A Subsidiary of Textron, Inc.
October 10, 2003
INFORMATION LETTER GEN-03-94
TO:
All Owners/Operators of Bell Helicopters
SUBJECT:
EXPANDED USE OF RETIREMENT INDEX NUMBERS (RIN)
This Info Letter supersedes Info Letter GEN-94-54.
For several years, Bell Helicopter has used the Retirement Index Number (RIN)
system as a more realistic method for tracking cycle lifed components. The
factoring approach brought by the RIN system eliminates the need to reduce
indiscriminately the retirement life of components.
The RIN system has so far been applied to drive train and dynamic components
which are most affected by cyclic and repetitive loading. For this reason, the RIN
system had been based exclusively on torque events that are recorded and
factored according to different fatigue requirements.
Bell is now expanding the scope of RIN application to include the landing gear.
This additional application is expanded to include Model 407 and 427 landing
gear crosstubes involved in run-on landings.
Currently, the operator is responsible for recording the “torque events” that will
serve to compute the RIN. The best way to record those events is to enter them
in a specific column in the helicopter log book. Run-on landing events should be
recorded separately from torque events in a different column in the helicopter log
book.
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Therefore, in view of the expanded RIN applications, the following definitions now
apply:
Torque event:
A torque event may be defined as a significant change in power setting. Two
types of power setting changes may be encountered:
1. Ground-air-ground (GAG) events, i.e. a take-off plus a landing
2. External or internal load lifts such as:
• All cargo hook lift operations (including long line)
• Water bucket lift operations
• Airborne replenishment of fixed internal or external reservoirs such as
fire fighting tanks
No RIN record is required for the following events:
• Power recovery autorotation where no landing occurs
• In-flight power changes where no external load is lifted such as:
approach to hover and departure, power assurance procedure,
climbing over terrain, individual in-sequence drops of carousel hook
loads.
Run-on landing event:
A run-on landing event may be defined as a landing where there is forward
ground travel of the helicopter greater than three (3) feet with weight on the
skids.
In the future, Bell Helicopter may define other operational events that are subject
to RIN counts, as required.
Recording Retirement Index Number (RIN)
It is the responsibility of the pilot in command to enter the events in the flight
log book. It is the responsibility of the maintainer to assign predetermined RIN
values to the events per BHT recommendations for the purpose of tracking a
components life.
Components that are assigned a RIN value are (or will be) listed in Chapter 4 of
the applicable Maintenance Manual (MM).
Some components may have been previously assigned a life limit based on
fatigue events such as landings or other. These components are presently listed
in chapter 4 of the applicable MM, but will not be assigned a RIN count at this
time.