TB 1-1520-240-20-91
f. Component/Parts in Stock at All Levels (Depot and Others) Including War Reserves - Upon receipt of this TB, the
materiel condition tags of all items listed in paragraph 7 below in all condition codes shall be annotated to read 'TB 1-1520-
240-20-91, One Time Visual Inspection of Forward Transmission Mounting (Barrel) Nuts, P/N NAS 577B20A", must be
complied with prior to issue.
1) Wholesale Stock - Upon receipt of this TB, depot commanders shall ensure inspection of all items listed in
paragraph 7 below located in all wholesale depots including all satellite wholesale depots and war reserve depots. Upon
receipt of this TB deport commanders and other maintaining wholesale stock shall ensure that serviceable materiel
(condition codes "A", "B", and "C") is placed in condition code "J" and tagged with a suspended tag/label - DD Form
1576/1576-1. The authority block must reference inspection required per TB 1-1520-240-20-91. Report compliance with
this TB in accordance with paragraph 14d(1) below.
(2) Retail Stock - Upon receipt of this TB commanders and other maintaining retail stock of items listed in
paragraph 7 below shall contact their support aviation organization to perform the inspection required by paragraph 8
below and to perform the correction procedures of paragraph 9 below on discrepant materiel. All items listed in paragraph
7 below shall be immediately placed in condition code 'D" and re-tagged with a test/modification tag/label - DD Form
1576/1576-1 (blue color). The authority block must reference inspection required per TB 1-1 520-240-20-91. Items
identified as serviceable IAW paragraph 8 below shall be re-tagged with a serviceable tag/label - DD Form 1574/1574-1
(yellow color). Indicate compliance with TB 1-1520-240-20-91 in the remarks block. Item identified as discrepant IAW
paragraph 8 below shall be re-tagged with unserviceable (reparable) tag/label - 1577/1577-3 (green color). Annotate
remarks block to indicate that the item is unserviceable lAW TB 1-1520-240-20-91. Any items found discrepant per the
inspection procedures cited in paragraph 8 below shall be disposed of by mutilation/demilitarized to prevent resale. Report
compliance with this TB in accordance with paragraph 14d(2) below.
g. Components/Parts in Work - All items listed in paragraph 6 below shall not be issued until compliance with this TB
has been completed.
2. Task/Inspection Suspense Date - Within 10 hours/14 days.
3. Reporting Compliance Suspense Date - No later than 06 December 1996 per paragraph 14a of this TB.
4. Summary of the Problem.
a. Safety-of-flight messages (see paragraphs 13a and 13b below) issued in April 1990 required the
inspection/replacement of NAS577B20A barrel nuts to purge the supply system of nuts manufactured by Hartford Aircraft
Products (HAP) Inc., CAGE 66861. These nuts mount the forward transmission to the airframe, and four (4) nuts are
required per aircraft. Analysis of several failed barrel nuts manufactured by this vendor indicated impurities in steel and
alloy segregation. All other manufacturers NAS577B20A barrel nuts are acceptable.
b. A report was just received that another subject barrel nut manufactured by this vendor was found in the field
assets. It is logical to assume that additional discrepant nuts manufactured by Hartford Aircraft Products, Inc. maybe
installed on CH-47 Chinook Aircraft.
c . For Manpower/Downtime and Funding Impacts - See paragraph 12 below.
d. The purpose of this TB is to require another one time visual inspection of forward transmission NAS577B20A
mounting (barrel) nuts prior to next flight and removal of nuts manufactured by Hartford Aircraft Products Inc. which can be
identified by an impression stamp marking of HAP, or CAGE code 66861, on the exposed barrel nut carrier.
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
Forward Transmission Assembly
145D1300-9
2