The FAA gives aircraft manufacturers more latitude than you might think when it comes to choosing what they decide to lay down to us pilots as the crucial speeds we rely on for takeoff and landing. Some of those speeds are more critical to your well being than you may think, others less so, and some are just down right misleading.
[14 CFR 1.2] 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.
Most sources call this "Decision Speed" implying you make the decision then, but that is not true. The decision must have been made by then.
More about this: V1 — Decision (Action) Speed
[14 CFR 1.2] V2 means takeoff safety speed.
V2 is aptly named, it keeps you safe with a margin above stall and minimum control speeds, it even gives you maneuverability.
More about this: V2 — Takeoff Safety Speed.
[14 CFR 1.2] VA means design maneuvering speed.
14 CFR 25 does not specify the weight or altitude for which this speed is determined so the number in your flight manual does not work for most of the flight conditions you will find yourself in. There are generations of Gulfstream pilots convinced 206 knots will get them out of any situation; they are all wrong.
More about this: VA — Maneuvering Speed.
VEF (Engine Failure Speed)
[14 CFR 1.2] VEF means the speed at which the critical engine is assumed to fail during takeoff.
[14 CFR 25.107(a)(1)] VEF is the calibrated airspeed at which the critical engine is assumed to fail. VEF must be selected by the applicant, but may not be less than VMCG determined under § 25.149(e).
VFE (Maximum Flap Extended Speed)
[14 CFR 1.2] VFE means maximum flap extended speed.
VFTO (Final Takeoff Speed)
[14 CFR 1.2] VFTO means final takeoff speed.
[14 CFR 25.107 (g)] VFTO, in terms of calibrated airspeed, must be selected by the applicant to provide at least the gradient of climb required by § 25.121(c), but may not be less than—
(1) 1.18 VSR; and
(2) A speed that provides the maneuvering capability specified in § 25.143(h).
The maneuvering capabilities in a constant speed coordinated turn at forward center of gravity, as specified in the following table, must be free of stall warning or other characteristics that might interfere with normal maneuvering:
|Configuration||Speed||Maneuvering bank angle in a coordinated turn||Thrust/Power setting|
|Takeoff||2V2 + XX||40°||All-engines-operating-climb.3|
|En route||VFTO||40°||Asymmetric WAT-Limited.1|
|Landing||VREF||40°||Symmetric for -3° flight path angle.|
1 A combination of weight, altitude, and temperature (WAT) such that the thrust or power setting produces the minimum climb gradient specified in § 25.121 for the flight condition.
2 Airspeed approved for all-engines-operating initial climb.
3 That thrust or power setting which, in the event of failure of the critical engine and without any crew action to adjust the thrust or power of the remaining engines, would result in the thrust or power specified for the takeoff condition at V2, or any lesser thrust or power setting that is used for all-engines-operating initial climb procedures.
VLE (Maximum Landing Gear Extended Speed)
[14 CFR 1.2] VLE means maximum landing gear extended speed.
VLO (Maximum Landing Gear Operating Speed)
[14 CFR 1.2] VLO means maximum landing gear operating speed.
VLOF (Lift Off Speed)
[14 CFR 1.2] VLOF means lift off speed.
[14 CFR 25.107 (f)] VLOF is the calibrated airspeed at which the airplane first becomes airborne.
[14 CFR 1.2] VMC means minimum control speed with the critical engine inoperative.
[14 CFR 25.149] VMC is the calibrated airspeed at which, when the critical engine is suddenly made inoperative, it is possible to maintain control of the airplane with that engine still inoperative and maintain straight flight with an angle of bank of not more than 5 degrees.
VMC is the minimum speed you will have directional control of the aircraft in takeoff configuration with the critcal engine failed. Some Gulfstreams call this speed VMCA, perhaps recognizing its parallel relationship with VMCL.
More about this: VMC — Minimum Control Speed.
[14 CFR 25.149 (e)] VMCG, the minimum control speed on the ground, is the calibrated airspeed during the takeoff run at which, when the critical engine is suddenly made inoperative, it is possible to maintain control of the airplane using the rudder control alone (without the use of nosewheel steering), as limited by 150 pounds of force, and the lateral control to the extent of keeping the wings level to enable the takeoff to be safely continued using normal piloting skill.
VMCG is the lowest speed you have control of the aircraft following a failure of the critical engine without the aid of the nosewheel; where you have enough rudder effectiveness to keep the airplane within 30 feet of runway centerline with the critical engine failed.
More about this: VMCG — Minimum Ground Control Speed.
VMCL (Minimum Control Speed, Landing)
[14 CFR 25.149 (f)] VMCL is the minimum control speed during approach and landing with all engines operating, is the calibrated airspeed at which, when the critical engine is suddenly made inoperative, it is possible to maintain control of the airplane with that engine still inoperative, and maintain straight flight with an angle of bank of not more than 5 degrees. VMCL must be established with—
(1) The airplane in the most critical configuration (or, at the option of the applicant, each configuration) for approach and landing with all engines operating;
(2) The most unfavorable center of gravity;
(3) The airplane trimmed for approach with all engines operating;
(4) The most favorable weight, or, at the option of the applicant, as a function of weight;
(5) For propeller airplanes, the propeller of the inoperative engine in the position it achieves without pilot action, assuming the engine fails while at the power or thrust necessary to maintain a three degree approach path angle; and
(6) Go-around power or thrust setting on the operating engine(s).
VMO / MMO (Maximum Operating Limit Speed)
[14 CFR 1.2] VMO / MMO means maximum operating limit speed.
VMU (Minimum Unstick Speed)
[14 CFR 1.2] VMU means minimum unstick speed.
[14 CFR 25.107 (d)] VMU is the calibrated airspeed at and above which the airplane can safely lift off the ground, and con- tinue the takeoff. VMU speeds must be selected by the applicant throughout the range of thrust-to-weight ratios to be certificated. These speeds may be established from free air data if these data are verified by ground takeoff tests.
VNE (Never-Exceed Speed)
[14 CFR 1.2] VNE means never-exceed speed.
VNO (Maximum Structural Cruising Speed)
[14 CFR 1.2] VNO means maximum structural cruising speed.
VR (Rotation Speed)
[14 CFR 1.2] VFTO means rotation speed.
[14 CFR 25.107 (e)] VR, in terms of calibrated airspeed, must be selected in accordance with the conditions of paragraphs (e)(1) through (4) of this section:
(1) VR may not be less than—
(ii) 105 percent of VMC;
(iii) The speed (determined in accordance with § 25.111(c)(2)) that allows reaching V2 before reaching a height of 35 feet above the takeoff surface; or
(iv) A speed that, if the airplane is rotated at its maximum practicable rate, will result in a VLOF of not less than —
(A) 110 percent of VMU in the all-engines-operating condition, and 105 percent of VMU determined at the thrust-to-weight ratio corresponding to the one-engine-inoperative condition; or
(B) If the VMU attitude is limited by the geometry of the airplane ( i.e., tail contact with the runway), 108 percent of VMU in the all-engines-operating condition, and 104 percent of VMU determined at the thrust-to-weight ratio corresponding to the one-engine-inoperative condition.
(2) For any given set of conditions (such as weight, configuration, and temperature), a single value of VR, obtained in accordance with this paragraph, must be used to show compliance with both the one-engine-inoperative and the all-engines-operating takeoff provisions.
(3) It must be shown that the one-engine-inoperative takeoff distance, using a rotation speed of 5 knots less than VR established in accordance with paragraphs (e)(1) and (2) of this section, does not exceed the corresponding one-engine-inoperative takeoff distance using the established VR. The takeoff distances must be determined in accordance with § 25.113(a)(1).
(4) Reasonably expected variations in service from the established takeoff procedures for the operation of the airplane (such as over-rotation of the airplane and out-of-trim conditions) may not result in unsafe flight characteristics or in marked increases in the scheduled takeoff distances established in accordance with § 25.113(a).
[14 CFR 25, §25.1517] A rough air speed, VRA, for use as the recommended turbulence penetration airspeed in §25.1585(a)(8), must be established, which—
(1) Is not greater than the design airspeed for maximum gust intensity, selected for VB; and
(2) Is not less than the minimum value of VB specified in §25.335(d); and
(3) Is sufficiently less than VMO to ensure that likely speed variation during rough air encounters will not cause the overspeed warning to operate too frequently. In the absence of a rational investigation substantiating the use of other values, VRA must be less than VMO—35 knots (TAS).
VRA is one of those numbers that has to be established during certification but one the manufacturer is given so much latitude that it is pretty much meaningless once it is published. The published VRA in the G450, for example, is so much higher than VA, one would be foolish to use it in truly rough air.
[14 CFR 1.2] VREF means reference landing speed.
More about this: VREF — Reference Landing Speed.
VS (Stalling Speed)
[14 CFR 1.2] VS means means the stalling speed or the minimum steady flight speed at which the airplane is controllable.
VSR0 (Stalling Speed in Landing Configuration)
[14 CFR 1.2] VSR0 means the reference stall speed in the landing configuration.
[14 CFR 1.2] VSR means reference stalling speed.
While VS is defined by 14 CFR 1.2 as "the stalling speed or the minimum steady flight speed at which the airplane is controllable," VSR is further defined by 14 CFR 25.103 as "not less than a 1-g stall speed.
More about this: VSR — Reference Stall Speed.
[14 CFR 1, §1.2]
- VX means speed for best angle of climb.
14 CFR 25 does not mention VX at all.
For what it really means: VX — Best Angle of Climb Speed.
[14 CFR 1, §1.2]
- VY means speed for best rate of climb.
14 CFR 25 does not mention VY at all.
For what it really means: VY — Best Rate of Climb Speed.
14 CFR 1, Title 14: Aeronautics and Space, Definitions and Abbreviations, Federal Aviation Administration, Department of Transportation
14 CFR 25, Title 14: Aeronautics and Space, Airworthiness Standards: Transport Category Airplanes, Federal Aviation Administration, Department of Transportation
Gulfstream G450 Airplane Flight Manual, Revision 35, April 18, 2013