Flight test identification and simulation of a UH-60A helicopter and slungload

Helicopter slung-load operations are common in both military and civil cont exts. Helicopters and loads are often qualified for these operations by mea ns of flight tests that can be expensive and time consuming. There is signi ficant potential to reduce such costs both through changes in flight-test m ethods and by using validated simulation models. To these ends, flight test s were conducted at Moffett Field to demonstrate the identification of key dynamic parameters during flight tests (aircraft stability margins and hand ling-qualities parameters, and load pendulum stability), and to accumulate a data base for simulation development and validation. The test aircraft wa s a UH-60A Black Hawk and the primary test load was an instrumented 8- by 6 - by 6-ft cargo container. Tests were focused on the lateral and longitudin al axes, which are the axes most affected by the load pendulum modes in the frequency range of interest for handling qualities; tests were conducted a t airspeeds from hover to 80 knots. Using telemetered data, the key dynamic parameters were evaluated in near real time after each test airspeed, and before clearing the aircraft to the next test point. These computations wer e completed in under I min. A simulation model was implemented by integrati ng an advanced model of the UH-60A aerodynamics, dynamic equations for the two-body slung-load system with multi-cable suspension, and load static aer odynamics obtained from wind-tunnel measurements. Comparisons with flight d ata for the helicopter alone and with a slung load showed good overall agre ement for all parameters and test points; however, unmodeled secondary dyna mic losses around 10 rad/sec were found in the helicopter model and they re sulted in conservative stability margin estimates.