ASB 412-13-155 

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ECCN EAR99 

 ALERT SERVICE BULLETIN 412-13-155 

4 February 2013 

MODEL AFFECTED: 412/412EP 

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

INSPECTION OF 

HELICOPTERS AFFECTED: Serial numbers 33001 through 33213, 34001 

through 34036 and 36001 and subsequent. 

 

COMPLIANCE: Within the next 25 hours and every 25 hours 

thereafter 

DESCRIPTION: 

Bell Helicopter has recently examined a fractured tail rotor blade; the fracture 

originated from surface damage. Present BHT-412-MM Special Inspection 

requirements call for a 3X magnifying glass inspection of the tail rotor blade surface 

for damage every 25 hours. Any damage is to be investigated by removing paint and 

inspecting skin condition with 10X magnification. Due to the critical nature of this 

inspection and requirements to fully comply, Bell Helicopter is adding a local 

inspection with 10X magnification of blade between stations 20.00 to 35.00 from the 

leading edge to the trailing edge. This is in addition to the 3X requirement for the full 

blade. Operators are reminded that it is critical to investigate any paint and skin 

imperfections should the inspection warrant. If anomalies are noted during the 3X/10X 

inspections of the blade surface, remove the paint and check skin condition again with 

10X magnification. Skin damage exceeding Maintenance Manual limits requires blade 

removal from service. Applicability of this bulletin to any spare part shall be 

determined prior to its installation on an affected helicopter. 

APPROVAL: 

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

 
ASB 412-13-155 

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ECCN EAR99 

CONTACT INFO: 

For any questions regarding this bulletin, please contact: 

Bell Helicopter Product Support Engineering - Medium Helicopters 

Tel: 450-437-6201 / 1-800-363-8028 / psemedium@bh.com 

MANPOWER: 

Approximately 1.0 man-hour is required to complete this bulletin. This estimate is 

based on hands-on 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: 

Required Material: 

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

may be obtained through your Bell Helicopter Textron Supply Center. 

Part Number Nomenclature Qty 

 

212-010-750-133 Blade A/R 

Consumable Material: 

The following material may be 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-C-451 Abrasive Cloth or Paper, 

Aluminum Oxide 

A/R C-406

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

SPECIAL TOOLS: 

None required. 

WEIGHT AND BALANCE: 

Not affected. 
ASB 412-13-155 

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ECCN EAR99 

ELECTRICAL LOAD DATA: 

Not affected. 

REFERENCES: 

BHT-412-IPB Illustrated Parts Breakdown 

BHT-412-MM Maintenance Manual 

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

PUBLICATIONS AFFECTED: 

BHT-412-MM Maintenance Manual. 

ACCOMPLISHMENT INSTRUCTIONS: 

-NOTERemoval of the tail rotor blades is not required for this 

inspection. 

1. Upon completion of the 25-hour Special Inspection of tail rotor blade per BHT-412-

MM, Chapter 5, carry out a further detailed visual inspection with 10X magnification 

of the shaded area shown in Figure 1 between stations 20.00 to 35.00 of both 

sides of the blade with a bright light. 

2. If any blistering, peeling, flaking, bubbling or cracked paint is detected, remove the 

paint from the affected area by sanding in a spanwise direction only with an 

abrasive cloth or paper (C-406) 240 grit or finer and a final sanding using an 

abrasive cloth or paper (C-406) 400-grit or finer. After paint removal, visually 

inspect the affected area for damage using a 10X magnifying glass. Damage 

beyond the limits of the Maintenance Manual requires blade removal from service. 

3. Only superficial corrosion that can be removed with aluminum wool or very fine 

grade abrasive pad (C-407) is permissible. Corrosion on the spar 0.003 inch deep 

or less is acceptable when polished out. Replace any blade that has corrosion on 

the spar greater than 0.003 inch. 

4. If a nick, scratch or dent is found, visually inspect for crack using a 10X magnifying 

glass or higher, and measure the depth of the damage. (A digital optical 

micrometer is one tool that can be used for this measurement). 

5. Repair damage and/or corrosion found on tail rotor blades in accordance with the 

Maintenance Manual. 

6. Replace any blade that has a crack. No cracks are permitted. 
ASB 412-13-155 

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ECCN EAR99 

7. If paint was removed during the above steps, carry out paint touch up/refinishing as 

per BHT-412-CR&O, Chapter 64. 

8. Make an entry in the helicopter logbook and historical service record to indicate 

accomplishment of this ASB. Enter exact location of blend repair (if applicable) in 

the historical service record. Location shall include blade station as well as 

distance from the leading edge. 

Figure 1