5.2.1 The probability of total failure of all
directional control systems should be extremely remotefootnote when the craft is operating normally, i.e. excluding
emergency situations such as grounding, collision or a major fire.
5.2.2 A design incorporating a power drive or
an actuation system employing powered components for normal directional
control should provide a secondary means of actuating the device unless
an alternative system is provided.
5.2.3 The secondary means of actuating the device
may be manually driven when the Administration is satisfied that this
is adequate, bearing in mind the craft's size and design and any limitations
of speed or other parameters that may be necessary.
5.2.4 As far as is practicable, the directional
control systems should be constructed so that a single failure in
one drive or system, as appropriate, will not render any other one
inoperable.
The Administration may allow a short period of time to permit
the disconnexion of a failed power drive or directional control device
when the design of the craft is such that such delay will not in their
opinion hazard the craft.
5.2.5 Power drives for directional control devices
should become operative automatically, and respond correctly, as soon
as power is restored after a power failure.
5.2.6 Directional control devices involving variable
geometry of the craft or its lift system components should, so far
as is practicable, be so constructed that any failure of the drive
linkage or actuating system will not significantly hazard the craft.