What component measures the position of the collective and signals the EEC to schedule fuel?

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The correct answer is based on how the collective position is measured and communicated to the engine control systems in the TH-73 helicopter. The Linear Variable Differential Transformer (LVDT) is specifically designed to provide precise measurements of linear position. In the context of the collective control, the LVDT detects the position of the collective lever, which is critical for adjusting engine power output appropriately.

When the pilot changes the pitch of the collective, the LVDT converts this position change into an electrical signal. This signal is then sent to the Engine Electronic Control (EEC) unit, which utilizes the information to schedule fuel flow to the engine based on the demand. This process ensures that the engine responds properly to changes in collective input, maintaining optimal performance and safety during flight.

The other components listed don’t serve this specific role. The pneumatic actuator is involved in controlling mechanical movement and isn't focused on positional measurement. The fuel control unit deals with the metering and delivery of fuel but does not measure the collective's position. The swash plate is part of the rotor craft's flight control mechanism that translates pilot inputs into rotor blade pitch changes, but it does not measure or communicate collective position to the EEC.