TB 1-1520-240-20-89
f. Component/Parts in Stock at All Levels (Depot and Others) Including War Reserves - N/A.
(1) Wholesale Stock - N/A.
(2) Retail Stock - N/A.
g. Components/Parts in Work - N/A.
2. Task/Inspection Suspense Date - Within 100 flight hours.
4. Summary of the Problem.
a. Several recent incidents have been reported of aircraft losing the aft pylon clamshell doors in-flight due to failure
from vibration of the lower latch pin or fitting which holds the doors together. In-flight separation of the clamshell doors
from the aircraft has caused damage to the rotor system, engine tail cones, and airframes.
b. Maintenance Work Order (MWO) 55-1520-240-50-8 (ECP-D082R1) and MWO 1-1520-240-50-62 (ECP D190R1)
were issued to improve the latch system. Although the incident rate of doors separating in-flight has decreased, there
have been several reports of clamshell latch fittings cracked and broken.
c. For Manpower/Downtime and Funding Impacts - See paragraph 12 below.
d. The purpose of this TB is to check (inspect) the aft pylon clamshell doors for proper fit and affix a strap
assembly, with latch, to the lower left hand door assembly at the bottom edge of the opening. This repair has been
approved by U.S. Army Aviation and Troop Command (ATCOM) Engineering and the SMART Program, and published
in the PS Magazine, March 1996 issue.
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
Door, Access, LH
145S4906-2
Door, Access, RH
145S4906-3
7. Parts to be Inspected - N/A.
8. Inspection Procedures -
a. Prepare the aircraft for safe ground maintenance.
b. Visually inspect aircraft for installation of the Chinook latch fitting fix TB 43-PS-520 (paragraph 13a below).
NOTE
If you do not have a copy of TB 43-PS-520, contact your local Logistics Assistance
Representative (LAR).
c. If the latch fitting fix per TB 43-PS-520 has been applied, no further action is required. Record and report
compliance with this TB in accordance with paragraph 14 below.
d. If the latch fitting fix per TB 43-PS-520 has not been applied, proceed to paragraph 9 below for corrective action.
9. Correction Procedures -
a. Check the aft pylon clamshell doors for proper fit per TM 55-1520-240-23, Task 2-281 (D model), and TM 1-
1520-252-23, Task 2-273 (E model).
b. Locally manufacture, assemble, and install the strap assembly per TB 43-PS-520 (paragraph 13a below).
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