[4910-13-P]

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2010-XXXX; Directorate Identifier 2010-SW-031-AD]

RIN 2120-AA64

Airworthiness Directives; MD Helicopters, Inc. Helicopters

AGENCY: Federal Aviation Administration, DOT.

ACTION: Notice of proposed rulemaking (NPRM).

SUMMARY: We propose to adopt a new airworthiness directive (AD) for the MD 

Helicopters, Inc. (MDHI) Model MD900 helicopters with certain main rotor blade 

retention bolts (bolts) installed. This proposed AD would require a daily check of the 

position of each bolt and for a gap, and a repetitive inspection of each bolt for a gap. The 

proposed AD would also require, if necessary, removing and inspecting the bolt for a 

crack and replacing any cracked bolt with an airworthy bolt. This proposed AD is 

prompted by multiple reports of in-service bolt failures. The proposed actions are 

intended to prevent failure of a bolt, which could lead to loss of main rotor blade (MRB) 

structural integrity, and subsequent loss of control of the helicopter.

DATES: We must receive comments on this proposed AD by [INSERT DATE 60 

DAYS AFTER DATE OF PUBLICATION IN THE FEDERAL REGISTER].

ADDRESSES: You may send comments by any of the following methods:

 Federal eRulemaking Docket: Go to http://www.regulations.gov. Follow the 

online instructions for sending your comments electronically.
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 Fax: 202-493-2251.

 Mail: Send comments to the U.S. Department of Transportation, Docket 

Operations, M-30, West Building Ground Floor, Room W12-140, 1200 New Jersey

Avenue SE, Washington, DC 20590-0001.

 Hand Delivery: Deliver to the “Mail” address between 9 a.m. and 5 p.m., 

Monday through Friday, except Federal holidays.

EXAMINING THE AD DOCKET: You may examine the AD docket on the Internet at 

http://www.regulations.gov or in person at the Docket Operations Office between 9 a.m. 

and 5 p.m., Monday through Friday, except Federal holidays. The AD docket contains 

this proposed AD, the economic evaluation, any comments received, and other 

information. The street address for the Docket Operations Office (telephone 

800-647-5527) is in the ADDRESSES section. Comments will be available in the AD 

docket shortly after receipt.

For service information identified in this proposed AD, contact MDHI, Attn: 

Customer Support Division, 4555 E. McDowell Rd., Mail Stop M615, Mesa, 

AZ 85215-9734, telephone (800) 388-3378, fax (480) 346-6813, or at

http://www.mdhelicopters.com. You may review copies of the referenced service 

information at the FAA, Office of the Regional Counsel, Southwest Region, 

2601 Meacham Blvd., Room 663, Fort Worth, Texas 76137.

FOR FURTHER INFORMATION CONTACT: Roger Durbin, Aerospace Engineer, 

FAA, Los Angeles Aircraft Certification Office, Airframe Branch, ANM-120L, 3960 

Paramount Blvd., Lakewood, CA 90712, telephone (562) 627-5233, fax (562) 627-5210, 

email roger.durbin@faa.gov.
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SUPPLEMENTARY INFORMATION:

Comments Invited

We invite you to participate in this rulemaking by submitting written comments, 

data, or views. We also invite comments relating to the economic, environmental, energy, 

or federalism impacts that might result from adopting the proposals in this document. The 

most helpful comments reference a specific portion of the proposal, explain the reason for 

any recommended change, and include supporting data. To ensure the docket does not 

contain duplicate comments, commenters should send only one copy of written 

comments, or if comments are filed electronically, commenters should submit only one 

time.

We will file in the docket all comments that we receive, as well as a report 

summarizing each substantive public contact with FAA personnel concerning this 

proposed rulemaking. Before acting on this proposal, we will consider all comments we 

receive on or before the closing date for comments. We will consider comments filed 

after the comment period has closed if it is possible to do so without incurring expense or 

delay. We may change this proposal in light of the comments we receive.

Discussion

We propose to adopt a new AD for MDHI Model MD900 helicopters with certain 

bolts installed. This proposed AD is prompted by multiple reports of in-service bolt 

failures, which could lead to loss of the MRB structural integrity and subsequent loss of 

control of the helicopter. Although these bolt failures have primarily occurred in the 

United Kingdom, it is possible that the failures affect MDHI Model 900 helicopters in the 
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United States. This condition, if not detected, could lead to loss of MRB structural 

integrity and subsequent loss of control of the helicopter.

FAA’s Determination 

We are proposing this AD because we evaluated all known relevant information 

and determined that an unsafe condition exists and is likely to exist or develop on other 

products of the same type design.

Related Service Information

We have reviewed MDHI Alert Service Bulletin SB900-116R1, dated April 9, 

2010 (ASB SB900-116R1), which supersedes ASB SB900-116, dated February 24, 1010 

(ASB SB900-116). 

ASB SB900-116 specifies a repetitive check of the blade retention bolts, part 

number (P/N) 900R3100001-103 and 900R3100001-105, for a gap, and, depending on 

the outcome of the inspection, removing and inspecting the bolt for damage. The ASB 

also specifies a repetitive force check of each bolt, P/N 900R3100001-103, and a torque 

check of each bolt, P/N 900R3100001-105. Lastly, the ASB specifies a daily preflight 

check of each bolt to examine the position of the bolt and for a gap, and, if any bolt has

moved up or down or if there was no gap, removing and inspecting the bolt. 

Superseding ASB SB900-116R1 retains the same specifications as ASB 

SB90016, except that it revises the interval for the bolt force and torque checks from 4-6 

flight-hours to 8-10 flight-hours. ASB SB90016R1 also revises the change of force or 

torque from not more than 10 percent to not more than ±10 percent.

Proposed AD Requirements

The proposed AD would require:
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 Before the first flight of each day, visually checking the position of each bolt for 

up or down displacement and visually checking for a gap between the thrust washer and 

the retainer. If any bolt has moved up or down, or if there is no gap between the thrust 

washer and retainer, before further flight, a qualified mechanic must remove and inspect 

the bolt for a crack and replace any unairworthy bolt with an airworthy bolt. An 

owner/operator (pilot) may perform the visual check required by paragraph (e) of this 

proposed AD and must enter compliance with that paragraph into the helicopter 

maintenance records. In accordance with 14 CFR 43.9(a)(1)-(4) and 91.417(a)(2)(v), a 

pilot may perform this check because it involves only a visual check for the position of 

the bolt and a check for a gap between the thrust washer and retainer and can be 

performed equally well by a pilot or mechanic.

 Within 300 hours TIS and thereafter at intervals not to exceed 300 hours TIS, 

inspecting each bolt for a gap between the thrust washer and the retainer.

°If there is a missing O-ring, installing any missing O-ring, P/N NAS617-10.

°If there is no gap, before further flight, removing and inspecting the bolt for a 

crack and replacing any unairworthy bolt with an airworthy bolt. 

°If there is a gap, measuring the gap in two locations, 180 degrees apart, with a 

feeler gage. If the gap is more than 0.100 inch (2.54 mm), before further flight, removing 

and inspecting the bolt for a crack and replacing any unairworthy bolt with an airworthy 

bolt.

Differences between this Proposed AD and the Service Information
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This proposed AD uses the term “inspect” when describing the action of 

inspecting a bolt for a crack and inspecting for a gap between the thrust washer and the 

retainer. The ASB uses the term “check.”

Costs of Compliance

We estimate that this proposed AD would affect 29 helicopters in the U.S. 

registry. We estimate that operators may incur the following costs in order to comply

with this AD: It would take .5 work hour to do a gap inspection of each bolt, assuming 2 

inspections per year, and 2 work hours to check for up or down displacement of each 

bolt, assuming 365 checks per year, at $85 per hour. The required parts would be $800. 

Authority for This Rulemaking 

Title 49 of the United States Code specifies the FAA’s authority to issue rules on 

aviation safety. Subtitle I, section 106, describes the authority of the FAA Administrator. 

“Subtitle VII: Aviation Programs,” describes in more detail the scope of the Agency’s 

authority.

We are issuing this rulemaking under the authority described in “Subtitle VII, 

Part A, Subpart III, Section 44701: General requirements.” Under that section, Congress 

charges the FAA with promoting safe flight of civil aircraft in air commerce by

prescribing regulations for practices, methods, and procedures the Administrator finds 

necessary for safety in air commerce. This regulation is within the scope of that authority 

because it addresses an unsafe condition that is likely to exist or develop on products 

identified in this rulemaking action.
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Regulatory Findings

We determined that this proposed AD would not have federalism implications 

under Executive Order 13132. This proposed AD would not have a substantial direct 

effect on the States, on the relationship between the national Government and the States, 

or on the distribution of power and responsibilities among the various levels of 

government.

For the reasons discussed, I certify this proposed regulation:

1. Is not a “significant regulatory action” under Executive Order 12866;

2. Is not a “significant rule” under the DOT Regulatory Policies and Procedures 

(44 FR 11034, February 26, 1979); 

3. Will not affect intrastate aviation in Alaska to the extent that it justifies making 

a regulatory distinction; and

4. Will not have a significant economic impact, positive or negative, on a 

substantial number of small entities under the criteria of the Regulatory Flexibility Act.

We prepared an economic evaluation of the estimated costs to comply with this 

proposed AD and placed it in the AD docket.

List of Subjects in 14 CFR Part 39

Air transportation, Aircraft, Aviation safety, Incorporation by Reference, Safety.

The Proposed Amendment

Accordingly, under the authority delegated to me by the Administrator, the FAA 

proposes to amend 14 CFR part 39 as follows:

PART 39 - AIRWORTHINESS DIRECTIVES

1. The authority citation for part 39 continues to read as follows:
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Authority: 49 U.S.C. 106(g), 40113, 44701.

§ 39.13 [Amended]

2. The FAA amends § 39.13 by adding the following new Airworthiness Directive 

(AD):

MD HELICOPTERS, INC. (MDHI): Docket No. FAA-2011-XXXXX; Directorate 

Identifier 2010-SW-031-AD.

(a) Applicability. 

This AD applies to Model MD 900 helicopters with a main rotor blade retention 

bolt (bolt), part number (P/N) 900R3100001-103 or 900R3100001-105, installed;

certificated in any category.

(b) Unsafe Condition. 

This AD defines the unsafe condition as bolt failure. This condition could result in 

loss of main rotor blade (MRB) structural integrity and subsequent loss of control of the 

helicopter.

(c) Compliance.

You are responsible for performing each action required by this AD within the 

specified compliance time unless it has already been accomplished prior to that time.

(d) Required Actions.

(1) Before the first flight of each day:

(i) Visually check each bolt for failure. Failure of a bolt may be indicated by

movement of the bolt out of the bolt hole or inconsistent extension of the bolt above or 

below the other bolts being inspected (failed bolt is migrating out of the bolt hole).
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(ii) Visually check for a gap between the thrust washer and the retainer. The 

thrust washer is depicted as item 2 and the retainer is depicted as item 8 in Figure 1 to 

paragraph (d).

(iii) The actions required by paragraphs (d)(1)(i) and (d)(1)(ii) may be performed 

by the owner/operator (pilot) holding at least a private pilot certificate and must be 

entered into the aircraft maintenance records showing compliance with this AD in 

accordance with 14 CFR §§ 43.9(a)(1)-(4) and 14 CFR § 91.417(a)(2)(v). The record 

must be maintained as required by 14 CFR §§ 91.417, 121.380, or 135.439.

(iv) If there is any indication of bolt failure, or if there is no gap between the 

thrust washer and retainer, before further flight, remove and inspect the bolt for a crack. 

Replace any cracked bolt with an airworthy bolt. 

(2) Within 300 hours time-in-service (TIS), and thereafter at intervals not to 

exceed 300 hours TIS, inspect each bolt for a gap between the thrust washer and the 

retainer, P/N 900R2100009-101 or -103, as depicted in Figure 1 to paragraph (d) of this 

AD.
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(i) Determine whether an O-ring, P/N NAS617-10, is installed. Install any missing

O-ring.

(ii) If there is no gap between the thrust washer and retainer, before further flight, 

remove and inspect the bolt for a crack. Replace any cracked bolt with an airworthy bolt.

(iii) If there is a gap between the thrust washer and retainer, measure the gap in 

two locations, 180 degrees apart, with a feeler gage. If the gap is more than 0.100 inch 

(2.54 mm) at either location, before further flight, remove and inspect the bolt for a crack. 

Replace any cracked bolt with an airworthy bolt.

(e) Alternative Methods of Compliance

(1) The Manager, Los Angeles Aircraft Certification Office, Airframe Branch 

(ANM-120L), FAA, may approve AMOCs for this AD. Send your request to

Roger Durbin, Aerospace Engineer, FAA, Los Angeles Aircraft Certification Office, 

Airframe Branch, ANM-120L, 3960 Paramount Blvd., Lakewood, CA 90712, telephone 

(562) 627-5233, fax (562) 627-5210, email roger.durbin@faa.gov.

(2) For operations conducted under a 14 CFR part 119 operating certificate or 

under 14 CFR part 91, subpart K, we suggest that you notify your principal inspector or 

lacking a principal inspector, the manager of the local flight standards district office or 

certificate holding district office before operating any aircraft complying with this AD 

through an AMOC.

(f) Additional Information. 

MDHI Alert Service Bulletin SB900-116R1, dated April 9, 2010, which 

supersedes ASB SB900-116, dated February 24, 1010, neither of which is incorporated 

by reference, contains additional information about the subject of this AD. For service 
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information identified in this AD, contact MDHI, Attn: Customer Support Division, 4555 

E. McDowell Rd., Mail Stop M615, Mesa, AZ 85215-9734, telephone (800) 388-3378, 

fax (480) 346-6813, or at http://www.mdhelicopters.com. You may review copies of the 

service information at the FAA, Office of the Regional Counsel, Southwest Region, 2601 

Meacham Blvd., Room 663, Fort Worth, Texas.

(g) Subject. 

Joint Aircraft System Component: 6210: Main rotor blade retention bolts.

Issued in Fort Worth, Texas, on