NO.

DATE

PAGE DATE

REV 

### 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 412-09-136

12-08-09 Nov 09, 2009

A 1 of 5

MODEL AFFECTED: 412, 412EP

SUBJECT: TAIL ROTOR BLADE P/N 212-010-750-ALL,

INSPECTION OF.

HELICOPTERS AFFECTED : All Model 412 helicopters

Tail Rotor Blades P/N 212-010-750-ALL serial numbers A-17061 and subseq uent will have the intent of this bulletin accomplished prior to delivery.

COMPLIANCE: Within the next 200 flight hours or 180 days, whichever comes first. Applicable to all installed or spare tail rotor blades.

DESCRIPTION:

Bell Helicopter has discovered that certain tail rotor bl ades may have manufacturing anomalies in the spar area as a result of the chemical milling process. The anomalies may be identified as pits and/or corrosion on the spar. Serviceability of the spar will consist of removing the pain t on the spar between blade stations 22.5 and 40.0 and carrying out a detailed visual inspection wit h a 3-power or higher magnifying glass. A

filet filled with adhesive r uns spanwise between the blade spar and the skin 2.25 inches aft of the blade leading edge, bot h inboard and outboard sides. The area to be inspected runs along the edge of the spar filet and a half inch forward of this point. (Between 1.75 and 2.25 inch from the leading edge of the blade and from Blade Stations 22.5 to 40.0, both inboard and outboard sides).

APPROVAL:

The engineering design aspects of th is bulletin are FAA/ODA approved.

MANPOWER:

Approximately 10.0 man-hours ar e required to complete this bulletin. Man-hours are based on hands-on time, and may vary wit h personnel and facilities available. A A

AASB 412-09-136 Page 2 of 5

WARRANTY:

Owners / Operators of Bell Helico pters who comply with the inst ructions in this Bulletin and find chemical milling pits in excess of 0.003 inch deep (Between 1.75 and 2.25 inch from the leading edge of the blade and from Blade Stati ons 22.5 to 40.0, both inboard and outboard sides) will be eligible to receive a pro-rated credit towards the cost of replacement blades. In order to receive this credit send an e-mail with detailed clear photographs of the corrosion pitti ng together with depth measurements to Product Support Engineering psemedium@bellhelic opter.textron.com

. Please ensure that you include the sh ip number, blade part numbers, and serial numbers with TT on the parts. Once this has been reviewed by Product Support Engineering you will be notified with their approval/disapproval.

In addition special warranty consideration to cover the cost of the labor to perform the inspection @ $750.00 USD per blade will apply only to those tail rotor blades which are new in stock, installed on new ships still under warranty, and or new spare parts installed on ships still within the one year /1000hour warranty period. To receive credit, file a VISTA warranty claim referencing this ASB for labor.

To receive the above warranty:

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

this ASB.

• Purchase the required applicable TR Blade/Blades from a Bell approved source.

• Submit an MMIR to the Bell Warr anty Department referencing this

ASB.

Customers who fail to comply wit h the instructions in this Bulletin before the 30 July 2010 are not eligible for the special warr anty credit listed above. There is no other

labor or consumables cove red under this bulletin.

MATERIAL:

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

Part Number Nomenclature Quantity

212-010-750-133 Tail Rotor Blade Assembly 2 (if required) AASB 412-09-136 Page 3 of 5

Consumable Material: The following material is required to acco mplish this bulletin, but may not require ordering, depending on the operat or’s consumable material stock levels. This material may be obtained through your Bell He licopter Textron Supply Center.

Part Number Nomenclature Quantity Reference

MIL-PRF-23377,TYICLC

EPOXY Primer A/R C-204

MILC85285TYI-27925 Polyur ethane Coating semigloss white No. 27925 A/R C-245

MILC85285,TYI,37038 Poly urethane Coating

lusterless black No. 37038 A/R C-245

MILC87936TYI 5GAL Cleaning Compound A/R C-318

TURCO W.O.1 GAL Cleaner A/R C-344 TT-N-95,TYII 1GAL A liphatic Naphtha A/R C-305 SCOTCHBRITE TY-A Abrasive pad A/R C-407 ABRASIVE 240 GRIT Abrasive Cloth or paper A/R C-423

TT-I735 ISOPROPYL Solvent A/R C-385

SPECIAL TOOLS:

None required

WEIGHT AND BALANCE:

Not affected.

ELECTRICAL LOAD DATA:

Not affected

REFERENCES:

BHT-412-IPB Illustra ted Parts Breakdown

BHT-412-MM Maintenance Manual BHT-412-CR&O Component Repair and Overhaul Manual

BHT-ALL-SPM AASB 412-09-136 Page 4 of 5

PUBLICATIONS AFFECTED:

BHT-412-MM Maintenance Manual

ACCOMPLISHMENT INSTRUCTIONS:

1. Remove tail rotor hub and blade assemb ly from the helicopt er as per BHT-412-

MM.

2. Remove blades from the ta il rotor hub as per BHT-412-CR&O.

3. Remove paint from the spar between t he doubler tip to station 40.0 by sanding in a spanwise direction only using 180-grit or finer abras ive cloth (C-423). Use finer grade abrasive cloth once the coat of primer is reached to prevent damaging the spar.

CAUTION

Pay particular attention not to damage the underlying spar,

adhesive and aluminum skin dur ing sanding operation. Any damage greater than 0.003 inch deep is cause for rejection

and the blade must be removed fr om service. Do not remove paint from the skin.

4. Ensure that all paint (on the spar only) is removed from the first 2.25 inches of the leading edge (chordwise) and from t he B.S 22.5 (doubler ti p) to B.S. 40.0. Refer to Figure 1. This wi ll expose the spar up to the filet between the blade spar and skin. A filet f illed with adhesive runs span wise between the blade spar

and the skin 2.25 inches aft of t he blade leading edge, both inboard and outboard sides. The area to be inspected runs along the edge of the spar filet and a half inch forward of this poin t. (Between 1.75 and 2.25 inch from the leading edge of the blade and from Blade Stations 22 .5 to 40.0, both inboard and outboard sides).

5. Wipe area with a clean cloth dampened with alcohol (C-385) or aliphatic naphtha (C-305) and dry thoroughly.

6. Carry out a detailed visual inspection of the spar for corrosion and/or pitting using a 3-power or higher magnifying gla ss. Anomalies on the steel spar 0.003 inch deep or less must be polished out in accordance with BHT-412-MM. AASB 412-09-136 Page 5 of 5

CAUTION

Any defect greater than 0.00 3 inch deep is cause for rejection and the blade must be removed from service.

7. If repairs are required, the surface finish of the repair shall be similar to surrounding area.

8. Carry out paint touch-up on tail rotor blade as per BHT-412-CR&O.

9. Install tail rotor blades on tail rotor hub and statically balance.

10. Install tail rotor hub and blade assembly on helicopter and carry out operational check as per BHT-412-MM.

Annotate records to indicate co mpliance with this bulletin.



## Figure 1