CS 25.1331 Instruments using a power supply
ED
Decision 2003/2/RM
(a) For each instrument required by CS 25.1303(b)
that uses a power supply, the following apply:
(1) Each instrument must have a visual means
integral with the instrument, to indicate when power adequate to sustain
proper instrument performance is not being supplied. The power must be
measured at or near the point where it enters the instruments. For electric
instruments, the power is considered to be adequate when the voltage is within
approved limits.
(2) Each instrument must, in the event of the
failure of one power source, be supplied by another power source. This may be
accomplished automatically or by manual means. The failure of one power source
must not affect the same instrument of both pilot stations.
(3) If an instrument presenting flight and/or
navigation data receives information from sources external to that instrument
and loss of that information would render the presented data unreliable, a
clear and unambiguous visual warning must be given to the crew when such loss
of information occurs that the presented data should not be relied upon. The
indication must be incorporated in the instrument.
(b) As used in this paragraph, ‘instrument’
includes devices that are physically contained in one unit, and devices that
are composed of two or more physically separate units or components connected
together (such as a remote indicating gyroscopic direction indicator that
includes a magnetic sensing element, a gyroscopic unit, an amplifier, and an
indicator connected together).
Aircraft instruments needing power must have a visual warning for inadequate power. Backup power sources are required, ensuring single failures don't impact both pilot stations. Instruments relying on external data must warn of data loss. This applies to single-unit and multi-component instrument systems for reliable flight data.
* Summary by Aviation.Bot - Always consult the original document for the most accurate information.
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