Why still no dive acceleration difference?

[Crumpp]

it's the change in the sum of the two vector forces, not simply "the sum of" the two vector forces.

well said.

You understand Blackberry that is the excess force that moves the aircraft it is new equilibrium point.

The summing of the forces determines the vector of motion but the rate of change in motion along that vector is a function of the excess force.

For example, when the engine is off our thrust = 0 but our drag force remains. The summing of the forces results in a negative vector and our aircraft slows down as it seeks a new equilibrium point.

If the pilot pushes the stick forward to control the angle that he can shift a component of weight in order to counter act that drag force to maintain velocity or even speed up.