Hi
I think it is a problem that cruise profiles are based on IAS instead of TAS. No propeller airplane can maintain the same IAS when altitude increases, and most POHs show TAS in their performance tables, not IAS.

Consider a standard profile which gives 100 kt at sea level. At most aircraft, the aircraft is still able to maintain 100 kt TAS at FL100, but when skydemon calculates TAS, 100 kt IAS will give about 116 kt TAS, which is not realistic for prop aircraft.

Consider changing this to TAS or let users choose between IAS or TAS when creating profiles.

Regards
Karsten

We're gradually enhancing our flight modelling engine so that this can be supported, in fact we're nearly there. It remains to be seen how we're able to expose the functionality in the user interface, though. We want to keep the aircraft configuration stuff simple and unintimidating for those that don't have complex or powerful aircraft, but to be able to offer the powerful calculations for those that do.

Assuming we were to implement level-dependent configuration based on TAS, how would you envisage the user interface working to select the cruise configuration? Would you still want to select a given power level and have the software work out what TAS you could achieve at the selected level?

I think it could work like the climb performance. For each cruise profile (75% or 55% power for example) you enter the TAS and fuel consumption at ground level, and do the same at service ceiling; to keep things simple you could have that default at the ground values (wich won't be far from the truth for non turbos, which is why it's probably better to do this in TAS rather than IAS). Linear interp in between. It would be really useful for complex/ high performance aircrafts to be able to insert perf figures at additional levels, as many aircrafts start to see a loss of perfomance at a certain level.

It won't be more complicated than entering weight&balance stats I think, and by having a default for people who don't care about this it should keep things user friendly. The one issue is what can appear as the inconsistency of indicating IAS for climb and descent, but TAS for cruise; but this is what you have in POHs.