Altimeter/temperature correction
Hi,
I recently read a question about altimer error in regard to temperature deviation from ISA. The question is: "What is the error of an altimeter at 10000' PH at ISA -34 degrees? Answer over reads by 14%.
As far as I remember, the rule of thumb is 4' increase/decrease for each degree deviation from ISA per 1000'. Since ISA temperature at 10000' should be -5 degrees there is a difference of 29 degrees. As a result, 29 x 4 x 10= Altimeter overreads by 1,160 '. That is not even 12% certainly not 14%. I do not want to be nitpicking, but is there another formular which is more suitable?
Thank you for any help in advance.