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BOLLETTINO TECNICO

The technical content of this document is approved

under the authority of DOA nr. EASA.21J.005.

N° 412-136

DATE August 13, 2013 

REV.

Compliance with

this bulletin is:

DERIVED FROM BELL ALERT SERVICE BULLETIN 

412-13-155 DATED FEBRUARY 4, 2013 

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

REASON: Inspect the subject tail rotor blades for presence of damages.

HELICOPTERS AFFECTED:

COMPLIANCE:

Within the next 25 hours time-in-service (TIS) or 30 days, whichever occurs first, and 

thereafter at intervals not to exceed 25 hours TIS or 30 days, whichever occurs first.

DESCRIPTION:

Some cases of failured tail rotor blades have been reported by Bell Helicopter; the 

investigations conducted by Bell determined that the failure originated from a crack deriving 

from surface damages. A periodic inspection of the blade surfaces has been required by Bell. 

Even if no similar failure has ever been reported on blades installed on AW helicopters, due to 

the P/N commonality this BT is issued to introduce the same inspection on TR blades 

installed on AW helicopters.

This Bollettino requires a 3X magnifying glass inspection of the tail rotor blade surface for 

damages (crack, corrosion, nick, scratch, or dent) every 25 hours or 30 days. Any damage is 

AgustaWestland S.p.A

Via Giovanni Agusta, 520

21017 Cascina Costa di Samarate (VA) Italy

Tel.: +39 0331 229111 - Fax: +39 0331 229605/222595

MANDATORY

An appropriate entry should be made in the aircraft log book upon accomplishment.

If ownership of aircraft has changed, please, forward to new owner.
B.T. 412-136

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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, a further local 

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

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

the full blade. If anomalies are noted during the 3X/10X inspections of the blade surface, this 

Bollettino requires to remove the paint and check skin condition again with 10X 

magnification. Skin damages exceeding limits reported in the Maintenance Manual or 

presence of crack requires blade removal from service. 

 

MANPOWER REQUIRED: 

Approximately 2 man-hours are required to complete this Bollettino. 

WARRANTY:

N.A. 

MATERIAL REQUIRED: 

The following material is required for the accomplishment of this Bollettino. 

Consumable Material:

P/N DENOMINATION Q.TY

----------- Abrasive cloth or paper 240 grit and 400 grit A.R.

----------- Wax pencil / piece of chalk A.R.

SPECIAL TOOLS: 

N.A. 

WEIGHT AND BALANCE CHANGE: 

N.A. 

REFERENCES: 

AB412-IPC Illustrated Parts Catalogue 

AB412EP-IPC Illustrated Parts Catalogue 

BHT-412-CR&O Component Repair and Overhaul Manual 
B.T. 412-136

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AB412-MM Maintenance Manual

PUBBLICATIONS AFFECTED:

AB412-MPM Maintenance Planning Manual Chapter 5

ACCOMPLISHMENT INSTRUCTIONS:

1. Prepare helicopter for safe ground maintenance, disconnect battery and all the electric power

source and/or the external power supply.

NOTE

Removal of the tail rotor blades is not required for this inspection.

2. Clean each tail rotor blade by hand using mild soap and cheesecloth in a spanwise direction. 

Dry thoroughly.

3. Carry out a detailed visual inspection of both sides of the entire blade with a 3X magnifying 

glass and bright light. Inspect the tail rotor blade skin, leading edge spar, doublers, grip 

plates and trailing edge for cracks, corrosion, nicks, dents and scratches. Refer to 

Maintenance Manual Chapter 64-11-01 step 7 for damage limits.

4. Create a proper control grid on the blade surface (see an example in figure 1) to be used as a

reference during the inspection. Carry out a further detailed visual inspection with 10X 

magnifying glass of the shaded area shown in figure 2 between stations 20.00 to 35.00 of 

both sides of the blade with a bright light. During the check tick every grid square inspected. 

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

from the affected area by sanding in a span wise direction only with an abrasive cloth or 

paper 240 grit or finer and a final sanding using an abrasive cloth or paper 400 grit or finer. 

After paint removal, wipe area with a clean cloth dampened with alcohol and dry 

thoroughly, visually inspect the affected area for damage using a 10X magnifying glass. 

Damage beyond the limits of the Maintenance Manual Chapter 64-11-01 step 7 requires 

blade removal from service.

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

abrasive pad is permissible. Corrosion on the spar 0,076 mm (0.003 inch) deep or less is 

acceptable when polished out. Replace any blade that has corrosion on the spar greater than 

0,076 mm (0.003 inch).

7. 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).
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8. Repair damage and/or corrosion found on tail rotor blades in accordance with the 

Maintenance Manual Chapter 64-11-01 step 8. 

9. Replace any blade that has a crack. No cracks are permitted. 

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

Component Repair and Overhaul Manual Chapter 64. 

11. Return the helicopter to flight configuration and make an entry in helicopter applicable 

documentations to indicate accomplishment of this Bollettino. Enter exact location of blend 

repair (if applicable), location shall include blade station as well as distance from the leading 

edge. 
B.T. 412-136

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FIGURE 1

Example of inspection reference grid
B.T. 412-136

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FIGURE 2

409.6 mm (16.125 inches)

790.6 mm (31.125 inches)
Note: 

Remarks:

Informazioni: 

Information:

Al fine di gestire le varianti alla configurazione base, in relazione all’emissione del Bollettino Tecnico, preghiamo di voler compilare il presente modulo in tutte le sue parti e spedirlo all’indirizzo sopra indicato. Si ringrazia per la gentile collaborazione data. 

We request your cooperation in filling this form, in order to keep out statistical data relevant to aircraft configuration up-to-date. The form should be filled in all 

its parts and sent to the above address. We thank you beforehand for the information given.

MODULO APPLICAZIONE BOLLETTINO TECNICO

TECHNICAL BULLETIN COMPLIANCE FORM

Data: 

Date:

Numero: 

Number:

Revisione: 

Revision:

Prego spedire a questo indirizzo: 

Please send to the following address: 

AGUSTAWESTLAND S.p.A. 

CUSTOMER SUPPORT & SERVICES - ITALY

PRODUCT SUPPORT ENGINEERING DPT.

Via del Gregge, 100

21015 Lonate Pozzolo (VA) - ITALY 

Tel.: +39 0331 664905

Fax: +39 0331 664684

Telefono: 

Telephone:

Fax:

Data Applicazione B.T.: 

B.T. Compliance Date:

Denominazione Cliente ed Indirizzo: 

Customer Name and Address:

Modello Elicottero 

Helicopter Model S/N Matricola Tail Number

Ore Totali 

Total Hours

Ore D.U.R. 

T.S.O.