Helicopters are affected by lateral imbalance more than
airplanes. If a helicopter is loaded with heavy occupants
and fuel on the same side, it could be out of balance
enough to make it unsafe to fly. It is also possible that if
external loads are carried in such a position to require large
lateral displacement of the cyclic control to maintain level
flight, the fore-and-aft cyclic control effectiveness will be
limited.
Sweptwing airplanes are more critical due to fuel
imbalance because as the fuel is used from the outboard
tanks, the CG shifts forward, and as it is used from the
inboard tanks, the CG shifts aft. [Figure 1-5] For this
reason, fuel-use scheduling in sweptwing airplanes
operation is critical