Consider the helicopter in Figure 1. The first leg of the flight consumes 26 gallons of fuel, and at the end of this leg, the passenger deplanes. Is the helicopter still within allowable CG limits for takeoff? To find out, make a new chart like the one in Figure 2 to show the new loading conditions of the helicopter at the beginning of the second leg of the flight.
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| Figure 1. Determining the longitudinal CG and the lateral offset moment |
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| Figure 2. Determining the longitudinal CG and the lateral offset moment for the second leg of the flight |
Under these conditions, according to the helicopter CG envelopes in Figure 3, both the longitudinal CG and the lateral offset moment fall outside of the approved area of the envelope. The aircraft longitudinal CG is too far aft and the potential for excessive tail-low attitudes is very high. Under these conditions, it is possible that there will not be enough forward cyclic authority to maintain level flight The helicopter’s lateral offset moment is too far right and may lead to control issues, as well as an increased hazard of dynamic rollover. One possible option to bring the aircraft loading conditions within the approved envelope is to load either ballast or a passenger, as computed in Figure 4 and plotted in Figure 3.
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| Figure 3. Typical helicopter CG envelopes |
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| Figure 4. Determining the longitudinal CG and the lateral offset moment for the second leg of the flight with ballast and/or a different passenger |