Hello guys. Recently I'm very interested in Atmosphere things.. and there were so many great articles and replies.. I thank you. This topic is discussed so many places, so many times but everytime I search web, couldn't get answer.Most answers are it depends on weather, temp, weight.. etc. It is so right but would be better with some examples with standard ISA. Two questions, First, from this interesting article, (http://goo.gl/dp4Z1)there seems two patterns within short tip. (I never depart for more than 2 hours and don't like heavies.. 737 lover since DF737) Generally, I thought cruise altitude for short trip is for minimun 20mins for fuel efficiency(saving for higher alt > lower alt),it seems it does not always right.. many posts shows that gliding after more climb(despite more fuel costs) is better than staying at low altitude. Second, I also have this image.. FMC calculates short trip optimum altitude with left one if there's any altitude constraint,And right one for general short trip. I don't think this is implemented with NGX.. So, 1. For a short trip, If density altitude is high(hot weather), will it be better climb to FL220~260 for 10~20mins cruise than FL360~390 and descent immediatly? (because it's hard to climb OAT is high) Any examples would be appreciated. (ISA, below ISA, above ISA, etc..) 2. And which method for optimum altitude would be better? Normally we don't stay at low altitude in FSX.. right? AND, is there charts for NGX like below? (seems represents left one) source : http://goo.gl/KAlRf

There's always FCOM Vol I PD.31.5 and the like. No graphs in there, but tables for short trips. That might give you an idea about possible altitudes. I personally have seen 100nm flights conducted at FL150 but also 300nm flights conducted at only FL270 (where one definately could have gone higher, performance wise). BTW I have not heard any number as to minimum cruise time. I'm pretty sure you'd go as high as you can no matter how short your cruise phase would be (as long as T/C and T/D don't exactly coincide, obviously).

Threads like this make me feel bad about my over-all flight simulator knowledge. I've got insane reading to do.

Deho, thank you for your experience and let me know reference page. It's always true the higher altitude, the better.But I'm certain there're flights always level off at FL200/220/240 in my country. They never go up over that even they can climb.I'd rather glad there's only one rule as you mentioned, T/C then T/D. But it's not true in real world and that's why I asked.. :) Bassue, believe me I got a headache to learning this but it's a disease want to know more and more when I fly everytime..I know it is comfortable using prog page for fule calculation and always fly max altitude and don't care about time, etc.. it's easy and fun.But many years of my simulation life, now i feels more fun to know these things than fly with joystick or autopilot.. just fun to know.

Deho, thank you for your experience and let me know reference page. It's always true the higher altitude, the better.But I'm certain there're flights always level off at FL200/220/240 in my country. They never go up over that even they can climb.I'd rather glad there's only one rule as you mentioned, T/C then T/D. But it's not true in real world and that's why I asked.. :) Bassue, believe me I got a headache to learning this but it's a disease want to know more and more when I fly everytime..I know it is comfortable using prog page for fule calculation and always fly max altitude and don't care about time, etc.. it's easy and fun.But many years of my simulation life, now i feels more fun to know these things than fly with joystick or autopilot.. just fun to know.

There is also ATC to consider. They're not going to want to deal with aircraft descending as soon as they've reached TOC! That said, I'm almost certain that for shorter flights there becomes a point where it is more economical to level off before optimum altitiude, although I can't give you anything to back that up.