76 |url=https://books.google.com/books?id=LEg5fVCKOngC |access-date=26 October 2022 |language=en}}</ref><ref name="Gunston">{{cite book |last1=Gunston |first1=Bill |title=Airbus |date=1988 |publisher=Osprey |isbn=978-0-85045-820-6 |page=60 |url=https://books.google.com/books?id=FecJAQAAMAAJ |access-date=26 October 2022 |language=en}}</ref> typically minimum 5 knots,<ref name="Vapp accident">{{cite book |title=Aircraft Accident Report: Runway Overrun During Landing |date=12 April 2007 |publisher=U.S. Government |location=viii |url=https://books.google.com/books?id=sPs5AQAAMAAJ |access-date=26 October 2022 |language=en}}</ref> and maximum 15 knots<ref name="Brenner"/> to avoid exceeding flap limiting speeds. Typically it is calculated as half the headwind component plus the gust factor.<ref name="Brenner"/> The purpose is to ensure that turbulence or gusts will not result in the airplane flying below V_REF at any point on the approach.<ref name="Brenner"/> Also known as V_FLY. |- id="VBE" | style="text-align:center;"| V<sub id="vbe">BE</sub> | Best endurance speed – the speed that gives the greatest airborne time for fuel consumed.{{Citation needed|date=December 2019}} |- id="VBG" | style="text-align:center;"| V<sub id="vbg">BG</sub> | Best power-off glide speed – the speed that provides maximum lift-to-drag ratio and thus the greatest gliding distance available. |- id="VBR" | style="text-align:center;"| V<sub id="vbr">BR</sub> | Best range speed – the speed that gives the greatest range for fuel consumed – often identical to V_md.<ref name="Brandon">{{cite web|url = http://www.auf.asn.au/groundschool/umodule2.html#vspeed |title = Flight Theory: Airspeed and the properties of air |website = FlySafe.raa.asn.au |archive-url = https://web.archive.org/web/20081101165006/http://www.auf.asn.au/groundschool/umodule2.html#vbr |archive-date = 1 November 2008 |last = Brandon|first = John |date=October 2008}}</ref> |- id="VFS" | style="text-align:center;"| V_FS | Final segment of a departure with one powerplant failed.<ref name="VFS">{{cite web |url = http://www.airplanedriver.net/study/part25.htm |title = Cessna Citation |access-date = 2009-02-14 |last = airplanedriver.net |archive-date = 21 September 2008 |archive-url = https://web.archive.org/web/20080921202350/http://www.airplanedriver.net/study/part25.htm |url-status = dead }}</ref> |- id="Vimd" | style="text-align:center;"|V<sub id="vimd">imd</sub> |Minimum drag<ref name="Bristow">{{cite book|url = https://books.google.com/books?id=aGL035btsg4C&pg=PA8 |title = Ace the Technical Pilot Interview|access-date = 2009-01-20|last = Bristow |first = Gary|date = 22 April 2002| publisher=McGraw Hill Professional |isbn = 9780071396097}}</ref> |- id="Vimp" | style="text-align:center;"|V<sub id="vimp">imp</sub> |Minimum power<ref name="Bristow" /> |- id="VLLO" | style="text-align:center;"| V<sub id="vllo">LLO</sub> | Maximum landing light operating speed – for aircraft with retractable landing lights.<ref name="Peppler" /> |- id="VLS" | style="text-align:center;"|V<sub id="ls">LS</sub> |Lowest selectable speed<ref>{{cite web|url= https://www.skybrary.aero/bookshelf/books/4071.pdf|title= Procedures|access-date= 4 March 2022|last1= Castaigns|first1= Philippe|last2= De-Baudus|first2= Lorraine |work= skybrary.aero|date= July 2017|archive-url= https://web.archive.org/web/20210824001914/https://www.skybrary.aero/bookshelf/books/4071.pdf|archive-date= 24 August 2021|url-status= dead}}</ref> |- id="Vmbe" | style="text-align:center;"|V<sub id="vmbe">mbe</sub> |Maximum brake energy speed<ref name="Bristow" /><ref name="Croucher">{{cite book|url = https://books.google.com/books?id=wfiGiY2ixTkC&q=Vt+Threshold+speed&pg=RA3-PR26|title = Canadian Professional Pilot Studies|access-date = 2009-01-20|last=Croucher |first=Phil |year = 2007| publisher=Lulu.com |isbn = 9780968192894}}</ref> |- id="Vmd" | style="text-align:center;"|V<sub id="vmd">md</sub> |Minimum drag (per lift) – often identical to V_BE.<ref name="Brandon" /><ref name="Croucher" /> (alternatively same as V_imd<ref name="Transportation Safety Board of Canada">{{cite web|url = http://www.tsb.gc.ca/eng/rapports-reports/aviation/2005/a05w0109/a05w0109.asp|title = Transportation Safety Board of Canada – A05W0109|date = 27 July 2006|access-date = 2010-03-26}}</ref>) |- id="Vmin" | style="text-align:center;"|V<sub id="vmin">min</sub> |Minimum speed for instrument flight (IFR) for helicopters<ref name="Bell212" /> |- id="Vmp" | style="text-align:center;"|V<sub id="vmp">mp</sub> |Minimum power<ref name="Croucher" /> |- id="Vms" | style="text-align:center;"|V<sub id="vms">ms</sub> |Minimum sink speed at median wing loading – the speed at which the minimum descent rate is obtained. In modern gliders, V_ms and V_mc have evolved to the same value.<ref name="Wills Wing">{{cite web|url = https://www.willswing.com/key-to-hang-glider-specifications/|title = Wills Wing Hang Glider Mfg.|date = 25 September 2014|access-date = 2016-05-31}}</ref> |- id="Vp" | style="text-align:center;"|V<sub id="vp">p</sub> |Aquaplaning speed<ref name="Croucher" /> |- id="Vpd" | style="text-align:center;"|V<sub id="vpd">PD</sub> |Maximum speed at which whole-aircraft parachute deployment has been demonstrated<ref>{{Cite book | title = SR20 Pilot's Operating Handbook | publisher = Cirrus Design | year = 2004 | page = 8 }}</ref> |- id="Vra" | style="text-align:center;"|V<sub id="vra">ra</sub> |Rough air speed (turbulence penetration speed).<ref name="Peppler" /> |- id="Vsl" | style="text-align:center;"|V<sub id="vs1">SL</sub> |Stall speed in a specific configuration<ref name="Peppler" /><ref name="Croucher" /> |- id="Vs1g" | style="text-align:center;"|V<sub id="vs1g">s_1g</sub> |Stall speed at 1g load factor<ref>

{{Cite book | title = Performance. ATPL ground training series. | publisher = CAE OXFORD AVIATION ACADEMY | year = 2016 | page = 15 }} </ref> |- id="Vsse" | style="text-align:center;"|V<sub id="vsse">sse</sub> |Safe single-engine speed<ref name="FltSim">{{cite web|url = http://www.flightsimaviation.com/rule-of-thumb/27_VSpeeds_Abbreviations_List.html|title = Aviation Rules of Thumb – V-Speeds Abbreviations List|access-date = 2009-01-19|last = Flight Sim Aviation|year = 2009}}</ref> |- id="Vt" | style="text-align:center;"|V<sub id="vt">t</sub> |Threshold speed<ref name="Croucher" /> |- id="Vtd" | style="text-align:center;"|V<sub id="vtd">TD</sub> |Touchdown speed<ref>E.G. Tulapurkara, [http://nptel.ac.in/courses/101106041/Chapter%2010%20Lecture%2032%2022-12-2011.pdf Chapter 10 Performance analysis VI – Take-off and landing], retrieved 18 November 2015</ref> |- id="Vtgt" | style="text-align:center;"|V<sub id="vtgt">TGT</sub> |Target speed{{Citation needed|date=December 2019}} |- id="Vto" | style="text-align:center;"| V_TO | Take-off speed. (see also V_LOF)<ref>{{cite web|url=https://www.elitetest.com/sites/default/files/downloads/c130h_pretold_card_v1_0.pdf|title=C-130 Takeoff and Landing Data Card|publisher=Elite Electronic Engineering, Inc.|archive-url=https://web.archive.org/web/20180819014933/https://www.elitetest.com/sites/default/files/downloads/c130h_pretold_card_v1_0.pdf|archive-date=19 August 2018|url-status=live|access-date=18 August 2018}}</ref> |- id="VTocs" | style="text-align:center;"|V<sub id="vtocs">tocs</sub> |Take-off climbout speed (helicopters)<ref name="Bell212" /> |- id="VTos" | style="text-align:center;"|V<sub id="vtos">tos</sub> |Minimum speed for a positive rate of climb with one engine inoperative<ref name="Croucher" /> |- id="Vtmax" | style="text-align:center;"|V<sub id="vtmax">t_max</sub> |Max threshold speed<ref name="Croucher" /><ref name="FD">{{cite web|url = http://acronyms.thefreedictionary.com/Maximum+Threshold+Speed+(aviation)|title = VTMAX |access-date = 2009-01-19|work = The Free Dictionary|year = 2009}}</ref> |- id="Vwo" | style="text-align:center;"|V<sub id="vwo">wo</sub> |Maximum window or canopy open operating speed<ref name="blueridgeairworks">{{cite web|url = http://www.blueridgeairworks.com/specs.htm|title = Cessna 152 – 4843H General Info|access-date = 2009-02-13|last = Blue Ridge Air Works|date = n.d.|archive-url = https://web.archive.org/web/20080705202030/http://www.blueridgeairworks.com/specs.htm|archive-date = 5 July 2008|url-status = dead}}</ref> |- id="VXSE" | style="vertical-align:top; text-align:center;"|V<sub id="vxse">X_SE</sub> |Best angle of climb speed with one engine inoperative (OEI) 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.<ref name="FltSim" /> |- id="VYSE" | style="vertical-align:top; text-align:center;"|V<sub id="yse">Y_SE</sub> |Best rate of climb speed with one engine inoperative (OEI) 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.<ref name="PEAK"/><ref name="FltSim" /> |- id="VZF" | style="text-align:center;"|V<sub id="zf">ZF</sub> |Minimum zero flaps speed<ref>{{cite web |url=http://faculty.sdmiramar.edu/faculty/sdccd/dbuser/101H/101H_ref/Speeds.pdf |title=Speeds: Various Aviation Authorities |website=sdmiramar.edu |accessdate=2022-03-04 |archive-date=23 June 2021 |archive-url=https://web.archive.org/web/20210623061901/http://faculty.sdmiramar.edu/faculty/sdccd/dbuser/101H/101H_ref/Speeds.pdf |url-status=dead }}</ref> |- id="VZRC" | style="text-align:center;"|V<sub id="zrc">ZRC</sub> |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.<ref name="Croucher" /> The aircraft cannot be recovered without loss of height.<ref name="Davies" />{{rp|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. V_MO: Maximum operating speed, M_MO: Maximum operating Mach number.<ref name="faacfr"/><ref name="TCAIM"/>

==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.<ref name="Peppler" /> 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.<ref>{{cite web|title=Takeoff Safety Training Aid|url=http://www.iata.org/iata/RERR-toolkit/assets/Content/Contributing%20Reports/Reference/TakeoffTrainingSafetyAid.pdf|publisher=Federal Aviation Administration|page=3|quote=" 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;"|access-date=18 June 2015|archive-date=4 March 2016|archive-url=https://web.archive.org/web/20160304001429/http://www.iata.org/iata/RERR-toolkit/assets/Content/Contributing%20Reports/Reference/TakeoffTrainingSafetyAid.pdf|url-status=dead}}</ref>

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 V_EF, at which the pilot can continue the takeoff and achieve the required height above the takeoff surface within the takeoff distance."<ref name="faacfr"/> V₁ thus includes reaction time.<ref name="CFR 25.107">{{cite web |title=Code of Federal Regulations. Title 14 Chapter I Subchapter C Part 25 Subpart B Performance, Section 25.107 Takeoff speeds |url=https://www.ecfr.gov/current/title-14/chapter-I/subchapter-C/part-25/subpart-B/subject-group-ECFR14f0e2fcc647a42/section-25.107 |website=ecfr.gov |publisher=Federal Register |access-date=12 October 2022}}</ref> In addition to this reaction time, a safety margin equivalent to 2 seconds at V₁ is added to the accelerate-stop distance.<ref name="CFR 25.109">{{cite web |title=Code of Federal Regulations. Title 14 Chapter I Subchapter C Part 25 Subpart B Performance, Section 25.109 Accelerate-stop distance |url=https://www.ecfr.gov/current/title-14/chapter-I/subchapter-C/part-25/subpart-B/subject-group-ECFR14f0e2fcc647a42/section-25.109 |website=ecfr.gov |publisher=Federal Register |access-date=12 October 2022}}</ref><ref name="Albright">{{cite journal |last1=Albright |first1=James |title=Aircraft Performance: Certification versus the real world |journal=Business & Commercial Aviation |date=November 2014 |pages=46–52 |url=https://code7700.com/pdfs/bca/bca_aircraft_performance_2014-11.pdf |access-date=12 October 2022}}</ref> *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."<ref name="TCAIM"/>

== See also == * ICAO recommendations on use of the International System of Units * Balanced field takeoff

== Notes == {{Reflist|group="Note"}}

==References== {{reflist}}

== Further reading == * {{cite book |title=Flight Operations Support & Line Assistance: Getting to grips with aircraft performance |publisher= Airbus Customer Services |date= January 2002 |url= http://www.skybrary.aero/bookshelf/books/2263.pdf}}

{{Flight instruments}}

Category:Airspeed Category:Aircraft performance