Induced drag is not caused just by wingtip vortices. Induced drag is created anytime you create lift. Increase the angle of attack and you get more drag. This is caused by the lift vector pointing backwards.The reason induced drag decreases as airspeed increases is that you decrease the AOA to gain airspeed. When you slow down, you increase the AOA to maintain altitude. Parasitic drag is also made up of several different forms of drag. FS just simplifies it into one formula.

Hello Steffan,The max speed exists when there is no more acceleration left as thrust equals drag. Is the thrust too high? Propulsion power = thrust*speed. Or is drag too low. Drag = q*Af=q*CD*S. q is the dynamic pressure due to motion and Af is the effective frontal drag area which has several components. CDo the profile drag coefficient Rec 1101 entry 20 CDi is the vortex induced drag coefficient CDm is the compression/Mach drag coefficient Rec 430 * 2048 e = [1204]:7 *65536 S = [1204]:1 * sq.ft b = [1204]:2 * in !!!!!! CDi = CL^2/(A*pi*e) A = b^2/S If you only change the drag then decelleration with engines idle, gliding will also be effected. Fuel consumption will be increased and range decreased. If you only change thrust then acceleration, ceiling and max. rate of climb will also be effected. Propulsion power depend on: Number of engines [311] Propellor type [330] Piston torque vs. RPM [501] Prop efficiency vs. J[503] etc... So for max endurance this is the condition CDo = CDi so you need to change the ratio K/CDo a CDo = K*CL^2. Max endurance speed is also proportional to the max range speed which may be higher depending on the type of power plant.Ian

The lift force is defined as the force acting at right angles to the airflow: drag as the force parallel to the airflow. The lift vector doesn't rotate as the angle of attack increases.A textbook definition of induced drag is "the contribution to aerofoil drag associated with the continuous production of the kinetic enegy of the complete residual vortex system. Induced drag is due essentially to the three-dimensional character of the flow, vanishing for aerofoils of infinite span".Induced drag varies with the aspect ratio of the wing (Span^2/Area). Thus sailplanes have high aspect-ratio wings to minimise the induced drag for a given lift.

Thanks a lot guys !Well, this thread really got me to "dust off" the old physics knowledge. Even if these things never came up in school. :-lolWill try to "digest" all info. And we see what will come up. ;-)

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