A descent during air travel is any portion where an aircraft decreases altitude, and is the opposite of an ascent or climb. In Aviation, the term climb refers both to the actual operation of increasing the altitude of an Aircraft and to the logical phase of a typical flight (often Descents are an essential component of an approach to landing. Landing is the last part of a Flight, where a flying Animal, Aircraft, or Spacecraft returns to the ground Other intentional descents might be to avoid traffic, poor flight conditions (turbulence, icing conditions, or bad weather), clouds (particularly under visual flight rules), to see something lower, to enter warmer air (see adiabatic lapse rate), or to take advantage of wind direction of a different altitude, particularly with balloons. In Aviation, icing conditions are those atmospheric conditions that can lead to the formation of water Ice on the surfaces of an aircraft or within the engine The lapse rate is defined as the negative of the rate of change in an atmospheric variable usually Temperature, with height in an atmosphere As well what may require an aircraft descent is during emergencies, such as a sudden decompression forcing an emergency descent to below 10,000ft, the maximum safe altitude for an unpressurized aircraft. Cabin pressurization is the active pumping of compressed Air into an Aircraft cabin when flying at altitude to maintain a safe and comfortable environment for crew An example of this is Aloha Flight 243. Aloha Airlines Flight 243 was a scheduled Aloha Airlines Boeing 737-297 flight between Hilo and Honolulu in Hawaii. Involuntarily descent might occur from a decrease in power, lift (wing icing), an increase in drag, or flying in an air mass moving downward, such as a terrain induced downdraft, rotor, near a thunderstorm, in a downburst or microburst. In Fluid dynamics, drag (sometimes called fluid resistance) is the force that resists the movement of a Solid object through a Fluid (a An updraft or downdraft ( air pocket) is the vertical movement of Air as a Weather related phenomenon Downburst damagejpg|thumb|right|300px|Downburst damages in a straight line A microburst is a very localized column of sinking air producing damaging divergent and Straight-line winds at the surface that are similar to but distinguishable from
Rapid descents relate to dramatic changes in cabin air pressure—even pressurized aircraft—and can result in discomfort in the middle ear. Cabin pressurization is the active pumping of compressed Air into an Aircraft cabin when flying at altitude to maintain a safe and comfortable environment for crew The middle ear is the portion of the ear internal to the Eardrum, and external to the Oval window of the Cochlea. Relief is achieved by decreasing relative pressure by equalizing the middle ear with ambient pressure ("popping ears") through swallowing, yawning, chewing, or the valsalva maneuver. Pressure (symbol 'p' is the force per unit Area applied to an object in a direction perpendicular to the surface The Valsalva maneuver is performed by forcibly exhaling against a closed airway
Normal descents take place at a constant airspeed and constant angle of descent (3 degree final approach at most airports). A final approach is the last leg in an aircraft's approach to landing The pilot controls the angle of descent by varying engine power and pitch angle (lowering the nose) to keep the airspeed constant. Flight dynamics is the science of air and space vehicle orientation and control in three dimensions Unpowered descents (such as engine failure) are steeper than powered descents but flown in a similar way as a glider. Terminology A "glider" is an unpowered Aircraft. The most common types of glider are today used for sporting purposes If the nose is too high for the chosen power the airspeed will decrease until eventually the aircraft stalls, or loses lift. For other uses see Stall. In Aerodynamics, a stall is a sudden reduction in the lift forces generated by an Airfoil
Helicopters which lose power don't simply fall out of the sky. In a maneuver called autorotation, the pilot configures the rotors to spin faster driven by the upward moving air, which limits the rate of descent. In Aviation, the word autorotation is applied to operation of Fixed-wing aircraft and Rotary-wing aircraft. Very shortly before meeting the ground, the pilot changes the momentum stored in the rotor to increased lift to slow the rate of descent to a normal landing (but without extended hovering).
See also
References
- FAA terminal procedures index
- Flight school ground course on landing
- A helicopter school autorotation guide
- FAA rotorcraft pilot testing standards
- FAA airplane pilot testing standards
Dapyx Software network: MP3 Explorer | Ebook Manager | Zenithic