L-1011 - CPT - AC Power Planning

L-1011 AC Power Distribution Schematic

AC power is used on the L-1011 a lot more abundant than DC power. On the actual aircraft, AC Power is produced by the engine driven generators, the Auxiliary Power Unit (APU) or the on-board battery via an Inverter. AC power on the ground can also be supplied by an external power source. As you can see in the image above, each AC source produces 3 phase output. Therefore, each of the buses, like the AC1, 2 and 3 and the AC Tie Bus are all depicted as 3 phase buses. For the simulator we will not implement a 3 phase system but will use a single (1) phase AC distribution. A single phase will be more than sufficient for the cockpit instruments and the few motor devices that would require 3 phases, such as the standby horizon, we will simply simulate them with DC motors. In the diagram above you can see that there is a AC Flight Station bus that hangs off each of the main AC busses ... the three flight station AC buses are what we are most interested in.

Another key difference between the actual L-1011 AC power system and the one we are using on the simulator is that we will not use 115V 400Hz power for everything. Without motor generators, creating 400Hz power is quite complicated (it requires inverters) and therefore we will only use the 400Hz power for instruments that need them. So here are the AC sources that we will use on the simulator:

• 120V 60Hz Regular AC Single Phase Commercial Power (standard outlet power in the USA) aka. Mains Power
• 115V 400Hz AC Power (Created by an inverter from a 120V 60Hz source)
• 28V 400Hz AC Power (Created with a Transformer from the 115V 400Hz Source)

Below is a diagram outlining how the AC essential bus is controlled.

L-1011 AC Essential Bus

So, for the simulator, all DC Transformer/Rectifiers will be driven from the normal 1 phase commercial power source (120V 60Hz) and the 400Hz instrumentation will be driven by the 400Hz inverter that we have for the simulator. The 400Hz inverter will act as the simulated engine generator power sources and will supply power to the AØ phase.