Wed, Feb 26, 2003
AWB 63-3 Issue 1, Robinson R44
Applicability: Robinson R44 Lower
Actuator Bearing Mounting Bracket
Purpose: Advise operators and maintainers of
R44 helicopters of the potential of unanticipated loss of power to
the rotor, resulting in a forced autorotative landing and with the
additional possibility of the engine exceeding design RPM.
Background: Routine maintenance discovered an
extensive crack in the mounting bracket.
This bracket
is a vital part of the R44 drive train from the engine to the
rotor. If this bracket should fail, main drive belt tension would
be lost almost immediately. This would result in a forced
autorotative landing. At the same time, because the engine would be
suddenly disconnected from the drive train while running at almost
full power, the engine may well exceed design RPM.
The R22 has an almost identical lower actuator bearing mounting
bracket arrangement to the R44. Robinson Service Bulletin No. 144,
and CASA AD/R22/24 directs the maintainer to inspect the R22 for
loose rivets in this bracket every 50 hours. There is currently no
similar direction for the R44, and integrity checks on this bracket
rely on the person doing the inspection in this area including the
lower actuator bearing mounting bracket as part of the inspection
of the scroll.
Recommendation: CASA recommends that people
maintaining the R44 pay critical attention to this bracket during
routine maintenance inspection of the scroll, and ensure any
damaged brackets are replaced, and that any minor damage to the
edges at the ends of the bracket are removed in an approved manner.
All instances of cracking in this bracket should be reported
immediately to CASA.
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