4 Helicopter Sling Loading Capacities ReferenceHelicopter Weight External Load Weight Load Mass RatioCable Length 3 ( Handling Qualities Requirements for Military Rotorcraft, Aeronautical Design Standard) NA 0.33NA 4 (Requirements for the Certification of Sling Loaded Military Equipment for External Transportation by Department of Defense Helicopters ) NA 39800 lbs (max)NA12-16 ft 7UH-60A14600 lbs1130-6384 lbs0.07-0.30 23 ft (single) 15.83 ft - (4-legged) 7NA 40000 lbsNA3-140 ft 11UH-6016000 lbs1102-4409 lbs0.06-0.229.84-26.2 ft Superior Helicopter Kaman K-1200 12000 lbs6000 lbs0.33NA
5 Helicopter Sling Loading Load is suspended beneath the helicopter Free to rotate in all 3 axis Long cable lines are used Requires pilot effort
6 Literature Survey Dukes, T. A., “Maneuvering Heavy Sling Loads Near Hover, Part I: Damping the Pendulous Motion,” Journal of the American Helicopter Society, Vol. 18, (2), Apr. 1973. Dukes, T. A., “Maneuvering Heavy Sling Loads Near Hover, Part II: Some Elementary Maneuvers,” Journal of the American Helicopter Society, Vol. 18, (3), July 1973. Poli, C., and Cromack, D., “Dynamics of Slung Bodies Using a Single-Point Suspension System,” Journal of Aircraft, Vol. 10, (2), Feb. 1973. Cliff, E. M., and Bailey, D. B., “Dynamic Stability of a Translating Vehicle with a Simple Sling Load,” Journal of Aircraft, Vol. 12, (10), Oct. 1975. Nagabhushan, B. L., “Low-Speed Stability Characteristics of a Helicopter With a Sling Load,” Vertica, Vol. 9, 1985. Sheldon, D. F., “An Appreciation of the Dynamic Problems Associated with the External Transportation of Loads from a Helicopter—State of the Art,” Vertica, Vol. 1, 1977. Prabhakar, A., “Stability of a Helicopter Carrying an Underslung Load,” Vertica, Vol. 2, 1978. Cicolani, L. S., Kanning, G., and Synnestvedt, R., “Simulation of the Dynamics of Helicopter Slung Load Systems,” Journal of the American Helicopter Society, Vol. 40, (4), Oct. 1995. Gabel, R., and Wilson, G. J., “Test Approaches to External Sling Load Instabilities,” Journal of the American Helicopter Society, Vol. 13, (3), July 1968.
7 HSL Flight Tests 
8 Stability of HSL - I 
9 Stability of HSL - II 
10 Stability of HSL - III [ 11] Level 1 – Load maintains directional stability throughout the maneuvers. Minimal oscillation. Requires minimal concentration by the flight crew Level 2 – Load may oscillate, rotate. Directional orientation is not stable. Does not pose a threat to the aircraft. ost maneuvers. Moderate oscillation.
11 Safety - I Manwaring, J. C., Conway, G. A., Garrett, L. C., “Epidemiology and Prevention of Helicopter External Load Accidents,” Journal of Safety Research, Vol. 29, No. 2, pp. 107-121, 1998.
12 Safety - II …The helicopter departed with a 150-foot long-line attached and no external load on the hook… After lift- off, the long-line tangled in the trees, causing the helicopter to crash… …An Aerospatiale 316B was moving equipment in mountainous terrain with a 100-foot long cable… the cargo hook snagged on an equipment trailer adjacent to the take-off area. As the tension on the line increased, the hook broke free of the trailer and the cable recoiled into the main rotor blades, rendering the helicopter uncontrollable… …During the flight to reposition the helicopter that was transporting seismic equipment with a 100-foot long line, the load caught on a nearby fence…
13 Literature Survey Lucassen, L. R., and Sterk, F. J., “Dynamic Stability Analysis of a Hovering Helicopter With A Sling Load,” Journal of the American Helicopter Society, Vol. 10, (2), Apr. 1965. - 2001 (Dynamics and Stability) Stiles et al, (2004, ,) mention sling load active stabilization as a future direction of research in his review of Helicopter AFCS.
14 Statement of the Problem Keep the oscillations of the payload under a critical angle, or deviation The effect of the load on the helicopter dynamics should not exceed more than 10% of the static weight of the load. System should be adjustable to different line length and load weight and should be robust to 10% changes of the nominal values.
15 Approach - I Modified AFCS that stabilizes the slung load Stand-alone stabilizing system –Cartesian mechanism –Spherical mechanism
16 Approach - II Cho, S.-K., Lee, H. H., “An Anti-Swing Control of a 3-Dimensional Overhead Crane,” Proceedings of the American Control Conference, Chicago, Illinois, pp. 1037-1041, 2000. 
17 Future Work Anti-sway control of shipboard boom cranes Simulations of a quadrotor suspended mass Update the statement of the problem Stabilization of a 3D suspended pendulum with a cartesian mechanism Stabilization of a 3D suspended pendulum with a spherical mechanism UH-60 helicopter MatLAB model Simulations of 3D suspended pendulum attached to UH-60
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