-
the Yellow system pressurized by a pump driven by the right engine. On the ground, an electric pump can pressurize directly the Yellow system. A reversible power transfer unit (PTU) can pressurize the Yellow or Green system from the other system. A ram air turbine (RAT) can pressurize the Blue system in the event of an ultimate-emergency electrical supply.

 EFCS Architecture Figure 002
 1EFF : 1 1R 1CES  ALL  1 11 1 27-90-00 Page 7 May 01/04

 Flight Control Hydraulic Power Supply Figure 003
 1EFF : 1 1R 1CES  ALL  1 11 1 27-90-00 Page 8 May 01/04

 B. Electrical Power Supply
 (1) General Schematic diagram (Ref. Fig. 004, 005) The main power supply system has two generators. Each one is located on one engine . A third generator, of equivalent power and driven by the APU can be used on the ground or in flight to replace a main generator. In normal configuration, each main generator supplies its side which has:
 -
a three-phase 400 Hz 115VAC main busbar

 -
a transformer rectifier unit (TRU)

 -
a 28VDC main busbar.
 The two sides are completely separated.
 The AC and DC essential busbars are connected to the side 1.
 If a main generator fails, an automatic switching facility enables
 the simultaneous supply of the two main AC busbars by the other main
 generator.
 However, the TRUs keep the two DC sides isolated.
 If a main TRU fails, the essential DC busbars are automatically
 isolated from the rest of the DC network and are supplied by the AC
 busbar 1XP through a third TRU.
 The main DC busbars are simultaneously connected together and
 supplied through the remaining TRU.
 If the AC busbar 2XP is failed, the sequence is the same.
 If the AC busbar 1XP is failed, the DC and AC essential busbars will
 be connected to the side 2 after action of the crew.
 In the event of a power supply loss on the two sides (standby power
 configuration) :