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### ALERT SERVICE BULLETIN

AN APPROPRIATE ENTRY SHOULD BE MADE IN TH E AIRCRAFT LOGBOOK UPON ACCOMPLISHMENT

IF OWNERSHIP OF AIRCRAFT HAS CHANGED PLEASE FORWARD TO NEW OWNER 407-10-93

Aug 30, 2010 May 03, 2010

A 1 of 11

MODEL AFFECTED: 407

SUBJECT: TAILBOOM ATTACHMENT HARDWARE,

REPLACEMENT OF.

HELICOPTERS AFFECTED: Model 40 7 Helicopters serial number 53000 through 53990.

[Model 407 helicopters se rial number 53991 and subsequent will have the in tent of this bulletin accomplished prior to delivery.]

COMPLIANCE: For helicopters with cumulative flight time of 7,000 flight-hours or less: Accomplish this

bulletin at the next 600 Hour scheduled inspection but no later than December 31 st , 2010.

For helicopters with cumu lative flight time of more than 7,000 flight-hours: Accomplish this bulletin within 150 hours or 90 days, whichever comes first, following release date of this

bulletin.

DESCRIPTION:

Bell Helicopter has reviewed the tailboom atta chment installation of the Model 407. It has been determined that the torque values s pecified in the maintenance manual and used during assembly of the 407 for the tailboom attachment bolts exceed the specified torque range recomm ended for subject bolts.

This bulletin mandates the re moval of the existing tailb oom attachment hardware and

the installation of new hardware with reduced torque values. In addition, specific hardware installation/torquing procedure is pr ovided for the tailboom to aft fuselage joint.ASB 407-10-93 Page 2 of 11

APPROVAL:

The engineering design aspects of this bulletin are Transport Canada Civil Aviation (TCCA) approved.

MANPOWER:

Approximately 2.0 man-hours ar e required to complete this bulletin. Man-hours are based on hands-on time, and may vary with pers onnel and facilities available. This time estimated does not include post installation torque checks as required.

WARRANTY:

Owners / Operators of Bell Heli copters who comply with the in structions in this Bulletin will be eligible to receive a credit for the replacement parts outlined in the materials

section of this bulletin.

To receive this credit:

• Comply with the instructions contained in this Bulletin no later than the applicable hours in the “compliance section” of this ASB, or before December

31 st , 2010.

• Purchase replacement parts as required in the materials section of this bulletin from a Bell approved source.

• Submit an MMIR to the Bell Warranty Department.

Customers who fail to comply with the instruct ions in this Bulletin after December 31 st

, 2010 are not eligible for the special warrant y credit listed above. There is no labor

credit associated with this bulletin.

MATERIAL:

Required Material: The following material is required for the ac complishment of this bulletin and may be obtained through your Bell Helico pter Textron Supply Center.

Part Number Nomenclature Quantity

NAS627-30 Bolt 2

42FLW-720 Nut 2

NAS626-26 Bolt 2

42FLW-624 Nut 2 AASB 407-10-93 Page 3 of 11

Consumable Material:

The following material is required to acco mplish this bulletin, but may not require ordering, depending on t he operator’s consumable material stock levels. This material may be obtained through your Bell He licopter Textron Supply Center.

Part Number Nomenclature Quantity Reference

CA1000 6OZ Anti-corrosion compound 1 C-586( Note 1)

Note 1: Mastinox 6858KD (C-128) can be used as an alternate as prescribed in

the current maintenance manual. This product can be obtained from BHTapproved supply sources under P/N XMAS6856K/160CTG.

SPECIAL TOOLS:

Socket P/N 407-230-001-101 or equivalent

Note: an equivalent tool may be locally fabricated using a commercial 12-point socket. Refer to Figure 1.

WEIGHT AND BALANCE:

Not affected

ELECTRICAL LOAD DATA:

Not affected

REFERENCES:

BHT-407-IPB Illustrated Parts Breakdown

BHT-407-MM Maintenance Manual

BHT-ALL-SPM Standard Practices Manual

PUBLICATIONS AFFECTED:

BHT-407-MM Maintenance Manual AASB 407-10-93 Page 4 of 11

ACCOMPLISHMENT INSTRUCTIONS:

1. Prepare helicopter for maintenance.

2. Remove the access panel fr om the right aft fuselage to gain access to the tailboom

attachment hardware. Refe r to BHT-407-MM, chapter 53

3. Support weight of the tailboom with an appropriate s upport device or stand.

Replacement of tailboom attachment bolts and nuts;

NOTE

To prevent using the discrepa nt hardware again, it is recommended to use a hacksaw or an equivalent tool and make a .125 to .250 inch (3.175 to 6.35 mm) deep cut at any location on the bolt (1) and the nut (2) removed before discarding.

1. (Ref. Figure 2) Remove left upper attach ment bolt (1) and nut (2) but retain the chamfered washer (4) and the regular washers (3). Discard the nut (2) and the bolt (1) you have removed.

NOTE

Replacement hardware (bolt (1 ) and nut (2)) shall be new. Hardware with unknown origin should not be used and must be discarded appropriately to prevent further usage.

2. Install a new bolt (1) procured from a BHT-Approved supply source as follows:

a) Coat the shank of the new bolt (1) and the faying surfaces of the chamfered washer (4) with anti-corrosion compound (C-586). Do not apply compound on any threads of the bolt (1).

b) Fit the new bolt (1) ( with the chamfered washer (4 ) against head of bolt (1)) through the tailboom and the fuse lage upper mating fittings.

c) Select a sufficient number of washers (3) for opposite end of bolt (1) to obtain a

minimum of 1 to a maximum of 3 th reads showing beyond the nut (2) after proper torque is obtained. C oat the faying surfaces of these washers (3) with anti-corrosion compound (C-586) and fit ov er shank of the new bolt (1). AASB 407-10-93 Page 5 of 11

NOTE

Upper nut (2) must have a minimu m tare value of 14 inch/lbs (1.58 Nm) or more.

3. Install a new nut (2) on the forw ard end of the bolt (1) as follows;

a) Coat the nut (2) faying surface prior to assembly. Do not apply compound on any threads of the nut (2).

b) Run the nut (2) on the thr eads of the mating bolt (1) with a dial indicator type torque wrench and measure existing tare.

c) Torque the nut (2) between 570 to 580 inch /lbs (64.4 to 65.5 Nm) of torque plus the tare of the nut (2), using socket P/N 407-230-001-101 or equivalent tool.

d) Back off nut (2) at least a minimum of 3⁄4 of a turn before re-applying the same torque between 570 to 580 inch/lbs (64.4 to 65.5 Nm) plus the existing tare of the nut (2).

e) Coat bolt (1) head, nut (2) and washer s (3, 4) with anti-c orrosion compound (C586).

4. Repeat Steps 1 through St ep 3 for the opposite right upper bolt (1) and mating nut (2).

NOTE

To prevent using the discrepa nt hardware again, it is recommended to use a hacksaw or an equivalent tool and make a .125 to .250 inch (3.175 to 6.35 mm) deep cut at any location on the bolt (10) and the nut (7) removed before discarding.

5. (Ref. Figure 2) Remove left lower attach ment bolt (10) and nut (7) but retain the chamfered washers (8) and the regular washers (9). Discard the nut (7) and the bolt (10) you have removed.ASB 407-10-93 Page 6 of 11

NOTE

Replacement hardware (bolt (10) and nut (7)) shall be new. Hardware with unknown origin should not be used and must be discarded appropriately to prevent further usage.

6. Install a new bolt (10) procured from a BHT-Approved supply source as follows:

a) Coat the shank of the new bolt (10) and the faying surfaces of the chamfered washer (8) with anti-corrosion compound (C-586). Do not apply compound on any threads of the bolt (10).

b) Fit the new bolt (10) (with the chamfer ed washer (8) against head of bolt (10)) through the tailboom and the fuselage lower mating fittings.

c) Select a sufficient number of washers (9) for opposite end of bolt (10) to obtain

a minimum of 1 to a maximum of 3 th reads showing beyond the nut (7) after proper torque is obtained. C oat the faying surfaces of these washers (9) with anti-corrosion compound (C-586) and fit ov er shank of the new bolt (10).

NOTE

Lower nut (7) must have a minimum tare value of 9.5 inch/lbs (1.07Nm) or more.

7. Install a new nut (7) on the forw ard end of the bolt (10) as follows;

a) Coat the nut (7) faying surface prior to assembly. Do not apply compound on any threads of the nut (7).

b) Run the nut (7) on the threads of the ma ting bolt (10) with a dial indicator type torque wrench and measure existing tare.

c) Torque the nut (7) between 360 to 370 inch /lbs (40.6 to 41.8 Nm) of torque plus the tare of the nut, (7 ) using proper tool.

d) Back off nut (7) at least a minimum of 3⁄4 of a turn before re-applying the same torque between 360 to 370 inch/lbs (40.6 to 41.8 Nm) plus the existing tare of the nut (7).

e) Coat bolt (10) head, nut (7) and washers (8, 9) with anti-corrosion compound (C-586)

8. Repeat Steps 5 through Step 7 for the oppos ite right lower bolt (10) and nut (7).ASB 407-10-93 Page 7 of 11

9. Reinstall aft fuselage access cove r using the screws retained earlier.

10. Annotate technical records to indicate replacement of the tailboom assembly attachment hardware in compliance with this bulletin.

SPECIAL INSPECTION:

Torque check 1 to 5 flight hours fo llowing initial installation;

NOTE

For torque check purposes, the assembly torque to be applied is the minimum specifi ed torque (see Figure 2) plus the minimum acceptable tare torque of 14 inch/lbs(1.58 Nm) for the upper nuts (2) and 9.5 inch/Lbs (1.07Nm) for the lower nuts(7).

1. Torque check the upper and lower nuts (2, 7) as per procedure found in Chapter 2

of the Standard Practices Manual every 1 to 5 flight hours until torque stabilized.

2. Annotate technical records to indicate compliance with this special inspection.

SCHEDULED INSPECTION:

Recurring torque check every 300 hours of operations.

NOTE

For torque check purposes, the assembly torque to be applied is the minimum specifi ed torque (see Figure 2) plus the minimum acceptable tare torque of 14 inch/lbs(1.58 Nm) for the upper nuts (2) and 9.5 inch/Lbs (1.07Nm) for the lower nuts(7).

1. (Ref. BHT-ALL-SPM, Chapter 2)Gain a ccess and perform a recurring torque check at all four attachment positions;

a) Attachment that has not retained proper torque will r equire disassembly and inspection. The assembly shall be insp ected for damage, corrosion, improper assembly, and condition. b) The mating hardware (fastener(s) and nut (s)) must be replaced with new one(s) and torqued to the Assembly Torque value following the procedure

outline in this bulletin.ASB 407-10-93 Page 8 of 11

c) The affected hardware(s) would have to be Torque Checked again at the same scheduled intervals (special inspections) set following initial installation.

2. Annotate technical records to indicate compliance with this special inspection.

3. Repeat this torque check at ev ery 300 hours of com ponent operation.

MAINTENANCE OF TAILBOOM HARDWARE:

1. Discard all hardware (mating nuts (2, 7) and bolts (1, 10)) each time the tailboom assembly is removed from or installed on the fuselage;

a) Use a hacksaw or an equivalent tool and make a .125 to .250 inch (3.175 to 6.35 mm) deep cut at any location on th e bolt (1) and the nut (2) removed before discarding.

b) Install only new hardware using the procedure outlined in this bulletin.ASB 407-10-93 Page 9 of 11

FIGURE 1: Maximum and minimum re ference dimensions of socket AASB 407-10-93 Page 10 of 11

FIGURE 2: Replacement of tailboom upper attachment bolts (Sheet 1 of 2)ASB 407-10-93 Page 11 of 11

LEGEND

FIGURE 2: Replacement of tailboom uppe r attachment bolts (Sheet 2 of 2)