A couple of posts ago I thought we were getting somewhere, but now I'm not so sure. Part of the problem here, and I say this with the greatest respect, is that the whole FE/RE thing deals with many concepts which, in isolation, can take a career to get your head around, and you can't expect to get the same level of understanding from a few hours or days on the interweb. I'm happy to concede that Einstein, relativity and bendy space are completely outside my comfort zone, so I don't even go there. I do, however, have a background in aviation.
First of all, what's the obsession with Terminal Velocity? Its just a speed (downwards or upwards, depending on your take) at which the force of aerodynamic drag equals the accelerating force of gravity or UA. (And please stop referring to gravity and suchlike as "drag"; drag is a specific force only caused by aerodynamics). There is no single "Terminal Velocity", it is dependent on the mass, size, shape and orientation of the object, and upon air density. So, for instance, in air;
TV of a one Metre sphere of styrofoam is less than a one metre sphere of iron (mass)
TV of a one kilogram sphere of styrofoam is less than a one kilogram sphere of iron (size)
TV of a one kilogram cube of iron is less than a one kilogram sphere of iron (shape)
TV of a 500lb Mk 82 bomb minus its fins, is less than that of one fitted with fins (orientation)
TV of anything dropped from 1000 metres above the sea is less than the same object dropped from 1000 metres above Mount Everest (air density).
So our typical human has a TV of around 300 kmph at typical skydiving heights, due to sea-level air density. Felix Baumgartner on the other hand achieved over 1300 kmph on his dive from 39 km, due to the reduced air density at altitude. The WW2 Tallboy bomb achieved a TV of around 1200 kmph, due to its shape and orientation. So; TV is just a number.
Lets look at the Wiki on TV;
"In the Round Earth model, terminal velocity happens when the acceleration due to gravity is equal to the acceleration due to drag. In the Flat Earth model, however, there are no balanced forces: terminal velocity happens when the upward acceleration of the falling object is equal to the upward acceleration of the Earth".
OK, happy with the RE bit. FE part; why are the forces not balanced? What is causing the "upward acceleration of the falling object"? Wouldn't it make more sense to say that aerodynamic drag of the rising atmosphere is accelerating the falling object? Therefore the forces are balanced.
Everyone happy with the concept of a windtunnel? You stick aerodynamic models in it and switch it on, and you can see how they will react in flight. In other words, static-object, moving-air, gives identical results to moving-object, static-air. Surely this is analogous to falling object-static air, and static-object, rising-air.
Finally, lift, drag, thrust and weight. Don't run away with the idea that all these forces are working at 90 degrees to each other; they aren't.
Thrust is always aligned along the axis of the engine so, in conventional aeroplanes, can be considered (more or less) to be along the longitudinal axis of the aircraft, regardless of its orientation.
Weight is always vertically down, regardless of orientation of the aircraft.
Drag is always in line with the relative airflow on the wings. If the aircraft has an angle of, say, 15 degrees nose-up to the relative airflow, drag will not be aligned with thrust.
Lift is always at 90 degrees to the relative airflow, so is only ever directly opposing weight if the aircraft is in straight and level flight, and almost never when flying a parabolic zero-g flight.
The flight of a Vomit-Comet (and there are several), requires a complex balance of entry speed and orientation (typically at 45 degrees nose-up), thrust and lift-management by the use of flying controls to ensure that the aircraft follows the exact free-fall trajectory of its occupants.
Terminal Velocity has nothing to do with it.
(Oh yes, and acceleration does not cause drag. Velocity causes drag).