DATE 

ALERT SERVICE BULLETIN 

REVISION NOTICE 

A Subsidiary of Textron Inc.

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

IF OWNERSHIP OF AIRCRAFT HAS CHANGED PLEASE FORWARD TO NEW OWNER

AUG 27, 2007 

TO: All Owners/Operators of Bell 407 Helicopters

SUBJECT: REVISION “C” TO ALERT SERVICE BULLETIN 407-01-48: 

 (TAILBOOM ASSEMBLY 407-030-801-101, /-105, /-107, 

 MODIFICATION OF, AND NEW AIRWORTHINESS 

 LIMITATION/INSPECTION SCHEDULE, INTRODUCTION OF.)

Revision “C” to this bulletin makes the changes that follows: 

• Clarifies that once a tailboom 407-530-014-101,/-103 or 407-030-801-107 

reaches 5000 hours in service, it cannot have a new skin installed and must be 

retired. 

• Replaces the inspection requirements as guided under PART IV and PART V. 

Operators/maintainers are now instructed to refer to new inspection requirements 

for modified tailbooms 407-530-014-101, /-103 and 407-030-801-107 as defined 

under Alert Service Bulletin 407-07-80.
NO. 

 

DATE 

PAGE 

 DATE 

 REV 

ALERT SERVICE BULLETIN 

A Subsidiary of Textron Inc.

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

IF OWNERSHIP OF AIRCRAFT HAS CHANGED PLEASE FORWARD TO NEW OWNER

407-01-48 

AUG 27, 2007 20-12-01 

C 1 of 32 

MODEL AFFECTED: 407

SUBJECT: TAILBOOM ASSEMBLY 407-030-801-101, /-105, 

/-107 MODIFICATION OF, AND NEW 

AIRWORTHINESS LIMITATION/INSPECTION 

SCHEDULE, INTRODUCTION OF. 

HELICOPTERS AFFECTED: 407, Serial Number 53000 through 53475. 

[Helicopters Serial Number 53476 and subsequent 

have been delivered with tailboom assembly 407-

030-801-201 or later part number installed, and are 

not affected by this bulletin] 

 [Helicopters Serial Number 53000 through 53475 

that have spare tailboom assembly 407-030-801-

201 or later part number installed, are not affected 

by this bulletin] 

COMPLIANCE: 1. Immediately upon receipt of this bulletin if 

tailboom 407-030-801-107 is installed. As 

directed by Parts IV and V of this bulletin. 

2. No later than 31 January 2003 if tailboom 407-

030-801-101 or /-105 is installed. As directed by 

Parts I through III of this bulletin. 

-NOTEYou must ensure that the intent of Technical Bulletin 407-

01-33 is met at the same time as you do this bulletin. 

Continue to examine the tailbooms assemblies 407-030-

801-101 and /-105 in accordance with Alert Service Bulletin 

407-99-26, Revision C or later revision until you have 

complied with this bulletin. 
ASB 407-01-48 

Page 2 of 32 

DESCRIPTION: 

Since release of ASB 407-99-26, Bell Helicopter has received additional reports of 

tailboom upper skins found cracked in service. Cracks were found during daily 

inspection or scheduled maintenance. The cracks originated from the holes where the 

fasteners (NAS1738MW5) are installed at the forward and aft section (B.S. 98.89 and 

B.S. 120.75 respectively) of the left upper stabilizer support 407-023-800-117. 

This bulletin gives instructions to remove sixteen fasteners on the left side of the 

tailboom only, do an inspection of each hole by Eddy Current method and install 

oversize fasteners. It also assigns a new airworthiness life to the specific tailbooms 

and introduces new inspection requirements. 

PART I gives instructions to inspect by Eddy Current method, and modify with new 

fastener type, the tailbooms 407-030-801-101, /-105. The tailboom 407-030-801-107 

meets the intent of this bulletin and does not require inspection and modification. 

Part II makes mandatory the installation of the horizontal stabilizer by improved 

method introduced by Technical Bulletin 407-01-33. 

Part III assigns new part numbers to the tailbooms 407-030-801-101, /-105 that have 

been modified. Those modified tailbooms are considered equivalent to, and 

interchangeable with, the /-107 configuration. 

Part IV assigns a service life of 5000 hours since new to tailboom 407-030-801-107 

and 5000 hours from time of rework to modified tailbooms 407-530-014-101, /-103 and 

guides owners/operators to applicable inspection requirements. 

Part V of this bulleting giving new inspection requirements applicable for the modified 

tailbooms 407-530-014-101, /-103 and tailboom 407-030-801-107 is being cancelled 

and replaced by new inspection requirements as defined under Alert Service Bulletin 

407-07-80. 

APPROVAL: 

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

MANPOWER: 

Approximately 10.0 man-hours are necessary to complete PART I of this bulletin. 

Man-hours are based on hands-on time, and can vary with personnel and facilities 

available. 

C. 
ASB 407-01-48 

Page 3 of 32 

WARRANTY: 

Owners/operators of 407 helicopters who comply with the instructions outlined in this 

bulletin will receive a special 100% warranty credit for the PART I kit contained in the 

“Required Material” section of this bulletin. In addition, labor to incorporate the PART I 

kit will be allowed in the amount of $600 USD. 

Special Warranty Note 

Owners/Operators of 407 helicopters that are required to incorporate Technical 

Bulletin 407-01-33 will receive a special 100% warranty credit for the parts contained 

in the “Required Material” section of that bulletin. In addition, labor to incorporate that 

bulletin TB 407-01-33 will be allowed in the amount of $480 USD. 

To receive this credit: 

 Purchase the required parts from a BHTI-approved supply source. 

 Place your order no later than 30 September 2002. 

 Submit a completed malfunction report to BHTI Warranty no later that 30 days 

after completion of this bulletin. 

Note: Customers who fail to order parts for this bulletin before 30 September 2002 are 

not eligible for the special warranty credit provisions listed above. 

MATERIALS: 

The following material is needed to modify tailboom assemblies 407-030-801-

101, /-105 only. If you have tailboom 407-030-801-107, you do not need to order 

the parts. 

Required Material: 

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

through your Bell Helicopter Textron Supply Center. 

Order hardware kit CA-407-01-48 that includes the parts that follow: 

Part Number Nomenclature Quantity

M7885/2-5-02 Rivet 12 

100-071-7 Identification plate 1 

MS20604B3W1 Rivet 2 

HL22093-6-4 Fastener and collar 4 (see Note 1) 

110-164-1 Rivet 2 (see Note 2) 

B. 
ASB 407-01-48 

Page 4 of 32 

Notes: 

1. Fastener and collar can be ordered separately under P/N HL220PB-6-4

 and HL93-6 respectively. 

2. Required for tailbooms 407-030-801-101 that were upgraded to the 

 equivalent of /-105 configuration, in accordance with the BHT-Approved 

 procedure covered by Transport Canada Approval form AE-100-1 only. See 

 additional identification plate (locally manufactured) installed adjacent to the 

 BHT identification plate. 

Consumable Material: 

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

is considered consumable (bench stock) material and may not require ordering 

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

procured through your Bell Helicopter Textron Supply Center. 

Part Number Nomenclature Reference

 

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) 

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

P-P-101 Aluminum Oxide 

Sandpaper C-423 

150-021-10C2-4 Al Alloy 2024T3 (0.032 

inch (0.81 mm) thick) N/A (Note 4) 

 

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. Use only if required. Refer to page 20 and 24 of this bulletin for details. 

SPECIAL TOOLS: 

 Reamer 0.1875 inch (4.7625 mm) diameter 

 Reamer 0.1935 inch (4.915 mm) diameter 

 Reamer 0.2185 inch (5.55 mm) diameter 

 Reamer 0.1635 inch (4.15 mm) diameter 

 Reamer 0.177 inch (4.50 mm) diameter 

 Hocking Phasec 2200 or Zetec Miz 20 or equivalent Eddy Current 

inspection equipment. 

 Eddy Current probes MBD2-10/12-1WL and MBD2-12/14-1WL or equivalent 

tuned to a frequency between 100 KHz – 1.0 MHz. 

 Eddy Current Inspection Reference Standard (calibrating coupon) part number 

BHTI EC-10-20 (see Note below) 

B. 

B. 
ASB 407-01-48 

Page 5 of 32 

Note: The reference standard can be procured from BHT-Approved supply centers or 

from the following addresses; 

EC/NDT LLC PH Tool 

1020 S 344TH, Suite 214 10 Callowhill Road 

Federal Way, WA 98003 New Britain, PA 18901 

Tel: (877) 565-0797 Fax: (215) 822-6799 

Fax: (253) 815-0827 Tel: (888) 553-9245 

E-mail :EC-NDT@worldnet.att.net E-mail:sales@phtool.com

WEIGHT AND BALANCE: 

Not affected. 

ELECTRICAL LOAD DATA: 

Not affected. 

REFERENCES:

BHT-407-MM-5, Rev. 23, 07 November 2006 

 Chapter 53, Fuselage 

BHT-407-IPB, Rev 05, 22 December 2006 

 Chapter 53, Fuselage 

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

BHT-ALL-SPM, Reissue, 20 August 1999 

Corrosion Control Guide CSSD-PSE-87-01, issue 6 August 1987 

Technical Bulletin 407-01-33 

 Horizontal Stabilizer 407-023-800-ALL Installation, Improvement of. 

Bell Helicopter Textron drawing number 407-799-046 

C. 
ASB 407-01-48 

Page 6 of 32 

PUBLICATIONS AFFECTED: 

BHT-407-MM-5, Rev. 23, 07 November 2006 

 Chapter 4, Mandatory Retirement 

 Chapter 5, Inspections 

 Chapter 53, Fuselage 

BHT-407-IPB, Rev 05, 22 December 2006 

 Chapter 53, Fuselage 

ACCOMPLISHMENT INSTRUCTIONS: 

TABLE 1 

If you have the following tailboom 

You must comply with the 

following sections of this 

bulletin 

Original tailboom P/N 407-030-801-101 

or /-105 

Part I, Part II, Part III, Part IV 

and Part V 

Tailboom 407-030-801-101 upgraded by 

BHT-Approved procedure to 

equivalence of /-105 configuration. 

Part I, Part II, Part III (see 

Note 2 below), Part IV and 

Part V 

Tailboom 407-030-801-101or /-105 

modified by BHT drawing 407-799-046 

Part I (see Note 1 below), 

Part III, Part IV and Part V 

Tailboom 407-030-801-107 Part IV and Part V 

NOTES: 

1. Tailboom inspected and modified in accordance with BHT drawing 407-799-046 

meets the intent of Step 1 through 5 of Part I but must complete Steps 6 

through 8. Following completion of Steps 6 through 8 of Part I, destroy 

identification plate installed during the previous modification. Mark the new 

plate with applicable part number in cross-reference with the original BHT 

identification plate and install in the same location. 

2. For all tailbooms 407-030-801-101 that were upgraded to equivalent of /-105 

configuration, in accordance with BHT-Approved procedure covered with 

Transport Canada Approval form AE-100-1, remove the added identification 

plate that was locally manufactured and installed adjacent to the BHT 

identification plate and destroy. Plug existing holes with two rivets 110-164-1. 

Mark the new plate with applicable part number cross-referenced by the original 

BHT identification plate and install at the location indicated in this bulletin. 

C. 
ASB 407-01-48 

Page 7 of 32 

PART I: Inspection and modification of tailboom assemblies 407-030-801-

 101, /-105 

-NOTETailboom assembly 407-030-801-107 meets the intent of 

the inspections and modifications described in Part I of this 

bulletin. Part I does not apply to tailboom assembly 407-

030-801-107. 

1. Initial inspection, existing fasteners and upper stabilizer support (left 

stabilizer cut-out area, Ref. B.S. 98.89 and B.S. 120.75). 

a. Refer to Figure 3 (Views B and C). Examine as follows for acceptable 

conditions at the affected fastener locations to determine if your tailboom is 

eligible to be modified. 

(1.) Look at the left stabilizer upper support (3) and verify that the two upper 

fasteners as shown in Views B and C are original NAS1738MW5. 

(Correct identification letters/number “T, M, 04 and +” can be seen with a 

magnifying glass on the head of the fastener when paint and primer is 

removed). If an oversize fastener has been installed, the inspection as 

described by Table 2 and Appendix A cannot be done and the tailboom 

assembly (5) must be replaced. 

(2.) Look at the left stabilizer upper support (3) and verify that the two lower 

fasteners as shown in Views B and C are original 100-048-6 (Hi-Lok 

identification number “HL 20 6” can be seen with a magnifying glass on 

the head of the fastener when paint and primer is removed). If an 

oversize fastener has been installed, the inspection/modification as 

described by Table 2 and Appendix A cannot be done and the tailboom 

assembly (5) must be replaced. 

(3.) Examine each of the four fastener locations for acceptable edge distance 

of 0.33 inch (8.38 mm) minimum. If edge distance is not acceptable, 

replace the existing left upper support (3) and doubler (2) using part 

number 407-023-800-127 and 407-023-800-135 respectively before you 

go to Part II of this bulletin. 

b. If all the conditions described above are acceptable, continue with step 2. 

c. If one of the conditions described above is not acceptable, contact Product 

Support Engineering at the numbers that follow: 
ASB 407-01-48 

Page 8 of 32 

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

2. Preparation of fastener holes for inspection by Eddy Current method (left 

stabilizer cut-out area, Ref. B.S. 98.89 and B.S. 120.75). 

a. Refer to chapter 53-00-00 of the maintenance manual and remove the following 

components: 

(1.) The aft oil cooler blower fairing from the aft section of fuselage. 

(2.) The two fiberglass driveshaft covers from top of tailboom assembly. 

(3.) The tail rotor driveshaft assembly located between B.S. 42.00 and B.S. 

75.00. 

CAUTION 

IF SEALANT NEEDS TO BE REMOVED, USE A THIN 

BLADE PUTTY KNIFE. BE CAREFUL TO NOT 

DAMAGE THE ELECTRIC WIRES AT THE TRAILING 

EDGE OF THE STABILIZER. 

(4.) The left auxiliary finlet from end of stabilizer. Keep the screws for later 

installation. 

-NOTEDo not disassemble the lower support angles from the 

closure plates. 

(5.) Both lower stabilizer attachment support assemblies. 

CAUTION 

USE PROTECTIVE DEVICE OR PADDING ON TOP OF 

THE ELECTRIC WIRE STAND-OFF BRACKET 

LOCATED ON BALLAST TRAY INSIDE THE TAILBOOM 

TO PREVENT DAMAGING PAINT FINISH AND/OR 

LOWER SURFACE OF STABILIZER. 

(6.) The stabilizer (6) from the tailboom (5). 
ASB 407-01-48 

Page 9 of 32 

CAUTION 

DO NOT DAMAGE OR ENLARGE HOLES DURING 

REMOVAL PROCESS OF THE FASTENERS.

b. Refer to Figure 3 (Views B and C). Remove the upper rivet NAS1738MW5 and 

the Hi-Lok fastener 100-048-6 located at the front and aft end of the left 

stabilizer support only. 

c. Refer to Table 2. Enlarge holes as follows; 

CAUTION 

MAKE SURE THE TOOL IS PERPENDICULAR TO THE 

TAILBOOM SURFACE AT ALL TIMES WHEN YOU 

DRILL OR REAM. 

(1.) Initial ream each upper hole location (2 places), to 0.1875 inch (4.7625 

mm) diameter where the fasteners NAS1738MW5 were initially installed. 

(2.) Initial ream each lower hole location (2 places) to 0.1935 inch (4.915 mm) 

diameter where the Hi-Lok fasteners 100-048-6 were initially installed. 

3. Inspection of fastener holes by Eddy Current method (left stabilizer cutout 

area, Ref. B.S. 98.89 and B.S. 120.75). 

-NOTEThe Eddy Current inspection procedure recommended 

herein by Bell Helicopter Textron should only be used for 

inspection of Bell 407 tailbooms 407-030-801-101 and /-

105 

a. Refer to Figure 4 (views G and H) and do the inspection of each hole by the 

Eddy Current inspection procedure as recommended by Attachment “A”. 

(1.) If you detect a crack, remove the upper support (3) and the doubler (2) and 

inspect hole again to verify if the crack detected affects the upper tailboom 

skin (7) or the adjacent bulkhead. (Ref. B.S. 98.89 or B.S. 120.75). If a 

crack is confined in the tailboom skin (7) or the adjacent bulkhead, the 

tailboom (5) must be removed from service and replaced with a 

serviceable unit. 

(2.) If there is no crack detected in the tailboom skin (7) or the adjacent 

bulkhead. (Ref. B.S. 98.89 or B.S. 120.75), install a serviceable doubler (2) 

with a serviceable support (3) before you go to step 4. 
ASB 407-01-48 

Page 10 of 32 

4. Inspection of fastener holes for interference with flange radius of bulkheads 

(left stabilizer cut-out area, Ref. B.S. 98.89 and B.S. 120.75). 

a. Refer to Figure 4 (views G and H). Use a mirror to inspect the inboard surface 

of the flange of each bulkhead located at B.S. 98.89 and B.S. 120.75. Examine 

for possible interference from the new fastener retaining collar with the bend 

radius of each bulkhead flange. 

(1.) If there is no interference, go to step 5. 

(2.) Refer to Detail J. If there is interference, fabricate locally a radius block 

for the affected location. Install the radius block (19) against the inboard 

surface of the affected bulkhead flange before increasing the affected 

holes to final dimension described in Table 2. Install the radius block (19) 

as follows: 

(a) Find the best fit and locate the radius block (19) against the internal 

surface of the affected bulkhead flange. Make sure a minimum of 2D 

edge distance will exist at each end of the radius block. 

CAUTION 

MAKE SURE THE TOOL IS PERPENDICULAR TO THE 

TAILBOOM SURFACE AT ALL TIMES WHEN YOU 

DRILL OR REAM. 

(b) Clamp the radius block (19) in place and transfer the existing upper hole 

initial-reamed diameter of 0.1875 inch (4.7625 mm) and lower hole 

initial-reamed diameter of 0.1935 inch (4.915 mm) to the radius block. 

(c) Remove the radius block (19) and deburr each hole. Apply a light coat 

of primer (C-204) to all bare metal surfaces and let dry. 

(d) Install temporarily the radius block (19) against the internal surface of the 

bulkhead flange with two Clecos until the hole final diameter is obtained. 

(e) Go to step 5 and install the new fasteners HL22093-6-4. 

5. Installation of new fasteners HL22093-6 (left stabilizer cut-out area, Ref. B.S. 

98.89 and B.S. 120.75). 

a. Refer to Figure 4 (views G and H) and Table 2. Increase the size of the holes 

to their final dimension as follows: 

B. 
ASB 407-01-48 

Page 11 of 32 

CAUTION 

MAKE SURE THE TOOL IS PERPENDICULAR TO THE 

TAILBOOM SURFACE AT ALL TIMES WHEN YOU 

DRILL OR REAM. 

-NOTEMake sure that the radius block (19), if applicable, remains 

undisturbed when you drill or ream. 

(1.) Increase the diameter of the two upper holes (B.S. 98.89 and B.S 120.75) 

to final reamed dimension of 0.2185 inch (5.55 mm) diameter where the 

NAS1738MW5 were originally installed. 

(2.) Increase the diameter of the two lower holes (B.S. 98.89 and B.S 120.75) 

to final reamed dimension of 0.2185 inch (5.55 mm) diameter where the 

Hi-Lok fasteners 100-048-6 were originally installed. 

(3.) Deburr each hole and install two new fasteners HL22093-6-4 at B.S. 98-

89 and B.S. 120.75 respectively. 

6. Preparation of fastener holes for inspection by Eddy Current method 

(tailboom forward area, Ref. B.S. 45.515, B.S. 58.995 and B.S. 72.475). 

CAUTION 

DO NOT DAMAGE OR ENLARGE HOLES DURING 

REMOVAL PROCESS OF THE FASTENERS.

a. Refer to Figure 4,View J. Remove the rivets located left of B.L. 0.0 at each of 

the driveshaft cover brackets installed at B.S 45.515, B.S. 58.995 and B.S. 

72.475(4 each, total of 12 rivets). 

b. Refer to Table 2. Enlarge holes as follows: 

CAUTION 

MAKE SURE THE TOOL IS PERPENDICULAR TO THE 

TAILBOOM SURFACE AT ALL TIMES WHEN YOU 

DRILL OR REAM. 

(1.) Drill and ream each hole (4 per bracket, 3 places, total of 12 holes) to 

0.1635 inch (4.15 mm) diameter where the fasteners M7885/6-4-02 were 

initially installed. 

(2.) Deburr edges of each hole. 
ASB 407-01-48 

Page 12 of 32 

7. Inspection of fastener holes by Eddy Current method (tailboom forward area, 

Ref. B.S. 45.515, B.S. 58.995 and B.S. 72.475). 

-NOTEThis inspection must also be completed on tailbooms 

modified and identified in accordance with BHT drawing 

407-799-046. 

-NOTEThe Eddy Current inspection procedure recommended 

herein by Bell Helicopter Textron should only be used for 

inspection of Bell 407 tailbooms 407-030-801-101 and /-

105 

a. Refer to Figure 4, View J. Do the inspection of each hole (4 per bracket, 3 

places, total of 12 holes) by Eddy Current inspection procedure as 

recommended in Attachment “A”. 

(1.) If you detect a crack in the tailboom skin (7), the tailboom (5) will have to 

be removed from service and replaced with a serviceable unit. 

(2.) If there is no crack detected in the tailboom skin (7), install new fasteners 

M7885/2-5-02 wet with unreduced primer (C-204) in each hole before you 

go to step 8. 

8. Inspection of left hand and right hand stabilizer cutouts in tailboom 407-030-

801-101, /-105 and tailbooms field-modified by BHT drawing 407-799-046. 

-NOTEThe factory has inspected edges of cutouts on tailboom 

407-030-801-107. Step 8 does not apply to tailboom 407-

030-801-107. 

-NOTEThis inspection must also be completed on tailbooms 

modified and identified in accordance with BHT drawing 

407-799-046. 

a. Refer to Figure 4 and View H. Examine the edges of the left and right stabilizer 

cutouts made in the tailboom skins for cracks, burrs, nicks, and tool marks. 

(1.) If there is a crack at the edge of the stabilizer cutout, notify BHT Product 

Support Engineering with details. 
ASB 407-01-48 

Page 13 of 32 

(2.) If there is no crack, go to step b). 

b. Rework any burrs, nicks, and tools marks not exceeding 0.020 inch (0.508 mm) 

deep using 400 grit minimum Aluminum Oxide sand paper (C-423). 

c. Refinish all bare metal surfaces with a layer of primer (C-204). 

d. If desired, paint the areas of the tailboom were the paint was removed per ASB 

407-99-26 in order to match the aircraft paint scheme and colors. 

PART II: Improved installation of stabilizer assembly (Refer to Technical 

Bulletin 407-01-33 for applicability). 

a. Do the installation of the stabilizer assembly in accordance with Technical 

Bulletin 407-01-33. 

PART III: Identification of modified tailboom assemblies 407-030-801-101, /-105 

and tailbooms field-modified by BHT drawing 407-799-046. 

-NOTETailboom assemblies 407-030-801-101, /-105 inspected 

and modified in accordance with this bulletin are equivalent 

and interchangeable with tailboom assembly 407-030-801-

107. Tailboom 407-030-801-107 does not need new 

identification. 

1. Identification of modified tailboom 407-030-801-101. 

a. For tailboom 407-030-801-101 (see page 6, Table 1, Notes 1 and 2), mark the 

new identification plate 100-071-7 (Ref. Figure 5, item 17) by vibrating stylus 

as follows: 

(1.) Mark the first and second line of the new plate (17) with the existing part 

number and serial number found on the original tailboom identification 

plate (18). 

(2.) Mark on the third line “Modified to P/N 407-530-014-101”. 

(3.) Mark on the fourth line the name of the repair facility that has done the 

modification. 
ASB 407-01-48 

Page 14 of 32 

(4.) Mark on the fifth line, the date at which the modification was completed by 

the repair facility. 

b. Form the plate (17) to match the tailboom contour for the location shown in 

Figure 5. 

c. Locate the identification plate (17) on the top of the tailboom skin as seen in 

Figure 5 and use a # 40 drill (0.098 in/2.48 mm) to make two holes. 

d. Remove the plate (17) and deburr both sides of the two holes in the tailboom 

skin (7). 

e. Coat faying surface of identification plate (17) with sealant (C-392) and install 

using two rivets (16). 

f. Wipe excess sealant and make sure no void exists at the edges of the plate 

(17). 

2. Identification of modified tailboom 407-030-801-105. 

a. For tailboom 407-030-801-105 (see page 6, Table 1, Notes 1 and 2), mark the 

new identification plate 100-071-7 (Ref. Figure 5, Item 17) by vibrating stylus as 

follows; 

(1.) Mark the first and second line of the new plate with the existing part 

number and serial number found on the original tailboom identification 

plate. 

(2.) Mark on the third line “Modified to P/N 407-530-014-103”. 

(3.) Mark on the fourth line the name of the repair facility that has done the 

modification. 

(4.) Mark on the fifth line, the date at which the modification was completed by 

the repair facility. 

b. Form the plate (17) to match the tailboom contour for the location shown in 

Figure 5. 

c. Locate the identification plate (17) on the top of the tailboom skin as seen in 

Figure 5 and use a # 40 drill (0.098 in/2.48 mm) to make two holes. 

d. Remove the plate (17) and deburr both sides of the two holes in the tailboom 

skin (7). 
ASB 407-01-48 

Page 15 of 32 

e. Coat faying surface of identification plate (17) with sealant (C-392) and install 

using two rivets (16). 

f. Wipe excess sealant and make sure no void exists at the edges of the plate 

(17). 

PART IV: Assignment of retirement life and new recurring inspection 

requirements to tailboom assembly 407-030-801-107 and tailbooms 407-530-014-

101, /-103. 

1. For tailbooms 407-530-014-101, /-103: 

a. Create a new Historical Service Record sheet (HSR) for your modified tailboom 

and indicate the time since new in the appropriate box. 

b. Record date of the modification completed on your tailboom. 

-NOTEThe 5000 hours retirement life is assigned to the upper 

tailboom skin only, but for tracking purposes, is identified 

using the tailboom part number and serial number. When 

the tailboom assembly reaches a total of 5000 hours in 

service, a new skin cannot be installed and the tailboom 

must be retired. 

c. Assign a life of 5000 hours from the time at which the inspection/modification 

was completed and show in the appropriate box of the HSR, the total flight time 

at which the tailboom must be retired. 

d. Annotate the aircraft technical records to indicate compliance with this bulletin. 

e. Install all the components that were removed in Step 2 of PART I and return the 

tailboom to service. 

f. Inspect your tailboom as instructed by Alert Service Bulletin 407-07-80. 

g. When you have accumulated 5000 hours from the time of 

inspection/modification, retire from service the tailboom 407-530-014-101 or 

407-530-014-103 and install a serviceable unit. 

2. For tailbooms 407-030-801-107: 

a. Create a new Historical Service Record sheet (HSR) for your BHT-original 

tailboom and indicate the time since new in the appropriate box. 

C. 

C. 
ASB 407-01-48 

Page 16 of 32 

-NOTEThe 5000 hours retirement life is assigned to the upper 

tailboom skin only, but for tracking purposes, is identified 

using the tailboom part number and serial number. When 

the tailboom assembly reaches a total of 5000 hours in 

service, a new skin cannot be installed and the tailboom 

must be retired. 

b. Assign a life of 5000 hours Since New in the appropriate box of the HSR, i.e. 

the total flight time at which the tailboom must be retired. 

c. Annotate the aircraft technical records to indicate compliance with this bulletin. 

d. Inspect your tailboom as instructed by Alert Service Bulletin 407-07-80. 

e. When a Total Time Since New (T.T.S.N) of 5000 flight hours is reached, retire 

from service the tailboom 407-030-801-107. 

PART V: Maintenance and inspection of tailbooms 407-530-014-101, /-103 

and tailboom 407-030-801-107. 

1. Maintenance: 

a. Maintain your tailboom in accordance with your 407 Maintenance Manual BHT407-MM-1 and the BHT corrosion control guide CSSD-PSE-87-001. 

2. Inspection: 

a. The inspection requirements as originally defined by this bulletin for your 

tailboom 407-530-014-101/-103 or tailboom 407-030-801-107 are now 

cancelled and replaced by new inspection requirements defined under Alert 

Service Bulletin 407-07-80. 

C. 

C. 

C. 
ASB 407-01-48 

Page 17 of 32 

Figure 1. Tailboom 407-030-801-101, /-105, inspection, modification and 

identification of. 
ASB 407-01-48 

Page 18 of 32 

Figure 2. Tailboom 407-030-801-101, /-105, inspection and modification of 

(sheet 1 of 3) 
ASB 407-01-48 

Page 19 of 32 

Figure 2. Tailboom 407-030-801-101, /-105, inspection and modification of 

(sheet 2) 
ASB 407-01-48 

Page 20 of 32 

Figure 2. Tailboom 407-030-801-101, /-105, inspection and modification of 

(sheet 3) 

B. 

B. 

B. 
ASB 407-01-48 

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Figure 3. Tailboom 407-030-801-101, /-105, initial (visual) inspection of.
ASB 407-01-48 

Page 22 of 32 

Figure 4. Tailboom 407-030-801-101, /-105, inspection (Eddy Current) and 

modification of (sheet 1 of 3) 

B. 
ASB 407-01-48 

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Figure 4. Tailboom 407-030-801-101, /-105, inspection (Eddy current) and 

modification of (sheet 2) 
ASB 407-01-48 

Page 24 of 32 

Figure 4. Tailboom 407-030-801-101, /-105, inspection (Eddy current) and 

modification of (sheet 3) 

B. 
ASB 407-01-48 

Page 25 of 32 

Figure 5. Tailboom 407-030-801-101, /-105, identification of 
ASB 407-01-48 

Page 26 of 32 
ASB 407-01-48 

Page 27 of 32 

ATTACHMENT “A”

Inspection of fastener holes on tailbooms P/N 407-030-801-101/-105 

by Eddy Current method. 

This inspection shall be capable of detecting a 0.020 inch (0.508 mm) deep indication 

on the surfaces indicated. 

1.0 EQUIPMENT

NOTE 

Eddy Current equipment shall be capable of detecting surface 

and/or near surface discontinuities in electrically conductive 

materials, and shall be capable of detecting impedance 

changes induced by variations in material properties as well 

as metallurgically and mechanically induced discontinuities. 

The equipment shall also contain a means to display detected 

impedance changes. 

NOTE 

The probes shall be of the split shaft type (ref. Figure 1) and 

capable of inspecting hole diameters between 

0.160/0.195inch (4.064/4.953 mm). Manual bolthole probes 

shall also have adjustable collars to allow the operator to fix 

the depth of the probe inside the holes being inspected. The 

largest diameter of the collars shall not exceed 0.750 inch 

(19.05 mm). 

1.1 Hocking Phasec 2200 or Zetec Miz 20 or equivalent Eddy Current 

Inspection equipment. 

1.2 Eddy Current probes MBD2-10/12-1WL and MBD2-12/14-1WL or 

equivalent tuned to a frequency between 100 KHz – 1.0 MHz. 

1.3 Aluminum crack calibration standard number “BHTI EC-10-20” (ref. 

Figure 3). This standard may be obtained from the following sources: 

EC/NDT LLC PH Tool 

1020 S 344th 10 Callowhill Road 

Suite 214 New Britain, PA 18901 

Federal Way, WA 98003 Phone no. (888) 553-9245 

Phone no. (877) 565-0797 Fax no. (215) 822-6799 

Fax no. (253) 815-0827 E-mail sales@phtool.com 

E-mail EC-NDT@worldnet.att.net 
ASB 407-01-48 

Page 28 of 32 

2.0 PERSONNEL

2.1 All personnel performing Eddy Current inspection shall be qualified and 

certified to level II or level III requirements established in AIA/NAS 410, 

SNT-TC-1A, or equivalent. 

3.0 CALIBRATION

3.1 RIVET HOLES 

3.1.1 Choose the eddy current probe (as described in par.1.2) that best 

fits the rivet hole size being inspected. Adjust the probe coil depth 

so that the coil is centered between the upper and lower surface 

of the standard. Lock the probe collar in place to maintain the 

probe coil depth (ref. Figure 2). 

3.1.2 Adjust the Eddy Current instrument controls to reflect the 

following: 

Frequency: 500 KHz 

 V/H Gain: 15/10 OR a ratio of 1.5:1 

 Coarse Gain: 24 dB 

 Probe: Differential 

 Filters: Off 

3.1.3 Place the probe into the appropriate non-flawed hole of the 

standard and balance the probe. The balance point should be 

located in the center of the screen. 

3.1.4 Insert the probe into the appropriate hole of the standard 

containing the simulated 0.020” (0.508 mm) flaw and rotate the 

probe past the simulated crack. Adjust the instrument phase 

control so that the angle of the displayed signal response appears 

similar to that shown in Figure 4. 

3.1.5 Adjust signal amplitude similar to that of Figure 4 (15 - 20% of the 

screen height). 

NOTE 1: Automatic rotating bolthole guns and probes may be utilized for this 

inspection provided the intent of the referenced calibration and inspection procedures 

are followed. 

Some variations to the signals shown in Figure 4 may exist. Proper 

interpretation of signal response is the responsibility of the personnel performing the 

inspection. 
ASB 407-01-48 

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4.0 PRE-INSPECTION

4.1 All applicable holes shall be inspected in the initial-reamed condition. 

4.2 Verify the appropriate size probe for the holes being inspected. The 

probe diameter must be such that the coil is in contact with the inside 

diameter surface of the hole at all times. 

4.3 All holes requiring Eddy Current inspection shall be free of edge burrs. 

5.0 INSPECTION

5.1 RIVET HOLE INSPECTION 

5.1.1 Measure through the hole from the surface of the support member 

to the center of the tail boom skin thickness using a depth gage. 

Use this measurement to adjust the probe collar so that the 

inspection coil will inspect the center thickness of the skin member 

only. 

OR 

Monitor the displayed Eddy Current signal response from the 

probe as it is pushed through the fastener hole. Lock the 

adjustable collar in place when the displayed Eddy Current signal 

deflection is maximized between the upper and lower surfaces of 

the plate member requiring inspection. 

5.1.2 Eddy Current inspect the inside bore of the rivet hole for a flaw 

signal response similar to that of the standard. 

NOTE 2: Edge burrs around the holes must be removed from both inner and outer 

surfaces prior to Eddy Current inspection. Edge burrs will add unwanted electrical 

noise to the Eddy Current display and will complicate signal interpretation. 

6.0 ACCEPT/REJECT CRITERIA

6.2 RIVET HOLES - Any indication that appears 0.020 inch (0.508 mm) in 

length or greater in the initial-reamed fastener hole size (ref. Table 2) is 

cause for rejection. 
ASB 407-01-48 

Page 30 of 32 

 

Probe

Adjustable 

collar

Figure 2

Crack standard

RIVET HOLE 

CALIBRATION

First, calibrate the 

bolthole probe to 

the standard. 

Second, move the 

adjustable collar 

so that the probe 

coil will be at the 

same depth as the 

skin being 

inspected.

Figure 1 

SPLIT SHAFT BOLT HOLE PROBE 

SPLIT SHAFT 

COIL 

ADJUSTABLE 

COLLAR 
ASB 407-01-48 

Page 31 of 32 

Figure 3 

0.020 inch +/- 0.002 (0.508 mm +/- 0.050) 

length through wall EDM slot. 

0.020 inch +/- 0.002 (0.508 mm 

+/- 0.050) length through wall 

EDM slot. 

BHTI EC-10-20

(manufacturer info here)

0.040 inch +/- 0.002 

(1.016 mm +/- 0.050) 

length through wall EDM 

slot.

0.172” 

Dia. 

holes 

0.203” 

Dia. 

holes

S/N xxx 

 NOT TO SCALE 
ASB 407-01-48 

Page 32 of 32 

0.020” inch (0.508 mm) 

FLAW SIGNAL 

BALANCE POINT 

Figure 4 

This display is typical of that produced by a differential Eddy 

Current probe. 

Approx. 

15 – 20 % 

Screen 

Height