RE: V Speeds etc
V1- Maximum speed in the takeoff which the pilot must take the first action to stop the airplane within the accelerate-stop distance
Va- Design Maneuvering Airspeed
Vef- Speed at which the critical engine is assumed to fail during takeoff. Pilot must decide to stop or go.
Vf- Design flap speed
Vfe- Maximum flaps extended speed
Vle -Maximum speed with landing gear extended
Vlo- Landing gear operating speed
Vlof- Liftoff speed; the speed at which the wheels leave the ground
Vmc(a)- Minimal Controllable Airspeed (airborne)
Vmc(g)- Minimum controllable airspeed (ground)
Vne -Never exceed speed
Vno- Maximum structural cruising speed
Vr -Rotation speed with control input
Vsi- Stall speed in a specific configuration (usually gear & flaps up)
Vso- Stall speed in the landing configuration
Vx- All engines best angle-of-climb speed
Vxse -Engine-out best angle-of-climb speed
Vy- All engine best rate-of-climb speed
Vyse -Engine-out best rate-of-climb speed
Vzrc- Zero rate-of-climb speed for set weight & conditions
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B737-400 TAKE OFF SPEEDS:
TOW-737-400 23.5K
1000kg-V1 VR V2
70-158 162 168
65-152 154 162
60-144 147 155
55-137 139 149
50-129 131 143
45-121 123 136
40-112 115 130
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Bernoullis Principal:
P + ½ r V² = constant
The equation doesn’t take compressibility effects into account but at airflow velocities below 300 knots there are no such effects – thus no change in density. The equation then indicates that, in a moving airstream, if velocity increases static pressure must decrease.
Another aspect to the equation is that the constant is the stagnation pressure – the pressure energy needed to halt the airflow – thus it can be written P + ½ r V² = stagnation pressure. Note the stagnation pressure is the highest pressure in the system. This aspect of Bernoulli’s is used in the air speed indicator – as demonstrated below – but it is also the basis of the powered parachute wing. Those wings consist of an upper and lower fabric surface enclosing individual front opening cells. In a moving air stream the cells are at stagnation pressure – the highest – and thus form the semi-rigid wing shape.
There is another equation of aerodynamic interest to us – the continuity equation. This states that, in a moving airstream, the product of density, velocity and cross sectional area must always be a constant.
r × A × V = constant
If there is no change in density then we can state that
A × V = constant.
Thus if air flows into a smaller cross section area, or around an object, velocity must increase to maintain the constant and Bernoulli states that if velocity increases static pressure must decrease; so the velocity of a constricted airstream increases and its static pressure decreases.
Both these equations are related to the conservation laws – Bernoulli’s to the conservation of energy and the continuity equation to the conservation of mass.
NOTE: The V theories are also based on the flight envelopes.
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ON THE BASIS OF THIS LAW BY BERNOULLI AVIATIONS V THORIES OF TAKE OFFS AND LANDINGS ARE BASED ON.
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