That will be set by your cost index. I'm failing at explaining this apparently. Say you choose 280IAS for climb and .78 for cruise. The cross-over altitude will be that altitude at which 280KIAS results in the same TAS as M.78. TAS = EAS / sqr(ρ/ρ0) ρ stands for density.

Man, you guys complicate this stuff. Say your climb is set to 280/.78. The plane will climb at 280IAS until the Mach increases to .78 and then it climbs at that.The rest is for your ATPL written.

The rest is for your ATPL written.

...pretty much.

Man, you guys complicate this stuff. Say your climb is set to 280/.78. The plane will climb at 280IAS until the Mach increases to .78 and then it climbs at that. The rest is for your ATPL written.

While I agree with your first and last statement (I should say especially the last), your second one still doesn't help the OP's issue, as he was asking for exactly that altitude LOL This might be theoretical, but why not just use a TAS formula depending on altitude and use a Mach number depending on altitude (thinking about it, this one might be easier), insert your speeds and solve for altitude? This might be a good start (like so often). In fact, I'm gonna give it a try, maybe it's possible to come up with something that way.

While I agree with your first and last statement (I should say especially the last), your second one still doesn't help the OP's issue, as he was asking for exactly that altitude LOL This might be theoretical, but why not just use a TAS formula depending on altitude and use a Mach number depending on altitude (thinking about it, this one might be easier), insert your speeds and solve for altitude? This might be a good start (like so often). In fact, I'm gonna give it a try, maybe it's possible to come up with something that way.

You know the airplane figures that out all by itself right?

The relationship between true airspeed and mach number varies with temperature. Similarly the relationship between indicated airspeed and mach number varies with pressure. This all means that everytime you climb, the transition from airspeed to mach on the VNAV climb will be at a different altitude.Regarding the aircraft FMC being programmed with this knowledge, so the pilot is not required to understand basic aerodynamics, I beg to differ. If one is just playing a game, fine, just why play with an accurate replica of a fully complex aircraft. Isn't it like going to a Chinese theater play without understanding the language?

You know the airplane figures that out all by itself right?

Well yes, so? It still doesn't help the OP, because I'm sure he knows the FMS is capable of doing so, but he was asking for a way to get that altitude. The FMS does nowhere output that altitude except for when you just do the climb and watch when it switches over, but I doubt that's the way the OP was looking for.

FL260. Everybody happy now?

FL260. Everybody happy now?

Nice one, and 's got the temp in too. Thanks!

FL260. Everybody happy now?

wow.. amazing stuff.. I need a plenty of time for using this.. :)Thank you all! :)