TM 1-1520-240-BD
Lifting CH-47D by Rotor Shafts
(Prepared By Airframe Design)
1.
Basic sling configuration is established by the maximum angle that the sling may make relative to the aircraft
vertical axis. These angles are 15 degrees at the forward rotor and 19 degrees at the aft rotor. Angles were
established by stress engineering to limit horizontal loading induced into the fuselage during lifting operations.
2.
To meet this requirement and using a single hook on the lifting aircraft the sling lengths would need to be:
Forward rotor shaft - 822" (68'6")
Aft rotor shaft - 780" (65')
This configuration will result in the lifted aircraft hanging with a nose up angle of 3 degrees at hover.
3.
If tandem hooks are used on the lifting aircraft, the sling lengths should be:
Forward rotor shaft - 553" (46'1")
Aft rotor shaft - 502" (41'1 0")
This would result in the same 3 degree nose up attitude if the lifting aircraft hovers with 4.3 degree nose up
attitude.
4.
There is some merit to the use of a single hook configuration for this operation, since with the single hook the
geometry of the slings relative to the aircraft does not change with aircraft attitude or with swinging of the slung
aircraft. Dual hooks allow the aircraft/sling configuration to act as a four bar chain, with consequent changes in
sling geometry with load displacement, or changes in attitude of the lift aircraft. The dual hook configuration can
be made acceptable by increasing the length of the slings to ensure that the sling angles remain within limits
during all normal load displacement. (Note: This additional length has been calculated and the minimum sling
lengths should be 65 feet to the forward rotor and 63 feet to the aft rotor which will not exceed the critical angles
at airspeeds up to 80 knots.)
5.
Weight of an empty CH-47D with the rotor blades removed is approximately 21,319 lbs. with the dual hook
configuration shown this results in calculated hook loads of 10,386 on the forward hook and 10,933 lbs. on the
aft hook.
Figure 12-2. Dual Hook Lifting Configuration (Sheet 2 of 4)
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