Introduction
Weight and balance considerations of a helicopter are similar
to those of an airplane, except they are far more critical,
and the center of gravity (CG) range is much more limited.
[Figures 8-1 and 8-2] The engineers who design a helicopter
determine the amount of cyclic control authority that is
available, and establish both the longitudinal and lateral CG
envelopes that allow the pilot to load the helicopter so there
is sufficient cyclic control for all flight conditions
Weight and Balance Control—
Helicopter
Chapter 8
Figure 8-1. Weight and balance data needed to determine proper
loading of a helicopter.
Helicopter basic empty weight 1,545.0 lb, EWCG +101.4
(+0.2 lateral offset)
CG range (+92.0) to (+98.0) at 1,600 lb
(+92.0) to (+95.0) at 2,250 lb
Empty weight CG range None
Maximum weight 2,250 lb
Number of seats 2 at (+64.0) (L−13.5) (R+13.5)
lateral offset
Maximum baggage (100 lb) at +105.0 (0.0 lateral offset)
Fuel capacity 50 gal (48 gal usable);
288 lb at (+96.0) (−8.4 lateral offset)
Oil capacity 4.3 qt at (+90) (0.0 lateral)
Figure 8-2. Typical helicopter datum, flight stations, and butt line
locations.
Datum FS 0.0 FS 68.0 FS 254.5
BL 27.4 R
BL −38.7 L
BL 0
Butt
line
zero
Figure 8-3. Typical helicopter CG envelopes.
2,400
2,200
2,000
1,800
1,600 92 94 96 98 100
Longitudinal CG (inches aft of datum)
Gross Weight (lb)
Longitudinal CG Envelope
Approved Area
2,203
2,027
1,877
94.4 95.0 98.2
2,300
2,200
2,100
2,000
1,900
1,800
1,700
1,600
−5,000 −3,000 −1,000 0 1,000 3,000 5,000
Left Lateral Offset Moment Right
(lb-in)
Gross Weight (lb)
Lateral Offset Moment Envelope
2,203
2,027
1,877
−1,705 −326 1,699
If the CG is ahead of the forward limit, the helicopter tilts
and the rotor disk has a forward pull. To counteract this
and maintain a stationary position, rearward cyclic stick
displacement would be required. If the CG is too far forward,
there may not be enough available cyclic authority to allow
the helicopter to flare during landing, and it consequently
requires an excessive landing distance.
If the CG is aft of the allowable limits, the helicopter flies
with a tail-low attitude and may need more forward cyclic
stick displacement than is available to maintain a hover in a
no-wind condition. There might not be enough cyclic travel
to prevent the tail boom from striking the ground. If gusty
winds should cause the helicopter to pitch up during high
speed fl ght, there might not be enough forward cyclic control
to safely lower the nose.
Helicopters are approved for a specifi maximum gross
weight, but it is not safe to operate them at this weight under
some conditions. A high density altitude decreases the safe
maximum weight as it affects the hovering, takeoff, climb,
autorotation, and landing performance.
The fuel tanks on some helicopters are behind the CG,
causing it to shift forward as fuel is used. Under some flight
conditions, the balance may shift enough that there is not
sufficient cyclic authority to flare for landing. For these
helicopters, the loaded CG should be computed for both
takeoff and landing weights.
Lateral balance of an airplane is usually of little concern
and is not normally calculated. Some helicopters, especially
those equipped for hoist operations, are sensitive to the lateral
position of the CG and their Pilot’s Operating Handbook/
Rotorcraft Flight Manual (POH/RFM) include both
longitudinal and lateral CG envelopes, as well as information
on the maximum permissible hoist load. Figure 8-3 is an
example of such CG envelopes.