Departure Control The ATC service provided to departing IFR flights during the phase of flight immediately after take-off. Departure Manager That part of the automated system that assists controllers with sequencing, metering and advisory service for departing traffic. Departure Parking Position The parking position of a departing flight prior to push-back or taxi. Departure Slot A time frame for departing aircraft in which the aircraft has to be airborne. Dependent variable The response or the variable which is hypothesised to be affected by the independent variable. Descent below lowest usable flight level (MTCD) An aircraft is involved in a descent below lowest usable flight level if the minimum level at any probable position of the aircraft in airspace is less than the lowest usable flight level defined for that airspace. Descent Below lowest usable flight level data (MTCD) Consists of: trajectory identification; airspace identification; time of first descent below lowest usable flight level, plus worst probable position of aircraft at this time, plus nominal position of aircraft at this time. Designated RNAV Route An area navigation route based on the current high altitude or low altitude VOR/DME coverage, as designated by appropriate government agencies. Desired Course 1- True: A predetermined desired course direction to be followed (measured in degrees from true north);
2- Magnetic: A predetermined desired course direction to be followed (measured in degrees from local magnetic north)
3- Station: A predetermined desired course direction to be followed (measured in degrees from station north).
Detection Probability (Plot)
Probability that a correct radar Plot message is derived when a target is present.
Deviation
A specific written authorisation, granted prior to the manufacture of an item, to depart from a particular performance or design requirement of a specification, drawing or other document for a specific number of units or a specified period of time. A deviation differs from an engineering change in that an approved engineering change requires a corresponding revision of the documentation defining the affected items, whereas a deviation does not contemplate revision of the applicable specification or drawing.
Diagnosing
Another basic function of ATC. The active cognitive process which takes place in order to assimilate new unexpected situational conditions into the actual Mental Picture (MP) of the traffic situation or to change the MP to account for the new information.
Tip: to find a specific term, use the Acrobat search : click D on the binocular icon in the window bar menu
Dialogue For the purposes of PETAL, the term ‘dialogue’ refers to the human dialogue or, for example, that period from controller HMI input of a message to the time the controller sees the aircrew acknowledgement to that message displayed on his screen. Dialogue Request A Dialogue Request is the stating point of a dialogue. It conveys a request, an instruction or some specific information to be treated and responded upon by the receiving system or operator. The Dialogue Request can be human or system generated. A Dialogue Request may be followed by one Logical Response and/or one Operational Response. Difference Pattern The receiver (1090 MHz) characteristic of a monopulse SSR antenna, obtained by connecting together in anti phase the signals (replies) received by two partial antennas. The difference pattern has a minimum in the main radiation direction of the antenna, and an amplitude and phase characteristic which varies as a function of angle of arrival of the received signal. Used in conjunction with the sum output of the antenna, it enables the off bore sight angle to be found. Differential Global Navigation Satellite System Is an augmentation, the purpose of which is to determine position errors at one or more known locations and subsequently transmit derived information to other GNSS receivers in order to enhance the accuracy of the position estimate Differential Global Positioning System A technique for improving GPS solution accuracy. Error is reduced by determining the error at a known location, then subtracting that error from the solution at an unknown location. Digital Data Data in the form of digits or integral quantities. Contrast with analogue data. Digital Signal Processor A computer oriented toward math-intensive applications, often a single chip or small chip set. Dilution of Precision A numerical value expressing the confidence factor of the position solution based on current satellite geometry. The lower the value, the greater the confidence in the solution. DOP can be expressed in the following forms. GDOP - all parameters are uncertain (latitude, longitude, height, clock offset); PDOP - 3D parameters are uncertain (latitude, longitude, height); HTDOP - 2D parameters and time are uncertain (latitude, longitude, time); HDOP - 2D parameters are uncertain (latitude, longitude); VDOP - height is uncertain; TDOP - clock offset is uncertain. Direct Controller Pilot Communication A method of radio communication between air traffic control and the cockpit which features instantaneous voice responses, by either party, allowing the use of reduced separation criteria. Direct Support Tasks Tasks which contribute to the design and provision of the product and/or service in the short term. Direction Finding Displays the bearing of a transmitting aircraft Equipment DIF from the airport. Disabled Person Somebody with a physical or mental impairment that substantially limits one or more major life activities (Americans with Disabilities Act ADA, 1990). Discovery Computer Based Training Interactive discovery learning making use of a multimedia computer.
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