clocked in the X position. Propeller ground NACA found that the blades needed to be shorter was thus not an issue. and thinner and set at a reduced blade angle in order to make the blades supercritical. The regions The aircraft achieved speeds slightly exceeding of supersonic flow would thus form at higher Mach 1.0 during test flights through 1956. The speeds than is possible with standard props. maximum speed occurred during dives. The supersonic prop can operate at higher speeds The XF-88B was an experimental aircraft which by delaying the of shock waves and reducing was never put into production. The National their strength once they do form. Committee for Aeronautics (NACA) conducted the research. Aircraft Landing by Tom Irvine Figure 1. Main-wheel Bogie for the XB-70A aircraft Introduction that is forced at a controlled rate through an orifice as the strut is compressed on Commercial pilots must achieve smooth but touchdown. An efficient landing gear design firm landings by carefully controlling the sink thus reduces the loads transmitted into the rate, flare angle, and other settings. A smooth airframe during landing. It also damps the landing is desirable for the passengers. But vertical oscillations. the landing must also be firm enough to prevent runway overrun. Furthermore, wind and rain present hazards. Landing Gear Deflection As a result of these challenges, some aircraft experience hard landings, damaging the The shock strut static deflection varies per aircraft. Injuries to crew and passengers may aircraft model. The Boeing 737-200 has a occur. total stroke of 14.0 inches. The C-141 has a total stroke of 28.0 inches. The static Hard landings are the leading cause of aircraft accidents in terms of airframe structural deflection for transport aircraft is typically damage according to Flight Safety Digest. ~15% of the total stroke. In addition, the tires undergo static and dynamic deflection. The Fatalities have occurred in extreme hard preceding values were taken from Reference landing but are rare. The leading causes 3. of deaths are controlled flight into terrain (CFIT) and in loss of control cases. Landing Shock Environment There are many variables which affect the Landing Gear, Energy Dissipation touchdown shock level of an aircraft. These include: The aircraft’s kinetic energy at touchdown is dissipated by the landing gear, primarily by the oleo struts. Each strut is filled with oil Descent or sink rate
clocked in the X position. Propeller ground was thus not an issue. The aircraft achieved speeds slightly exceeding Mach 1.0 during test flights through 1956. The maximum speed occurred during dives. The XF-88B was an experimental aircraft which was never put into production. The National Committee for Aeronautics (NACA) conducted the research. NACA found that the blades needed to be shorter and thinner and set at a reduced blade angle in order to make the blades supercritical. The regions of supersonic flow would thus form at higher speeds than is possible with standard props. The supersonic prop can operate at higher speeds by delaying the of shock waves and reducing their strength once they do form. Aircraft Landing by Tom Irvine Figure 1. Main-wheel Bogie for the XB-70A aircraft Introduction Commercial pilots must achieve smooth but firm landings by carefully controlling the sink rate, flare angle, and other settings. A smooth landing is desirable for the passengers. But the landing must also be firm enough to prevent runway overrun. Furthermore, wind and rain present hazards. As a result of these challenges, some aircraft experience hard landings, damaging the aircraft. Injuries to crew and passengers may occur. Hard landings are the leading cause of aircraft accidents in terms of airframe structural damage according to Flight Safety Digest. Fatalities have occurred in extreme hard landing but are rare. The leading causes of deaths are controlled flight into terrain (CFIT) and in loss of control cases. Landing Gear, Energy Dissipation The aircraft’s kinetic energy at touchdown is dissipated by the landing gear, primarily by the oleo struts. Each strut is filled with oil that is forced at a controlled rate through an orifice as the strut is compressed on touchdown. An efficient landing gear design thus reduces the loads transmitted into the airframe during landing. It also damps the vertical oscillations. Landing Gear Deflection The shock strut static deflection varies per aircraft model. The Boeing 737-200 has a total stroke of 14.0 inches. The C-141 has a total stroke of 28.0 inches. The static deflection for transport aircraft is typically ~15% of the total stroke. In addition, the tires undergo static and dynamic deflection. The preceding values were taken from Reference 3. Landing Shock Environment There are many variables which affect the touchdown shock level of an aircraft. These include: Descent or sink rate
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