******, really? Hold on......
At 13000', ISA temp is -11 (15-26 at 2 degrees per 1000'). If the SAT is -31, it is 20 deg C colder than it should be, so 'T' is -20. 120 x -20 is -2400, so the answer should be DA of 10600'. Looks like I had the wrong abacus out earlier! Thanks loc-out. Anyway, I promise the method's right, even if I'm a cabbage! <img src="wink.gif" border="0">
[ 21 January 2002: Message edited by: fokker ]</p>