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4.2. SETTING UP ELECTRICAL, HYDRAULIC, AND PRESSURIZATION SYSTEMS 63
Finally, the “Inverters” box in the Electrical tab specifies the number of power inverters and
which systems are connected to them. Inverters are most commonly used for backup power, turning
DC power from the batter into AC power for (most) electronics.
With the backbone of the electrical system configured, you can use the Systems dialog’s Bus 1
and Bus 2 tabs to specify how much amperage each electrically-powered subsystem requires and
from which bus it draws its power. To the right of each subsystem’s label are up to four checkboxes,
corresponding to buses 1 through 4 (with buses 1 and 2 corresponding to the top two checkboxes and
buses 3 and 4 to the bottom two checkboxes). For instance, in Figure 4.18, the de-icing subsystem’s
window heater is drawing 6 amps from bus 1.
Figure 4.18: A single electrical subsystem, drawing 6 amperes from bus 1
In addition to the subsystems, there may be a base load on each of the buses—that is, some
number of amps drawn at all times, regardless of what other electronics are powered on. The base
load for each bus is set in the upper left of the Bus 1 tab. Note that generator loads will be affected
by the bus that each system is attached to, and the amperage drawn from it.
If the bus powering a system fails in X-Plane—that is, if the battery and generator for the bus
are off, the bus cross-tie is off, and there is no APU running for the bus-that system will fail.
Configuring the Hydraulics System
The hydraulics system is configured in the Systems dialog’s General tab. Here, the boxes labeled
“Hydraulic Sources” and “Hydraulic Systems that Depend on Hydraulic Sources” represent the
basics of the hydraulic system.
X-Plane can model up to four hydraulic pumps: one powered by the electrical system, one
powered by a ram air turbine, and two powered by the engine. Check the boxes in the Hydraulic
Sources portion of the General tab corresponding to the pumps your aircraft uses.
Each type of pump has a different max pressure, set beneath the pump’s checkbox. The units
on the maximum pressure are not specified; the hydraulics modeling is not detailed enough for the
units to matter, so they can be anything. The only thing that matters here is the ratio between
the different pumps, and it only matters then in the case of failure.
To the right of the hydraulic sources are the systems that depend on the hydraulics. If the
hydraulic pumps fail, the systems represented by each checked box will also fail.
Most of the systems here are self-explanatory. The final one, the stick shaker, is a device that
rapidly vibrates the control yoke as the aircraft approaches a stall. In X-Plane, this is indicated by
a loud noise. If the stick shaker box is checked near the bottom of the “Hydraulic Systems that
Depend on Hydraulic Sources” box, the stick shaker will fail along with the hydraulic system.
The box labeled “manual reversion” controls the extent to which, following a hydraulic system
failure, the flight controls continue to operate. This is set as a ratio of their normal full operation.
The group of settings in the middle specifies how the landing gear fails in the event of a hydraulic
failure. If the landing gear depends on hydraulics, it can have one of three behaviors in the event of
failure: it can remain retracted, remain extended, or extend and remain there if the craft’s indicated
airspeed is below a certain threshold. Select the radio button appropriate for your aircraft here. If