There are two dif ferent rotor r.p.m. limitations: power-on and power-off. Power-on limitations apply anytime the engine is turning the rotor and is depicted by a fairly nar- row green band.  A yellow arc may be included to show a transition range, which means that operation within this range is limited. Power-off limitations apply anytime the engine is not turning the rotor, such as when in an autoro- tation. In this case, the green arc is wider than the power- on arc, indicating a larger operating range. aircraft. A red line on the airspeed indicator shows the airspeed limit beyond which structural damage could occur. This is called the never exceed speed, or V$_{NE}$. The normal operating speed range is depicted by a green arc. A blue line is sometimes added to show the maxi- mum safe autorotation speed. [Figure 6-2] The Powerplant Limitations area describes operating limitations on the rotorcraft’ items as r.p.m. range, power limitations, operating tem- peratures, and fuel and oil requirements. Most turbine engines and some reciprocating engines have a maxi- mum power and a maximum continuous power rating. The the engine can generate and is usually limited by time. The maximum power range is depicted by a yellow arc on the engine power instruments, with a red line indi- cating the maximum power that must not be exceeded. “Maximum continuous the engine can generate continually, and is depicted by green arc. [Figure 6-4] If the rotorcraft has a maximum operating density alti- tude, it is indicated in this section of the flight manual. Sometimes the maximum altitude varies based on differ- ent gross weights. Like on a torque and turbine outlet temperature gauge, the red line on a manifold pressure gauge indicates the maximum amount of power. A yellow arc on the gauge warns of pressures approaching the limit of rated power. A placard near the gauge lists the maximum readings for specific conditions. [Figure 6-5] Low rotor r.p.m. does not produce sufficient lift, and high r.p.m. may cause structural damage, therefore rotor r.p.m. limitations have minimum and maximum values. A green arc depicts the normal operating range with red lines showing the minimum and maximum limits. [Figure 6-3] The Weight and Loading Distribution area contains the maximum certificated weights, as well as the center of gravity (CG) range. The location of the reference datum used in balance computations should also be included in this section.  Weight and balance computations are not provided here, but rather in the Weight and Balance Section of the FAA-Approved Rotocraft Flight Manual. WEIGHT  AND LOADING DISTRIBUTION 150 20 40 60 80 100 120 AIRSPEED KNO TS 17 14 12 8 6 4 MPH X 10 40 50 60 70 80 90 100 110 120 0 10 20 30 TORQ UE PERCENT 1 2 3 4 5 6 7 8 9 TURB OUT TEMP CX 100 ROTOR ENGINE RPM 100 5 l0 l 2 3 4 5 l5 20 25 30 35 40 ROTOR LIMITATIONS 6-2 Figure 6-4. T orque and turbine outlet temperature (TOT) gauges are commonly used with turbine-powered aircraft. Figure 6-2. Typical airspeed indicator limitations and mark- ings. Figure 6-3. Markings on a typical dual-needle tachometer in a reciprocating-engine helicopter. The outer band shows the limits of the superimposed needles when the engine is turn- ing the rotor. The inner band indicates the power-off limits. ALTITUDE LIMITATIONS POWERPLANT LIMIT ATIONS