If you are running FSNavigator, the below information may be inserted into the aircraft data for calculating time and fuel consumption.

[AC500 Aero Commander]
climbspeed=124
climbfuel=36
climbrate=1375
cruisespeed=180
cruisefuel=12
cruisealtitude=10000
descentspeed=180
descentfuel=10
descentrate=1375
fuelmeasure=0
revision=1