Hi everybody,
I would like to know if you can shed some light on this matter
. As an air traffic controller, I have often wondered which is best for fuel economy, reducing or doing a few more miles, which could be a path stretching or a holding pattern.
For example, consider an aircraft flying at FL 330 which is ten minutes before its top of descent and flying at M80. And imagine we need , in order to sequence that particular aircraft for the approach, to have him loose 20 NM. Consider the two following choices, both of which would make the aircraft loose 20 NM (about 3 or 4 minutes):
Choice 1: reduce speed during the whole descent phase, reduce speed to M77 instead of M80 at first, and then below FL 250 reduce speed to KT 220 instead of KT260/KT280.
Choice 2: let aircraft fly at own speed, and then loose the 3/4 minutes at a TMA entry point or clearance limit, by doing a full holding pattern at approximately FL 150.
Is one of the choices clearly better for fuel economy, or is there no universal truth and it depends on aircraft type?
Thanks in advance!