TB 1-1520-237-20-173
4. Summary of the Problem.
a. Tail rotor inboard retention plates manufactured by Aerex manufacturing company, cage code 5K840, and fenn
manufacturing, cage code 82001, have not completed testing to validate fatigue life. a weibayes analysis was performed
on the Aerex component and an interim fatigue life of 148 hours has been assigned. A strength reduction analysis was
performed on the fenn component to assign a reduced fatigue life. However, the analysis indicated level flight would
cause fatigue damage with any type of strength reduction. Based upon this analysis, a reduced fatigue life could not be
calculated and the Fenn manufactured components shall be removed from service until completion of fatigue testing.
b. For manpower/downtime and funding impacts, see paragraph 12
c. The purpose of this TB is to inspect for suspect tail rotor inboard retention plates. Fenn manufactured
components shall be removed from service until completion of the fatigue testing. Aerex manufactured components
shall be re identified as having an interim fatigue life of 148 hours. If the Aerex component exceeds this interim fatigue
life, it shall be removed from service until a new fatigue life can be established upon completion of the fatigue testing.
5. End Items to be Inspected. All H-60 aircraft. Aircraft serial numbers 95-26610 and subsequent will be
inspected/corrected by contractor during production and therefore records for aircraft serial numbers 95-26610 and
subsequent will not require identification of this action.
6. Assembly components to be inspected.
NOMENCLATURE
PART NUMBER
NSN
T/R GEARBOX ASSEMBLY
70358-06600-041
T/R GEARBOX ASSEMBLY
70358-06600-042
T/R GEARBOX ASSEMBLY
70358-06600-043
T/R GEARBOX ASSEMBLY
70358-06600-044
T/R GEARBOX ASSEMBLY
70358-06600-046
7. Part to be Inspected.
NOMENCLATURE
PART NUMBER
NSN
T/R RETENTION PLATE
70358-06612-042
8. Inspection Procedures. Inspect tail rotor inboard retention plate, P/N 70358-06612-042, for serial numbers C1324-
001 through C1324-150 and FM00001 through FM 00142. If the serial number is not in one of the ranges listed above,
the inspection is complete. If the serial number is in one of the ranges listed above, perform the correction procedures in
9. Correction Procedures.
a. If the inboard retention plate has serial number C1324-001 through C1324-150, change DA Form 2408-16 to
indicate an interim retirement life of 148 hours. If the inboard retention plate has over 148 hours, remove, replace, and
hold the suspect retention plate and complete the reporting requirements in paragraph 14b. See paragraph 10d for
disposition of component.
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