# ASB MBB-BK117 C-2-76A-005

PAGE 1 of 7 Revision 0, 2013-06-24 

## Valid for Version(s): C-2. 

# ALERT SERVICE BULLETIN

**SUBJECT**

**: ENGINE CONTROLS -- N2 Controls -- Visual inspection of the N2 control arm** 

**Revision No. Date of issue**  Revision 0 2013-06-24 **Summary:** Inspect the N2 control arm i.a.w. this Alert Service Bulletin. **Compliance:** Compliance with this Alert Service Bulletin is mandatory.

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# ASB MBB-BK117 C-2-76A-005

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## 1. PLANNING INFORMATION **1.A. EFFECTIVITY 1.A.1. Helicopters/installed equipment**  (a) MBB-BK117 C-2 (b) Control arm P/N B761K2202-101 or

P/N B761K2205-101 **1.A.2. Non-installed equipment** Not applicable. **1.B. ASSOCIATED REQUIREMENTS** Not applicable. **1.C. REASON** Eurocopter was informed about an in-service event on a MBB-BK117 C-2 where the aircrew noticed a drop of the rotor RPM (NR) within the green range, but could not beep it back to the nominal value. An inspection of the Engine N2 control system revealed a heavily corroded and broken control arm. This broken control arm was responsible for the loss of the engine droop compensation. For this reason the Safety Information Notice 2483-S-76 was published. Further analysis revealed that a broken control arm can cause under unfavorable conditions a significant and non recoverable drop in rotor rpm depending on flight condition and power demand. Therefore, this Alert Service Bulletin specifies a first time visual inspection and a periodical 12-MONTHS INSPECTION of the N2 control arm. **1.D. DESCRIPTION** Remove the center fairing. Inspect the N2 control arm visually. Install the center fairing. **1.E. COMPLIANCE 1.E.1. Compliance at the works**  Helicopters/installed equipment: **EFFECTIVITY** Helicopters with less than **2 years** from the date of manufacture. (a) The first time visual inspection of the N2 control arm i.a.w. Section 3.B must be accomplished together with the next **12-MONTHS INSPECTION** at the latest. Non-installed equipment: Not applicable.

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# ASB MBB-BK117 C-2-76A-005

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## 1.E.2. Compliance in service Helicopters/installed equipment: **EFFECTIVITY** Helicopters with less than **2 years** from the date of manufacture. (a) The first time visual inspection of the N2 control arm i.a.w. Section 3.B must be accomplished together with the next **12-MONTHS INSPECTION** at the latest. **EFFECTIVITY** Helicopters with more than **2 years** from the date of manufacture. (b) The first time visual inspection of the N2 control arm i.a.w. Section 3.B must be accomplished within the next **4 weeks** after receipt of this Alert Service Bulletin. **EFFECTIVITY** All helicopters. (c) The visual inspection of the N2 control arm i.a.w. Section 3.B must be accomplished together with every **12-MONTHS INSPECTION** . Until the inspection has been incorporated in the AMM, proceed i.a.w. Section 3.B of this Alert Service Bulletin. Non-installed equipment: Not applicable. **1.F. APPROVAL** Approval of this document: The technical content of this document is approved under the authority of DOA No. EASA.21J.034 **1.G. MANPOWER** Qualification Mechanic Electrician Pilot Others Time for the visual inspection of N2 control arm approx. 1 h
-- -- -- **1.H. WEIGHT AND BALANCE** Not applicable. **1.I. EFFECT ON ELECTRICAL LOADS** Not applicable. **1.J. SOFTWARE MODIFICATION EMBODIMENT RECORD** Not applicable. **1.K. REFERENCES** AMM MBB-BK117 C-2.

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# ASB MBB-BK117 C-2-76A-005

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## 1.L. DOCUMENTS AFFECTED The changes to AMM/MSM MBB-BK117 C-2 which are required as a result of this Alert Service Bulletin will be incorporated in the following revisions: AMM MBB-BK117 C-2 - Revision 014 MSM MBB-BK117 C-2 - Revision 013 **1.M.INTERCHANGEABILITY OR MIXABILITY OF PARTS** Interchangeability: Not applicable. Mixability: Not applicable.

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# ASB MBB-BK117 C-2-76A-005

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## 2. MATERIAL INFORMATION **2.A. MATERIAL: PRICE - AVAILABILITY - PROCUREMENT** Not applicable. **2.B. INFORMATION CONCERNING INDUSTRIAL SUPPORT** Not applicable. **2.C. MATERIAL REQUIRED FOR EACH HELICOPTER/COMPONENT** Not applicable. **2.D. MATERIAL TO BE RETURNED**  Not applicable.

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# ASB MBB-BK117 C-2-76A-005

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## 3. ACCOMPLISHMENT INSTRUCTIONS **3.A. GENERAL** Not applicable. **3.B. OPERATIONAL PROCEDURE CAUTION** 

**MAKE SURE THAT YOU EXAMINE ALL SIDES OF THE COMPONENTS OF THE N2 CONTROLS USE A**  **FLASHLIGHT AND A MIRROR TO HELP YOU DO THE INSPECTION. THE N2 CONTROLS ARE A SYSTEM**  **IMPORTANT FOR THE PROPER AND SAFE OPERATION OF THE HELICOPTER.**  **3.B.1. Prelimanary steps:** (a) De-energize the helicopter electrical system i.a.w. AMM, 24-00-00, 2-1. (b) Remove the center fairing i.a.w. AMM, 71-11-00, 4-2. **3.B.2. Inspect the N2 control arm for damage and corrosion i.a.w. Figure 1:** (a) If no signs of damage and/or corrosion are detected, proceed i.a.w. Section 3.B.3. (b) If signs of damage and/or corrosion are found: -- Replace parts in the case of suspicion of exfoliation corrosion -- Remove corrosion and/or scratches that are less than 0.5 mm (0.020 in) in depth i.a.w. AMM, 20-00-00, 2-17. Repair surface protection with one layer of primer (CM 456) and two layers of PUR finish coat (CM 466). -- Replace the parts with damage and/or corrosion and scratches that are more than 0.5 mm (0.020 in) in depth i.a.w. AMM, 76-12-00, 4-3. **3.B.3. Final steps:** (a) Install the center fairing i.a.w. AMM, 71-11-00, 4-2. **3.C. IDENTIFICATION** Identification of this document: Confirm accomplishment of this Alert Service Bulletin by an entry in the historical record of the helicopter. **3.D. OPERATING AND MAINTENANCE INSTRUCTIONS** The inspection i.a.w. Section 3.B of this Alert Service Bulletin must be repeated together with the accomplishment of every 12-MONTHS INSPECTION until this Alert Service Bulletin has been incorporated in the AMM. After accomplishment of the first time inspection and receipt of the AMM MBB-BK117 C-2, Revision 014 this Alert Service Bulletin is no longer effective. 

## 4. APPENDIX Not applicable.

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# ASB MBB-BK117 C-2-76A-005

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## Inspection N2 control arm -- Vartoms I and II Figure 1 Mirror

N2 control arm

N2 control arm
Example of a control arm showing exfoliation corrosion. **Vartoms I Vartoms II** 

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