I think our friend is asking "Why?" one would perhaps elect to climb at a constant TAS or a constant IAS.
For example, does either give an advantage in situations like..
- running late and want to achieve minimum sector time, fuel economy not a consideration?
- want to minimise fuel and time to top of climb?
- etc.
One example - in a Metroliner 23 turboprop, which surprisingly tended to burn the same kg/nm regardless of altitude (F050 to F250), you could drop the standard climb schedule and immediately accelerate to Vmo/Mmo after cleanup and achieve the same rate of climb with a 40kt speed gain that increased up to FL165, at which point the Mmo needle started marching back. This was good for picking up a few minutes on sectors over 200nm.
Another - best L/D ratio occurs at (roughly) the same IAS for a given weight. So if you decide that the best way to climb today is to climb at the IAS that gives you AoA for best L/D, then plug that speed into the panel. Whether you would actually do this or not depends on your powerplant charachteristics, such as fuel flow vs thrust vs altitude.
Oh dear, I shouldn't start these posts when I have had a few quiet ales. Somebody clever jump in and help the poor fellow.
Last edited by ITCZ; 25th May 2003 at 01:16.