NO. 

 

DATE

PAGE

 DATE 

 REV 

 ALERT SERVICE BULLETIN 

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

IF OWNERSHIP OF AIRCRAFT HAS CHANGED PLEASE FORWARD TO NEW OWNER

412-09-135 

Aug 25, 2009 

1 of 16 

MODEL AFFECTED: 412 /412EP

SUBJECT: HIGH AFT CROSSTUBE ASSEMBLIES P/N 412-

050-011-101, / -103, / -105, / -107, 412-050-045-

105: MANDATORY INSPECTION 

HELICOPTERS AFFECTED: Model 412 / 412EP helicopters serial numbers 

33001 through 33213, 36001 and subsequent. 

 

 The intent of this bulletin will be incorporated into the 

Model 412 Maintenance Manual at a future date. 

 

COMPLIANCE: Within 6 months after receipt of this bulletin. 

Part I

 Schedule and accomplish a reoccurring 12 month / 

2500 landing Fluorescent Penetrant Inspection of aft 

high crosstube.

Part II

Schedule and accomplish a reoccurring 12 month / 

2500 landing Deflection Check of aft high crosstube 

Part III

Establish a mandatory use of aft high crosstube 

towing retention kit per BHT-412-SI-58 at helicopter 

weight of 8900Ibs and higher. 
ASB 412-09-135 

Page 2 of 16 

DESCRIPTION: 

As a result of reported field failures, Bell Helicopter has completed a load survey, 

coupon testing and analysis of the high aft crosstubes. The results indicate repetitive 

cycle fatigue damage can occur during towing and landing operational events. These 

results warrant a 12 month / 2500 landing (which ever comes first) repetitive

Fluorescent Penetrant Inspection, Deflection Check, and a mandatory use of the aft 

crosstube retention kit (BHT-412-SI-58) at helicopter weights at or above 8900 lb. 

APPROVAL: 

The engineering design aspects of this bulletin are FAA/DER approved. 

MANPOWER: 

Approximately 10 man-hours are required to complete this bulletin not including paint 

and primer cure times. Man-hours are based on hands-on time, and may vary with 

personnel and facilities available. 

WARRANTY: 

There is no warranty provided for this bulletin. 

MATERIAL: 

Required Material: 

The following material is required for the accomplishment of this bulletin and may be 

obtained through your Bell Helicopter Textron Supply Center. 

Part Number Nomenclature Quantity

412-050-045-117 Clamp Assembly A/R 

206-050-301-111 Abrasion Strip A/R 

LARSON L101 Larson Film A/R 

412-706-031-101* Towing Provisions A/R 

412-250-100-101* Puller Equipment A/R 

212-070-600-143** Decal 2 

* See BHT-412-SI-58 

** Acceptable to locally manufacture per Figure 3 

 
ASB 412-09-135 

Page 3 of 16 

Consumable Material: 

The following material is required to accomplish this bulletin and may be obtained 

through your Bell Helicopter Textron Supply Center.

Part Number Nomenclature Quantity Reference

AMS-S-8802 Sealant 1 C-308 

LARSON L100 Adhesive A/R C-571 

MIL-R-81294 Paint Remover A/R C-436*

EWDE072 

3950 Scotchcal 

Primer Kit (1GAL,1QT) 

Edge Sealer 

A/R 

A/R 

C-246 

C-349 

MS-242N Quik-Freeze A/R C-137 

* Customers may also use Turco 5351(T-5469) 

SPECIAL TOOLS: 

None required 

WEIGHT AND BALANCE: 

Not affected 

ELECTRICAL LOAD DATA: 

Not affected 

REFERENCES: 

BHT-412-IPB Illustrated Parts Breakdown 

BHT-412-MM Maintenance Manual, Rev 12 

BHT OSN 412-07-32 

BHT-ALL-SPM Standard Practices Manual 

BHT ASB 412-08-129 (AAI ASB AA-07109) 

BHT-ASB 412-99-97 

BHT-412-SI-58 Gross Weight Towing Kit Provisions & Puller Equipment 

PUBLICATIONS AFFECTED: 

BHT-412-IPB Illustrated Parts Breakdown 

BHT-412-MM Maintenance Manual 

BHT-412-MD-1, 2, & 3 

BHT-412-SI-2 Emergency Float Kit 

BHT-412-SI-40 High Skid Gear / High Crosstube 
ASB 412-09-135 

Page 4 of 16 

BHT-412-SI-58 Gross Weight Towing Kit Provisions & Puller Equipment 

BHT-412-SI-60 Emergency Floats 

ACCOMPLISHMENT INSTRUCTIONS 

ESTABLISHING REQUIREMENTS:

1. Review the high landing gear aft crosstube component history card and determine 

bulletin applicability as indicated in Table 1 below. 

TABLE 1

Crosstube 

Assembly Part 

Number 

Sub Assembly 

Crosstube Part 

Number (See Note) 

Crosstube subassembly (Nonprocurable) (See note) Bare Crosstube 

(Non-procurable) 

412-050-011-101 412-050-010-101 N/A this level 412-050-010-103 

412-050-011-103 412-050-010-107 412-050-010-109 412-050-010-103 

412-050-011-105 412-050-010-107 412-050-010-109 412-050-010-103 

412-050-011-107 412-050-010-111 412-050-010-113 412-050-010-115 

412-050-045-105 412-050-045-107 N/A this level 412-050-044-101 

412-321-104 See AAI ASB AA-07109 / BHT ASB 412-08-129 

Note: Sub-assemblies are indicated above for tracking purposes. Tracking is 

accomplished at the sub assembly part number level on Bell 12-digit part 

numbers. The factory serial numbers or the company control serial numbers 

are visible in the cuff area above the skid tube saddle; refer to ASB 412-99-97. 

2. Amend the component history card to reflect the bulletin requirements for a 

recurring 12 month / 2500 landing aft crosstube Fluorescent Penetrant Inspection 

and a Deflection Check. Refer to accomplishment instructions Part I & II 

respectively. 

3. Establish maintenance practices to mandate towing with the aft crosstube 

retention kit. Refer to the Accomplishment Instructions Part III. 

 

ACCOMPLISHMENT INSTRUCTIONS 

PART I - Accomplish a reoccurring 12 month / 2500 landing aft crosstube 

Fluorescent Penetrant Inspection as indicated below. 
ASB 412-09-135 

Page 5 of 16 

-NOTEThe high aft crosstube Fluorescent Penetrant Inspection can 

be accomplished by any person meeting the personnel 

Qualification / Certification Requirements of the BHT-ALLSPM (ref. Chapter 6, Section 6-5). 

1. Remove the landing gear assembly from the helicopter as per BHT-412-MM. 

CAUTION 

TEMPORARILY INSTALLING A SECONDARY LANDING 

GEAR OR MAINTAINING A CONNECTION TO AN 

OVERHEAD CRANE IS RECOMMENDED DURING THIS 

MAINTENANCE ACTION. 

2. Remove the aft crosstube from the landing gear assembly. 

3. Remove the support beam from the aft crosstube as per BHT-412-MM

4. Remove the hardware retaining BL 14 clamp assemblies P/N 412-050-045-115 or / 

-117 (left & right hand) on the high aft crosstube. Refer to Figure 1 below. 

CAUTION 

CROSSTUBE TEMPERATURE NOT TO EXCEED 200oF 

(93.3oC) WHEN USING HEAT GUN. EXCESSIVE HEAT 

WILL DAMAGE CROSSTUBE. 

5. Use heat gun to soften sealant bonding the clamp assembly to the crosstube. 

Separate the clamp from crosstube and the abrasion strip (if installed). 

-NOTECrosstubes 412-050-011-ALL do not have the abrasion 

strips bonded to the under side at BL 14 or the Larson L101 

material bonded to the underside at BL 00. Fluorescent 

Penetrant Inspection is required in these areas prior to 

reworking these crosstubes to meet the protective 

requirements of 412-050-045 crosstubes, containing the 

above mentioned items. Refer to “Rework” section below for 

the 412-050-011-ALL high aft crosstubes. 
ASB 412-09-135 

Page 6 of 16 

-NOTECrosstube 412-050-045-107 with AAI replacement lower 

support 604-026-003 at BL 00 require Fluorescent Penetrant 

Inspection in this area. Refer to “Rework” section 

6. Remove abrasion strip P/N 206-050-301-111 at BL 14 from the crosstube lower 

surface only if it has become partially de-bonded; or, if further maintenance related 

investigation is deemed necessary. Removal of the abrasion strips from crosstubes 

412-050-045-107 or reworked 412-050-011-ALL series crosstubes is not necessary 

to accomplish the Fluorescent Penetrant Inspection. If abrasion strips must be 

removed, use a plastic scraper to separate the strip from the crosstube while 

cooling the strip with Quik-freeze C-137 to de-grade the bond line. Start at a corner 

and continue peeling carefully while maintaining the bond line in a cool / frozen 

state. 

-NOTEThe upper support 412-050-006-101 on the aft crosstube is 

bonded with structural adhesive and is not designed to be 

removed. 

7. Removal of the lower crosstube support P/N 412-050-007-101 incorporating the 

abrasion strip at BL 0.0 is unnecessary unless there are signs of looseness or 

debonding. If the abrasion strip must be removed, use a plastic scraper to separate 

the strip from the crosstube while cooling the strip with Quik-freeze C-137 to degrade the bond line. Start at a corner and continue peeling carefully while 

maintaining the bond line in a cool / frozen state. Crosstube assembly 412-050-

045-107 and reworked crosstubes 412-050-011-ALL have the abrasion strip under 

BL 0.0 support. Crosstubes P/N 412-050-011-ALL in the original condition without 

the Larson L101 under the lower support P/N 412-050-007-101 at BL 0.0 require 

removal of the lower support for the first Fluorescent Penetrate Inspection (refer to 

Rework section for 412-050-011-ALL high aft crosstubes). 

-NOTELower support P/N 604-026-003 comes with black nylon 

abrasion material bonded to the support. The Larson L101 

abrasion strip shall not be used with this support. 

8. Remove lower crosstube support P/N 604-026-003 (if installed) from Crosstubes 

412-050-011-ALL and 412-050-045-107 to accomplish the first Fluorescent 

Penetrant Inspection. 
ASB 412-09-135 

Page 7 of 16 

9. Remove Larson L101 abrasion strip bonded to the crosstube at BL 0.0 if using AAI 

replacement support P/N 604-026-003 to accomplish the first Fluorescent 

Penetrant Inspection. 

CLEANING AND PREPARATION 

1. Use a plastic scraper to remove residual sealant on the crosstube. It is not required 

to remove the sealant bead around the periphery of the 412-050-006-101 upper / 

412-050-007-101 lower supports at BL 00 unless the sealing bead has been 

damaged on crosstube series 412-050-045. Residual sealant, Larson L101 film 

and Larson adhesive will need to be removed from crosstubes affected by the 

installation of spare replacement lower support 604-026-003. Original crosstubes 

P/N 412-050-011-ALL without Larson L101 (adhesive film) under the lower support 

at BL 0.0 require the residual sealant to be removed for the first Fluorescent 

Penetrant inspection only. 

CAUTION 

PROTECT ABRASION STRIPS AND UPPER / LOWER 

SUPPORTS (BL 14, BL 00) FROM PAINT REMOVER 

CONTAMINATION AS REQUIRED 

2. Prepare crosstube for the inspection process by removing the paint on the 

crosstube in the area indicated in Figure 2. 

a. Crosstube P/N 412-050-045 will require the paint to be removed in area 

depicted in Figure 2 with the exceptions of the abrasion strip areas and the 

412-050-006-101 upper and 412-050-007-101 lower supports (BL 0.0). The 

paint and Larson abrasion strip will need to be removed in the lower support 

area at BL 00 if support P/N 604-026-003 has been installed. 

b. Crosstube P/N 412-050-011-ALL which does not have the abrasion strip 

under the clamp assembly at BL 14 or Larson L101 material under the lower 

support at BL.0.0 will require the paint to be removed under the lower center 

support. 

3. Apply chemical paint remover (C-436) to the crosstube with a brush following 

manufacturer’s directions and the BHT-ALL-SPM. 
ASB 412-09-135 

Page 8 of 16 

CAUTION 

A PLASTIC SCRAPER OR ABRASIVE PAD C-407 MAY BE 

USED TO GENTLY ASSIST THE PAINT REMOVAL 

PROCESS. USE OF THE PLASTIC SCRAPER OR 

ABRASIVE PAD IS TO BE ACCOMPLISHED IN A 

LONGITUDINAL DIRECTION ENSURING NOT TO 

ABRADE THE CROSSTUBE METAL SURFACE. 

4. Reapply the paint remover as required to completely remove the paint and primer. 

Rinse crosstube surface clean using potable water and dry thoroughly. Inspect 

crosstube to ensure the bare metal of the crosstube is clearly visible and free of paint 

and primer residue in the affected area. 

5. Protect crosstube immediately after cleaning by applying corrosion preventive oil if 

the inspection process is delayed. Wrap in barrier material and secure with tape.

INSPECTION 

CAUTION 

USE CARE TO PREVENT CONTAMINATION FROM 

FLUORESCENT PENETRANT CHEMICALS ON THE 

ABRASION STRIPS AND UPPER / LOWER SUPPORT 

(BL14, BL 00) AS APPLICABLE. 

-NOTEThe aft crosstube Fluorescent Penetrant Inspection can be 

accomplished by any person meeting the personnel 

Qualification / Certification Requirements of the BHT-ALLSPM (ref. Chapter 6, Section 6-5). 

1. Inspect the crosstube, with the exception of the areas covered by the protective 

abrasion strips (if installed) and upper center support using Fluorescent Penetrant 

method per ASTM E1417, Type 1 Method B, C or D using a penetrant sensitivity 

level of 2 or 3 (Refer to BHT-ALL-SPM Chapter 6). 

2. All penetrant inspection materials utilized shall be compatible, and shall meet 

requirements of SAE AMS 2644. 
ASB 412-09-135 

Page 9 of 16 

-NOTEThe use of visible dye systems is prohibited. 

3. Inspect crosstube damage per limits specified in the Maintenance Manual (BHT412-MM-5, Chapter 32) to determine allowable damage and cleanup. No cracks 

are permitted. To determine the appropriate Inspection Criteria Table in the 

Maintenance Manual for a specific high aft crosstube, refer to cross reference 

Table 2 below. 

TABLE 2 

Crosstube 

Assembly Part 

Number 

Sub Assembly 

Crosstube Part 

Number 

Crosstube With 10,000 

Takeoff/ Landing Limit 

using Standard 

Inspection Criteria 

Crosstube With 20,000 

Takeoff/ Landing Limit 

using Improved 

Inspection Criteria 

412-050-011-101 412-050-010-101 X 

412-050-011-103 412-050-010-107 X 

412-050-011-105 412-050-010-107 X 

412-050-011-107 412-050-010-111 X 

412-050-045-105 412-050-045-107 X 

412-321-104 X 

See AAI ASB AA-07109 / 

BHT ASB 412-08-129 

REPAIR 

1. Repair all damaged crosstubes that are found to be within acceptable limits as 

indicated in BHT-412-MM-5 Standard or Improved inspection criteria Tables, 

record all repairs. 

2. Replace crosstubes that are beyond the maximum allowable damage limits as 

indicated in the inspection Tables. 

REWORK OF CROSSTUBES 

-NOTEHigh aft crosstubes 412-050-011 -ALL shall incorporate the 

bonding procedures and abrasion strips at BL 00 and BL14 

locations, to provide an equivalent level of protection as 

used on replacement crosstubes P/N 412-050-045-105/-

107/-107A. 
ASB 412-09-135 

Page 10 of 16 

-NOTEIt is required to omit the Larson L101 abrasion strip on the 

412-050-011-ALL and 412-050-045-107 crosstubes at BL 00 

when installing lower support 604-026-003. 

1. Apply primer (C-246) to areas where paint has been removed for inspections as 

per BHT-ALL-SPM. 

CAUTION 

DO NOT SAND CROSSTUBE IN A CIRCUMFERENTIAL 

DIRECTION. SAND CROSSTUBE IN A LONGITUDINAL 

DIRECTION ONLY. 

-NOTEIt is required to complete the first Fluorescent Penetrant 

Inspection before installation of the abrasion strips at BL 0.0 

and BL 14 on the crosstubes 412-050-011-ALL. 

-NOTEAbrasion strip bonding is accomplished prior to the 

installation of the BL14 band clamp P/N 412-050-045-115 

and BL 00 lower support P/N 412-050-007-101 installation. 

2. Lightly abrade the primer on the crosstube common to the abrasion strip taking 

care not to expose bare material. 

-NOTEReplacement of abrasion strip material on the under side of 

the crosstubes at station BL 0.0 and BL 14 locations on 412-

050-045-ALL high aft crosstubes is not required if it has not 

been damaged during inspection. 

3. Install the abrasion strip material on the under side of the crosstubes at both BL 0.0 

and BL 14 locations on all high aft crosstubes series 412-050-011-ALL and 412-

050-045-107 per the BHT-412-MM, as required. Abrasion strip removal for 

subsequent Fluorescent Penetrant Inspections is not required. When installing 

replacement lower support 604-026-003 at BL 00 the Larson L101 abrasion strip is 

not required. The replacement support has a black nylon abrasion material bonded 

to the support. 
ASB 412-09-135 

Page 11 of 16 

-NOTEAll BL14 band clamps shall have an adhesive film on the 

inner surface prior installation. 

4. Use band clamp assembly 412-050-045-115 (replaced by 412-050-045-117) or 

prepare band clamp P/N 330C400-338-S (alt. P/N 333C400-338-S) by adding the 

adhesive film as indicated in the BHT-412-MM, BL 14 clamp preparation. Clamp 

assembly 412-050-045-117 and clamp 333C400-338-S both have longer “T” bolts 

to ease installation.

CAUTION 

CONFIRM BAND CLAMP POSITIONING PRIOR TO 

INSTALLATION AS PER BHT-412-MM. DO NOT POSITION 

BAND CLAMP OVERLAP AT CENTER OF RETENTION 

CAP RUBBER BUMPER. OVER ROTATION OF THE 

CLAMP ASSEMBLY COULD RESULT IN DAMAGE TO THE 

AIRFRAME TUNNEL FROM THE CLAMP “T” BOLTS. 

CAUTION 

DO NOT SAND CROSSTUBE IN A CIRCUMFERENTIAL DIRECTION. 

5. Lightly abrade the primer on the crosstube and abrasion strip common to the band 

clamp (P/N 412-050-045-117) taking care not to expose bare material. 

CAUTION 

REMOVE PROTECTIVE BACKING FILM TO EXPOSE 

ADHESIVE FILM PRIOR TO BONDING CLAMP. 

6. Install band clamp assembly P/N 412-050-045-117 using sealant (C-308) as per 

the BHT-412-MM. Ensure complete sealant coverage of the inner clamp surface, 

avoiding air pockets. 

7. Trim the “T” bolts on the clamp assembly 412-050-045-117 to provide adequate 

clearance from fuselage tunnel, as required. Normally the “T” bolt should have 

approximately 1⁄2 inch of threads visible after installation. Deburr as required. Prime 

(C-246) and paint (as required) bare metal on “T” bolt for corrosion protection. 
ASB 412-09-135 

Page 12 of 16 

8. Lightly abrade the abrasion strip or the crosstube primer on the crosstube at BL 0.0 

common to the lower support P/N 412-050-007-101 or 604-026-003 taking care not 

sand through abrasion strip or primer on crosstube exposing bare material. The 

Larson L101 abrasion strip is not required when installing replacement lower 

support 604-026-003. 

9. Install lower support P/N 412-050-007-101 or 604-026-003 using sealant (C-308) 

per the BHT-412 Maintenance Manual. Prior to bonding the replacement lower 

support 604-026-003 with sealant (C-308) lightly abrade the black nylon abrasion 

material taking care not to expose bare metal. 

10. Repaint crosstube as required per BHT-ALL-SPM. 

11. Annotate component records to indicate incorporation of abrasion strips on 412-

050-011 series crosstubes by the addition of “FM” to the end of the part number 

sequence (e.g. 412-050-011-107FM), for future reference. 

12. Annotate helicopter / component records to indicate Part I of this bulletin has been 

accomplished. 

ACCOMPLISHMENT INSTRUCTIONS 

PART II - ACCOMPLISH AFT CROSSTUBE DEFLECTION CHECK AND 

ESTABLISH A RECURRING 12 MONTH / 2500 LANDING 

DEFLECTION CHECK (WHICH EVER COMES FIRST). 

CAUTION 

ENSURE HELICOPTER IS STABILIZED ON JACKS 

BEFORE PROCEEDING TO ACQUIRING 

MEASUREMENTS. 

1. Hoist or jack the helicopter until the weight is removed from the landing gear. 

2. Determine the BL 0.0 from the walking beam pivot point position and hang a plumb 

line to obtain the measurement from BL 0.0 to the outside edge of the skid tubes as 

indicated. 

3. Confirm aft crosstube is within deflections limits indicated in the BHT-412-MM. 

4. Replace aft crosstubes that exceed the dimensional tolerances indicated. 

5. Annotate helicopter / component records to indicate Part II of this bulletin has been 

accomplished. 
ASB 412-09-135 

Page 13 of 16 

ACCOMPLISHMENT INSTRUCTIONS 

PART III - TOWING: 

Helicopter towing operations can result in fatigue damage to the aft crosstube. To 

prevent this damage, the recommendation to restrain the high aft crosstube as stated 

in the maintenance manual (BHT-412-MM-2), is now mandatory when towing at 

weights greater than or equal to 8900 lb. 

The puller assembly used in the Service Instruction BHT-412-SI-58 is equipped with a 

load limiter called a “Load Sentry”. The mechanism is preset to provide a 4000 pound 

tension load on the crosstube. This high load counteracts the loads being applied to 

the crosstube by the towing actions and weight of the helicopter. The Load Sentry is 

contained in the handle of the retention devise and works similar to a torque wrench. 

1. Install CAUTION decal P/N 212-070-600-143 per Figure 3 on pilot and co-pilot side 

and apply sealer (C-349) allowing 0.125 in (3.175) overlap on all sides of decal, as 

required. 

2. Review Bell Helicopter Service Instruction BHT-412-SI-58 to determine the items 

required to use of this kit. 

CAUTION 

ENSURE LANDING GEAR MEETS THE MINIMUM 

REQUIREMENTS FOR TOWING PER THE SERVICE 

INSTRUCTION. TOWING SHOULD ONLY BE ACCOMPLISHED 

USING THE FORGED TOW FITTINGS P/N 204-050-104-101 

AND SUPPORT BEAM ASSEMBLY P/N 412-050-003-109, 

INCLUDING SUBSEQUENT REPLACEMENTS OF EACH ITEM. 

3. Establish helicopter towing practices for high landing gear at weights greater than 

or equal to 8900 lb and incorporate the use of Service Instruction BHT-412-SI-58. 

4. Customers that use helicopter landing dollies (movable platforms) are also required 

to use the restraining devise per BHT-412-SI-58 at helicopter weights greater than 

or equal to 8900 lb for high landing gear. 

5. When towing a helicopter (at weights less than 8900 lbs) over unprepared surfaces 

or rough terrain with or without the use of a dolly, the use of Service Instruction 

BHT-412-SI-58 is strongly recommended. 

6. Annotate helicopter / component records to indicate Part III of this bulletin has been 

accomplished. 
ASB 412-09-135 

Page 14 of 16 

FIGURE 1 
ASB 412-09-135 

Page 15 of 16 

FIGURE 2 
ASB 412-09-135 

Page 16 of 16 

 

FIGURE 3