Glossary

Critical altitude. The maximum altitude under standard Decision altitude (DA). A specified altitude in the precision atmospheric conditions at which a turbocharged engine can approach, charted in feet MSL, at which a missed approach produce its rated horsepower. must be initiated if the required visual reference to continue the approach has not been established. Critical angle of attack. The angle of attack at which a wing stalls regardless of airspeed, flight attitude, or weight. Decision height (DH). A specified altitude in the precision approach, charted in height above threshold elevation, Critical areas. Areas where disturbances to the ILS localizer at which a decision must be made either to continue the and glideslope courses may occur when surface vehicles or approach or to execute a missed approach. aircraft operate near the localizer or glideslope antennas. Deice. The act of removing ice accumulation from an CRM. See crew resource management. aircraft structure. Cross-check. The first fundamental skill of instrument flight, Delta. A Greek letter expressed by the symbol Δ to indicate also known as “scan,” the continuous and logical observation a change of values. As an example, ΔCG indicates a change of instruments for attitude and performance information. (or movement) of the CG. Cruise clearance. An ATC clearance issued to allow a Density altitude. Pressure altitude corrected for nonstandard pilot to conduct flight at any altitude from the minimum temperature. Density altitude is used in computing the IFR altitude up to and including the altitude specified in the performance of an aircraft and its engines. clearance. Also authorizes a pilot to proceed to and make an approach at the destination airport. Departure procedure (DP). Preplanned IFR ATC departure, published for pilot use, in textual and graphic format. Current induction. An electrical current being induced into, or generated in, any conductor that is crossed by lines of flux Deposition. The direct transformation of a gas to a solid from any magnet. state, in which the liquid state is bypassed. Some sources use sublimation to describe this process instead of deposition. D Detonation. The sudden release of heat energy from fuel in DA. See decision altitude. an aircraft engine caused by the fuel-air mixture reaching its critical pressure and temperature. Detonation occurs as Datum (Reference Datum). An imaginary vertical plane a violent explosion rather than a smooth burning process. or line from which all measurements of arm are taken. The datum is established by the manufacturer. Once the datum Deviation. A magnetic compass error caused by local has been selected, all moment arms and the location of CG magnetic fields within the aircraft. Deviation error is different range are measured from this point. on each heading. D.C. Direct current. Dew. Moisture that has condensed from water vapor. Usually found on cooler objects near the ground, such as grass, as Dark adaptation. Physical and chemical adjustments of the the near-surface layer of air cools faster than the layers of eye that make vision possible in relative darkness. air above it. Dead reckoning. Navigation of an airplane solely by means Dewpoint. The temperature at which air reaches a state where of computations based on airspeed, course, heading, wind it can hold no more water. direction and speed, groundspeed, and elapsed time. DGPS. Differential global positioning system. Deceleration error. A magnetic compass error that occurs when the aircraft decelerates while flying on an easterly DH. See decision height. or westerly heading, causing the compass card to rotate toward South. G-9