TB 1--1520--240--20--144
c. Aircraft in Transit --
(1) Surface/Air Shipment -- Same as paragraph 1a.
(2) Ferry Status -- Same as paragraph 1a.
d. Maintenance Trainers (Category A and B) -- Same as paragraph 1a.
e. Components/Parts in Stock at All Levels (Depot and Others) including War Reserves -- Upon receipt
of this Technical Bulletin, Depot and Materiel Activity Commanders will ensure the materiel condition tags of
all items in all condition codes listed in paragraphs 6 and 7 are annotated to read: "CH-47-02-01 (TB
1-1520-240-20-144), swashplate lower seal retainer self-locking nut inspection not complied with."
(1) Wholesale Stock -- N/A.
(2) Retail Stock -- Upon receipt of this message, Commanders and Facility Managers maintain-
ing retail stock at installation level and below shall contact the supported aviation unit to perform the proce-
dures required in accordance with paragraphs 8 and 9 on suspect materiel. Dispose of discrepant materiel
in accordance with paragraph 10.
f. Components/Parts in Work (Depot Level and Others) -- Depot and other maintenance Activity Com-
manders will ensure items listed in paragraphs 6 and 7 are not issued until they are in compliance with this
message.
2. Task/Inspection Suspense Date. Complete the inspection in accordance with paragraph 8 prior to next
flight, but no later than 8 February 2002.
4.
Summary of the Problem.
a. A field unit has discovered the use of self-locking nut P/N NAS 1758-L6 on the swashplate lower
seal retainer. The overall height of these nuts does not allow full engagement of the locking features in the
nut. Use of the incorrect nuts could cause damage to the stationary ring due to inadequate clearance between
the nut and the stationary ring, especially if the nut were to back off the bolt. In addition, if a nut or bolt were
to back off and drop below the swashplate assembly, the possibility exists that a linkage could be jammed
by the fastner, which could cause a partial or complete loss of rotor control.
b. For manpower/downtime and funding impacts see paragraph 12.
c. The purpose of this Technical Bulletin is to --
(1) Require inspection for and replacement of incorrrect self-locking nuts installed on forward and
aft swashplate rotating ring assemblies.
(2) Require inspection of swashplate stationary ring for damage if incorrect self-locking nuts are
found.
(3) Require inspection of all swashplate lower seal retainer self-locking nuts on hand/in stock.
(4) Require a change to maintenance manuals to incorporate the correct nut torque valve and
change installation procedures from a wet installation to dry installation.
5.
End Items to be inspected. All H--47 series aircraft.
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