E7-43. Airworthiness Directives; Enstrom Helicopter Corporation Model F-28A, F-28C, F-28F, TH-28, 280, 280C, 280F, 280FX, 480, and 480B Helicopters

AGENCY:

Federal Aviation Administration, DOT.

ACTION:

Notice of proposed rulemaking (NPRM).

SUMMARY:

This document proposes adopting a new airworthiness directive (AD) for Enstrom Helicopter Corporation (Enstrom) Model F-28A, F-28C, F-28F, TH-28, 280, 280C, 280F, 280FX, 480, and 480B helicopters. The AD would require determining the installation dates for each main rotor push-pull control rod (push-pull rod), inspecting the push-pull rods for corrosion, replacing any push-pull rod which has corrosion that is severe enough to cause pitting, or has visible moisture inside the rod, and repairing each push-pull rod that has corrosion but no pitting. This proposal is prompted by one reported incident in which the helicopter pilot encountered severe in flight vibration due to the failure of a push-pull rod, requiring an emergency landing. The actions specified by the proposed AD are intended to detect corrosion and prevent failure of a push-pull rod, and subsequent loss of control of the helicopter.

DATES:

Comments must be received on or before March 9, 2007.

ADDRESSES:

Use one of the following addresses to submit comments on this proposed AD:

• DOT Docket Web site: Go to http://dms.dot.gov and follow the instructions for sending your comments electronically;
• Government-wide rulemaking Web site: Go to http://www.regulations.gov and follow the instructions for sending your comments electronically;
• Mail: Docket Management Facility; U.S. Department of Transportation, 400 Seventh Street, SW., Nassif Building, Room PL-401, Washington, DC 20590;
• Fax: [phone]; or
• Hand Delivery: Room PL-401 on the plaza level of the Nassif Building, 400 Seventh Street, SW., Washington, DC, between 9 a.m. and 5 p.m., Monday through Friday, except Federal holidays.

You may get the service information identified in this proposed AD from The Enstrom Helicopter Corporation, Twin County Airport, P.O. Box 490, Menominee, Michigan 49858.

You may examine the comments to this proposed AD in the AD docket on the Internet at http://dms.dot.gov.

FOR FURTHER INFORMATION CONTACT:

Shawn Malekpour, Aviation Safety Engineer, FAA, Chicago Aircraft Certification Office, 2300 East Devon Ave., Des Plaines, Illinois 60018, telephone [phone], fax [phone].

SUPPLEMENTARY INFORMATION:

Comments Invited

We invite you to submit any written data, views, or arguments regarding this proposed AD. Send your comments to the address listed under the caption ADDRESSES. Include the docket number “FAA-2006-26771, Directorate Identifier 2005-SW-07-AD” at the beginning of your comments. We specifically invite comments on the overall regulatory, economic, environmental, and energy aspects of the proposed AD. We will consider all comments received by the closing date and may amend the proposed AD in light of those comments.

We will post all comments we receive, without change, to http://dms.dot.gov, including any personal information you provide. We will also post a report summarizing each substantive verbal contact with FAA personnel concerning this proposed rulemaking. Using the search function of our docket Web site, you can find and read the comments to any of our dockets, including the name of the individual who sent or signed the comment. You may review the DOT's complete Privacy Act Statement in the Federal Register published on April 11, 2000 (65 FR 19477-78) or you may visit http://dms.dot.gov.

Examining the Docket

You may examine the docket that contains the proposed AD, any comments, and other information in person at the Docket Management System (DMS) Docket Office between 9 a.m. and 5 p.m., Monday through Friday, except Federal holidays. The Docket Office (telephone [phone]) is located at the plaza level of the Department of Transportation NASSIF Building in Room PL-401 at 400 Seventh Street, SW., Washington, DC. Comments will be available in the AD docket shortly after the DMS receives them.

Discussion

This document proposes adopting a new AD for Enstrom Model F-28A, F-28C, F-28F, TH-28, 280, 280C, 280F, 280FX, 480, and 480B helicopters. The proposed AD would require reviewing the helicopter maintenance records and determining the installation dates for the push-pull rods. If the dates cannot be determined from the maintenance records, using the “Date MFD”, which is located on the helicopter data plate, would be used as the installation date for the push-pull rods. The proposed AD would also require a visual inspection for corrosion on the exterior and interior of the three push-pull rods, part number (P/N) 28-16253-all dash numbers (for Model F-28A, F-28C, F-28F, 280, 280C, 280F, and 280FX helicopters) or P/N 4140532-all dash numbers (for Model TH-28, 480, and 480B helicopters), using the compliance times stated in the following table. Replacing any push-pull rod that has corrosion that is severe enough to cause pitting or has moisture inside the rod, and repairing any push-pull rod that has corrosion but no pitting, would be required before further flight. Repairing a push-pull rod consists of cleaning the push-pull rod, applying a protective coating, and sealing the push-pull rod before reinstalling it on a helicopter.

Helicopter models	Push-pull rod service life	Compliance times
Model F-28A, F-28C, F-28F, 280, 280C, 280F, and 280FX helicopters	Push-pull rod that has been installed for 20 or more years	Inspect within 10 hours time-in-service (TIS) or at next annual inspection, whichever occurs first.
Model F-28A, F-28C, F-28F, 280, 280C, 280F, and 280FX helicopters	Push-pull rod that has been installed for 10 or more years, but less than 20 years	Inspect within 50 hours TIS or at the next annual inspection, whichever occurs first.
Model F-28A, F-28C, F-28F, 280, 280C, 280F, and 280FX helicopters	Push-pull rod that has been installed for less than 10 years	Inspect before the service life of the push-pull rod reaches 10 years since initial installation.
Model TH-28, 480, and 480B helicopters	Push-pull rod that has been installed for 10 or more years	Inspect within 50 hours TIS or at the next annual inspection, whichever occurs first.
Model TH-28, 480, and 480B helicopters	Push-pull rod that has been installed for less than 10 years	Inspect before the service life of the push-pull rod reaches 10 years since initial installation.

This proposal is prompted by one reported incident in which severe in-flight vibrations required an emergency landing. Upon landing, the tail rotor, tail rotor gearbox, and horizontal stabilizer separated from the helicopter. A subsequent investigation revealed a rupture of the lower end of one of the three push-pull rods. The actions specified by the proposed AD are intended to detect corrosion on a push-pull rod and prevent failure of a push-pull rod, and subsequent loss of control of the helicopter.

We have reviewed the following service information:

• Enstrom Helicopter Corporation Service Directive Bulletin No. 0096, dated September 10, 2003, which describes visually inspecting the push-pull rods for corrosion and internal moisture, provides for repairing light corrosion, and is applicable to Model F-28A, F-28C, F-28F, 280, 280C, 280F, and 280FX helicopters.
• Enstrom Helicopter Corporation Service Directive Bulletin No. T-019, dated September 10, 2003, which describes visually inspecting the push-pull rods for corrosion and internal moisture, provides for repairing light corrosion, and is applicable to Model TH-28, 480, and 480B helicopters.
• Enstrom Helicopter Corporation Service Information Letter (SIL) No. T-019, dated December 9, 2003, applicable to Model TH-28, 480, and 480B helicopters, which describes visually inspecting each push-pull rod for a crack, nick, scratch, dent, corrosion, damaged threads, bending, and contact wear. We are not proposing to require the inspections specified in the SIL.
• Enstrom Helicopter Corporation Service Information Letter No. 0156, dated December 9, 2005, applicable to Model F-28A, F-28C, F-28F, 280, 280C, 280F, and 280FX helicopters, which describes visually inspecting each push-pull rod for a crack, nick, scratch, dent, corrosion, damaged threads, bending, and contact wear. We are not proposing to require the inspections specified in the SIL.

This unsafe condition is likely to exist or develop on other helicopters of the same type designs. Therefore, the proposed AD would require determining the installation date for the push-pull rods and inspecting each of the three push-pull rods for corrosion. If corrosion that is severe enough to cause pitting is found, or if moisture is visible on the inside of a push-pull rod, the AD would require replacing the push-pull rod. If there is corrosion without pitting on a push-pull rod, that push-pull rod may be repaired. Repairing a push-pull rod consists of cleaning the push-pull rod, applying a protective coating, and sealing the push-pull rod before remarking it and reinstalling it on a helicopter. The actions would be required to be accomplished in accordance with the specified portions of the Enstrom service directive bulletins described previously.

We estimate that this proposed AD would affect 378 helicopters of U.S. registry, and that the required actions would take the following numbers of work hours to accomplish on each helicopter at an average labor rate of $80 per work hour:

• 8 work hours to remove, disassemble, and inspect the 3 push-pull rods;
• 9 work hours to repair corrosion without pitting, remark each push-pull rod, and reassemble each push-pull rod; and
• 3 work hours to reinstall 3 push-pull rods on the helicopter. Required parts would cost approximately $900 per helicopter. Based on these figures, the total cost impact of the proposed AD on U.S. operators would be $945,000 ($2,500 per helicopter), assuming 3 push-pull rods are replaced on each helicopter.

Regulatory Findings

We have determined that this proposed AD would not have federalism implications under Executive Order 13132. Additionally, 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 above, I certify that the 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); and

3. 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 a draft economic evaluation of the estimated costs to comply with this proposed AD. See the DMS to examine the draft economic evaluation.

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.

List of Subjects in 14 CFR Part 39

• Air transportation
• Aircraft
• Aviation safety
• Safety

The Proposed Amendment

Accordingly, pursuant to the authority delegated to me by the Administrator, the Federal Aviation Administration proposes to amend part 39 of the Federal Aviation Regulations (14 CFR part 39) as follows:

PART 39—AIRWORTHINESS DIRECTIVES

1. The authority citation for part 39 continues to read as follows:

Authority: 49 U.S.C. 106(g), 40113, 44701.

§ 39.13

[Amended]

2. Section 39.13 is amended by adding a new airworthiness directive to read as follows:

Enstrom Helicopter Company: Docket No. FAA-2006-26771; Directorate Identifier 2005-SW-07-AD.

Applicability: Model F-28A, F-28C, and F-28F helicopters, excluding serial number (S/N) 816 and subsequent; Model 280, 280C, 280F, and 280FX helicopters, excluding S/N 2100 and subsequent; and Model TH-28, 480, and 480B helicopters, excluding S/N 5058 and subsequent, certificated in any category.

Compliance: Required as indicated, unless accomplished previously.

To detect corrosion and prevent failure of a main rotor push-pull control rod (push-pull rod), and subsequent loss of control of the helicopter, accomplish the following:

(a) Within 10 hours time-in-service (TIS) or at the next annual inspection, whichever occurs first, review the helicopter maintenance records and determine the date that each push-pull rod, part number (P/N) 28-16253-all dash numbers (for Model F-28A, F-28C, F-28F, 280, 280C, 280F, and 280FX helicopters) and P/N 4140532-all dash numbers (for Model TH-28, 480, and 480B helicopters), was installed. If the date cannot be determined from the maintenance records, use the “Date MFD”, which is located on the helicopter data plate, as the installation date for the push-pull rod.

(b) For Model F-28A, F-28C, F-28F, 280, 280C, 280F, and 280FX helicopters, using the compliance times stated in Table 1 of this AD, visually inspect the exterior and interior of each of the three push-pull rods for corrosion severe enough to cause pitting or any moisture, paying special attention to the area of the lower fitting, in accordance with section 5.1., INSPECTION, in Enstrom Helicopter Corporation Service Directive Bulletin No. 0096, dated September 10, 2003 (SDB 0096).

Table 1

Helicopter models	Push-pull rod service life	Compliance times
Model F-28A, F-28C, F-28F, 280, 280C, 280F, and 280FX helicopters	Push-pull rod that has been installed for 20 or more years	Inspect within 10 hours time-in-service (TIS) or at next annual inspection, whichever occurs first.
Model F-28A, F-28C, F-28F, 280, 280C, 280F, and 280FX helicopters	Push-pull rod that has been installed for 10 or more years, but less than 20 years	Inspect within 50 hours TIS or at the next annual inspection, whichever occurs first.
Model F-28A, F-28C, F-28F, 280, 280C, 280F, and 280FX helicopters	Push-pull rod that has been installed for less than 10 years	Inspect before the service life of the push-pull rod reaches 10 years since initial installation.

(1) Before further flight, if corrosion without pitting is found on a push-pull rod, then repair, reassemble, remark, and reinstall it in accordance with section 5.2., REPAIR/REASSEMBLY, in SDB 0096.

(2) Before further flight, if corrosion is found that is severe enough to cause pitting, or if any moisture is visible on the inside of a push-pull rod, replace it with an airworthy push-pull rod.

Note 1:

Determining continued serviceability of the push-pull rods by inspecting the exterior only of each push-pull rod is described in Enstrom Helicopter Corporation Service Information Letter No. 0156, dated December 9, 2003.

(c) For Model TH-28, 480 and 480B helicopters, using the compliance times stated in Table 2 of this AD, visually inspect the exterior and interior of each of the three push-pull rods for corrosion severe enough to cause pitting or any moisture, paying special attention to the area of the lower fitting, in accordance with section 5.1., INSPECTION, in Enstrom Helicopter Corporation Service Directive Bulletin No. T-019, dated September 10, 2003 (SDB T-019).

Table 2

Helicopter models	Push-pull rod service life	Compliance times
Model TH-28, 480, and 480B helicopters	Push-pull rod that has been installed for 10 or more years	Inspect within 50 hours TIS or at the next annual inspection, whichever occurs first.
Model TH-28, 480, and 480B helicopters	Push-pull rod that has been installed for less than 10 years	Inspect before the service life of the push-pull rod reaches 10 years since initial installation.

(1) Before further flight, if corrosion without pitting is found on a push-pull rod, then repair, reassemble, remark, and reinstall it in accordance with section 5.2., REPAIR/REASSEMBLY, in SDB T-019.

(2) Before further flight, if corrosion is found that is severe enough to cause pitting, or if any moisture is visible on the inside of a push-pull rod, replace it with an airworthy push-pull rod.

Note 2:

Determining continued serviceability of the push-pull rods by inspecting the exterior only of each push-pull rod is described in Enstrom Helicopter Corporation Service Information Letter No. T-019, dated December 9, 2003.

(d) To request a different method of compliance or a different compliance time for this AD, follow the procedures in 14 CFR 39.19. Contact Chicago Aircraft Certification Office, Small Airplane Directorate, FAA, for information about previously approved alternative methods of compliance.

Issued in Fort Worth, Texas, on December 26, 2006.

David A. Downey,

Manager, Rotorcraft Directorate, Aircraft Certification Service.