TB 1-1520-240-20-96
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 paragraphs 6 and 7 below in all condition codes shall
be annotated to read "TB 1-1520-240-20-96, One Time Visual Inspection and Replacement of Certain P/N
463074 Crissair Check Value Installed in the Power Control Module Assemblies in the Port Marked "FLT
CONT PUMP" only 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 paragraphs 6 and 7 below located in all wholesale depots including all satellite wholesale depots
and war reserve depot. Upon receipt of this TB, depot commanders and others 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 1575/1575-1 (brown color). The authority block must reference
inspection required per this TB (TB 1-1520-240-20-96). Report compliance with this TB in accordance with
paragraph 14d(1) below. Packages dated after 01 May 1991 do not need to be opened. They are acceptable.
(2) Retail Stock. Upon receipt of this TB, commanders and others maintaining retail stock of
items listed in paragraphs 6 and 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 paragraphs 6 and 7 below shall be immediately placed in condition code
"D" and retagged with a test/modification tag/label - DD Form 1576/1576-1 (blue color). The authority block
must reference inspection required per this TB (TB 1-1520-240-20-96). Items identified as serviceable in
accordance with paragraph 8 below shall be retagged with a serviceable tag/label - DD Form 1574/1574-1
(yellow color). Indicate compliance with this TB (TB 1-1520-240-20-96) in the remarks block. Items identified
as discrepant in accordance with paragraph 8 below shall be retagged with unserviceable (reparable) tag/
label - 1577-2/1577-3 (green color). Annotate remarks block to indicate that the item is unserviceable in
accordance with this TB (TB 1-1520-240-20-96) discrepant items shall be corrected in accordance with para-
graph 9 below. Report compliance with the TB in accordance with paragraph 14d(2) below. Packages dated
after 01 May 1991 do not need to be opened. They are acceptable.
g. Components/Parts in Work. All items listed in paragraphs 6 and 7 below shall not be issued until
compliance with this TB has been completed.
2. Task/Inspection Suspense Date. Within 10 hours/14 days.
3.
4.
Summary of the Problem.
a. Recent field reports revealed that the certain P/N 4C3074 hydraulic check valve, manufactured by
Crissair, Inc. (CAGE 99240) in power control modules P/N AE-A620-14 (145H1201-5) or P/N AE-A620-15
(145H1201-6) is being found with a rivet missing from the valve's poppet. Failure of the valve during auxiliary
power unit (APU) or external ground power unit (GPU) operation could cause the rotors to turn in the opposite
direction of normal rotation during operation of the No. 1 or No. 2 power transfer units (PTU). The missing
rivet can enter the hydraulic system causing damage to the flight control pump when the power source to the
hydraulic system is either the APU or an external GPU.
b. The failure occurs when the drive system is shut down and the flight control systems are being
powered by either the APU through the PTU pump or a ground power unit. Therefore, the failure poses no
safety of flight conditions. After compliance with this TB, do not control substitute/cannibalize from the
modules identified in paragraph 8c.
c. To eliminate the problem, the valve has been redesigned to replace the three-piece assembly (rivet,
washer, and poppet) with a one-piece poppet. There are two locations where the power control module P/N
AE-A620-14 (145H1201-5) or AE-A620-15 (145H1201-6) is used on the aircraft. Each power control module
has three check valves. However, only the check valve that is installed into the port marked "FLT CONT
PUMP" can cause the above problem. If any of the other four (4) check valves fail, the rivet becomes trapped
or lodged in the hydraulic system without causing any damage or failure of other components.
d. For manpower/downtime and funding impacts, see paragraph 12.
e. The purpose of this TB is to replace the old three-piece configuration of the 4C3074 Crissair check
valve with the current improved one-piece design, revision D. P/N 4C3074, revision D, can be identified by
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