A
Ab Initio Trainee Controllers Selected individuals, with no previous relevant qualifications, who are given basic instruction and training to enable them to obtain theoretical qualifications. Ability What a person brings to the job situation without specialised, job specific training, education or experience. There are many kinds or abilities. As regards ATCO selection the focus is on relatively broad mental abilities. Ability Tests A standardised and controlled method for measuring abilities in different areas (e.g. memory, spatial, perception, attention). Ability tests cover speed or power tests, paper and pencil or computer based. Absent Mode A The Mode A field in the original format was deter-mined as missing. Therefore, MADREC Mode A field is left in the default status (FFFF16). Quality bit is zero. Absent Mode C The Mode C field in the original format was determined as missing. Therefore, MADREC Mode C field is left in the default status (FFFF16). Quality bit is zero. Absolute accuracy Absolute accuracy is defined as the variance or the dispersion of the absolute position of a point in the global reference frame, defined in the co-ordinate axes of the global frame. Absolute co-ordinates Absolute co-ordinates of a point are determined directly by measurements in a global reference frame. Thus, we can say that the determination of absolute co-ordinates is a realisation of an absolute (global) reference frame. Abstract Syntax A set of formal rules describing the structure of objects, without regard to the details of how these objects are represented in a physical medium. Abstract Syntax Notation A notation which enables data types to be defined and values of those types specified, without determining the way in which they will be represented (encoded) for transfer by protocols. Abstract Syntax Notation One 1- An international standard for specifying data.
2- A standard definition approach that is consistent with the ISO orientation of the ATN and
specific ATN manual guidelines.

Accelerometer An inertial device for measuring acceleration, usually in three orthogonal axes (lateral X, longitudinal Y, and vertical Z); accelerometers usually consist of a mass, spring, and damper; accelerometers are usually included in inertial sensors, such as AHRS and INS.
Acceptability The acceptance of the system means whether the humans coming into contact with the system accept its existence and the way in which it operates. Acceptance tests The radar sensor performance is analysed and compared to that specified in the contract between the administration and the manufacturer.

Accident
An occurrence associated with the operation of an a/c which takes place between the time any person boards the a/c with the intention of flight until such time as all such persons have disembarked, in which a person is fatally or seriously injured, the a/c sustains damage or structural failure, or the a/c is missing or is completely inaccessible. (ICAO, 1994).
Accounting Management