Originally Posted by Mach75
I think I'm starting to get a clearer picture but could someone just confirm that I am understanding this correctly:
- For a given airspeed (ie. Vmo) a heavier aircraft would have to begin descent earlier than a light aircraft because, due to the increased momentum, it would require maintaining a lower rate of descent to avoid exceeding this speed?
Your deduction is correct, but I think the reason is more "apparent thrust" than momentum. Your weight acts as thrust in the descent as explained earlier by JonaLX.
Originally Posted by Mach75
- If asked to maintain a slower airspeed than normal on the descent, the aircraft would have to descend earlier because it would then be descending closer to its best Lift
rag angle of attack and would therefore have a lower rate of descent for the given airspeed?
Yes and no. For the same rate-of-descent, your speed would be lower for a lighter a/c at idle power. In other words, you would need a higher ROD for the same speed, compared to a heavy a/c.
I practice, I plan idle descents for heavy approaches and power-on descents for a very light a/c. This keeps my ROD constant (start descent at same point) and I then use power to maintain same speed profile.
The worst case scenario in my a/c, is a light a/c in icing conditions (Min N2 limit with anti-ice) with Radar slowing you down early. You are almost guaranteed to need flight spoiler.