"
Optimum Holding Level" - theory is, for Endurance, it does not matter. In practice, for the A320 I fly, it is slightly better to hold at high altitude, but only a few % in it.
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Suppose one is approaching destination say at FL 400 and ATC tells expect delays... Which is more cost effective?" I presume you mean "
what is least fuel consumption?." Min Fuel Flow is what you want, so:
- Power to idle
- Slow to Min Clean (Min Drag)
- Descend (& Hold) clean at Min Clean
You will get a
long time to await your turn to land at low fuel consumption.
Other factors clearly come into play:
- Are ATC happy with the slow RoD? Holding at these FLs?
- Are you sure you will land at Dest (or close to)? If a distant diversion is a possibility, then descending and needing to climb back is not a great idea...
It's partly energy management - PE (& KE). Use the PE wisely, flying at anything above Min Clean, or using the SB = throwing energy away which has to be replaced by fuel. Ditto, anytime thrust is above idle unnecessarily = wasted fuel.
Just start the descent where the computer says to and that is that
It really saddens me to see any pilot worth his salt saying such things
It is not possible to "program" an FMC with all the variables required, and pilots should understand the basic aerodynamics and factors - no matter how clever an Airbus or FMC is, it cannot alter basic physics. I am saddened by colleagues who will not fly a visual approach, or have to program the damn FMC/FD to fly it - and are unwilling (unable?) to look out of the window and fly accurately and appropriately for the conditions and efficiency.
NoD