Mad Jock
The need to recite your CV suggests that you have lost the argument (or at least your composure).
The validity or otherwise of a person's comments is determined by what they say, not by who they are or were.
You have not answered the fundamental question:
"If the rate of descent is determined by the amount of energy that an aircraft has, why is it that?
a. When the descent is carried out at the speed that is Vmp for the lighter aircraft, the heavier aircraft has the greater rate of descent.
b. But at typical airliner descent speeds the lighter aircraft has the greater rate of descent."
The heavier aircraft has the greater energy in both cases.
Jimmygill
Seems to me that our heavier 777 is a better glider than its lighter friend for the given descent airspeed.
Could it be that the heavier one is operating at a higher L/D than the lighter one? I believe so.
OK, here's the follow-on question.
We take an aircraft and carry out a glide at Vmp. We note the Power required, L/D ratio and the rate of descent.
We repeat the glide at the same weight but now at Vmd. The L/D ratio has increased, but so as the rate of descent.
We repeat the process at a speed greater than Vmd. The L/D has decreased but the rate of descent has again increased.
It appears that the link between L/D ratio and rate of descent has broken down when we accelerated beyond Vmd.
But in each case the power required and the rate of descent both increased.
Does this not suggest that the link between power required and rate of descent is more direct than the link between L/D ratio and rate of descent?