APEppink

True, but how's that relevant?

Ideas c variance are tenuous but some people think it does and are working on it.

Maybe you could explain a little more clearly how you think F=m*a is at work here.

The plane accellerates relative to the ground, thus Newton's Law obviously comes into play.

"I think someone stated that an aircraft cruising at 45 knots into a 45 knot headwind would have zero kinetic energy, that is not correct. Kinetic energy relates to mass multiplied by speed squared and the speed for an aircraft in normal flight is the true airspeed, so any airspeed above Vs1 can still be swapped for gravitational potential energy even if the aircraft was moving backwards relative to the ground."

No. It is correct. Even tho Kinetic Energy is a scalar (V^2 = V*V is a dot product). Kinetic energy exists only where there's a relative speed between the objects in question. Thus the guy sailing at 45kts IAS into a 45 kt headwind has no kinetic energy relative to the earth.

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yep so wouldnt it be correct to say the aircraft has more inertia when landing downwind? isnt that why it takes longer to stop

E

Hi Mike thanks for your response. There is one thing though that has not been taken into account in this explanation. The inertia of the aircraft. how about we talk about turning from downwind into a headwind. . If the aircraft was to suddenly turn into the?u wind wouldnt it pick up some speed for a moment because it would take time for the inertia of the aircraft to slow down. Or we can think of it in another way. Lets first say there is a 50 knot westerly. Now lets imagine an aircraft is climbing verticly up in the air until it almost stalls at this point the pilot kicks in full rudder and the nose comes around pointing straight down at the ground. When the pilot has some speed he pulls sharply out fo the dive into the tailwind. now with that sudden change in direction wouldnt the aircraft loose some speed until it ha time to catch back up with the wind. Or what about if he pulled out of the dive into the wind. wouldnt he suddenly have a 50 knots of extra airspeed that may last for 3 seconds or so until the inertial of the plane has been slowed back to the oringinal airspeed.

Everybody's ignoring F = m*a. An applied force is necessary to effect a linear accelleration. The force has to come from the air mass in the form of an initially reduced IAS. How else can it be?

"The aircraft is borne by the wind, and reference to GROUND SPEED has no impact at all on aerodynamics."

Impossible. By F = m*a, an applied force is required to effect a linear accelleration. HOW does the airmass impart this force? SPECIFICALLY?