CAT.IDE.A.140 Altitude alerting system
(a) The following aeroplanes shall be equipped with an altitude alerting system:
(1) turbine propeller powered aeroplanes with an MCTOM of more than 5700 kg or having an MOPSC of more than nine; and
(2) aeroplanes powered by turbo-jet engines.
(b) The altitude alerting system shall be capable of:
(1) alerting the flight crew when approaching a preselected altitude; and
(2) alerting the flight crew by at least an aural signal, when deviating from a preselected altitude.
(c) Notwithstanding (a), aeroplanes with an MCTOM of 5700 kg or less, having an MOPSC of more than nine, first issued with an individual CofA before 1 April 1972 and already registered in the United Kingdom on 1 April 1995 are exempted from being equipped with an altitude alerting system.