I have an 180hp aircraft that I'd like to reduce to 150hp. How do I do that?The situation is this - I would like to convert Jose Miranda's 180hp Grumman Tiger to a 150hp Grumman Cheetah. His aircraft.cfg file contains the following: &l;piston_engine&r; max_rated_hp=180.000and I changed it to: &l;piston_engine&r; max_rated_hp=150.000but nothing changed. As a matter of fact, I tried values from 50.000 to 500.000 yet I saw no noticeable change in aircraft performance.Any ideas are appreciated.Thanks,Robert

Hello Robert, :-)30 HP is significant and should be noticed.The max_rated_hp= parameter only effects sound change, and has nothing to do with thrust or power (according to Ron Fremuth and AirEd doc).Get the details from your 150HP engine and change these parameters.cylinder_displacement=compression_ratio=number_of_cylinders=max_rated_rpm=These parameters in the cfg will effect change in this regard. There are others of course but these will have the most affect. These parameters I believe override record 505 in the air file.A simpler method may work fine for you... that is use of the power_scalar. Reducing it to .83 may put you on it.Hope this helps.Milton

Milton,Thank you for sharing your knowledge and your insite.Your power_scalar suggestion worked very well, and I am now tuning that value to match my Cheetah. Once that tuning is done, I will try your other suggestion to enter the correct engine parameters.Thanks again,Robert