9.5.1 The transmission should be of adequate strength
and stiffness to enable it to withstand the most adverse combination
of the loads expected in service without exceeding acceptable stress
levels for the material concerned.
9.5.2 The design of shafting should be such that
hazardous whirling and excessive vibration do not occur at any speed
up to 105 per cent of the maximum speed that it can attain, e.g. the
speed attained at or after a governor trip.
9.5.3 The strength and fabrication of the transmission
should be such that the probability of hazardous fatigue failure under
the action of the repeated loads of variable magnitude expected in
service is extremely remote footnote throughout its
operational life. Compliance should be demonstrated either by suitably
conducted tests, and/or by designing for sufficiently low stress levels,
combined with the use of fatigue resistant materials and suitable
detail design.
9.5.4 Where a clutch is fitted in the transmission,
normal engagement of the clutch should not cause excessive stresses
in the transmission or driven items. Inadvertent operation of any
clutch should not produce dangerously high stresses in the transmission
or driven item.
9.5.5 The transmission system should be such that
a failure in any part of the transmission, or of a driven component,
will not apply a torque to the system which could cause damage which
might hazard the craft or its occupants. This could be accomplished
by the provision of "weak links", as appropriate.
9.5.6 Where failure of lubricating fluid supply
or loss of lubricating fluid pressure could lead to a hazardous condition,
provision should be made to enable such failure to be indicated to
the operating crew in adequate time to enable them as far as practicable
to take the appropriate action before the hazardous condition arises.