On Apr 24, 9:31 am, terry wrote:
On Apr 22, 10:16 am, tman inv@lid wrote: tman wrote:

, and also the day turned out to be +20F hotter than I thought it would. I've experienced that heat not only hurts the planes
performance, but the pilots too. Oh yeah, a slightly gusty xwind too.
Pretty happy I planned on leaving one pax behind.

If you look very closely at the take off performance data of a 172
( which I have) you will find that higher temperature actually
improves performance, for the same air density. Now I know that
contradicts what we get taught in flight school, and while it is
generally true that when temperature is lower the air will be more
dense , the atmosphere is a dyanmic system and pressure and
temperature can vary independantly. So it is possible to have the
same air density , or density altitude at 2 different temperature and
the day with the higher temperature wil give you better performance.
It is related to engine performance and the best explanation I have
got is that at the same density on a higher temperature day, the
pressure will also be higher ( since density = PM/RT where M is
molecular wt, R is gas constant, P and T press and temp), and the
higher pressure provides a greater driving force to suck air into the
engine. If you do the same analysis on the landing distance you see
no such temperature effect because landing distance is not power
related , only lift related.
In the next few days I will get around to providing a link to this
data, but you can easily prove it yourself if you have the Cessna
takeoff distance tables..
Terry
PPL Downunder

You can play with your C172 N weight and balance here
http://home.new.rr.com/trumpetb/alph/wb172N.html