Aerial cargo delivery, also known as airdrop, systems are heavily affected by atmospheric wind conditions. Guided airdrop systems typically employ onboard wind velocity estimation methods to predict the wind in real time as the systems descend, but these methods provide no foresight of the winds near the ground. Unexpected ground winds can result in large errors in landing location, and they can even lead to damage or complete loss of the cargo if the system impacts the ground while traveling downwind. This paper reports on a ground-based mechatronic system consisting of a cup and vane anemometer coupled to a guided airdrop system through a wireless transceiver. The guidance logic running on the airdrop system's onboard autopilot is modified to integrate the anemometer measurements at ground level near the intended landing zone with onboard wind estimates to provide an improved, real-time estimate of the wind profile. The concept was first developed in the framework of a rigorous simulation model and then validated in the flight test. Both simulation and subsequent flight tests with the prototype system demonstrate reductions in the landing position error by more than 30% as well as a complete elimination of potentially dangerous downwind landings.

Autonomous Airdrop Systems Employing Ground Wind Measurements for Improved Landing Accuracy

Nomenclature CD = drag coefficient based on S CDS — drag area of fully inflated parachute, ft2 (CiwS)r == drag area of reefed parachute, ft2 d = constructed parachute diameter across base of conical parachute, ft Di = inflated diameter, f d, ft hr — release altitude, msl, ft j£t = outflow coefficient (approximately 0.6) Ki = inflow coefficient (a value o^f 0.7 is used for a first approximation, and adjusted as determined by experimental data) Lr = circumferential length of reefing line, ft AP = pressure across canopy, lb/ft2 q = dynamic pressure JpF2, lb/ft2 R = radius of canopy during inflation normal to mean local canopy contour, ft Rm = maximum inflated radius of canopy, ft (approximately | of constructed radius) RQ = initial radius of canopy at start of inflation, ft (radius of suspension lugs or pack radius) s = tensile stress, lb/ft2 S = area of base of conical chute, 7rd2/4, ft2 t = thickness of ribbon, ft if = filling time, sec T — ribbon tensile load, Ib V = vehicle velocity, fps Fo = vehicle velocity at start of parachute filling, fps w = ribbon width, ft W = vehicle weight, Ib XG = geometric porosity of canopy p = air density, slugs/ft3

Aerodynamic decelerators - An engineering review

A concept for the remote delivery of carbon-supported sliding payloads deployment from circling fixed-wing aircraft is presented. The payload uses a taut cable deployed from a circling aircraft that supports structure for sliding payloads from high altitudes to the ground. The cable tip is anchored for accurate positioning of cable tip on the ground. The cable dynamics is simulated showing a compulsory use of braking to slow the descent of the payload. The numerical simulation studies show that certain cable configurations provide better stability during sliding payload development. Braking system is used to reduce the velocity of the payload at the ground and prevent the payload from tripping the cable dynamic instability. The studies also show that additional braking is used when payload approaches the ground to reduce impact velocities. Optimization design of an appropriate braking system is an important aspect that is considered for the realization of aircraft delivery system.

Cable-supported sliding payload deployment from a circling fixed-wing aircraft

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Method for the flight path optimization of the electric-powered reconfigurable rotor (EPR2) VTOL concept

Flight Test Results of Recent Advances in Precision Airdrop Guidance, Navigation, and Control Logic

For many reasons it is often impractical to land and off-load an aircraft or use conventional parachute delivery techniques to provide logistic support for military troops engaged in combat. This problem of getting supplies and equipment to the point of need involves both resupply and assault phases. Each phase has peculiar characteristics which, in addition to the type and quantity of cargo needed, permit one of a family of aerial delivery systems to provide the necessary support. Descriptions of these systems and their characteristics, which provide a high degree of flexibility in the aerial delivery of cargo, are presented. The impact of new aircraft such as the C-141, C-142, and C-5A on mission versatility and capability are discussed as well as problem areas associated with making more effective use of aircraft capability.

Richard J. Ducote

Papers

U. S. Air Force Concepts for Accurate Delivery of Equipment and Supplies