MANDATORY MANDATORY MANDATORY

MANDATORY MANDATORY MANDATORY

SERVICE BULLETIN

Copyright 1999-2014 by MD Helicopters Inc. This document may be reproduced and distributed

provided no fee is charged, the text is not modified, and this copyright notice is included.

ONEïTIME EDDY CURRENT INSPECTION OF THE 

MAIN ROTOR UPPER HUB ASSEMBLY

1. PLANNING INFORMATION

A. Aircraft Affected:

MD900 helicopters, serial numbers (SNs) 900-00008 thru 900-00140

B. Assembly/Components Affected By This Notice:

Main Rotor Upper Hub Assembly, Part No. (PN) 900R2101006-105/-107/-109/-111

C. Reason:

Four (4) cracks have been found on a high-time main rotor upper hub assembly. This is the

first reported cracks in the MD900 fleet.

Failure to comply with this bulletin can compromise the structural integrity of this

life-limited part. Failure to remove a cracked main rotor upper hub assembly from service

can cause main rotor vibrations which eventually can cause the failure of the main rotor

hub assembly, the loss of the rotorcraft, and injury to the occupants.

D. Description:

Procedures in this Bulletin give owners and operators information to inspect the main rotor

upper hub assembly for cracks.

E. Time of Compliance:

The requirements of this bulletin must be completed within 25 flight hours after receipt of

this bulletin or during the annual inspection (whichever one occurs first).

F. FAA Approval:

The technical design aspects of this Bulletin are FAA Approved.

G. Manpower:

Compliance with this bulletin will be approximately one (1) man-hour.

H. Interchangeability:

None.

I. Points of Contact:

For further assistance, contact the MDHI Field Service Department. Telephone:

1-800-388-3378 or 480-346-6387. DATAFAX: 480-346-6813.

J. Material/Part Availability:

Contact the MDHI Spare Parts Sales Department for parts availability. Telephone:

1-800-388-3378 or 480-346-6540. DATAFAX: 480-346-6821.

REPLACEMENT PARTS/SUPPLIES 

Nomenclature Part No. Qty. Source

Main Rotor Upper Hub Assembly 900R2101006ï109/ï111 1 MDHI

SB900-122

DATE: 8 APRIL 2014

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SERVICE BULLETIN

Copyright 1999-2014 by MD Helicopters Inc. This document may be reproduced and distributed

provided no fee is charged, the text is not modified, and this copyright notice is included.

K. Warranty Policy:

Standard warranty policy applies (ref. CSP-A-2).

L. Disposition of Parts Removed:

Return to MDHI for further investigation.

M. Tooling:

N/A

Ref. CSP-SPM, Section 91-00-00, for the item numbers and manufacturer / supplier

numbers.

TOOLS AND EQUIPMENT 

Nomenclature (Item) Source (Manufacturer / Supplier Code)

Cleaning Solvent (C425) Van Waters & Rogers Inc., PO Box 34325, Seattle,

WA 98124ï1325; Phone: 425ï889ï3400

Eddy Current Inspection Equipment Commercially Available

Extended Reach RightïAngle Pencil Probe (8 to 9

Inch [20 to 23 cm] overall length)

Commercially Available

Marker Commercially Available

N. Weight and Balance:

N/A

O. Electrical Load Data:

N/A

P. Other Publications Affected:

N/A

Q. Reference Publications:

Refer to the latest revision of these publications for procedures and additional information:

CSP-A-2 Warranty Manual

CSP-900RMM-2 Rotorcraft Maintenance Manual - Servicing and Maintenance

CSP-900IPL-4 Illustrated Parts List

SB900-122

DATE: 8 APRIL 2014

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MANDATORY MANDATORY MANDATORY

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SERVICE BULLETIN

Copyright 1999-2014 by MD Helicopters Inc. This document may be reproduced and distributed

provided no fee is charged, the text is not modified, and this copyright notice is included.

2. ACCOMPLISHMENT INSTRUCTIONS

A. Eddy Current Inspection of the Upper Hub Assembly

(Ref. Figure 1)

The eddy current inspection can be done on a upper hub assembly installed on the rotorcraft. It is not necessary to disassemble the main rotor hub assembly.

Eddy current inspection must be done by a Level II technician with ASNT-TC-1A, CEN EN

4179, MIL-STD-410, NAS410, or equivalent certification in eddy current inspections and

have done an eddy current inspection in the last 12 months.

Solvent, Cleaning (C425)

(1). Fully clean inspection areas (ref. Figure 1) with cleaning solvent (C425).

(2). Do a visual inspection of the areas adjacent to the bushings for cracks, corrosion, and

oxidation.

(a). If there is damage, go to Step (12).

(b). If there are no visible cracks, corrosion or oxidation, go to Step (3).

(3). Calibrate inspection unit and probe (ref. manufacturer instructions) with an aluminum

alloy model defect standard with a surface probe calibration slot equal to or less than a

0.010 inch (0.25 mm) depth.

Use eddy current inspection equipment with an extended reach right-angle pencil probe for

crack detection when the upper hub assembly is installed on the rotorcraft. Unit and probe

must be calibrated before inspection, each half hour during inspection, at the end of inspection, and if a cable or probe is changed.

The upper hub material is aluminum alloy 7149-T7352.

(4). Set inspection unit for inspection (ref. manufacturer instructions).

(5). Null the instrument with the probe in the inspection area after calibration and as

necessary to include the paint thickness.

The average paint thickness should be 0.003 inch (0.08 mm).

(6). Scan all of the inspection area shown by shadow adjacent to the bushings.

The probe must be held perpendicular to the surface to be examined.

(7). As necessary, turn the hub assembly and rotor blades 360 degrees several times to get

access to each location.

(8). Responses more than that of the calibration standard, which are not caused by lift-off,

are a cause for rejection.

(9). Mark each area on the upper hub assembly where there is an unsatisfactory result.

Solvent, Cleaning (C425)

(10). Fully clean inspection areas with cleaning solvent (C425).

SB900-122

DATE: 8 APRIL 2014

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NOTE:

NOTE:

NOTE:

NOTE:

NOTE:

NOTE:
MANDATORY MANDATORY MANDATORY

MANDATORY MANDATORY MANDATORY

SERVICE BULLETIN

Copyright 1999-2014 by MD Helicopters Inc. This document may be reproduced and distributed

provided no fee is charged, the text is not modified, and this copyright notice is included.

BUSHING (5 PL)

UPPER FLANGE INSPECTION AREAS

NOT SHOWN

Figure 1. Inspection of the Upper Hub Assembly (Top View)

SB900-122

DATE: 8 APRIL 2014

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SERVICE BULLETIN

Copyright 1999-2014 by MD Helicopters Inc. This document may be reproduced and distributed

provided no fee is charged, the text is not modified, and this copyright notice is included.

(11). Carefully scan marked areas again.

(12). If there is a crack, remove the upper hub assembly and replace it with an airworthy

upper hub assembly.

(13). Tag the unsatisfactory upper hub assembly as unairworthy.

(14). Contact MDHI for return instructions, engineering evaluation, and eventual disposition

as scrap of the removed upper hub assembly. Return the upper hub assembly with a

Service Operational Report (SOR).

B. Compliance Record

(1). Record compliance to this Service Bulletin in the Compliance Record section of the

Rotorcraft Log Book.

(2). Complete Bulletin Completed Record form (attached) and FAX or e-mail to MDHI Field

Service Department.

SB900-122

DATE: 8 APRIL 2014

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MANDATORY MANDATORY MANDATORY

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SERVICE BULLETIN

Copyright 1999-2014 by MD Helicopters Inc. This document may be reproduced and distributed

provided no fee is charged, the text is not modified, and this copyright notice is included.

SB900ï122 Completed Record

Eddy Current Inspection of the Main Rotor Upper Hub Assembly

MD Helicopters, Inc.

Field Service Department

4555 E. McDowell Road

Mesa, AZ 85215ï9734

800ï388ï3378 Phone (U.S. and Canada)

480ï346ï6387 Phone (International)

480ï346ï6813 Fax

FAX this form to MDHI (480) 346ï6813 or Eïmail to ServiceEngineering@mdhelicopters.com

Dear Sir:

This is to tell you that this Service Bulletin has been completed as follows:

Owner

/Operator:

Rotorcraft

Serial No:

Address:

Rotorcraft

Total Time:

Date:

Location:

Upper Hub 

Assembly:

Hours 

PN Phone:

Eïmail: SN 

The first inspection is

complete and the subsequent inspections have

been added to the inspection schedule:

(Signature)

(Print Name)

(Title)

Upper Hub Assembly was found: Airworthy / Cracked

(Circle One)

Comments: 

SB900-122

DATE: 8 APRIL 2014

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