In article ,
Andrew Sarangan wrote:

(Ben Jackson) wrote in news:fmLZc.105358$Fg5.1951@attbi_s53:

For a non-turbocharged piston airplane, does cruise altitude really
matter? I made a complicated spreadsheet which produces a fairly simple
answer: Unless you climb way above your critical altitude, trip time
and fuel burn don't vary much at all. Over a 500nm trip, it only takes
about 4% longer to fly at 3000MSL instead of 7000 (approximately critical
altitude) and 7% longer if you go clear up to 13000. For my plane that's
a difference of about 7-15 minutes out of 3+ hours.

How high does your critical altitude have to be (due to turbocharging
or jet/turbine) before it really starts to matter what your cruising
altitude is?


How are you factoring wind into your spreadsheet? I have tried the same on
DUATS and came to the same conclusion as you. The difference is pretty
minimal in most cases, except when there is an inversion layer with a high
speed flow above it. In that case, it makes sense to climb up to catch that
flow (or stay below if you are going against it). I found that in most
cases the difference in enroute time is less than 5 minutes even for trips
as long as 3 hours.

If you fly east of the Rockies, low altitude can be pretty damned HOT!
If you climb above 5000 ft in the summertime, you can get some natural
"air conditioning" that you, your pax and the engine like.