The Powerplant Limitations portion describes operating limitations on an aircraft’s reciprocating or turbine engine(s). These include limitations for takeoff power, maximum continuous power, and maximum normal operating power, which is the maximum power the engine can produce without any restrictions and is depicted by a green arc. Other items that can be included in this area are the minimum and maximum oil and fuel pressures, oil and fuel grades, and propeller operating limits. [Figure 8-3]

Figure 8-3. Minimum, maximum, and normal operating range markings on oil gauge.

All reciprocating-engine powered aircraft must have a revolutions per minute (rpm) indicator for each engine. Aircraft equipped with a constant-speed propeller or rotor system use a manifold pressure gauge to monitor power output and a tachometer to monitor propeller or rotor speed. Both instruments depict the maximum operating limit with a red radial line and the normal operating range with a green arc. [Figure 8-4] Some instruments may have a yellow arc to indicate a caution area.

Figure 8-4. Manifold pressure gauge (top) and tachometer (bottom).