V-Speeds
V1 (Decision / Action)
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.
V2 (Takeoff Safety Speed)
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.
VA (Maneuvering Speed)
VA means design maneuvering speed.Regulations 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.
VEF (Engine Failure Speed)
VEF means the speed at which the critical engine is assumed to fail during takeoff.
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
VFTO (Final Takeoff Speed)
VFTO means final takeoff speed.
VFTO, in terms of calibrated airspeed, must be selected by the applicant to provide at least the gradient of climb required, but may not be less than-
(1) 1.18 VSR; and
(2) A speed that provides the maneuvering capability
VLE (Maximum Landing Gear Extended Speed)
VLE means maximum landing gear extended speed.
VLO (Maximum Landing Gear Operating Speed)
VLO means maximum landing gear operating speed.
VLOF (Lift Off Speed)
VLOF means lift off speed.
VLOF is the calibrated airspeed at which the airplane first becomes airborne.
VMC (Minimum Control Speed)
VMC means minimum control speed with the critical engine inoperative.
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.
VMCG (Minimum Controllable Speed on the Ground)
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.
VMCL (Minimum Control Speed, Landing)
VMCL is the minimum control speed during approach and landing with all engines operating, it's 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)VMO / MMO means maximum operating limit speed.
VMU (Minimum Unstick Speed)
VMU means minimum unstick speed.
VMU is the calibrated airspeed at and above which the airplane can safely lift off the ground, and continue 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)
VNE means never-exceed speed.
VNO (Maximum Structural Cruising Speed)
VNO means maximum structural cruising speed.
VR (Rotation Speed)
VR means rotation speed.
VR, in terms of calibrated airspeed, must be selected in accordance with the conditions of paragraphs (1) through (4) of this section:
(1) VR may not be less than--
(i) V1;
(ii) 105 percent of VMC;
(iii) The speed 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 regulations
(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.
VREF (Reference Landing Speed)
VREF means reference landing speed.
VS (Stalling Speed)
VS means means the stalling speed or the minimum steady flight speed at which the airplane is controllable.
VSR0 (Stalling Speed in Landing Configuration)
VSR0 means the reference stall speed in the landing configuration.
VSR (Reference Stalling Speed)
VSR means reference stalling speed.
VSR is refrenced by "not less than a 1-g stall speed."
VX - Best Angle of Climb Speed
VX means speed for best angle of climb.
Force Analysis
What it Really Means
- When the airplane is in steady flight with moderate angle of climb, the vertical component of lift is very nearly the same as the actual lift. Such climbing flight would exist with the lift very nearly equal to the weight. The net thrust of the powerplant may be inclined relative to the flight path but this effect will be neglected for the sake of simplicity. Note that the weight of the aircraft is vertical but a component of weight will act along the flight path.
- If it is assumed that the aircraft is in a steady climb with essentially small inclination of the flight path, the summation of forces along the flight path resolves to the following:
Forces forward=Forces aft
T = D + W sin γ
T = D + W sin γ
where:
T = thrust available, lbs.
D = drag, lbs.
W = weight, lbs.
γ ("gamma") = flight path inclination or angle of climb
Of course some very high performance corporate aircraft, such as the G450, climb at angles where you cannot assume the inclination of the powerplant is negligible. Hence the section devoted to 1950's fighter type aircraft become suddenly applicable to us . . .
T = thrust available, lbs.
D = drag, lbs.
W = weight, lbs.
γ ("gamma") = flight path inclination or angle of climb
Of course some very high performance corporate aircraft, such as the G450, climb at angles where you cannot assume the inclination of the powerplant is negligible. Hence the section devoted to 1950's fighter type aircraft become suddenly applicable to us . . .
- This basic relationship neglects some of the factors which may be of importance of airplanes of very high performance. For example, a more detailed consideration would account for the inclination of thrust from the flight path, lift not equal to weight, subsequent change of induced drag, etc. However, this basic relationship will define the principal factors affecting climb performance. With this relationship established by condition of equilibrium, the following relationship exists to express the trigonometric sine of the climb angle, γ:
sinγ=T−D/W
- This relationship simply states that, for a given weight airplane, the angle of climb (γ) depends on the difference between thrust and drag (T - D), or excess thrust. Of course, when the excess thrust is zero (T - D = 0 or when T = D), the inclination of the flight path is zero and the airplane is in steady, level flight. When the thrust is greater than the drag, the excess thrust will allow a climb angle depending on the value of excess thrust. Also, when the thrust is less than the drag, the deficiency of thrust will allow an angle of descent.
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VX Best Angle of Climb Speed
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- The thrust curves for the representative jet aircraft show the typical turbojet thrust which is very nearly constant with speed. If the thrust available is essentially constant with speed, the maximum excess thrust and angle of climb will occur where the thrust required is at a minimum, (L/D)MAX. Thus, for maximum steady-state angle of climb, the turbojet aircraft would be operated at the speed for (L/D)MAX.
There are two key points here for pilots:
- Pilots transitioning from propeller powered aircraft to jet aircraft must unlearn their instinct to "hang on the props" when trying to achieve a maximum angle of climb. A jet aircraft reaches its best angle of climb, VX, at L/DMAX. That is usually found at 0.30 AOA.
- If trying to clear an obstacle close in with a jet aircraft, there is a trade off to consider. It takes distance to accelerate the aircraft to its best angle of climb speed, getting you closer to the obstacle. There will be a point where you are better off climbing at a lower speed than accelerating. The trade off is considered in flight test and pilots must rely on their flight manuals to make the determination.
