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The brownout phenomenon causes accidents during helicopter landing and take-off operations in arid desert terrain. Intense, blinding dust clouds stirred up by the helicopter rotor downwash during near-ground flight causes significant flight safety risks from aircraft and ground obstacle collisions, and dynamic rollover due to sloped and uneven terrain. [5]
The effect of downwash from a hovering Sikorsky Seahawk is clearly visible on the surface of water below.. In aeronautics, downwash is the change in direction of air deflected by the aerodynamic action of an airfoil, wing, or helicopter rotor blade in motion, as part of the process of producing lift. [1]
It includes several components, the most significant of which are wingtip vortices and jet-wash, the rapidly moving gases expelled from a jet engine. Wake turbulence is especially hazardous in the region behind an aircraft in the takeoff or landing phases of flight. During take-off and landing, an aircraft operates at a high angle of attack.
They wash their own planes and pump their own gas. They wear dumpy overalls. Most get paid a fraction of what captains at United and American airlines make, and they die at an alarming rate.
The signs of VRS are a vibration in the main rotor system [8] followed by an increasing sink rate and possibly a decrease of cyclic authority. [9]In single rotor helicopters, the vortex ring state is traditionally corrected by slightly lowering the collective to regain cyclic authority and using the cyclic control to apply lateral motion, often pitching the nose down to establish forward flight.
When a hovering rotor is near the ground the downward flow of air through the rotor is reduced to zero at the ground. This condition is transferred up to the disc through pressure changes in the wake which decreases the inflow to the rotor for a given disc loading, which is rotor thrust for each square foot of its area.
The shield improves communication and protects from rotor wash effects. A German Army door gunner mans an M3M on board a CH-53 helicopter. US Navy door gunner in 2000, in response to the attack on the USS Cole Navy door gunners now provide stand off security against attack by small craft.
(This can be described as aerodynamic wash-in.) Winglets also promote a greater bending moment at the wing root, possibly necessitating a heavier wing structure. Installation of winglets may necessitate greater aerodynamic washout in order to provide the required resistance to spinning , or to optimise the spanwise lift distribution.