9.5.1 The transmission shall 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, bearings and mounts
shall be such that hazardous whirling and excessive vibration could
not occur at any speed up to 105% of the shaft speed attained at the
designed overspeed trip setting of the prime mover.
9.5.3 The strength and fabrication of the transmission
shall 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 throughout its operational life. Compliance
shall be demonstrated by suitably conducted tests, and by designing
for sufficiently low stress levels, combined with the use of fatigue
resistant materials and suitable detail design. Torsional vibration
or oscillation likely to cause failure may be acceptable if it occurs
at transmission speeds which would not be used in normal craft operation,
and it is recorded in the craft operating manual as a limitation.
9.5.4 Where a clutch is fitted in the transmission,
normal engagement of the clutch shall not cause excessive stresses
in the transmission or driven items. Inadvertent operation of any
clutch shall not produce dangerously high stresses in the transmission
or driven item.
9.5.5 Provision shall be made such that a failure
in any part of the transmission, or of a driven component, will not
cause damage which might hazard the craft or its occupants.
9.5.6 Where failure of lubricating fluid supply
or loss of lubricating fluid pressure could lead to hazardous conditions,
provision shall 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.