Flight Loads Investigation of Combat Armed and Armored CH-47A Helicopters Operating in Southeast Asia

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Flight Loads Investigation of Combat Armed and Armored CH-47A Helicopters Operating in Southeast Asia

F. J. Giessler / J. F. Braun

From a structural flight loads program on three armed and armored CH-47A helicopters, 207 hours of valid multichannel flight data were recorded as the helicopters operated from air bases in Southeast Asia. Data were processed and analyzed according to four distinct flight phases, termed mission segments: (1) takeoff and ascent; (2) maneuver; (3) descent, flare, and landing; and (4) steady state. Data are presented in the form of time and occurrence tables, histograms, and exceedance curves. These data indicate the time spent in the mission segments and parameter ranges; the number of peak parameter values occurring in the ranges of the given parameter, during each of the mission segments, and in the ranges of one or more related parameters; and the time to reach or exceed given maneuver and gust normal load factors and lateral and longitudinal load factors. The largest normal load factor was 1.95, which occurred at a 100-knot airspeed and with a 28,027-pound gross weight. In contrast to previous studies of cargo and transport CH-47A's whose activity was mostly under steady-state conditions, the armed CH-47A's spent more than half of their time in the maneuver mission segment and had a much more pronounced loads spectrum. (Author)