Not saying I am an expert of any kind here but I know that with most older cessna types the book figures are rather generous to say the least. As a rule for field performance I typically add another 20% to the figures, as for climb I use a simple rule of thumb that I have tested over the years in various types at various altitudes. I always consult the POH first and then I use this formula that gives me figures slightly less than the best climb for max weight. As alt increases the rate reduces and after about 4-5000ft on a standard day it deteriorates quite rapidly, these are somewhat lower than the book figures and further below the higher you go but I find it easy to use while in flight. goes like this:
(Rule of thumb only based on max weight, so hopefully anything less should have marginal improvement)
Climb Rate C172
1000ft is roughly 650fpm averaged out, after that I use this formula:
Loose 50ft per 1000ft starting at 550fpm @ 2000ft
2000 = 550fpm
3000 = 500fpm
4000 = 450fpm
5000 = 400fpm
6000 = 350fpm
7000 = 300fpm
8000 = 250fpm
9000 = 200fpm
10 000 = 150fpm
This I have seen for the "N" and "R" models in particular with a 160Hp engine and old prop, one frame had something like 6500hrs on it and clearly a bit tired where it only "just" did better than the figures I have above, this was on a cool day with dense air and I am certainly no test pilot! Not being that familiar with mountain flying I am also looking in to doing Hotham one day but will perhaps jump in with an instructor who has some experience and also in something with a few more nags up front like a 182T and a light load. I have heard a few horror stories of weather around that part of the country and again I'd only do this flight on an almost perfect day.
Good luck and would really like to hear how your trip goes.
