If the rotor RPM is low and manifold pressure is high, what should be the initial corrective action?

In a situation where rotor RPM is low and manifold pressure is high, the initial corrective action should be to lower the collective pitch. This action reduces the amount of lift being generated by the rotor blades, which consequently decreases the load on the engine. By reducing the load, the engine can recover and generate adequate RPM to stabilize the rotor speed.

The relationship between rotor RPM and collective pitch is critical in maintaining optimal performance. Lowering the collective pitch helps to balance the power being produced by the engine with the demands placed upon it by the rotor system. This initial response helps to avoid further decline in rotor RPM and ensures that the helicopter remains controllable.

While increasing engine power or rotor speed may seem intuitive, these actions can exacerbate the issue by placing additional strain on the already compromised rotor RPM. Adjusting the fuel mixture would also not promptly address the immediate need to stabilize rotor speeds. Thus, lowering the collective pitch is the most effective and immediate corrective action in this scenario.