Page 1 of 1

VNE and ECO speed

Posted: Thu Jun 24, 2010 6:01 am
by MOW
I should be stupid, but I do not understand how it is possible that the ECO speed in the aircraft database could be higher than the VNE.

Example :
B738 eco speed : 453 / VNE : 340 (pending config FSX file).

A321 eco speed : 487 / VNE : 340 (pending config FSX file).


I'm sure I do not understand one main point somewhere, but currently, it does not sound clear to me...

If some can help!

Re: VNE and ECO speed

Posted: Fri Jun 25, 2010 7:55 pm
by CAPFlyer
The speeds expressed in the database are True Airspeed, not Indicated. True Airspeed is much more useful in planning than Indicated Airspeed as it accounts for the fact that the instruments (IAS) cannot compensate for the lack of air at higher altitudes.

In addition, aircraft like above do not use IAS above 18,000 feet or so. Their "VNE" becomes "MMO" as mach speed becomes a much higher concern as altitude increases since the MMO can be below VNE.

Re: VNE and ECO speed

Posted: Sat Jun 26, 2010 11:45 am
by MOW
Thk Cap' !

I understood that I may go back to my "studies" to make this point more clear for me! :D