F4BN Electrical

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Electrical System

The F-4B/N's electrical system consists of:

  • Two engine-driven generators providing power to the aircraft's system
  • A Ram Air Turbine (RAT), to be used in the event of dual generator loss
  • An external power receptacle

Generator Control Panel

The Generator Control Panel is located at the forward edge of the right console, in the front cockpit. It consists of two 3-position switches the generators and an annunciator panel to their left.

The three position switches are used to toggle the generators or use external power when available.

  • ON: The respective generator is turned on
  • OFF: The respective generator is turned off
  • EXT: The respective generator is off and power is provided to its subsystems through the external power source, if available

The annunciator panel has three lights that indicate generator status and whether the bus tie relay is open or closed.

  • LH GEN OUT: The port generator is off
  • RH GEN OUT: The starboard generator is off
  • BUS TIE OPEN: The light illuminates when one of the generator is turned off and the other is operating. When the bus tie relay closes, the remaining generator powers all of the aircraft systems. The light extinguishes when the relay closes after:
    • 5 seconds - F-4B pre-1966
    • 3.8 seconds - F-4B post-1966 and F-4N


The generators are driven from the Aircraft's engines and each provides power to its own set of systems. The two circuits are kept separate through a relay that remains open during normal generator operation.

Each generator comes online when the respective engine's RPM is at or above 53%.

In the event of a single generator failure the BUS TIE OPEN light illuminates, indicating that the relay is open. The relay closes and the BUS TIE OPEN light turns off after 5 seconds (F-4B pre-1966)/3.8 seconds (F-4B post-1966 and F-4N). The remaining generator then powers all of the aircraft's systems.

When either generator switch is placed on EXT, the BUS TIE OPEN light will illuminate.


The Ram Air Turbine is used to power the aircraft's essential systems in the event of a dual generator failure. The RAT is operated using pneumatic pressure. A 4.2 cubic inch air bottle is charged through the pneumatic system and provides pressure for the RAT's extension.

The RAT is operated through a lever located on the left wall of the front cockpit. When the lever is down, the RAT is extended. When it is up, the RAT retracts.

  • For safe extension of the RAT, a minimum pneumatic pressure of 1000psi is required.
  • For safe retraction of the RAT, the minimum pneumatic pressure required is:
    • 2000psi (F-4B pre-1966)
    • 200psi (F-4B post-1966 and F-4N)

If pressure is less than these limits, the RAT doors close prematurely and will damage the RAT. We are simulating this through a retraction and inability to operate the RAT.

The RAT provides provides maximum power at airspeeds above 180kts. At speeds below 180kts power output begins to decrease and turns off at 90kts.

In the event of loss of pneumatic pressure, the air bottle provides enough pressure for a single extension of the RAT.