RE: How to Correct Measured Thrust for Density Altitude?
A quick calculation that I use is :
2% loss of thrust per 1000 feet of corrected altitude
Of course, this is a generic formula, but certainly close. Often times thrust is lost from the turbines due to improper installations...ie: pipe to bellmouth length, poor inlet designs ect.
Not opening a can of worms here-please.....just saying that not to many of us can tell if the motor is putting out 31 pounds ...or 32.2 pounds of thrust, unless it is on the stand. There would be this much deviation from a 7 am flight compared to a 3 pm flight on the same day in the summertime. Like Dave says...I feel also that this issue has way to much thought put in to it! I know that the higher elevation pilots automatically figure these performance figures in to their choice of motor size when choosing a motor.
On the other hand...I have seen jet installs that have 6 additional do-hickies, a couple of reduction reducer thing-a ma-bobs, ten feet of additional airlines (spaghetti) and an additional half pound of epoxy!!!! And these guys are worried about a pound of thrust!!!
Todays turbine market has become very competitive, and this has resulted in much better customer support, dependability and pricing.
Chose what you are comfortable with and enjoy the hobby!!!