ASB 206L-09-158B 

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ECCN EAR99 

 ALERT SERVICE BULLETIN 206L-09-158 

9 April 2009 

Revision A, 31 August 2009 

Revision B, 1 June 2011 

MODEL AFFECTED: ALL 206L SERIES HELICOPTERS

SUBJECT: AIRWORTHINESS INSPECTION LIMITATION TO 

TAILBOOM LEFT UPPER ATTACHMENT FITTING 

P/N 206-032-409-001. 

HELICOPTERS AFFECTED: Serial number 45004 through 45790 and 46601 

through 46617, 51001 through 51612, 52001 and 

subsequent equipped with tailboom assemblies 

listed in Appendix “A”. 

 

COMPLIANCE: PART I: At the next 100-hour scheduled inspection 

and every period thereafter not exceeding 110 hours 

of flight time. 

PART II: When loose (working) rivets, a crack or 

mechanical damage is found on subject fitting 

following inspection under PART I. 

DESCRIPTION: 

This Alert Service Bulletin introduces a Chapter 4 limitation to the 100 Hours/Annual 

inspection currently published in the Chapter 5 of applicable 206L series maintenance 

manuals for the upper left tailboom attachment fitting Part Number 206-032-409-001. 

PART I of this bulletin elaborates the Chapter 4 inspection requirements of the upper 

left tailboom attachment fitting 206-032-409-001 and provides guidance to repair 

minor acceptable damage. 

Part II of this bulletin provides guidance to replace loose (working) rivets or to replace 

the fitting in case unacceptable damage is found. 

Revision “A” to this Alert Service Bulletin did introduce new damage limits and 

machining rework process for the fitting, clarified the inspection procedure and 

corrected the reference manuals. Revision “B” extends the inspection requirements to 

110 flight-hours to align with the 100-hour scheduled inspection tolerance. 
ASB 206L-09-158B 

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ECCN EAR99 

APPROVAL: 

The engineering design aspects of this bulletin are Transport Canada Civil Aviation 

(TCCA) approved. 

CONTACT INFO: 

For any question regarding this bulletin, please contact: 

Bell Helicopter Product Support Engineering - Light Helicopters 

Tel: 450-437-2862 / 1-800-363-8023 / pselight@bellhelicopter.textron.com 

MANPOWER: 

No additional manpower is required to complete Part I of this bulletin when carried out 

as part of the periodic 100-hour/Annual scheduled inspection. Approximately 8 manhours are required to complete PART II of this bulletin. Man-hours are based on handson 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: 

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 Nomenclature Qty Reference * 

P-P-101 Abrasive paper(400 grit) A/R C-423 

MIL-C-87936,TY I Aircraft soap cleaner 1 C-318 

MIL-C-81706 1 QT Chemical treatment (Alodine) 1 C-100 

MIL-PRF-23377TI,CLC Primer 1 C-204 

* C-XXX numbers refer to the consumables list in BHT-ALL-SPM Standard Practices Manual 

REFERENCES: 

BHT-206L-SERIES-IPB Illustrated Parts Breakdown (Rev 4, dated 12 June 2007) 

BHT-206L-MM-1 Maintenance Manual (Rev 34) 

BHT-206L1-MM-1 Maintenance Manual (Rev 31) 

BHT-206L3-MM-1 Maintenance Manual (Rev 17) 
ASB 206L-09-158B 

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BHT-206L4-MM-1 Maintenance Manual (Rev 14) 

BHT-206L4T-MM-1 Maintenance Manual (Rev 8) 

BHT-ALL-SPM Standard Practices Manual (Rev 2, dated 16 February 2007) 

BHT-206-SRM-1 Structural Repair Manual (Rev 1, dated 04 April 1995) 

PUBLICATIONS AFFECTED: 

BHT-206L-MM-1 Maintenance Manual, Chapter 4 

BHT-206L1-MM-1 Maintenance Manual, Chapter 4 

BHT-206L3-MM-1 Maintenance Manual, Chapter 4 

BHT-206L4-MM-1 Maintenance Manual, Chapter 4 

BHT-206L4T-MM-1 Maintenance Manual, Chapter 4 

ACCOMPLISHMENT INSTRUCTIONS:

PART I: VISUAL INSPECTION OF TAILBOOM UPPER LEFT ATTACHMENT 

FITTING 206-032-409-001.

1. Gain access to the four tailboom attachment fittings, intercostals and bulkheads 

(BS 31.87 and BS 42.59) inside the tailboom assembly by removing the tailboom 

access cover on the right side of the aft fuselage. 

-NOTEMake sure that each drain hole on lower skin of tailboom 

assembly, aft of each bulkhead, is free of dirt or debris and 

not clogged. 

2. (Ref. Figure 1) Inspect and mark head of any visible loose rivet found on 

attachment fittings with indelible ink felt pen before cleaning the complete tailboom 

attachment area with aircraft soap (C-318). Prepare soap solution per 

manufacturer’s recommendations to remove all traces of dirt, stains, exhaust 

residues and oil. Rinse area with water and let area to dry. 

-NOTEIf a crack is found in the upper left tailboom attachment fitting 

during the inspection described below, contact Product 

Support Engineering with details before installing a new 

fitting. 

3. (Ref. Figure 2) Use a bright light source with a mirror and inspect visually the left 

upper tailboom attachment fitting P/N 206-032-409-001 for loose (working) rivets, 
ASB 206L-09-158B 

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ECCN EAR99 

corrosion, condition and mechanical damage. Pay close attention on each leg of 

the fitting for a crack near the two most forward vertical rows of rivets. 

4. If a crack, loose (working) rivets, is found on upper left attachment fitting, 

accomplish PART II of this bulletin. 

5. If corrosion or mechanical damage is found on the fitting, refer to FIGURE 2 to 

determine if the fitting can be repaired. 

a. If damage is beyond repairable condition, replace the fitting in accordance with 

PART II. 

b. Repair acceptable damage as follows; 

-NOTEDepth of repair shall be twice the depth of corrosion not to 

exceed the repair limits of Figure 2. 

(1) Machine or sand the damage on the fitting in order to remove minimum 

material. A 20:1 width to depth ratio should be maintained. Electrical 

discharge and electro-chemical machining are not approved. If machining is 

chosen, lubricant and slow machining shall be used to prevent generating 

excessive heat that could affect existing heat treatment. 

(2) If damage is affecting the corner radius area of the fitting (see doublehatched area), blend to obtain minimum chamfer that will remove the 

damage. A maximum of 0.020 inch (0.508 mm) X 45° chamfer is allowed. 

(3) If damage removal is needed on inner end pad surface, ensure that the 

blend area is wide enough to guarantee that the tailboom attachment bolt 

head will sit on flat surface. Do not machine into the fitting radius. After 

machining or sanding, both end pad surfaces must be parallel and lie in 

plane within 0.002” inch (0.050 mm). 

(4) Use Sanding paper (C-423) 400 grit or finer to obtain a final surface finish of 

32 RMS or better. 

(5) Perform Fluorescent Penetrant Inspection of the fitting after blending is 

accomplished to ensure all damage is removed. Clean fitting to remove 

fluorescent Penetrant after inspection is done. 

(6) Apply chemical film treatment (C-100) to bare metal surfaces, followed by 

one coat minimum of primer (C-204). 
ASB 206L-09-158B 

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ECCN EAR99 

 

6. If no crack, loose (working) rivets, corrosion or mechanical damage is found, 

complete the 100-hour/annual scheduled inspection of the tailboom assembly as 

defined in Chapter 5 of your maintenance manual. 

7. Make an entry in helicopter historical service records indicating compliance with 

Part I of this Alert Service Bulletin 

8. Repeat PART 1 at recurring intervals not exceeding 110 hours of flight time. 

PART II: REPLACEMENT OF LOOSE (WORKING) RIVETS OR TAILBOOM 

ATTACHMENT FITTING 

2. Remove the upper left tailboom attachment fitting and the two mating intercostals 

as an assembly from the tailboom in accordance with procedure 6-3-1 of the 

Structural Repair Manual (BHT-206-SRM-1). If damage to fitting justifies its 

replacement, continue with the procedure 6-3-1 of the SRM manual (BHT-206-

SRM-1). 

3. If loose (working) rivets were found while performing inspection as per Part I of this 

bulletin, proceed as follows: 

a. Drill and remove the affected original MS20470DD5 (ice box rivets) or the 

MS20470E5 rivets. 

b. Inspect each affected hole(s) for dimension in accordance with Table 3-4 in the 

SRM manual (BHT-206-SRM-1). If affected hole(s) is/are within acceptable 

limits, go to Step 3. If holes are oversize or elongated, go to step 4. 

-NOTEWhen re-installing the same original type and size (5/32) 

solid rivets as delivered from the factory, no restriction 

exists. Proceed with the installation of the rivet(s) within the 

fitting/intercostals assembly as per the procedure 6-3-1 

described in the SRM manual (BHT-206-SRM-1). 

 
ASB 206L-09-158B 

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-NOTETailbooms were delivered from the factory with either all 

MS20470DD5 or all MS20470E5 as original rivets installed 

in fitting 206-032-409-001. 

When installing oversize rivets in any leg of the fitting, only 

the next oversize (3/16 dia. nominal) is allowed. Refer to 

Step 4. 

4. If the same type and size (5/32 diameter) rivet(s) are to be installed again, refer to 

the procedure 6-3-1 defined in the SRM manual (BHT-206-SRM-1) before 

proceeding with Step 6 below. 

-NOTEWhen installing oversize or different type of rivets common 

to one leg of the fitting, it is not necessary to replace (match) 

corresponding rivets in opposite leg of the fitting. 

5. If different type or size of rivets from factory original (5/32 dia.) are required due to 

hole(s) beyond the acceptable limit of Table 3-4 of the SRM manual (BHT-206-

SRM-1), you can install either MS20470DD or MS20470E (5/32 dia.) rivet types or 

its oversize (3/16 dia.) in the fitting provided the following restrictions are met: 

a. A minimum of 2D edge distance shall be maintained on all rivets replaced. 

b. 4d minimum pitch shall be maintained between all rivets. 

c. No rivet bigger than 3/16 diameter are allowed in any leg of the fitting. 

d. No rivets shall interfere with the installation of the hardware securing the 

tailboom assembly to the fuselage. 

e. No rivets should be located in the radii of the fitting. 

f. (Ref. Figure 3) Whenever one original 5/32 fasteners needs oversize 

replacement, all the rivets in that affected rivet group (Group “A”, “B” or “C”) are 

to be replaced with the same type and size of oversize fastener. 
ASB 206L-09-158B 

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ECCN EAR99 

g. It is acceptable to have a mix of “DD” and “E” type rivets in the same leg of the 

fitting as shown as group “D” but it is not acceptable to have such a mix within 

rivet respective groups “A”, “B” or “C”. 

Example 1: (Ref, Figure 3) A rivet hole in part of group “A” is elongated (oversize); 

both rivets in group “A” must be replaced. 

Example 2: (Ref. Figure 3) Two rivet holes, one in group “A” and the other in group 

“B” are elongated (oversize); all rivets in both groups (“A” and “B”) must be replaced. 

Although the rivets in group “C” do not require to be changed, it is acceptable if the 

operator chooses to replace those as well. 

6. Re-install the fitting and intercostals assembly back into the tailboom using the 

procedure 6-3-1 of the SRM manual (BHT-206-SRM-1). 

7. Make an entry in helicopter historical service records indicating compliance with 

Part II of this Alert Service Bulletin. 

 
ASB 206L-09-158B 

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ECCN EAR99 

NOTES 

1. Inspect upper left attachment fitting P/N 206-032-409-001 for a crack, corrosion, loose 

rivets, mechanical damage and general condition within a period not to exceed 110 

hours of flight time. 

2. Repair fitting in accordance with PART I and Figure 2 provided limitations are met after 

rework. 

3. Replace cracked or damaged fitting or loose rivets in accordance with Part II of this 

bulletin. 

4. Tailboom assembly remaining details not shown for clarity.

5. If a crack is found, replace damaged fitting in accordance with paragraph 6-3-1 of the 

Structural Repair Manual (BHT-206-SRM-1).

FIGURE 1: INTRODUCTION OF AIRWORTHINESS INSPECTION LIMITATION TO 

TAILBOOM ATTACHMENT FITTING P/N 206-032-409-001 
ASB 206L-09-158B 

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ECCN EAR99 

 

FIGURE 2: DAMAGE LIMITATION AND APPROVED REPAIR TO FITTING P/N 

206-032-409-001 (Sheet 1 of 2). 
ASB 206L-09-158B 

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ECCN EAR99 

FIGURE 2: DAMAGE LIMITATION AND APPROVED REPAIR TO FITTING P/N 

206-032-409-001 (Sheet 2 of 2). 
ASB 206L-09-158B 

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ECCN EAR99 

NOTES: 

When re-installing the same original type and size (5/32) solid rivets as delivered from the 

factory, no restriction exist. Proceed with the installation of the rivet(s) within the fitting and 

intercostals assembly and re-install unit within the tailboom as per the remaining steps of the 

procedure 6-3-1 found in the SRM manual. 

When installing oversize or different type of rivets common to one leg of the fitting, it is not 

necessary to replace (match) corresponding rivets in opposite leg of the fitting. 

When different type or size of rivets from factory original are required due to hole(s) beyond 

the limit of Table 3-4 of the SRM where oversize rivet(s) is/are needed, any number of 

different type or oversize rivets can be installed provided the following restrictions are met: 

a. Either MS20470DD or MS20470E rivet type may be used as replacement. Only these two can 

be used. 

b. A minimum of 2D edge distance shall be maintained on all rivets replaced. 

c. 4D minimum pitch shall be maintained between all rivets. 

d. No rivet bigger than 3/16 diameter are allowed in any leg of the fitting. 

e. No rivets shall interfere with the installation of the hardware securing the tailboom assembly to 

the fuselage. 

f. No rivets should be located in the radii of the fitting. 

g. Whenever one original 5/32 fasteners needs oversize replacement, all the rivets in that affected 

rivet group (Group “A”, “B” or “C”) are to be replaced with the same type and size of oversize 

fastener. 

h. It is acceptable to have a mix of “DD” and “E” type rivets in the same leg of the fitting as shown 

as group “D” but it is not acceptable to have such a mix within rivet respective groups “A”, “B” or 

“C”. 

Example 1: A rivet hole in part of group “A” is elongated (oversize); both rivets in group “A” 

must be replaced. 

Example 2: Two rivet holes, one in group “A” and the other in group “B” are elongated 

(oversize); all rivets in both groups (“A” and “B”) must be replaced. Although the rivets in group 

“C” do not require to be changed, it is acceptable if the operator chooses to replace those as well. 

FIGURE 3: REPLACEMENT OF LOOSE (WORKING) RIVETS IN TAILBOOM 

ATTACHMENT FITTING P/N 206-032-409-001 
ASB 206L-09-158B 

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APPENDIX “A”

DESCRIPTION OF TAILBOOM PART NUMBERS:

206-033-004-003: Basic tailboom part number (see Note below) as delivered on 206L 

model S/N 45003 through 45076. 

206-033-004-003FM: Basic tailboom modified under ASB 206L-87-47 (Addition of one piece 

driveshaft cover clip and doubler on upper skin) 

206-033-004-003FM1: -003FM configuration upgraded to -045 equivalence under TB 206L-90-

150. 

206-033-004-003FM2: -003FM configuration upgraded to -177 equivalence under TB 206L-96-

191. 

206-033-004-003FMA: -003FM configuration which has complied also with ASB 206L-99-

115(Addition of a riveted doubler at left horizontal stabilizer cutout). 

206-033-004-003FM1A: -003FM configuration upgraded to -045 equivalence under TB 206L90-150 which has complied also with ASB 206L-99-115(Addition of a riveted doubler at left 

horizontal stabilizer cutout). 

206-033-004-003FM2A: -003FM configuration upgraded to -177 equivalence under TB 206L96-191 which complied with ASB 206L-99-115(Addition of a riveted doubler at left horizontal 

stabilizer cutout). 

Note: The basic tailboom part number on the data plate could have been identified also with a suffix “A” 

from the factory. This suffix is not taken into account for the part numbers above representing field 

modifications as described herein. 

206-033-004-011: Basic tailboom part number (see Note below) as delivered on 206L 

model S/N 45077 through 45153 and S/N 46601 through 46617. 

206-033-004-011FM: Basic tailboom modified under ASB 206L-87-47 (Addition of one piece 

driveshaft cover clip and doubler on upper skin). 

206-033-004-011FM1: -011FM configuration upgraded to -045 equivalence per BHT 

instructions letter. 

206-033-004-011FM2: -011FM configuration upgraded to -103 equivalence per BHT 

instructions letter. 

206-033-004-011FM3: -011FM configuration upgraded to -045 equivalence under TB 206L-90-

150. 

206-033-004-011FM4: -011FM configuration upgraded to -177 equivalence under TB 206L-96-

191. 

206-033-004-011FMA: -011FM configuration which complied also with ASB 206L-99-

115(Addition of a riveted doubler at left horizontal stabilizer cutout). 

206-033-004-011FM1A: -011FM configuration upgraded to -045 equivalence per BHT 

instructions letter which complied also with ASB 206L-99-115(Addition of a riveted doubler at 

left horizontal stabilizer cutout). 

206-033-004-011FM2A: -011FM configuration upgraded to -103 equivalence per BHT 

instructions letter which complied also with ASB 206L-99-115(Addition of a riveted doubler at 

left horizontal stabilizer cutout). 

206-033-004-011FM3A: -011FM configuration upgraded to -045 equivalence under TB 206L90-150 which complied also with ASB 206L-99-115(Addition of a riveted doubler at left 

horizontal stabilizer cutout). 
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206-033-004-011FM4A: -011FM configuration upgraded to -177 equivalence under TB 206L96-191which complied with ASB 206L-99-115(Addition of a riveted doubler at left horizontal 

stabilizer cutout). 

Note: The basic tailboom part number on the data plate could have been identified also with a suffix “A” 

from the factory. This suffix is not taken into account for the part numbers above representing field 

modifications as described herein. 

206-033-004-103: Basic tailboom part number (see Note below) as delivered on 206L 

model S/N 45154 through 45283. 

206-033-004-103FM: Basic tailboom modified under ASB 206L-87-47 (Addition of one piece 

driveshaft cover clip and doubler on upper skin). 

206-033-004-103FM1: -103FM configuration upgraded to -045 equivalence under TB 206L-90-

150. 

206-033-004-103FM2: -103FM configuration upgraded to -177 equivalence under TB 206L-96-

191. 

206-033-004-103FMA: -103FM configuration which complied also with ASB 206L-99-

115(Addition of a riveted doubler at left horizontal stabilizer cutout). 

206-033-004-103FM1A: -103FM configuration upgraded to -045 equivalence under TB 206L90-150 which complied also with ASB 206L-99-115(Addition of a riveted doubler at left 

horizontal stabilizer cutout). 

206-033-004-103FM2A: -103FM configuration upgraded to -177 equivalence under TB 206L96-191 which complied with ASB 206L-99-115(Addition of a riveted doubler at left horizontal 

stabilizer cutout). 

Note: The basic tailboom part number on the data plate could have been identified also with a suffix “A” 

from the factory. This suffix is not taken into account for the part numbers above representing field 

modifications as described herein. 

206-033-004-045: Basic tailboom part number( see Note below) as delivered on 206L-1 

model S/N 45284 through 45790 and on 206L-3 model S/N 51001 

through 51283. 

206-033-004-045FM: Basic tailboom modified under ASB 206L-87-47 (Addition of one piece 

driveshaft cover clip and doubler on upper skin) 

206-033-004-045FM1: -045FM configuration upgraded to -143 equivalence per BHT 

instructions letter. 

206-033-004-045FM2: -045FM configuration upgraded to -177 equivalence under TB 206L-96-

191. 

206-033-004-045FMA: -045FM configuration which complied also with ASB 206L-99-

115(Addition of a riveted doubler at left horizontal stabilizer cutout). 

206-033-004-045FM1A: 045FM configuration upgraded to -143 equivalence per BHT 

instructions letter which complied with ASB 206L-99-115(Addition of a riveted doubler at left 

horizontal stabilizer cutout). 

206-033-004-045FM2A: -045FM configuration upgraded to -177 equivalence under TB 206L96-191 which complied with ASB 206L-99-115(Addition of a riveted doubler at left horizontal 

stabilizer cutout). 
ASB 206L-09-158B 

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Note: The basic tailboom part number on the data plate could have been identified also with a suffix “A” 

from the factory. This suffix is not taken into account for the part numbers above representing field 

modifications as described herein. 

206-033-004-143: Basic tailboom part number (see Note below) as delivered on 206L-3 

model S/N 51284 through 51612. 

206-033-004-143FM1: Basic tailboom upgraded to -177 equivalence under TB 206L-96-191. 

206-033-004-143FM1A: -143FM configuration upgraded to -177 equivalence under TB 206L96-191 which complied with ASB 206L-99-115(Addition of a riveted doubler at left horizontal 

stabilizer cutout). 

Note: The basic tailboom part number on the data plate could have been identified also with a suffix “A” 

from the factory. This suffix is not taken into account for the part numbers above representing field 

modifications as described herein. 

206-033-004-175: Basic tailboom part number (see note below) as delivered on 206L-4 

model S/N 52001 through 52026. 

206-033-004-175FM1: Basic tailboom upgraded to -177 equivalence under TB 206L-96-191. 

206-033-004-175FM1A: -175FM configuration upgraded to -177 equivalence under TB 206L96-191 which complied with ASB 206L-99-115(Addition of a riveted doubler at left horizontal 

stabilizer cutout). 

Note: The basic tailboom part number on the data plate could have been identified also with a suffix “A” 

from the factory. This suffix is not taken into account for the part numbers above representing field 

modifications as described herein. 

206-033-004-177: Basic tailboom part number (see Note below) as delivered on 206L-4 

model S/N 52027 through 52232. 

206-033-004-177A: Basic tailboom which complied with ASB 206L-99-115(Addition of a riveted 

doubler at left horizontal stabilizer cutout). 

Note: The basic tailboom part number on the data plate could have been identified also with a suffix “A” 

from the factory. 

206-033-004-181: Basic tailboom part number (see Note below) as delivered on 206L-4 

models S/N 52233 through 52245. 

Note: The basic tailboom part number on the data plate could have been identified also with a suffix “A” 

from the factory. 

 

206-033-004-199: Basic tailboom part number (see Note below) as delivered on 206L-4 

models S/N 52246 through 52340. 
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Note: The basic tailboom part number on the data plate could have been identified also with a suffix “A” 

from the factory. 

206-033-004-203: Basic tailboom part number (see Note Below) as delivered on 206L-4 

model S/N 52341 through subsequent. 

Note: The basic tailboom part number on the data plate could have been identified also with a suffix “A” 

from the factory. 

206-704-727-103: Any tailbooms listed above upgraded to -199 part number equivalence 

by BHT-Approved Customer Service Facilities CSF) holding copies of 

drawings 206-530-127 and 206-704-727. This upgrade involves 

replacement of the upper skin along with meeting compliance with TB 206L96-191 as the initial baseline. 

206-704-727-105: Any tailbooms listed above upgraded to -199 part number equivalence 

by BHT-Approved Customer Service Facilities CSF) holding copies of 

drawings 206-530-127 and 206-704-727.This upgrade involves 

replacement of the lower skin along with meeting compliance with TB 

206L-96-191 as the initial baseline. 

206-704-727-101: Any tailbooms listed above upgraded to -199 part number equivalence 

by BHT-Approved Customer Service Facilities CSF) holding copies of 

drawings 206-530-127 and 206-704-727.his upgrade involves 

replacement of both the upper and lower skins along with meeting 

compliance with TB 206L-96-191 as the initial baseline.