A Pragmatic Analysis of Helicopter Response to Turbulent Air Wake in a Shipboard Flight Deck Environment

An experiment consists of a remote-controlled T-REX 600E Pro helicopter piloted above an underway 108-foot Patrol Craft’s (YP) flight deck to analyze the effect of ReH ≈ 3.4×10 5 turbulent ship air wake on helicopter angular motion. The motion is measured by an inertial measurement unit (IMU) sensor mounted on the helicopter transmitting variably-spaced data in a 3-D Cartesian reference frame. Data is collected with the helicopter in locations above the flight deck which closely match actual takeoff/landing positions of US Navy H-60 helicopters above flight decks of air-capable ships (CG/DDG/FFG). This method is both an indirect way of qualifying the flow field and a practical way of measuring the actual effects of ship air wake turbulence on rotary-wing aircraft. Fourier analysis is performed on helicopter angular velocities to determine predominant frequencies of motion. Frequencies of this motion are compared with both pilot input frequencies and vortex shedding frequencies of incompressible, subsonic flow around 2-D and 3-D backward-facing step (BFS) geometries. These frequencies of motion are discussed in relation to the pilot’s perception of motion and the phenomena of spatial disorientation. The spectra of pilot inputs in roll and pitch were found to have cutoff frequencies of 0.5 Hz and 0.7 Hz, respectively, which agree well with full-size helicopter pilot autospectra. A 3 Hz non-pilot initiated disturbance is noted; the source of this disturbance is thought to be due to interactions with airflow over the flight deck hangar or dynamic effects of the flybar on the helicopter