TECHNICAL BULLETIN
407-12-97
8 March 2012
MODEL AFFECTED:
407
SUBJECT:
SOLID MACHINED ALUMINUM SHIMS UNDER
TRANSMISSION
SUPPORT
BEAMS,
INSTALLATION OF.
HELICOPTERS AFFECTED:
Serial numbers 53000 through 53900,
through 54299 and 54300 and subsequent.
COMPLIANCE:
At customer’s option.
53911
DESCRIPTION:
This bulletin provides approval to install solid aluminum shims as replacement for the
CRES peelable shims P/N 407-010-222-101 and P/N 407-010-222-103 installed under
the pylon support beams. Shims can be fabricated locally or procured directly from BHT
approved supply centers before being machined to the requirements of the applicable
shim records.
APPROVAL:
The engineering design aspects of this bulletin are Transport Canada Civil Aviation
(TCCA) approved.
CONTACT INFO:
For any questions regarding this bulletin, please contact:
Bell Helicopter Product Support Engineering - Light Helicopters
Tel: 450-437-2862 / 1-800-363-8023 / [email protected]
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MANPOWER:
Approximately 8.0 man-hours are required to replace all four pylon support shims. This
time does not include the fabrication and the machining of the shims to reflect those that
were removed. This estimate is based on hands-on time, and may vary with personnel
and facilities available.
WARRANTY:
There is no warranty credit applicable for parts or labor associated with this bulletin.
MATERIAL:
Required Material:
The following material is required for the accomplishment of this bulletin and may be
obtained commercially
Part Number
407-010-222-105
407-010-222-107
Nomenclature
Aluminum shim (FS. 113.965)
Aluminum shim (FS. 140.650)
Qty
2(see note)
2(see note)
NOTE: Aluminum alloy, 6013-T6, 0.125 inch (3.175 mm) thick per AMS 4216, 7075-T6,
0.125 inch (3.175 mm) thick per AMS-QQ-A-250/12 or 2024-T3, 0.125 inch
(3.175 mm) thick per AMS-QQ-A-250/4 can be used as an alternate to fabricate
the shims locally.
Consumable Material:
The following material is required to accomplish this bulletin, but may not require
ordering, depending on the operator’s consumable material stock levels. This material
may be obtained through your Bell Helicopter Textron Supply Center.
Part Number
299-947-100TY2CL2PT
MIL-C-81706 1 QT
MIL-PRF-23377, TY I
MIL-PRF-81733 2.5 OZ
Nomenclature
Adhesive
Chemical treatment (Alodine)
Primer
Sealant **
Qty
1
1
1
1
Reference *
C-317
C-100
C-204
C-392
* C-XXX numbers refer to the consumables list in BHT-ALL-SPM Standard Practices Manual
** Sealants under MIL-S-8802 or MIL-S-81733 are acceptable alternates.
SPECIAL TOOLS:
None required.
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REFERENCES:
BHT-407-IPB Illustrated Parts Breakdown
BHT-407-MM Maintenance Manual
BHT-206-SRM-1 Structural Repair Manual
Technical Bulletin 407-10-92
PUBLICATIONS AFFECTED:
. BHT-407-IPB Illustrated Parts Breakdown
ACCOMPLISHMENT INSTRUCTIONS:
-NOTEThe following procedure shall refer to the shim values found
in the active shim records, in order to machine the solid
shim(s) correctly.
For helicopters which have sustained structural damage
requiring the use of a BHT approved repair fixture, contact
the repair facility for a copy of the applicable shim records.
Verify that your helicopter serial number is not listed in
Technical Bulletin 407-10-92. If so, ensure you have the
latest copy of the production shim record showing “Post TB
407-10-92” in order to be valid.
1. Verify helicopter records to ensure that the applicable shim record is available. If it is
not available, contact Product Support Engineering to obtain a copy of the original
production shim record.
2. Prepare helicopter for maintenance.
3. Remove the transmission and both pylon beams (Ref. BHT-407-MM, Chapter 63).
4. Remove the CRES peelable shims (3, 4, 5 and 6, Figure 1) bonded to the roof under
each beam assembly and inspect exposed areas of the roof forward and aft hotbonded doublers (1 and 2).
-NOTELight surface corrosion will only be seen in the form of a
white powder on the aluminum surface. More severe
corrosion in the form of corrosion pits or intergranular
corrosion may also be present along with surface corrosion.
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5. If corrosion is observed, repair per instructions provided by Product Support
Engineering before proceeding further.
-NOTEInstallation of solid Al alloy shim(s) in replacement of CRES
peelable shim(s) is approved only if active shim record
indicates value(s) 0.025 inch (0.635mm) thick or above.
6. Verify all four pylon beam shim values on active shim record;
a. If thickness value for any shim (3, 4, 5, or 6) is less than 0.025 inch (0.635mm)
thick, reinstall CRES peelable shim(s) P/N 407-010-222-101 and/or P/N 407-010222-103 as required (Ref. BHT-407-MM, Chapter 63).
b. For shim(s) with thickness values at or above 0.025 inch (0.635mm) for that
particular location, solid Al alloy shim(s) can be machined per the next steps.
-NOTEIndicated shim thickness will have to be adjusted when postcertification repair doubler is installed on roof assembly at
affected location by subtracting added material.
7. Refer to shim record and make reference to the applicable shim area before
transferring values to Table 1. Ensure the transfer of values is accurate.
-NOTEQualified milling shop should use a Sinus table or
programmable 3 axis milling equipment to make the tapered
shim(s).
-NOTEMachined face of the solid aluminum shim(s) shall be facing
the roof shell assembly hot-bonded doublers (1 and 2).
8. Have the solid shim machined from the applicable part number or material described
in the material section of this bulletin. Machining shall be based on the values which
were transferred to Table 1 and applicable detail (B, C, D or E). Ensure shim is
oriented in the proper direction while machining, in order to obtain the proper
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thickness at the positions indicated by the shim record. Note that the machined
surface will mate with the roof surface.
9. Apply surface film treatment (C-100) to all bare metal surfaces of the new shim(s)
and the roof assembly and let dry.
10. Apply primer (C-204) to all surfaces of the shim(s) and all reworked or bare surfaces
of the roof and let dry. Once dry, remove gloss finish of primer using 400 grit or finer
aluminum oxide sanding paper.
11. Bond the shim(s) in place, with the machined tapered surfaces against the roof at
the applicable location using instructions detailed in BHT-407-MM, Chapter 63.
Make certain that the inboard, outboard, forward and aft values do match the
positions indicated by the shim record when shim is facing roof surface.
12. Apply a filet of sealant (C -392) around each shim after installation and let cure.
13. Reinstall the transmission and beam assemblies (Ref. BHT-407-MM, Chapter 63).
14. Make an entry in helicopter historical service records indicating compliance with this
Technical Bulletin.
TABLE 1
Shim location on roof
DETAIL B
DETAIL C
DETAIL D
DETAIL E
Shim Area
A
B
C
D
E
F
G
H
J
K
L
M
N
P
Q
R
Roof hole location
Forward inboard
Forward outboard
Aft Inboard
Aft outboard
Forward inboard
Forward outboard
Aft Inboard
Aft outboard
Forward outboard
Forward inboard
Aft outboard
Aft Inboard
Forward outboard
Forward inboard
Aft outboard
Aft Inboard
Shim record value
NOTE: Transfer shim values from active shim record to above table. Use these values
later in reference to the applicable area of detail (B, C, D or E) to machine
applicable thicknesses and taper as applicable.
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Figure 1: Installation of Pylon Beam Shims Made
From Solid Al Alloy Material (Sheet 1 of 5)
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Figure 1: Installation of Pylon Beam Shims Made
From Solid Al Alloy Material (Sheet 2)
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Figure 1: Installation of Pylon Beam Shims Made
From Solid Al Alloy Material (Sheet 3)
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Figure 1: Installation of pylon beams shims made
from solid Al alloy material (Sheet 4)
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Figure 1: Installation of Pylon Beam Shims Made
From Solid Al Alloy Material (Sheet 5)
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