AN APPROPRIATE ENTRY SHOULD BE MADE IN THE AIRCRAFT LOGBOOK UPON ACCOMPLISHMENT

IF OWNERSHIP OF AIRCRAFT HAS CHANGED PLEASE FORWARD TO NEW OWNER

 

MODEL AFFECTED: 407

SUBJECT: HORIZONTAL STABILIZER INSTALLATION 407-

023-800-ALL, IMPROVEMENT OF

HELICOPTERS AFFECTED: 407, Serial Number 53000 through 53339.

[Helicopters Serial Number 53340 and subsequent 

will have the intent of this bulletin completed before 

delivery]

COMPLIANCE: At the option of the operator. However, BHT

recommends that you do this bulletin at the next

scheduled inspection.

DESCRIPTION:

Bell Helicopter has received reports of upper horizontal stabilizer attachment supports 

found cracked in service. All cracks were found during routine or scheduled

maintenance in the same location of the left or right upper stabilizer supports 407-023-

800-117 or /-118.

Investigation showed that gaps can exist between the attachment flange of the stabilizer 

supports and the stabilizer upper or lower surfaces. To eliminate these gaps and 

reduce the loads affecting each stabilizer attachment supports, BHT has approved the 

installation of shims in the form of shimming compound (full length of each support 

attachment flange) and solid shim(s) riveted to the stabilizer upper surface. Once 

installed, the cured shimming compound and solid shim(s) will eliminate the risk of the 

stabilizer supports to crack in service.

This bulletin gives instructions to check for, measure and correct any gap(s) that can 

exist between each of the stabilizer attachment supports and the surface of the

stabilizer.

No. 407-01-33

Date 08-29-01

Page 1 of 23 

 DATE

 REV

TECHNICAL BULLETIN

 A Subsidiary of Textron Inc.
TB 407-01-33

Page 2 of 23

APPROVAL:

The engineering design aspects of this bulletin are Transport Canada approved.

MANPOWER:

Approximately 8.0 man-hours are necessary to complete this bulletin. Man-hours are 

based on hands-on time, and can vary with personnel and facilities available.

MATERIALS:

Required Material:

The material that follows is necessary to complete this bulletin and can be procured 

through your Bell Helicopter Textron Supply Center.

Part Number Nomenclature Quantity

100-204-2 Identification plate 3

MS27039-1-05 Screw 32

Consumable Material:

The material that follows is necessary to complete this bulletin, however this material is 

considered consumable (bench stock) material and may not need to be ordered

depending on the operators consumable material stock levels. This material can be 

procured through your Bell Helicopter Textron Supply Center.

Part Number Nomenclature Reference

EC2216 B/A TAN N/S Adhesive C-322 (Note 4)

299-947-100TY2CL2PT Adhesive C-317

MIL-PRF-81733 Sealant C-392 (Note 1)

Acetone Acetone (per Q-A-51) C-316 (Note 2)

MIL-P-85582, TY1, CL2 Primer C-204 (Note 3)

MIL-C-81706 1 GAL Chem Film C-100

P-P-101 Aluminum Oxide Sandpaper C-423

299-947-110TY3CL1 2I Teflon tape (2 inch wide) C-460

PETROLATUM 16 OZ Petrolatum (Petrolatum Jelly) C-008

Notes:

1. Formerly MIL -S-81733

2. As an alternative, use Methyl Ethyl Ketone (C-309)

3. As an alternative, use MIL-P-23377

4. A quantity of 4 Oz. Minimum is needed to do the installation on one aircraft.
TB 407-01-33

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SPECIAL TOOLS:

Not required

WEIGHT AND BALANCE:

The modification of the stabilizer installation as described in this bulletin has a negligible 

effect to the Weigh and Balance of the aircraft.

ELECTRICAL LOAD DATA:

Not affected

REFERENCES:

BHT-407-MM-5, Rev. 10, 16 February 2001

Chapter 53, Fuselage

BHT-407-IPB, Rev 01, 09 February 2000

Chapter 53, Fuselage

BHT-206-SRM-1, Rev. 1, 04 April 1995

BHT-ALL-SPM, Reissue, 20 August 1999

PUBLICATIONS AFFECTED:

BHT-407-MM-5, Rev. 10, 16 February 2001

Chapter 53, Fuselage

BHT-407-IBP, Rev 01, 09 February 2000

Chapter 53, Fuselage

PART 1: IMPROVED INSTALLATION OF HORIZONTAL STABILIZER

1) Refer to Figure 1. Remove the lower left and right stabilizer support assemblies 

(1, 2) from the tailboom (5) and the stabilizer (6) and examine for condition.
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-NOTEIt is not necessary to disassemble the lower support angles 

(14,15) from the closure plates (16,17).

2) Use a plastic scrapper to remove any cured sealant or debris from faying 

surfaces of each support (1, 2).

-NOTEA thin strip of sealant installed at the factory covers the 

stabilizer attachment inserts to create a dissimilar metal

barrier. This strip of sealant is not necessary and can be 

removed after you have done this bulletin.

3) Refer to the Maintenance Manual, chapter 53, and remove the stabilizer (6) from 

the tailboom (5). Examine the stabilizer (6) for condition. 

4) Use a plastic scrapper to remove the cured sealant strips covering each row of 

inserts, which serve to attach the stabilizer (6) to the tailboom (5).

5) Use a plastic scrapper to remove any cured sealant or debris from attachment 

flanges of upper stabilizer supports (3, 4) riveted to tailboom (5).

6) Refer to Figure 1, View B-B. Install the stabilizer (6) into the tailboom (5). Use 

four screws (10) at hole locations #2 and #8 to temporarily secure the stabilizer 

(6) to the upper left and right supports (3, 4). Do not tighten the screws at this 

time.

-NOTEThe gap should be set using a feeler gauge and should be 

0.003 inch (0.08 mm) at the minimum gap location.

7) Hand tighten each screw (10) at hole locations #2 and #8 on each side of the 

tailboom (5) until you can run with slight restriction, a 0.003 inch (0.08 mm) feeler 

gage. Run the feeler gage between the stabilizer (6) and the horizontal flange of 

each support (3 and 4) along the full length and width of the attachment flange 

forward of screw #8. This 0.003 inch (0.08 mm) minimum clearance along the 

flange of each support will make sure that there is no preload condition.

-NOTEAn “L-shaped” riveted shim (18) (Ref. To Figure 1, view B-B, 

Detail C) may have been installed on the stabilizer (6) new 

from the factory or because of previous field accomplishment 
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of this procedure. If this “L-shaped” shim (18) interferes with 

the shimming procedure below, remove shim (18). The

instructions that follow will determine if a new “L-shaped” 

shim is needed. If “L-shaped” shim (18) is no longer

needed, plug unused rivet holes in trailing edge of the

stabilizer (6) with rivets MS20470AD3.

8) With the stabilizer (6) installed as per Step 6 and Step 7, measure gap between 

both upper supports (3, 4) and horizontal stabilizer (6) upper surface, aft of hole 

#8. Measure aft of screw at location #8 to the trailing edge of the stabilizer (6) 

and across full width of the attachment flange of upper support (3, 4).

a) If measured gap at the trailing edge area of the stabilizer (6) exceeds 0.085 inch 

(2.16 mm), contact Product Support Engineering for procedural guidance at the 

following;

Bell Helicopter Textron

Product Support Engineering

Tel: 1-800-243-6407 (Continental USA and Canada)

Tel: 1-800-363-8023 (Continental USA)

Tel: 1-800-361-9305 (within Canada)

Tel: 1-450-437-2862 (all other areas-call collect)

Fax: 1-450-433-0272

Internet: pselight@bellhelicopter.textron.com

b) If measured gap in the trailing edge area of the stabilizer (6) is less than 0.050 

inch (1.27 mm), the gap will be shimmed later using “shimming compound” (C322). Go to Step 9.

c) If measured gap at the trailing edge area of the stabilizer (6) is between 0.050 

inch (1.27 mm) and 0.085 inch (2.16 mm) maximum, remove the stabilizer (6) 

from the tailboom (5) and rework the trailing edge as follows; 

i. Refer to Figure 1, View B-B and Detail C. Fabricate a “L-shaped” solid shim 

(18) using the appropriate thickness of 2024T3 Al Alloy material. Taper the 

shim (18) as needed to fill the gaps measured earlier. The leg extending 

inboard must have a constant thickness equivalent to thickness of gap at 

inboard radius of upper support (3, 4), but no less than 0.015 inch. .

ii. Locate formed shim (18) in position on stabilizer (6) and drill for installation 

of additional MS20470AD3 rivets (Qty 2 each) as indicated in Detail C. 

Maintain proper rivet edge distance of 2D and spacing of 4 D minimum. 

iii. Transfer the existing #9 fastener hole (0.209 inch (5.30 mm) diameter) from 

the stabilizer (6) to the shim (18).
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iv. Remove the shim (18) and deburr all holes. Break all sharp edges and 

remove debris and loose material.

v. Prepare the upper surface of stabilizer (6) and the shim (18) in accordance 

with paragraphs 3-2-3 and 3-2-7 of the Structural Repair Manual (BHT-206-

SRM-1). Bond and secure the shim in place on the stabilizer using

adhesive (C-317) and rivets MS20470AD3 (grip length to suit). Remove 

excess adhesive squeeze-out and apply a pressure between 0.5 to 1.0 PSI 

before you let cure at room temperature for 24 hours. 

vi. Seal all the edges of the shim (18) with sealant (C-392) and let cure.

9) Do Steps 6, 7 and 8 again.

10) Attach each lower support assemblies (1, 2) to the tailboom (5) using the screws 

(13). Tighten each screw . Do not install the screws common to the stabilizer 

at this time. 

11) Verify that you have acceptable gaps between the stabilizer (6) and the

horizontal flange of the lower support angles 14, 15) as follows;

a) Run a 0.003 inch (0.08 mm) feeler gage, between the stabilizer (6) and the 

horizontal flange of each lower support assembly (1, 2). The feeler gage should 

be run along the full length and width of the attachment flange. This 0.003 inch 

(0.08 mm) minimum clearance along the flange of each support will make sure 

that there is no pre-load condition. 

b) Gaps must not exceed 0.050 inch (1.27 mm) at any location. 

c) If you cannot obtain a clearance between 0.003 inch (0.08 mm) and 0.050 inch 

(1.27 mm) do the following:

-NOTEYou can enlarge and slot the holes of the lower support

assemblies (1, 2), common to the tailboom skin only. Slot 

the holes as necessary in the upward direction perpendicular 

to the tailboom (5) only as shown in Figure 1 Detail D.

i. Increase in the affected lower support assembly (1, 2), all the existing .214 

inch (5.44 mm) diameter holes (qty. 18) that are common with the tailboom 

skin (5). Do not exceed a maximum diameter of .231 inch (5.87 mm). This 

will help to get clearance between the stabilizer (6) lower surface and the 

flange of the affected lower support.
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Page 7 of 23

ii. Install the reworked lower support assembly (1, 2) and do Step 11a and 

Step 11b. If you get a correct gap, go to Step 12.

iii. If more clearance is needed, slot all the holes (qty. 18) in the upward 

direction only, by an equal amount, not exceeding the 0.250-inch (6.35 mm) 

vertical dimension shown in Detail D. 

iv. Install the reworked lower support assembly (1, 2) and do Step 11a and 

Step 11b. If you get a correct gap, go to Step 12.

v. If you do not get a correct gap, replace the affected lower support (14, 15) in 

accordance with Part II of this bulletin (refer to 407 IPB for replacement part 

numbers) before you do Step 11a and 11b again.

12) Remove both lower support assemblies (1, 2) and the stabilizer (6) from tailboom 

(5).

13) Record the stabilizer (6) part number and serial number indicated on the

identification plate located on the upper surface, near the trailing edge of the 

stabilizer at BL 0.00.

CAUTION

DO NOT SOAK PARTS TO BE CLEANED WITH

CLEANER (M.E.K., ACETONE, ETC.). DO NOT EXPOSE 

BARE METAL.

14) Use a cloth moist with Acetone (C-316) to clean the upper and lower surfaces of 

the stabilizer.

15) Apply a strip of Teflon tape (C-460) over surfaces of the stabilizer (6) mating with 

the horizontal flanges of the upper and lower supports (1, 2, 3, 4) as follows;

a) The tape must be centered with each row of the stabilizer inserts.

b) The tape must be free of wrinkles or entrapped air bubbles after installation.

c) Do not puncture tape at any insert location.

16) Carefully abrade the primer coating on each horizontal flange of the upper

supports (3,4) and each lower support assemblies (1, 2), including bend radius 

area. Use a cloth moist with Acetone (C-316) to clean reworked areas.
TB 407-01-33

Page 8 of 23

17) Put the stabilizer (6) back into position through tailboom (5). Do not attach the 

stabilizer to the upper supports (3, 4) at this time, but leave it resting with 

adequate protection on lower edge of tailboom skin cutouts.

-NOTEA minimum quantity of 4 ounces (118 ml) is needed to do 

this modification on one aircraft. The pot life of the shimming 

compound (C-322) is approximately 1 hour.

18) Mix an acceptable quantity of shimming compound (C-322).

19) Apply a liberal amount of shimming compound (C-322) to the horizontal flange of 

each upper support (3, 4). The amount of shimming compound must be 

sufficient so that the squeeze-out, which will occur, will cover the inboard bend 

radius of each horizontal flange.

-NOTEDo not over tighten the screws (10). During the curing 

process, the screws (10) will be used for alignment purpose 

only.

CAUTION

DO NOT PUT EXCESSIVE PETROLATUM (C-008) ON

THE SCREWS (10) BECAUSE THIS CAN CONTAMINATE 

THE SHIMMING COMPOUND (C-322).

20) Apply a light layer of Petrolatum (C-008) to four screws (10) and four washers 

(11).

-NOTEA minimum of two persons is needed to do the following 

Steps.

-NOTEPuncture the Teflon tape (C-460) on the stabilizer (6) only 

where indicated, using applicable screw (10).

21) Slowly lift the stabilizer (6) close to the upper supports (3, 4) and install the

screws (10) and the washers (11), two per side, at the #2 and #8 hole locations. 

Use the screws (10) to make a hole in the tape (C-460). 
TB 407-01-33

Page 9 of 23

22) Engage each screw (10) between two to three threads maximum into the

stabilizer insert but do not tighten. The screw (10) through the Teflon tape (C460) creates a seal to prevent inserts contamination. Make sure that the surface 

of the stabilizer (6) does not contact the shimming compound (C-322) at this time 

or it may cause voids. The four screws (10) will support the stabilizer (6) away 

from the wet compound.

23) Apply a liberal amount of shimming compound (C-322) to horizontal flange of 

each lower supports assemblies (1, 2). The amount of shimming compound must 

be sufficient so that the squeeze-out, which will occur, will cover the inboard 

bend radius of each horizontal flange.

-NOTEDo not over tighten the screws (12). During the curing 

process, the screws (12) will be used for alignment purpose 

only.

CAUTION

DO NOT PUT EXCESSIVE PETROLATUM ON THE

SCREWS (12) AND THE WASHERS (11) BECAUSE THIS 

CAN CONTAMINATE THE SHIMMING COMPOUND (C322).

24) Apply a light layer of Petrolatum (C-008) to four screws (12) and four washers 

(11).

25) Install two screws (12) and two washers (11), through the #2 and #8 hole location 

of each flange of the lower support assemblies (1, 2).

26) Slowly lift each lower support assembly (1, 2) to the lower surface of the

stabilizer (6) but do not make contact at this time. Align each screw (12) with the 

mating insert of the stabilizer (6). Use each screw (12) to make a hole in the tape 

(C-460). Make sure that the compound (C-322) on the flange of each support 

assembly (1, 2) does not contact the stabilizer (6) at this time or it may cause 

voids.

27) Engage each screw (12) between two to three threads maximum into the 

stabilizer insert but do not tighten. The screw (12) through the Teflon tape (C460) creates a seal to prevent inserts contamination. The four screws (12) will 

not be tightened but will serve as alignment pins at this time. 

28) Use each lower support assembly (1, 2) to raise and counteract the weight of 

stabilizer. Raise the stabilizer (6) until the holes in the closure plates (16, 17) are 
TB 407-01-33

Page 10 of 23

in line with the holes in the tailboom skins (7, 8). Install the screws (13) to secure 

the lower support assemblies (1, 2). Torque each screw (13) .

-NoteDo not attempt to remove shimming compound (C-322) 

squeeze-out at bend radius of upper supports (3, 4) or lower 

support assemblies (1, 2).

29) Remove unwanted shimming compound (C-322) at all screw holes.

30) Clean edges of flanges of upper and lower supports (1, 2, 3, 4) as follows;

a) Make sure that the wet compound does not go beyond the edges of the 

Teflon tape (C-460), onto the stabilizer (6) surfaces.

b) Make sure that the wet compound (C-322) from upper and lower supports (1, 

2, 3, 4) do not mate together at the leading and trailing edge locations or it will 

bond parts with each other. 

-NOTEAccelerated cure can be achieved by using 150 Deg F (66 

Deg C) for 2 hours.

31) Let the shimming compound (C-322) to cure at room temperature for 16 hours 

minimum. 

32) After the adhesive has cured, delicately remove lower support assemblies (1, 2) 

and the stabilizer (6) from the tailboom (5).

33) Examine the cured shimming compound (C-322) on horizontal flange of each

supports (1, 2, 3, 4) for condition as follows;

a) The cured compound must cover the inboard bend radius and all mating 

surfaces. 

b) Small pinholes or porosity are acceptable.

c) Small void areas no bigger than 0.15-inch (3.81 mm) diameter and 1 inch 

(25.4 mm) apart or more are acceptable. If voids exist in excess of these 

limitations, remove cured compound (C-322), clean the flange and do the 

shimming procedure again.

d) The compound must not exceed 0.050 inch (1.27 mm) thick at any

location except in bend radius area. If the maximum thickness is

exceeded, replace lower support unit in accordance with Part II before you 

do Steps 14 through 33 again.
TB 407-01-33

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CAUTION

IF A POWER DEVICE (EXAMPLE: ROTARY OR BELT

SANDER) IS USED TO TRIM THE SHIMMING

COMPOUND (C-322), MAKE SURE YOU DO NOT

DAMAGE THE BEND RADIUS OF THE SUPPORTS (1, 2, 

3, 4).

34) Remove the cured shimming compound (C-322) that is in excess at each bend 

radius and outboard edges of the supports (1, 2, 3, 4).

35) Clean all screw holes in the flange of each support (1, 2, 3, 4). Footprint of 

stabilizer inserts in shimming compound may be visible and can serve as a 

reference to clean the shimming compound (C-322) in the flange of each

support.

-NOTEDo not prime the cured shimming compound (C-322).

36) Refinish all bare metal surfaces on each support (1, 2, 3, 4) using primer (C-204). 

Let primer dry.

37) Cover the cured shimming compound (C-322) of each support (1, 2, 3, 4) with a 

strip of Teflon tape (C-460). Trim tape to match the faying surface of each 

horizontal flange. Puncture the tape for each screw holes. 

38) Remove the Teflon tapes (C-460) from the stabilizer (6).

CAUTION

AFTER THE SHIMMING PROCEDURE IS DONE, THE

STABILIZER ASSEMBLY (6), THE TAILBOOM

ASSEMBLY (5) AND THE ATTACHMENT SUPPORTS (1, 

2, 3, 4) ARE CONSIDERED A MATCHED SET. THE

TAILBOOM ASSEMBLY (5), THE STABILIZER

ASSEMBLY (6) AND/OR THE LOWER ATTACHMENT

SUPPORT ASSEMBLIES (1,2) ARE NOT

INTERCHANGEABLE BETWEEN AIRCRAFT, UNLESS

THIS SHIMMING PROCEDURE IS REPEATED.

39) Refer to Figure 2, Detail F. Use a pen and mark two identification plates (19) with 

the appropriate information as follows;

a) Mark the first line of each plate (19) to read: “THIS PART IS MATCHED 

SET TO”.
TB 407-01-33

Page 12 of 23

b) Mark the second line to read: “TAILBOOM P/N AND S/N REF”.

c) Mark the third and fourth line of each plate (19) to show the existing 

tailboom part number and serial number respectively 

d) Mark the fifth line to read: “HORIZONTAL STABILIZER P/N AND S/N 

REF”.

e) Mark the sixth and seventh line of each plate (19) to show the existing 

horizontal stabilizer part number and serial number respectively.

f) Install the identification plates (19) on each support at location indicated 

by Figure 2, Detail E.

40) Refer to Figure 2, Detail G. Use a pen and mark one identification plate (19) with 

the appropriate information as follows; 

a) Mark the first line of the plate (19) to read: “THIS PART IS MATCHED 

TO”.

b) Mark the second line to read: “TAILBOOM P/N AND S/N REF”.

c) Mark the third and fourth line of the plate (19) to show the existing 

tailboom part number and serial number respectively.

d) Leave the fifth, the sixth and seventh lines of the plate (19) 

unmarked.

e) Install plate (19) on upper surface of the stabilizer (6) at the 

area shown in Figure 2, View H.

CAUTION

MAKE SURE THAT ALL SCREWS MS27039-1-05 USED 

TO ATTACH THE STABILIZER (6) TO THE TAILBOOM (5) 

ARE THE CORRECT AND IDENTICAL LENGTH AT ALL 

LOCATIONS. IF TOO LONG A SCREW IS USED, IT MAY 

PUNCTURE AN INSERT AND THE INSERT WILL NEED 

TO BE REPLACED.

-NOTEMake sure that there is no debris inside the insert of the 

stabilizer (6).
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Page 13 of 23

41) Before you install the stabilizer (6), install a screw (10) in each insert of the 

stabilizer (6). Tighten each screw (10) until they bottom out in the insert but do 

not exceed 25 inch/lbs of torque.

a) Measure the gap between the underside of each screw head and the upper 

surface of the insert. 

b) A gap of less than 0.063 inch (1.60 mm) for each insert location is

acceptable. This will make sure that a proper clamp-up of the stabilizer (6) 

by each supports (1, 2, 3, 4) will be obtained. Go to Step 42.

c) A gap at any insert location in excess of 0.063 inch (1.60 mm) is not 

acceptable. Contact Product Support Engineering with details before you 

continue with the installation of the stabilizer (6).

42) Use the sequence that follows to permanently install the stabilizer (6) to the 

tailboom (5);

a) Attach the stabilizer (6) loosely to each upper support (3, 4), using the 

screw (10) and the washer (11) (Qty. 16 each).

b) Attach each lower support assembly (1, 2) loosely to the stabilizer (6) and 

the tailboom (5) using the screw (12) and the washer (11) (Qty. 16).

c) Tighten the screws (10) attaching the stabilizer (6) to each upper support 

(3, 4) first. 

d) Tighten the screws (12) attaching the stabilizer (6) to the horizontal 

flange of each lower support assembly (1, 2).

e) Tighten the screws (13) common to the tailboom skins (7, 8) last. 

f) Complete the installation by installing the aft screw, nut and washer (9) at 

the most aft hole location on each side of the tailboom (5). 

43) Apply a bead of sealant (C-392) to seal outboard edges of upper & lower

supports (3, 4 1 and 2) and gaps forward of stabilizer leading edge and aft of 

stabilizer trailing edge. Allow sealant to cure.

44) Restore the primer (C-204) and aircraft paint finish as required.

45) Annotate aircraft technical records to indicate that you completed this Technical 

Bulletin.
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PART II: Replacement of lower support angles (14 or 15).

-NOTEDo this part only if you cannot get an acceptable gap

between the upper or lower supports (1, 2, 3, 4) and the 

stabilizer (6) surface.

1) Remove the affected lowers support assembly (1,2) from the tailboom (5).

2) Remove all the rivets that hold the support angle (14, 15) to the mating closure 

plate (16,17). Separate parts and discard the drilled support (14,15).

3) Install the closure plate (16,17) onto the tailboom (5) and secure in place with the 

screws (13). Tighten each screw . .

4) Put the new angle (14,15) in position against the lower surface of the stabilizer (6) 

and the outboard face of the closure plate (16 or 17).

-NOTEBHT recommends that you create an artificial gap to help 

with the shimming process described in Part I. Insert a strip 

of 2024T3 Al Alloy (1 inch wide X 2 inches long X 0.010 inch 

maximum thick (25.4 mm X 50.8 mm X .254 mm thick)) at 

two locations between flange of support angle (14,15) and 

lower surface of stabilizer (6).

5) Find the best fit with a 0.003 to 0.010 inch (0.08 to .254 mm) clearance between 

the stabilizer lower surface and the flange of the lower angle. Hold this position 

while you mark with a fine tip felt pen on the horizontal flange of the angle, the 

center location of the 8 holes that will be in line with the center of each insert in 

the stabilizer (6). 

6) Mark the outline of the outer edge of the support angle (13, 14) onto the closure 

plate (16, 17) and draw one line near the front end of the angle (13, 14) running 

vertically through the lower edge of the angle, extending onto the closure plate 

(16, 17). Draw a similar line near the aft end of the angle (16, 17).

7) Remove the support angle (14 or 15) and the closure plate (16 or 17).

8) Use the marks that were made in Step 6 to align the support angle (14,15) with 

the closure plate (16,17) and clamp both parts together.

9) Use a drill #20 (0.160 inch (4.09 mm) diameter) to transfer the 20 rivet holes 

from the closure plate (16, 17) to the support angle (14,15).
TB 407-01-33

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10) Use a drill #4 (0.209 inch (5.30 mm) diameter) to transfer the front and aft screw 

holes from the closure plate (16, 17) to the support (14, 15).

11) Use a #40 drill (0.098 inch (2.49 mm) diameter) to pilot drill the centerline of 

each marks made earlier on the horizontal flange of the support angle (14, 15). 

12) Use a #4 drill (0.209 inch (5.30 mm) diameter) to increase to final size, the 9 

holes in the horizontal flange of the support angle (14, 15). Deburr all holes.

13) Coat the faying surface of the support (14, 15) that will mate with the closure 

plate (16, 17) with a thin layer of sealant (C-392) and assemble both parts using 

20 rivets MS20470AD5.

14) Let sealant cure and prime all bare metal surfaces using primer (C-204).

15) Install the new support assembly (1, 2) and do Part I of this bulletin.
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Figure 1. Horizontal Stabilizer Installation Procedure (sheet 1 of 8).
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Figure 1. Horizontal Stabilizer Installation Procedure (sheet 2).
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Figure 1. Horizontal Stabilizer Installation Procedure (sheet 3).
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Figure 1. Horizontal Stabilizer Installation Procedure (sheet 4).
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Figure 1. Horizontal Stabilizer Installation Procedure (sheet 5).
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Figure 1. Horizontal Stabilizer Installation Procedure (sheet 6).
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Figure 1. Horizontal Stabilizer Installation Procedure (sheet 7).
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Figure 1. Horizontal Stabilizer Installation Procedure (sheet 8).