"The heavier aircraft has more potential energy than the lighter one and at a constant airspeed they both remove the same amount of energy via drag in the decent. Therefore for over a period of time the lighter aircraft would have lost more altitude than the heavy one ie the lighter one has a higher rate of decent"
How can they remove same amount of energy via drag when they have different magnitude of drag? Did the initial question state that they have same drag?
Isn't it from the very basic physics that force (Drag) multiplied by displacement in the direction of force is energy, and rate of change of energy is power.
Since the mistake lies in the very first sentence, we should not move on to the second sentence.
When Galileo threw the 1 pound and 10 pound weights from the Leaning tower of Pisa he found both traveled at the same speed. If you do not include the aerodynamics, them you can replace the airplanes with stones and get results in variance with Galileo's experiment.
In the following quote I am replacing the word "aircraft" with stone. Do we see something wrong here?
"The heavier stone has more potential energy than the lighter one and at a constant airspeed they both remove the same amount of energy via drag in the decent. Therefore for over a period of time the lighter stone would have lost more altitude than the heavy one ie the lighter one has a higher rate of decent"
Role of L/D in descent seems sexy thats fine, and thats the only correct and consistent way of explaining the phenomenon.
Thats the answer they are looking for which for wannabies is the answer they should give if they get to a oral tech interview.
They are looking for these answers because the so called "experienced aviators" get most of their knowledge from folklore in and around the airport bar.
The only environmental I introduced is same TAS, to make sure that we are comparing apples to apples. Please note the word "constant airspeed" which you too have used in your explanation, I have emphasized it above.
And one more thing, I know it may again sound sexy.
When I limit myself to the ratio L/D, in deriving the Rate of descent relation, I am doing basic Kinematics and not aerodynamics.
Aerodynamics is not considered until I explain the relation between L/D and TAS, Weight and Angle of Attack.