A & C
yes, i think this thread has gone into the depths of mathematics.
Can you just agree, from the calculation listed by me about two posts up that it may not be suitable for light aircraft.
I am in favour of this rule of thumb stuff to save time and make life easier.
But can somenone be adult enough to look at the calculations and say 'it probably is not suitable for this purpose'. The calculation is very clear and relevant to light aircraft flying. And I totally agree with you about light aircraft descending at 5-600fpm. And in that case the 3 times clearly is not suitable.
But, please do the same calculation as i did for your A320 and your DR400 with exactly the same figures. 5000 feet to lose using the 3times rule and transpose it to the DR400 and let me see what the ROD is for both for the time/distnace covered to the destination.
If the figures are close together then i stand corrected. If not, then please do the same.
I am not looking for a debate and I too use this for my RHS job and as an FI.