TB 1--1520--240--20--114
(1)Wholesale Stock. N/A.
(2)Retail Stock. Upon receipt of this TB commanders and others maintaining retail stock at instal-
lation level and below shall contact the supported aviation unit to perform the inspection required by para-
graph 8 and the correction procedures of paragraph 9 on discrepant materiel. Report compliance with this
message in accordance with paragraph 14d(2).
g. Components/Parts in Work (Depot Level and Others. Items listed in paragraphs 6 and 7 in work will
not be issued until compliance with this TB.
2.
Task/Inspection Suspense Date. Within 5 working days from date of this TB.
3. Reporting Compliance Suspense Date. No later than 21 September 1999 in accordance with para-
graph 14a of this TB..
4.
Summary of the Problem.
a. One discrepant second stage planetary transmission gear/bearing assembly identifiable to "VB" se-
rial number prefix was found. Four discrepant second stage planetary transmission gear/bearing assemblies
identifiable to "GG" serial number prefix were found. The discrepancies were not detected by the required
inspection procedures at time of manufacture. These gears are located in the forward and aft transmissions.
An analytical investigation and research of historical data have led to a risk determination that gear/bearing
assemblies identifiable by a serial number prefix "VB" are considered serviceable with improbable risk of fail-
ure (i.e. crack propagation) if the operating limitation identified by paragraph 9 are adhered to.
NOTE
Gear/bearing assemblies with serial number prefix "GG" are considered
unserviceable and must be inspected in accordance with CH--47--99--03.
b. For manpower/downtime and funding impacts, see paragraph 12.
c. The purpose of this TB is to inspect all forward and aft transmission records for specific part number/
serial number combinations. Transmissions with all first and second stage gear/bearing assemblies identified
by serial number prefix "VB" are considered serviceable with operating limitation.
5.
End Items to be inspected. All CH--47D, MH--47D, and MH--47E aircraft.
6.
Assembly Components to be Inspected.
NOMENCLATURE
PART NUMBER
NATIONAL STOCK NUMBER
TRANSMISSION, FORWARD
145D1300 -- ALL
TRANSMISSION, AFT
145D2300 -- ALL
7.
Parts to be Inspected.
NOMENCLATURE
PART NUMBER
NATIONAL STOCK NUMBER
GEAR/BEARING ASSY
145DS010-3
N/A
GEAR/BEARING ASSY
145DS010-5
3110-01-228-1647
2
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