Download the Plane Maker Manual - X-Plane

4.1. CREATING THE ENGINES 61
Beneath the three thrust settings is the engine’s optimum altitude, the altitude at which the
rocket achieves maximum thrust, in feet above mean sea level.
In the upper right of the Rocket Engine Specs box is the “nozzle exit area” parameter, the
size of the exhaust nozzle. This is used only to calculate how large an exhaust flame to display in
X-Plane.
The final parameter in the Rocket Engine Specs box is the engine’s specific fuel consumption
(SFC). Specific fuel consumption in rocket engines is much simpler than in combustion engines; this
parameter applies at all altitudes, at all power settings. It defines the pounds of fuel burned per
hour for each pound of the engine’s thrust. Note that the specific fuel consumption is the inverse
of the engine’s specific impulse (Isp), the number usually discussed in relation to a rocket’s fuel
consumption.
Working with Twin- and Multi-Engine Aircraft
Creating multiple engines in Plane Maker is quite straightforward; in the Location tab, each engine
has its position defined independently (as described in the “Location” section above), as well as
its propeller characteristics, if applicable, as described in the “Customizing the Propeller” section
above. Engines of the same type (propeller-driving, jet, or rocket) are assumed to have the same
characteristics-that is, all propeller-driving engines on an aircraft will have the same maximum
allowable horsepower, the same redline RPM, and so on.
The only thing significantly different about setting up multiple engines is the use of the Engine
Specs dialog’s Transmission tab. This, of course, applies only to engines that turn propellers.
Most aircraft designs will have one transmission per engine. Thus, a single-engine aircraft will
have a single transmission, a twin-engine aircraft will have two transmissions, and so on. Exceptions
are designs which use a common transmission to connect multiple engines to multiple propellers,
as seen in the V-22 Osprey, as well as helicopter designs, where all rotors are geared together.
The number of transmissions is defined in the far left of the Transmission tab, seen in Figure 4.16.
Figure 4.16: The Engine Specs dialog’s Transmission tab
To the right of the “number of transmissions” parameter are the transmission settings for each
engine and each propeller; engine settings are in the center of the window, and propeller settings are
on the right. With multiple engines created in the Location tab, there will be one row of settings for
each engine. Note that the topmost engine here corresponds to the leftmost engine in the Location
tab, and the topmost propeller here corresponds to the leftmost propeller in the Location tab.
Each engine can drive one transmission, as defined in the “transmission that this engine feeds”
box. Each propeller, in turn, can be driven by one transmission (set in the “transmission that feeds
this prop” box). Thus, in a twin-engine plane, the port-side engine might feed transmission 1, and