In forward flight helicopters carrying slung loads frequently encounter load instability problems that reduce their speed envelope to well below the power limit of the helicopter/slung‐load system. The paper presents a procedure for the development and flight test verification
of passive stabilizers designed to increase the maximum flight speed of the system. Most of the development is carried out during wind tunnel tests. A scale model is suspended from the tunnel ceiling by a gimbaled setup that simulates the hook‐sling attachment. The model is free to
perform lateral and longitudinal pendulum motions, as well as yaw rotation. All three motions are recorded as functions of time. The model dynamics are studied as a function of the wind tunnel speed. Various techniques for stabilizing the load can be investigated by wind tunnel tests, which
are much cheaper, faster, and less risky than equivalent flight tests. The present study investigates the use of passive vertical fins to stabilize the 6 × 6 × 8 ft CONEX cargo container. The optimal geometry and location of the fins are determined in wind tunnel tests. Later on
this optimal configuration is built and tested in full‐scale flight tests. The dynamic behavior during these flight tests is compared with the wind tunnel results. Good agreement between both can result in a significant reduction in the number and duration of the flight tests that are
required to certify the stabilization method. By using the above‐described technique, the maximum flight speed of a UH‐60/CONEX system is increased from 60 kt (the operational limit for the unstabilized CONEX) to 110 kt (the power limit of the system).
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Document Type: Research Article
Technion-Israel Institute of Technology, Haifa, Israel
Publication date: 01 July 2010
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