Hi.

I have noticed that when setting up a flight plan the cruise altitude defaults to FL280. The Phenom 300 will of course fly considerably higher except in the shortest of hops. FL280 seems to correspond to the ESA (enroute safe altitude), as in the bottom box of the active flight plan it displays "FPL ENR SAFE ALT 28000 FT". What is the significance of the ESA, and why does the flight plan default to this? Is there any way of changing this? I am finding that I am having to change the altitude for many waypoints in the flight plan. Thanks.

Adrian

FL280 is usually the fastest flight level (where the change over from IAS to MACH occurs). If you want to get somewhere fast in a jet you have to fly at this low altitude.  

I thought that the changeover point from IAS to MACH is at FL295 in the Phenom. I also thought that the aim is to fly higher where ground speeds will increase and fuel economy will improve due to the thinner air. 

Why is it called "enroute safe altitude", and what is the significance? Is flying at FL450 (the service ceiling for the Phenom) therefore somehow unsafe?

Adrian

The change over altitude depends on the IAS/Mach ratio, it's approximately FL280 (+ a few thousand feet) 

TAS starts to decrease with higher altitude once you keep the Mach number.

Enroute safe altitude usually indicates the lowest useable altitude. FL280 doesn't make sense IMO.