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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 including fixed-wing aircraft, gliders, autogiros, helicopters, and dirigibles.[1] These speeds are derived from data obtained by aircraft designers and manufacturers during flight testing and verified in most countries by government flight inspectors during aircraft type-certification testing. 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, and are expressed in terms of the aircraft's indicated airspeed, so that pilots may use them directly, without having to apply correction factors.

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 green arc and the white arc are the stalling speed with wing flaps retracted, and stalling speed with wing flaps fully extended, respectively. These are the stalling speeds for the aircraft at its maximum weight.[3][4]

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

Regulation

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 or FARs.[7] In Canada, the regulatory body, Transport Canada, defines 26 commonly used V-speeds in their Aeronautical Information Manual (AIM).[8]

Regulatory V-speeds

These V-speeds are defined by regulations.

V-speed designator Description
V1 Critical engine failure recognition speed. (See V1 definitions below)[7][8][9]
V2 Takeoff safety speed. The speed at which the aircraft may safely become airborne 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 feet.[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 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. If both VS0 and VS1g are available, the higher resulting Vat shall be applied.[12] Also called "approach speed".
VB Design speed for maximum gust intensity.[7][8][9]
VC Design cruise speed, used to show compliance with gust intensity loading.[13]
Vcef See V1; generally used in documentation of military aircraft performance.[14]
VD Design diving speed.[7][8][9]
VDF Demonstrated flight diving speed.[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 it is safe to fly a retractable gear aircraft with the landing gear extended.[7][8][9][15]
VLO Maximum landing gear operating speed. This is the maximum speed at which it is safe to extend or retract the landing gear on a retractable gear aircraft.[7][8][9][15]
VLOF Lift-off speed.[7][9]
VMC Minimum control speed with Critical engine inoperative.[7][8][9]
Vmca Minimum control speed in the take-off configuration – the minimum calibrated airspeed at which the aircraft is directionally controllable in flight with a sudden Critical engine failure and takeoff power on the operative engine(s).[9]
Vmcg Minimum control speed on the ground - the minimum airspeed at which the aircraft is directionally controllable during acceleration along the runway with one engine inoperative, takeoff power on the operative engine(s), and with nose wheel steering assumed inoperative.[9][16]
Vmcl Minimum control speed in the landing configuration with one engine inoperative.[9][16]
VMO Maximum operating limit speed.[7][8][9]
VMU Minimum unstick speed.[7][8][9]
VNE Never exceed speed.[7][8][9][17]
VNO Maximum structural cruising speed or maximum speed for normal operations.[7][8][9]
VO Maximum operating maneuvering speed.[18]
VR Rotation speed. The speed at which the aircraft's nosewheel leaves the ground.[7][8][9] Also see note on Vref below.
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).[14]
VRef Landing 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.[14] Incorrectly, or as an abbreviation, some documentation refers to Vref and/or Vrot speeds as "Vr."[19]

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]
VTO Take-off speed. (see also VLOF)[20]
VTOSS Category A rotorcraft takeoff safety speed.[7][17]
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
VBE Best endurance speed – the speed that gives the greatest airborne time for fuel consumed.
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.[21]
VFS Final segment of a departure with one powerplant failed.[22]
Vimd Minimum drag[23]
Vimp Minimum power[23]
VLLO Maximum landing light operating speed – for aircraft with retractable landing lights.[9]
Vmbe Maximum brake energy speed[24][23]
Vmd Minimum drag (per lift) - often identical to VBR.[21][24] (alternatively same as Vimd[25])
Vmin Minimum speed for instrument flight (IFR) for helicopters[17]
Vmp Minimum power[24]
Vp Aquaplaning speed[26]
VPD Maximum speed at which whole-aircraft parachute deployment has been demonstrated[27]
Vra Rough air speed (turbulence penetration speed).[9]
VSL stall speed in a specific configuration[9][24]
Vs1g stall speed at 1g load factor
Vsse Safe single engine speed[28]
Vt Threshold speed[24]
Vtocs Take-off climbout speed (helicopters)[17]
Vtos Minimum speed for a positive rate of climb with one engine inoperative[24]
Vtmax Max threshold speed[29][24]
Vwo Maximum window or canopy open operating speed[30]
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.[28]
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.[15][28]
VZRC Zero rate of climb speed in a twin-engine aircraft[24]

Mach numbers

Whenever a limiting speed is expressed in terms of Mach number, it is expressed as an "M speed", e.g. VMO: Maximum operating limit speed (in knots), MMO: Maximum operating limit Mach.[7][8]

V1 definitions

V1 is the critical engine failure recognition speed or takeoff decision speed. It is the decision speed nominated by the pilot which satisfies all safety rules, and above which the takeoff will continue even if an engine fails.[9] The speed will vary between aircraft types and also due to aircraft weight, runway length, wing flap setting, engine thrust used, runway surface contamination and other factors.

V1 is defined differently in different jurisdictions:

  • The US Federal Aviation Administration defines it as: V1 means 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]
  • 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]

References

  1. ^ Love, Michael C. (2005). "2". Better Takeoffs & Landings. Mc-Graw Hill. pp. 13–15. ISBN 0-07-038805-9. Retrieved 2008-05-07.
  2. ^ Craig, Paul A. (2004). "1". Multiengine Flying (3rd ed.). McGraw Hill. pp. 3–6. ISBN 0-07-142139-4. Retrieved 2008-05-07.
  3. ^ Federal Aviation Administration (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". Retrieved 2008-08-01. {{cite web}}: Unknown parameter |month= ignored (help)
  4. ^ "Pilot's Handbook of Aeronautical Knowledge - Chapter 7" (PDF). FAA. Retrieved 2010-01-29.
  5. ^ "Pilot's Handbook of Aeronautical Knowledge - Chapter 8" (PDF). FAA. Retrieved 2010-01-29.
  6. ^ Federal Aviation Administration (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". Retrieved 2008-08-01. {{cite web}}: Unknown parameter |month= ignored (help)
  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 "Electronic Code of Federal Regulations - Chapter 14.1". Federal Aviation Administration. Retrieved 2008-05-07.
  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 z aa ab Transport Canada (2008). "Aeronautical Information Manual GEN - 1.0 GENERAL INFORMATION". Retrieved 2008-05-12. {{cite web}}: Unknown parameter |month= ignored (help)
  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 ab ac ad ae 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. Retrieved 2009-12-09.
  11. ^ FAA Advisory Circular 23-19A Airframe Guide for Certification of Part 23 Airplanes, Section 48 (p.27) Retrieved 2012-01-06
  12. ^ PANS-OPS, Volume I, Part I, Section 4, Chapter 1, 1.3.3
  13. ^ FAR Part 23.335
  14. ^ a b c MIL-STD-3013A
  15. ^ a b c Pilot's Encyclopedia of Aeronautical Knowledge. Federal Aviation Administration. 2007. pp. G–16. ISBN 978-1-60239-034-8. Retrieved 2008-05-12.
  16. ^ a b Federal Aviation Administration. (2009). "Title 14: Aeronautics and Space PART 25—AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY AIRPLANES Subpart B—Flight Controllability and Maneuverability § 25.149 Minimum control speed". Retrieved 2009-02-16. {{cite web}}: Unknown parameter |month= ignored (help)
  17. ^ a b c d Bell Helicopter Textron: Bell Model 212 Rotorcraft Flight Manual, page II. Bell Helicopters Textron Publishers, Fort Worth, Texas, Revision 3, 01 may 1998. BHT-212IFR-FM-1
  18. ^ USA 14CFR §23.1557 Retrieved 2012-01-06
  19. ^ TPUB INTERMEDIATE FLIGHT PREPARATION WORKBOOK APPENDIX A
  20. ^ C-130 Hercules Performance Charts.
  21. ^ a b Brandon, John (2008). "Airspeed and the properties of air". Retrieved 2009-04-07. {{cite web}}: Unknown parameter |month= ignored (help) [dead link]
  22. ^ airplanedriver.net (undated). "Cessna Citation". Retrieved 2009-02-14. {{cite web}}: Check date values in: |year= (help)CS1 maint: year (link)
  23. ^ a b c Bristow, Gary (undated). "Ace the Technical Pilot Interview". Retrieved 2009-01-20. {{cite web}}: Check date values in: |year= (help)CS1 maint: year (link)
  24. ^ a b c d e f g h Croucher, Phil (2007). "Canadian Professional Pilot Studies". Retrieved 2009-01-20.
  25. ^ "Transportation Safety Board of Canada - A05W0109". Retrieved 2010-03-26.
  26. ^ Croucher, Phil (2007). "Canadian Professional Pilot Studies". Retrieved 2009-01-20.
  27. ^ "SR20 Pilot's Operating Handbook" (Document). Cirrus Design. 2004. p. 8.{{cite document}}: CS1 maint: postscript (link)
  28. ^ a b c Flight Sim Aviation (2009). "Aviation Rules of Thumb - V-Speeds Abbreviations List". Retrieved 2009-01-19.
  29. ^ TheFreeDictionary (2009). "VTMAX". Retrieved 2009-01-19.
  30. ^ Blue Ridge Air Works (undated). "Cessna 152 - 4843H General Info". Retrieved 2009-02-13. {{cite web}}: Check date values in: |year= (help)CS1 maint: year (link)
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