SPECIAL AIRWORTHINESS

[Worldcrime]

FAA

Aircraft Certification Service

SPECIAL AIRWORTHINESS

INFORMATION BULLETIN

 

SUBJ: MD900 Main Rotor Blade Retention Bolt Check

SAIB: SW-08-05

Date: November 14, 2007

This is information only. Recommendations aren’t mandatory.

 

 

Introduction

 

This Special Airworthiness Information Bulletin (SAIB) advises you, owners, and operators of

McDonnell Douglas Helicopters Inc.(MDHI) model MD900 helicopters to follow certain practices

when performing the required daily preflight inspections of the main rotor blade (MRB) retention

bolts.

Background

Nine MDHI Model MD900 MRB retention bolts, part number 900R3100001-103, have developed

fatigue cracks which propagated and severed the bolt. The cracked bolts were retained during flight

and provided normal retention and control of the main rotor blade. The cracked bolts were detected

during preflight inspections, during maintenance or as a result of moderate increases in aircraft

vibration during flight. The cause of the fatigue crack initiation is under investigation.

Recommendations

Although a cracked MRB retention bolt is retained by the blade centrifugal loads and by the bolt

retainer clip, experience has shown that a cracked bolt will migrate upward slightly with aircraft

usage. The MD900 Rotorcraft Flight Manual (RFM) requires a visual check of the MRB retention

bolts during the helicopter daily preflight inspection. MDHI has issued service letter SL900-056

which provides additional guidance regarding the procedures to follow when doing a visual check of

the MRB retention bolts (www.mdhelicopters.com). We recommend doing a visual check of the

main rotor retention bolts before or after each flight with particular care taken to check for upward

migration of the MRB retention bolt head. We also recommend following the guidance of MDHI

service letter SL900-056 when doing the visual check of the MRB retention bolts as required by the

MD900 RFM. We request that operators and maintenance facilities inform the Los Angeles Aircraft

Certification Office of any MRB bolt service difficulties.

 

For Further Information, Contact

Roger Durbin, Aerospace Engineer,

Los Angeles Aircraft Certification Office, ANM-120L

3960 Paramount Blvd, Lakewood CA 90712

Telephone (562) 627-5233, fax: (562) 627-5210

Email: roger.durbin@faa.gov

 

Posted on Vertical Reference for information only

 

REHRENBERG

FAAST TEAM REP (EASTERN REGION)

 

http://rgl.faa.gov.

 

 

Heli-Safety

Heli-Wear