MANDATORY

SERVICE BULLETIN
Beech

TITLE: FUSELAGE - INSTALLATION OF DRAIN HOLES IN THE MIXER BAY PANELS

1. Planning Information
A. Effectivity

(1) Airplanes
PART I - DRILLING OF FIVE DRAIN HOLES IN EACH SPOILER MIXER BAY ACCESS PANEL
(a) Civil
Raytheon Aircraft Model 400 Beechjet, Serials RJ-1 through RJ-65;
Raytheon Aircraft Model 400A Beechjet, Serials RK-1 through RK-308, RK-310, RK-311, RK-
313, and RK-314.
(b) Military
Raytheon Aircraft Model 400T (T-1A) Beechjet, Serials TT-1 through TT-180;
Raytheon Aircraft Model 400T (TX) Beechjet, Serials TX-1 through TX-10.
(c) Spares
All spares installed on Model MU-300 airplanes with the following Part Numbers: 45A33673-11,
45A33673-12, 45A33673-21, 45A33673-22, 45A33673-32, 45A33673-42, 45A33673-52,
45A33673-621, 45A33673-642, and 45A33673-652 access panels. Spares in stock should be
reworked prior to installation.
PART II - DRILLING OF ONE ADDITIONAL DRAIN HOLE IN EACH SPOILER MIXER BAY ACCESS
PANEL
(a) Civil
Mitsubishi Aircraft Model MU-300, Serials A003SA through A091SA;
Raytheon Aircraft Model 400A Beechjet, Serials RK-309, RK-312, and RK-315 through RK-328.

The export of these commodities, technology or software are subject to the US Export Admin- (a) RAC Authorized Service Centers.
istration Regulations. Diversion contrary to U.S. law is prohibited. For guidance on export
control requirements, contact the Commerce Department’s Bureau of Export Administration (b) Owners of record on the FAA Aircraft Registration Branch List and the RAC
at 202-482-4811 or at www.bxa.doc.gov. International Owner Notification/Registration Service List.
Raytheon Aircraft Company (RAC) issues Service Information for the benefit of owners and (c) Those having a publications subscription.
fixed base operators in the form of two classes of Service Bulletins. The first class, Information on Owner Notification Service or subscription can be obtained through any RAC
Mandatory Service Bulletins (red border) includes changes, inspections and modifications Authorized Service Center. As Mandatory Service Bulletins and Service Bulletins are issued,
that could affect safety or crashworthiness. RAC also issues Service Bulletins with no red temporary notification in the Service Bulletin Master Index should be made until the index is
border which are designated as either recommended or optional in the compliance section revised. Warranty will be allowed only when specifically defined in the Service Bulletin and in
within the bulletin. In the case of recommended Service Bulletins, RAC feels the changes, accordance with the RAC Warranty Policy.
modifications, improvements or inspections will benefit the owner/operator and although
highly recommended, Recommended Service Bulletins are not considered mandatory at the Unless otherwise designated, RAC Mandatory Service Bulletins, Service Bulletins and RAC
time of issuance. In the case of Optional Service Bulletins, compliance with the changes, Kits are approved for installation on RAC airplanes in original or RAC modified
modifications, improvements or inspections is at the owner/operator’s discretion. Both configurations only. RAC Mandatory Service Bulletins, Service Bulletins and Kits may not
classes are mailed to: be compatible with airplanes modified by STC installations or modifications other than RAC
approved kits.

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(b) Military
Raytheon Aircraft Model 400T (TX) Beechjet, Serials TX-11 and TX-12.
(c) Spares
None.
PART III - ADDITION OF SEALANT AT FS 322.44 BULKHEAD AND LBL 19.13 BAFFLES ON LH
PANEL AND RBL 10.43 ON RH PANEL:
(a) Civil
Mitsubishi Aircraft Model MU-300, Serials A003SA through A091SA;
Raytheon Aircraft Model 400 Beechjet, Serials RJ-1 through RJ-65;
Raytheon Aircraft Model 400A Beechjet, Serials RK-1 through RK-308, RK-310, RK-311, RK-
313 through RK-315.
(b) Military
Raytheon Aircraft Model 400T (T-1A) Beechjet, Serials TT-1 through TT-180;
Raytheon Aircraft Model 400T (TX) Beechjet, Serials TX-1 through TX-10.
(c) Spares
All MU-300 spares installations with the following Part Numbers: 45A33673-11, 45A33673-12,
45A33673-21, 45A33673-22, 45A33673-32, 45A33673-42, 45A33673-52, 45A33673-621,
45A33673-642, and 45A33673-652 access panels. Spares in stock should be reworked prior to
installation.
If you are no longer in possession of the airplane, please forward this information to the present
owner.
B. Reason

Raytheon Aircraft Company (RAC) has received an operator report of fuel odor in the aft baggage
compartment. Fuel leakage from the motive flow shutoff valve is suspected of being the source of the fuel
leakage. A subsequent investigation by RAC revealed that both the left and right spoiler bay mixer panels
did not incorporate required drain holes per type design.
This Service Bulletin is being issued to provide required fuselage drain holes in the lower fuselage spoiler
mixer bay access panels. It also prescribes the application of fuel-resistant sealant to the relief cutout area
at BL 0.0 on the FS 322.44 aft pressure bulkhead and the baffles at LBL 19.13 on the LH panel and at RBL
10.43 on the RH panel to reduce fire/explosion potential.
C. Description

The left and right P/N 45A33673-XXX spoiler mixer bay access panels (Mid-Fuselage Access Panels) are
inspected for the presence of 0.236 to 0.276 inch-diameter drain holes. If no holes are present, they are
drilled. An additional drain hole is added to the panels that have preexisting holes (for a total of five drain
holes). Voids or inadequate sealant at the BL 0.0 relief cutout on the FS 322.44 (8190) aft pressure
bulkhead are filled with MIL-S-8802, Type II sealant. The baffles at LBL 19.13 on the LH panel and at RBL
10.43 on the RH panel are sealed with MIL-S-8802, Type II sealant.

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D. Compliance

An Airworthiness Directive will be requested on the matter covered by this Service Bulletin.
(1) Civil Airplanes
Raytheon Aircraft Company considers this to be a mandatory modification and it should be
accomplished at the next scheduled inspection not to exceed 400 flight hours after receipt of this
Service Bulletin, but no later than 12 months, whichever occurs first.
(2) Military Airplanes
For compliance information on military airplanes affected by this Service Bulletin, contact the
appropriate headquarters.
E. Approval

The engineering data contained in this Service Bulletin is FAA approved.

F. Manpower

The following information is for planning purposes only:

Estimated man-hours for drilling task: 2.5 hours.
Estimated man-hours for sealing task: 0.5 hour.
Suggested number of men: 1 man.
The above is an estimate based on experienced, properly equipped personnel complying with this Service
Bulletin. Occasionally, after work has started, conditions may be found which could result in additional
man-hours.

G. Weight and Balance

None.

H. Electrical Load Data

Not changed.

I. Software Accomplishment Summary

Not applicable.

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J. References

Mitsubishi MU-300 Maintenance Manual, P/N MR-0462 or subsequent revision;

Mitsubishi MU-300 Structural Repair Manual, P/N MR-0468-2 or subsequent revision;
Raytheon Aircraft Beechjet 400/400A Maintenance Manual, P/N 128-590001-9C1 or subsequent revision,
Chapters 6-50, 20-40, 25-00, and 53-30;
Raytheon Aircraft Beechjet 400/400A Structural Repair Manual, P/N 128-590001-17C5 or subsequent
revision, Chapter 51-00;
BEECH Beechjet 400T(T-1A) Corrosion Control Manual, TO 1T-1A-23;
BEECH Beechjet 400T(T-1A) Technical Manual Job Guide, TO 1T-1A-2-53JG-30-1;
BEECH Beechjet 400T(T-1A) Structural Repair Manual, TO 1T-1A-3;
Raytheon Aircraft Beechjet 400T(TX) Aircraft appropriate Japanese Defense Agency (JDA) Technical
Manuals.
K. Publications Affected

It is recommended that a note “See Service Bulletin No. 53-3486” be made in the following:
Mitsubishi MU-300 Maintenance Manual, P/N MR-0462 or subsequent revision;
Mitsubishi MU-300 Structural Repair Manual, P/N MR-0468-2 or subsequent revision;
Mitsubishi MU-300 Illustrated Parts Catalog, P/N MR-0465-1 or subsequent revision;
Raytheon Aircraft Beechjet 400/400A Illustrated Parts Catalog, P/N 128-590001-11F or subsequent
revision, Chapter 52-10;
Raytheon Aircraft Beechjet 400/400A Maintenance Manual, P/N 128-590001-9C1 or subsequent revision,
Chapter 6-50, 25-00, and 53-30;
Raytheon Aircraft Beechjet 400/400A Structural Repair Manual, P/N 128-590001-17C5 or subsequent
revision, Chapter 51;
BEECH Beechjet 400T(T-1A) Corrosion Control Manual, TO 1T-1A-23;
BEECH Beechjet 400T(T-1A) Illustrated Parts Breakdown, TO 1T-1A-4-53;
BEECH Beechjet 400T(T-1A) Technical Manual Job Guide, TO 1T-1A-2-53JG-30-1;
BEECH Beechjet 400T(T-1A) Storage of Aircraft, TO 1T-1A-17;
BEECH Beechjet 400T(T-1A) Structural Repair Manual, TO 1T-1A-3;
Raytheon Aircraft Beechjet 400T(TX) Aircraft appropriate Japanese Defense Agency (JDA) Technical
Manuals.
L. Interchangeability of Parts

Not applicable.

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M. Warranty Credit

(1) Civil Airplanes

Warranty credit for labor only to the extent noted under MANPOWER and MATERIAL will be allowed
on all affected airplanes.
Warranty coverage offered in this Service Bulletin will expire 12 months from the last day of the
month this Service Bulletin is issued. After that date, the owner/operator assumes the responsibility
for compliance cost. Raytheon Aircraft Company reserves the right to void warranty coverage in the
area affected by this Service Bulletin until the date the Service Bulletin is accomplished by a
Raytheon Aircraft Company Authorized Service Center.
All warranty work must be accomplished by a Raytheon Aircraft Authorized Service Center rated to
perform maintenance on the specific model of Beech Airplane.
All warranty reimbursements are handled through Raytheon Aircraft Company Authorized Service
Centers. The owner/operator should arrange for an Authorized Service Center to perform the work
and the Authorized Service Center must submit the standard Raytheon Aircraft Company warranty
claim.
(2) Military Airplanes
For warranty information on military airplanes affected by this Service Bulletin, contact the
appropriate headquarters.

2. Material Information
A. Materials - Price and Availability

Contact a Raytheon Aircraft Authorized Service Center for information.

B. Industry Support

Not applicable.

C. Airplanes

The following parts required for this modification may be ordered through a Raytheon Aircraft Authorized
Service Center, RAPID, or may be obtained locally:

Part Number Quantity Per

Description
Airplane

A-A-58054 (Scotchbrite - Abrasive Pads As Required

Product of 3M, St. Paul, MN
55144) or equivalent

ASTM D239 Acetone As Required

TT-N-95, Type II Aliphatic Naphtha As Required

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Part Number Quantity Per
Description
Airplane

MIL-C-5541 or MIL-DTL- Chemical Conversion Coating for Aluminum As Required

81706 (Alodine 1200, and Aluminum Alloys
1200S, 1201, or equivalent)

CCC-C-440, A-A-1491, or Cotton Cheesecloth As Required

equivalent

No. 312X (NSN 8415-01- Cotton Gloves, White, Lint-Free As Required

211-7178)(Obtain from John
Plant Company, P.O. Box
527, Ramseur, NC 27316 or
Eastman Kodak Company,
343 State Street, Rochester,
NY 14650)

MIL-P-23377 or equivalent Epoxy Polyamide Primer As Required

TS-1480 Fairing and Cutting Tools, Sealant As Required

BMS 10-20G or 454-4-1 Fuel Cell Epoxy Coating/Primer As Required

(Obtain from Dexter
Corporation, Adhesive and
Coating Systems, 2850
Willow Pass Road, Bay
Point, CA 94565-0031

A-A-53513 or equivalent or Gloves, Polyethylene, Industrial, As Required

P/N 187 7711 (Obtain from Solvent Handling
Eastman Kodak Company,
343 State Street, Rochester,
NY 14650)

TT-I-735A Isopropyl Alcohol As Required

A-A-2758, ASTM-D4236, or Marker, Tube Type, Felt Tip, Nonpermanent Ink As Required
equivalent (or equivalent)

Obtain from Barton Methyl Propyl Ketone As Required

Solvents, 201 S. Cedar,
Valley Center, KS 67147 or
Eastman Chemical
Products, Inc., P.O. Box 431,
Kingsport, TN 37662

DOD-R-003081 Rags As Required

ANSI B74.18 Sandpaper, 100 Grit As Required

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Part Number Quantity Per
Description
Airplane

Make from L-P-513, Type Scraper, Plexiglas or Hardwood, As Required

PBE-P, L-P-391, Type I, Locally Manufactured for Sealant
Grade C Plexiglas, or MM-L- Removal, Cutting, and Shaping
736 Hard Maple Lumber
(Wood Tongue Depressor)

MIL-S-8802, Type II Sealant, Fuel Cell As Required

(PR-1440, MC-236, or
equivalent)

MIL-PRF-85285 or Paint, Touchup As Required

equivalent

Raytheon Aircraft Company expressly reserves the right to supersede, cancel and/or declare obsolete,
without prior notice, any parts or publications that may be referenced in this Service Bulletin.

D. Spares

None.
E. Reidentified Parts

None.
F. Tooling - Price and Availability

Not applicable.

3. Accomplishment Instructions
This Service Bulletin shall be accomplished as follows:

NOTE
Should any difficulty be encountered in accomplishing this Service Bulletin,
contact Raytheon Aircraft Company at 1-800-429-5372 or 316-676-3140 for
commercial aircraft, and appropriate headquarters for military aircraft.

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A. Airplane

Observe all Warnings and Cautions contained in the aircraft manuals

referred to in this Service Bulletin.

Whenever any part of this system is dismantled, adjusted, repaired or

renewed, detailed investigation must be made on completion to make sure
that distortion, tools, rags or any other loose articles or foreign matter that
could impede the free movement and safe operation of the system are not
present, and that the systems and installations in the work area are clean.

PART I - COMMERCIAL AIRPLANES - MODELS MU-300, 400, AND 400A

(1) Remove all power from the airplane and disconnect the battery. Display warning notices prohibiting
reconnection of airplane electrical power.
(2) Refer to Figure 1 and Figure 2 for locations and inspect for the presence of drain holes in the lower
Fuselage Access Panels (311AB and 312AB Covers). If five drain holes are present, proceed to step
(5) for determination of presence of sealant at FS 322.44 (FS 8190) aft pressure bulkhead relief
cutout and LBL 19.13 (LBL 486) and RBL 10.43 (RBL 265) baffles. If less than five drain holes are
present, proceed to step (3) for instructions to locate, drill, and treat the new hole location(s).
(3) Accomplish the following procedures to mark, drill, and treat drain hole(s):

NOTE
At the technician’s option, procedures may be accomplished on one side of the
airplane and then repeated on the opposite side, or similar operations may be
worked concurrently.

NOTE
If some drain holes already exist, mark locations only for missing drain holes. A
total of five drain holes in each Spoiler Mixer Bay access panel location is
required.
(a) Remove the Fuselage Access Panel(s) (311AB and 312AB Covers) and place in suitable work
area. Refer to the appropriate airplane Maintenance Manual.
(b) Refer to Figure 3 and locate the access doors (311BB and 312BB) and required locations of
drain holes. Mark each 0.236 to 0.276 (1/4”) inch-diameter drain hole location using an A-A-
2758 or equivalent nonpermanent marking pen.

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Use care when drilling to avoid overdrilling and damaging surrounding structure or
components.

(c) Using a 1/4” drill bit and a drill stop set to 0.375 inch depth, drill drain holes at the locations
marked in the previous step.
(d) Deburr edges of each hole.
(e) Remove debris from the rework area.

Solvents are flammable and toxic to skin, eyes, and respiratory tract. Avoid
eye and repeated skin contact. Use in a well-ventilated area. Keep away from
sparks and flames.

(f) Clean the rework area with suitable solvent (TT-N-95, Type II aliphatic naphtha, ASTM D239
acetone, TT-I-735A isopropyl alcohol, or methyl propyl ketone) and CCC-C-440 clean cotton
cheesecloth to remove grime, oily films, and other contaminants. Use nonmetallic, non-woven
A-A-58054 (Scotchbrite or equivalent) abrasive pads and TT-N-95, Type II aliphatic naphtha or
equivalent solvent to remove tough foreign contaminants such as grease, oil, water-based grime,
mud, etc. Wipe the surface dry with clean cotton cheesecloth. Repeat cleaning procedures until
a waterbreak-free surface is achieved. Refer to the appropriate airplane Maintenance Manual.

Chemical conversion coating (Alodine) may affect skin, eyes, and

respiratory tract. Chemical goggles and neoprene gloves should be worn.
Use in a well-ventilated area.

(g) Apply Alodine 1200, 1200S, or 1201 (MIL-C-5541) Chemical Conversion Coating to the edges of
the holes and all bare surfaces. Allow the Alodine to dwell for approximately five minutes. After
the dwell time has elapsed, wash the treated area with water, and blot away water with clean
cotton cheesecloth or blow dry (do not wipe dry). Refer to the appropriate airplane Maintenance
Manual.

Many paints, primers, and top coatings are flammable and toxic to skin,
eyes and respiratory tract. Eye, skin, and respiratory protection is required.

(h) After Alodine 1200, 1200S, or 1201 (MIL-C-5541) Chemical Conversion Coating has dried, apply
a coat of MIL-P-23377 Epoxy Polyamide Primer or equivalent primer to the treated edges of the
hole and any bare metal surfaces previously treated with Alodine. Allow adequate drying time.

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(i) Apply appropriate color of top coat finish over the primer coat. Allow adequate drying time.
(4) Repeat steps (3)(a) through (i) to rework the opposite Fuselage Access Panel if both sides are not
reworked concurrently.
(5) Inspect for presence of sealant in the relief cutout area at the FS 322.44 (FS 8190) aft pressure
bulkhead area as shown in Figure 4. Also, refer to Figure 3, Detail B (both LH and RH Panels) and
inspect for presence of sealant around the small triangular-shaped baffles (dog ears) at LBL 19.13
(LBL 486) and RBL 10.43 (RBL 265). If sealant is present in both locations, skip steps (5) (a) through
(f) below and proceed to step (6). If sealant is missing or inadequate at either location, accomplish
the following as required:

NOTE
In step (5) above, an inadequate sealant condition is defined as sealant applied to
an unclean surface that does not adhere properly, sealant that is flaking or
peeling, or sealant that has voids, gaps, or pin holes.
(a) Clean surfaces where sealant is required with appropriate solvent (TT-N-95, Type II aliphatic
naphtha, ASTM D239 acetone, TT-I-735A isopropyl alcohol, or Methyl Propyl Ketone). Use CCC-
C-440 cheesecloth or DOD-R-003081 wiping rags dampened with solvent to wipe up foreign
contaminants. For tough foreign contaminants such as grease, oil, water-based grime, mud, etc.,
it may be necessary to use solvent and A-A-58054 (Scotchbrite or equivalent) abrasive pads.
Wipe the surface dry with clean cotton cheesecloth or clean wiping rags.
(b) Repeat step (a) above as required to obtain a satisfactory waterbreak-free bond surface.

Sealants and adhesives present a health hazard. Many sealants are

flammable and/or moderately toxic to eyes, skin, and respiratory tract. Wear
skin and eye protection. Wear protective gloves when handling sealant.
Avoid repeated contact. Wash hands thoroughly after use and before eating,
drinking, or smoking. Good ventilation or exhaust ventilation is required for
work in enclosed space or use breathing apparatus.

Adhere to sealant manufacturer’s instructions for mixing and applying

sealant.

(c) Mix sealant (MIL-S-8802, Type II, PR-1440, or MC-236) in accordance with sealant
manufacturer’s instructions.

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(d) Use a sealer gun, spatula, sealant-filled syringe, or wood tongue depressor to apply sealant to
the relief cutout area in the FS 322.44 (FS 8190) aft pressure bulkhead area at BL 0.00. Apply
sealant along seams and around fasteners. Apply sufficient sealant such that cavities are filled
and squeeze-out is observed. Also, use a sealer gun, spatula, or wood tongue depressor to
apply sealant to the area around the small triangular-shaped baffles (dog ears) at LBL 19.13
(LBL 486) on the P/N 45A33673-XXX LH Spoiler Mixer Bay Access Panel and at RBL 10.43
(RBL 265) on the P/N 45A33673-XXX RH Spoiler Mixer Bay Access Panel. Refer to the
appropriate airplane Maintenance Manual.
(e) Inspect for and fill voids in sealant. Refer to Chapter 20-40-00 of the airplane Maintenance
Manual. Use locally obtained fairing sealant tools to fair along the edges of parts and form a fillet
seal. Use a solvent-dampened cloth to clean up excess sealant.
(f) Allow adequate sealant drying time. Sealant drying time and full cure times are dependent on
the class of sealant used (i.e. B1/2, B2, B4, etc.).
(6) Install Fuselage Access Panels (311AB/312AB Access Covers), if removed for rework.
(7) Reconnect the airplane battery, remove warning notices, and restore power.
(8) Ensure all work areas are clean and clear of tools and miscellaneous items of equipment.
(9) Return airplane to service.
PART II - MILITARY AIRPLANES - MODELS 400T(T-1A) AND 400T(TX)
(1) Accomplish Make Safe for Maintenance procedures (05-00-01) and disconnect the battery (05-01-
09). Refer to TO 1T-1A-2-05JG-00-1 or appropriate JDA Technical Manual.
(2) Refer to Figure 1 for locations and inspect for the presence of drain holes in the lower Mid-Fuselage
(Spoiler Mixer Bay) Access Panels (324LL/LR). If five drain holes are present, proceed to step (5) for
determination of presence of sealant at FS 322.44 (FS 8190) aft pressure bulkhead relief cutout and
LBL 19.13 (LBL 486) and RBL 10.43 (RBL 265) baffles. Refer to Figure 1. If less than five drain holes
are present, proceed to step (3) for instructions to locate, drill, and treat the new hole location(s).
(3) Accomplish the following procedures to mark, drill, and treat drain holes:

NOTE
At the technician’s option, procedures may be accomplished on one side of the
airplane and then repeated on the opposite side, or similar operations may be
worked concurrently.

NOTE
If some drain holes already exist, mark locations only for missing drain holes. A
total of no more than five drain holes at the mixer bay panel location is required.
(a) Remove the Mid-Fuselage Access Panel(s) (324LL/LR) (53-30-14-003) and place in suitable
work area. Refer to TO 1T-1A-2-53JG-30-1 or appropriate JDA Technical Manual.

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(b) Refer to Figure 3 and locate the Mid-Fuselage Access Panels (324 LL/LR) and required
locations of drain holes. Mark each 0.236 to 0.276 (1/4”) inch-diameter drain hole location using
an A-A-2758 or equivalent nonpermanent marking pen.

Use care when drilling to avoid overdrilling and damaging surrounding structure or
components.

(c) Using a 1/4” size drill bit and a drill stop set to 0.375 inch depth, drill drain holes at the locations
marked in the previous step.
(d) Deburr edges of each hole.
(e) Remove debris from the rework area.

Solvents are flammable and toxic to skin, eyes, and respiratory tract. Avoid
eye and repeated skin contact. Use in a well-ventilated area. Keep away from
sparks and flames.

(f) Clean the rework area with TT-N-95, Type II aliphatic naphtha, methyl propyl ketone or other
suitable solvent and CCC-C-440 clean cotton cheesecloth to remove grime, oily films, and other
contaminants. Use nonmetallic, non-woven A-A-58054 (Scotchbrite or equivalent) abrasive pads
and TT-N-95, Type II aliphatic naphtha or equivalent solvent to remove tough foreign
contaminants such as grease, oil, water-based grime, mud, etc. Wipe the surface dry with clean
cotton cheesecloth. Repeat cleaning procedures until a waterbreak-free surface is achieved.

Chemical conversion coating (Alodine) may affect skin, eyes, and

respiratory tract. Chemical goggles and neoprene gloves should be worn.
Use in a well-ventilated area.

(g) Apply Alodine 1200, 1200S, or 1201 (MIL-C-5541) Chemical Conversion Coating to the edges of
the holes and all bare surfaces. Allow the Alodine to dwell for approximately five minutes. After
the dwell time has elapsed, wash the treated area with water, and blot away water with clean
cotton cheesecloth or blow dry (do not wipe dry).

Many paints, primers, and top coatings are flammable and toxic to skin,
eyes and respiratory tract. Eye, skin, and respiratory protection is required.

(h) After Alodine 1200, 1200S, or 1201 (MIL-C-5541) Chemical Conversion Coating has dried, apply
a coat of MIL-P-23377 Epoxy Polyamide Primer or equivalent primer to the treated edges of the
hole and any bare metal surfaces previously treated with Alodine. Allow adequate drying time.

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(i) Apply appropriate color of top coat finish over the primer coat. Refer to TO 1T-1A-23 or
appropriate JDA Technical Manual. Allow adequate drying time.
(4) Repeat steps (3) (a) through (i) to rework the opposite Mid-Fuselage Access Panels (324 LL/LR) (if
not reworked concurrently).
(5) Inspect for presence of sealant in the relief cutout area at the FS 322.44 (FS 8190) aft pressure
bulkhead area as shown in Figure 4. Also, refer to Figure 3, Detail B (both LH and RH Panels) and
inspect for presence of sealant around the small triangular-shaped baffles (dog ears) at LBL 19.13
(LBL 486) and RBL 10.43 (RBL 265). If sealant is present in both locations, proceed to step (6). If
sealant is missing or inadequate in either location, accomplish the following as required:

NOTE
In step (5) above, an inadequate sealant condition is defined as sealant applied to
an unclean surface that does not adhere properly, sealant that is flaking or
peeling, or sealant that has voids, gaps, or pin holes.
(a) Clean surfaces where sealant is required with appropriate solvent (TT-N-95, Type II aliphatic
naphtha, ASTM D239 acetone, TT-I-735A isopropyl alcohol, or Methyl Propyl Ketone). Use CCC-
C-440 cheesecloth or DOD-R-003081 wiping rags dampened with solvent to wipe up foreign
contaminants. For tough foreign contaminants such as grease, oil, water-based grime, mud, etc.,
it may be necessary to use solvent and A-A-58054 (Scotchbrite or equivalent) abrasive pads.
Wipe the surface dry with clean cotton cheesecloth or clean wiping rags. Refer to TO 1T-1A-23
or appropriate JDA Technical Manual.
(b) Repeat step (a) above as required to obtain a satisfactory waterbreak-free bond surface.

Sealants and adhesives present a health hazard. Many sealants are

flammable and/or moderately toxic to eyes, skin, and respiratory tract. Wear
skin and eye protection. Wear protective gloves when handling sealant.
Avoid repeated contact. Wash hands thoroughly after use and before eating,
drinking, or smoking. Good ventilation or exhaust ventilation is required for
work in enclosed space or use breathing apparatus.

Adhere to sealant manufacturer’s instructions for mixing and applying

sealant.

(c) Mix sealant (MIL-S-8802, Type II, PR-1440, or MC-236) in accordance with sealant
manufacturer’s instructions. Refer to TO 1T-1A-3 and TO 1T-1A-23 or appropriate JDA Technical
Manuals.

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(d) Use a Semco No. 250 sealant gun, A-A-51679 spatula, sealant-filled syringe, or wood tongue
depressor to apply sealant to the relief cutout area in the FS 322.44 (FS 8190) aft pressure
bulkhead area at BL 0.00. Apply sealant along seams and around fasteners. Apply sufficient
sealant such that cavities are filled and squeeze-out is observed. Also, use a Semco No. 250
sealant gun, A-A-51679 spatula, or wood tongue depressor to apply sealant to the area around
the small triangular-shaped baffles (dog ears) at LBL 19.13 (LBL 486) on the P/N 45A33673-
XXX LH Access Panel and at RBL 10.43 (RBL 265) on the P/N 45A33673-XXX RH Spoiler Mixer
Bay Access Panel.
(e) Inspect for and fill voids in sealant. Refer to TO 1T-1A-23 or appropriate JDA Technical Manuals.
Use locally obtained or TS-1480 fairing sealant tools to fair along the edges of parts and form a
fillet seal. Use a solvent-dampened cloth to clean up excess sealant.
(f) Allow adequate sealant drying time. Sealant drying time and full cure times are dependent on
the class of sealant used (i.e. B1/2, B2, B-4, etc.). Refer to TO 1T-1A-23 or appropriate JDA
Technical Manuals.
(6) Install Mid-Fuselage Access Panels (324LL/LR) (53-30-14-005) (Spoiler Mixer Bay access panels) if
removed for rework. Refer to TO 1T-1A-2-53JG-30-1 or appropriate JDA Technical Manual.
(7) Reconnect the airplane battery (05-02-01), remove warning notices, and restore power.
(8) Ensure all work areas are clean and clear of tools and miscellaneous items of equipment.
(9) Return the airplane to service.
B. Spares

Modify all MU-300 spares installations with Part Numbers 45A33673-11, 45A33673-12, 45A33673-21,
45A33673-22, 45A33673-32, 45A33673-42, 45A33673-52, 45A33673-621, 45A33673-642, and
45A33673-652 by drilling drain holes at locations specified in Figures 1, 2, and 3. Accomplish in
accordance with applicable procedures in steps (3) through (5) of PART I, ACCOMPLISHMENT
INSTRUCTIONS for commercial airplanes and steps (3) through (5) of PART II, ACCOMPLISHMENT
INSTRUCTIONS for military airplanes.
C. Record of Compliance

Upon completion of this Service Bulletin, make an appropriate maintenance record entry.

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Drain Hole Locations in LH Access Panel (Panel Shown Removed)

Figure 1

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Drain Hole Locations in RH Panel (Panel Shown Installed, Looking Forward)

Figure 2

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NOTE -
FUSELAGE STATIONS, BUTTOCK
LINES, AND DIMENSIONS LISTED
ARE IN INCHES.
METRIC DIMENSIONS ARE
IN PARENTHESES.

A
B MODEL 400A LOCATOR SHOWN,
LH PANEL SHOWN,
RH PANEL SIMILAR MODEL MU-300. 400 AND 400T
ARE SIMILAR

DETAIL A
INSPECT FOR SEALANT IN THIS AREA. IF
MISSING, APPLY IN ACCORDANCE WITH
ACCOMPLISHMENT INSTRUCTIONS

REF ACCESS
DOOR FRAME
BL 19.96 BL 13.39 1.38
(507) (340) (35.00)
1.38
(35.00)
FS 307.20
(7803)

FS 309.17
(7853)

FS 311.22
(7905)
0.20 1.18
(5.00) (30.00)
0.20
0.20 (5.00)
(5.00)
FS 315.94
(8025)

FS 319.02
(8103)

FS 322.44
(8190) 4.33 BL 19.13 CL
(110.00) (486)
B
DETAIL
LH PANEL LOOKING DOWN
B348601.AI

Hole Drilling Locations for LH Panel

Figure 3 (Sheet 1 of 3)

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NOTE -
FUSELAGE STATIONS, BUTTOCK LINES, AND
DIMENSIONS LISTED ARE IN INCHES.
METRIC DIMENSIONS ARE IN PARENTHESES.

NOTE - DOUBLER INSTALLED

INSPECT FOR SEALANT IN THIS AREA. IF
ON MODEL 400A AIRPLANES
MISSING, APPLY IN ACCORDANCE WITH
ONLY.
ACCOMPLISHMENT INSTRUCTIONS

REF ACCESS
DOOR FRAME
BL 5.16 BL 11.73 BL 15.98
1.38 (131) (289) (406)
(35.00)
1.38
(35.00)
FS 307.20
(7803)

FS 309.17
(7853)

FS 311.22
(7905)

0.20 HOLE
1.18
(5.00) LOCATION.
(30.00)
PLACE
0.20 MIDWAY
(5.00) BETWEEN
FS 315.94 EXISTING
(8025) RIVETS.

FS 319.02
(8103)

FS 322.44
(8190)
CL
BL 10.43 4.02
(265) (102.00)
INSPECT FOR SEALANT IN THIS AREA. IF
MISSING, APPLY IN ACCORDANCE WITH
ACCOMPLISHMENT INSTRUCTIONS

DETAIL B
RH PANEL LOOKING DOWN
MODEL 400A AIRPLANES B348604.AI

Hole Drilling Locations for RH Panel (400A Airplanes Only)

Figure 3 (Sheet 2 of 3)

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NOTE -
FUSELAGE STATIONS, BUTTOCK LINES, AND
DIMENSIONS LISTED ARE IN INCHES.
METRIC DIMENSIONS ARE IN PARENTHESES.

INSPECT FOR SEALANT IN THIS AREA. IF

MISSING, APPLY IN ACCORDANCE WITH
ACCOMPLISHMENT INSTRUCTIONS NOTE - HOLE LOCATION
TYPICAL FOR MU-300, 400
REF ACCESS AND 400T AIRPLANES
DOOR FRAME
BL 5.16 BL 11.73 BL 15.98
1.38 (131) (289) (406)
(35.00)
1.38 0.20
(35.00) (5.00)
FS 307.20
(7803)

FS 309.17
(7853)

FS 311.22
(7905)

1.18 0.20
(30.00) (5.00)
0.20
(5.00)
FS 315.94
(8025)

FS 319.02
(8103)

FS 322.44
(8190)
CL
BL 10.43 4.02
(265) (102.00)
INSPECT FOR SEALANT IN THIS AREA. IF
MISSING, APPLY IN ACCORDANCE WITH
ACCOMPLISHMENT INSTRUCTIONS

DETAIL B B348606.AI
RH PANEL LOOKING DOWN
MODEL MU-300, 400, AND 400T AIRPLANES
Hole Drilling Locations for RH Panel (MU-300, 400, 400T Airplanes)
Figure 3 (Sheet 3 of 3)

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A
MODEL 400T (T-1A) SHOWN
MODEL MU-300, 400, 400A
AND 400T (TX) SIMILAR

INSPECT FOR PRESENCE

OF SEALANT. IF MISSING,
APPLY SEALANT IN
ACCORDANCE WITH
ACCOMPLISHMENT
INSTRUCTIONS.
DETAIL A B348605.AI

Addition of Sealant at F.S. 322.44 Aft Pressure Bulkhead at B.L. 0.0

Figure 4

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