Unsteady Aerodynamic Loading on a Helicopter Fuselage in a Ship Airwake

On Aerodynamic Modelling and Simulation of the Dynamic Interface

“…In this technique, the fluctuating aerodynamic loads due to ship airwake that act on a helicopter fuselage model were measured [27]. These unsteady loads impact on the fuselage and lead to changes in rotorcraft attitude, heading or position.…”

Development and Experimental Validation of a Shipboard Helicopter On-Deck Maneuvering Simulation

“…The effect of the air wake on rotor thrust and fuselage loads during hover has been addressed aerodynamically by Zan 3 and Lee and Zan. 4 McKillip et al, 5 Lee et al, 6 Aponso and Jewell, 7 and Keller and Smith 8 have also considered the effect the ship's air wake has on an approaching and hovering helicopter. Colwell 9 studied the effects of deck motion on pilot response using Fourier analysis and flight-test data.…”

“…= kinematic matrix C = vector representing the nonlinear components of the kinematic equations C B = coefficient of viscous damping at the castor pivot joint C fix = torsional damping coefficient used to fix the castor assembly C P = probe damping coefficient C ty = tire lateral damping coefficient C tz = vertical tire force constant dependent on the tire type c = Gauss elimination demonstration vector D = matrix used to isolate the unknown forces D Ps = small probe deflection stiffness transition displacement d = vector of tire deflections d ssy = steady-state lateral tire deflection for a given slip angle E = elements of governing dynamic equation forcing vector F = vector containing the sum of generalized forces and moments Received = force vector acting on the joint pivot point B F c = probe force vector caused by the probe damping F ct 1 = force vector acting on the first (left) castor tire F ct 2 = force vector acting on the second (right) castor tire F dx = aerodynamic drag force vector acting in the helicopter longitudinal direction F dy = aerodynamic drag force vector acting in the helicopter lateral direction F k = vector containing known forces and moments F mlt 1 = force vector acting on the first (left) main left tire F mlt 2 = force vector acting on the second (right) main left tire F mrt 1 = force vector acting on the first (left) main right tire F mrt 2 = force vector acting on the second (right) main right tire F P = force vector acting on the probe F rr = rolling resistance force F s = probe force vector caused by the probe stiffness F ssy = steady state lateral tire force for a given slip angle F t = vector of tire forces F u = vector containing unknown forces and moments F κ = force acting on the castor tires caused by the kingpin inclination angle F act = actual force vector acting on the probe F mea = measured force vector acting on the probe h = height between castor pivot point and wheel pivoting arm perpendicular to the ground I C = mass moment of inertia of the castor assembly body I H = mass moment of inertia of the main helicopter body K fix = torsional stiffness used to fix the castor assembly K P = probe stiffness coefficient K Ps = small displacement probe stiffness coefficient K t = vector of tire stiffnesses k h = radius of gyration of the helicopter L h = half-footprint length of tire L u = unyawed relaxation length L y = yawed relaxation length l = distance perpendicular to the pivot axis to a plane perpendicular to the ground M = mass matrix M B = sum of the reaction torques acting on the castor joint m C = mass of the castor assembly body m H = mass of the main helicopter body N = cornering power of tire n = polytropic exponent P = instantaneous tire pressure P r = rated tire pressure P 0 = tire inflation pressure at zero vertical load (gauge) P oa = tire inflation pressure at zero vertical load (absolute) p l = projected length q = state vector q 1 = helicopter X position in global coordinates q 2 = helicopter Y position in global coordinates q 3 = helicopter orientation in global coordinates q 4 = castor assembly orientation relative to helicopter coordinate system …”

Numerical investigation of the aerodynamic interaction between a tiltrotor and a tandem rotor during shipboard operations

“…In the past, several experimental investigations were carried out to understand the effect of the ship airwake during shipborne operations. The loads on a rotor and a fuselage were measured in wind-tunnel experiments at the National Research Council of Canada (NRC) based on the Canadian Patrol Frigate (CPF) to give an indication of the corresponding pilot workload [6][7][8]. Furthermore, wind-tunnel investigations of the rotor-ship interaction were conducted at the Old Dominion University to assess the effect of the coupling between a ship and rotor wake [9,10].…”