AFT CG and Stall Speed... need diagram

[tgrayson]

So, you're telling me if I have an aircraft flying at max gross, at cruise altitude, all I need is thrust?

You first need Lift = Weight. If that's all you have, the aircraft will be in a steady descent. If you add in thrust, then you can achieve level flight, or a climb.

<<A heavily weighted aircraft will be flying with a higher AoA at cruise as opposed to the same aircraft with a lighter load. >>

Yes.

<<assuming two identical aircraft flying along, one 3800 lbs. and one 2800 lbs., the wing loading on the heavier aircraft is obviously needing to support a greater load so if both aircraft are cruising at 120 knots and 10,000', the heavier aircraft will have to fly with a greater AoA to increase our coefficient of lift as opposed to a light aircraft.>>

Yes.

 

[tgrayson]

To stop such a descent, the variable that would need to be changed would be lift assuming keeping an identical AoA. This can be accomplished through increasing our coefficient of lift.

One caveat: When transitioning to level flight, there is a temporary deviation of your load factor from one. During a pullup, you will have a larger than 1 load factor, which is what actually creates the curved flight path. However, your aircraft will not stay in level flight unless Thrust = Drag.

This is why a even glider can temporarily achieve level flight. Our discussion so far has been targeted towards sustained, equilibrium conditions.

 

[E6BAV8R]

Now, you can stop the descent by increasing your AOA, but that works by slowing the aircraft towards your L/D max speed. In other words, pulling back on the yoke reduces drag.

How would drag be reduced by pulling back on the yoke - essentially increasing AoA, or increasing lift, to regain a more level-flight attitude? I do realize you would be going back down towards L/Dmax which would be reducing parasite drag and then increasing induced drag - or were you referring to parasate drag in your example there?

 

[tgrayson]

How would drag be reduced by pulling back on the yoke - essentially increasing AoA, or increasing lift, to regain a more level-flight attitude? I do realize you would be going back down towards L/Dmax which would be reducing parasite drag and then increasing induced drag - or were you referring to parasate drag in your example there?

Just as you say...increasing your AOA reduces your parasite drag, but increases your induced drag slightly. If you're on the front side of the drag curve, the overall drag is reduced and you may achieve level flight if your thrust matches your new, reduced drag.

Don't be distracted by the increasing of lift...it's only temporary. Lift = Weight in unaccelerated flight and the airplane itself will take care of this relationship. Most of our piloting worries have to do with thrust and drag.