E6-15342. Airworthiness Directives; Pilatus Aircraft Ltd. Model PC-7 Airplanes

AGENCY:

Federal Aviation Administration (FAA), Department of Transportation (DOT).

ACTION:

Notice of proposed rulemaking (NPRM).

SUMMARY:

We propose to adopt a new airworthiness directive (AD) for certain Pilatus Aircraft Ltd. (Pilatus) Model PC-7 airplanes. This proposed AD would require you to do repetitive eddy-current, non-destructive inspections of the nose skin and adjacent structure above the left and right main landing gear bay and repetitive visual inspections of the forward support structure of the floor panel for crack damage. If you find any crack damage, this proposed AD would require you to contact Pilatus to obtain a repair solution and incorporate the repair. This proposed AD results from mandatory continuing airworthiness information (MCAI) issued by the airworthiness authority for Switzerland. We are proposing this AD to detect and correct cracks in the nose skin and adjacent structure above the left and right main landing gear bay and in the forward support structure of the floor panel. Crack propagation in certain areas could lead to failure of the main wing torsion box, which could result in loss of control.

DATES:

We must receive comments on this proposed AD by October 16, 2006.

ADDRESSES:

Use one of the following addresses to comment 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 20590-0001.
• Fax: [phone].
• 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.

For service information identified in this proposed AD, contact Pilatus Aircraft Ltd., Customer Liaison Manager, CH-6371 Stans, Switzerland; telephone: [phone]; fax: [phone].

FOR FURTHER INFORMATION CONTACT:

Doug Rudolph, Aerospace Engineer, FAA, Small Airplane Directorate, 901 Locust, Room 301, Kansas City, Missouri 64106; telephone: [phone]; facsimile: [phone].

SUPPLEMENTARY INFORMATION:

Comments Invited

We invite you to send any written relevant data, views, or arguments regarding this proposed AD. Send your comments to an address listed under the ADDRESSES section. Include the docket number, “FAA-2006-25582; Directorate Identifier 2006-CE-42-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 we receive concerning this proposed AD.

Discussion

The Federal Office for Civil Aviation (FOCA), which is the airworthiness authority for Switzerland, notified FAA that an unsafe condition may exist on certain Pilatus PC-7 airplanes. The FOCA reports crack damage in some radii at the rear edge of the nose skin, part number (P/N) 111.34.07.434. The radii are adjacent to the left and right corners at the forward edge of the floor panel, P/N 111.34.07.530. Crack damage can also occur in the forward support structure of the floor panel adjacent to the skin panel.

This condition, if not detected and corrected, could result in crack propagation in certain areas, which may lead to failure of the main wing torsion box. This failure could result in loss of control.

Relevant Service Information

We have reviewed Pilatus PC-7 Service Bulletin No. 57-009, dated January 29, 2004. The service information describes procedures for visually inspecting the forward support structure of the floor panel and eddy-current, non-destructive inspecting the nose skin and adjacent structure above the left and right main landing gear bay for crack damage.

Foreign Airworthiness Authority Information

The FOCA classified this service bulletin as mandatory and issued Swiss AD HB 2006-374, effective date August 2, 2006, to ensure the continued airworthiness of these airplanes in Switzerland.

These Pilatus PC-7 airplanes are manufactured in Switzerland and are type-certificated for operation in the United States under the provisions of section 21.29 of the Federal Aviation Regulations (14 CFR 21.29) and the applicable bilateral airworthiness agreement.

Under this bilateral airworthiness agreement, the FOCA has kept us informed of the situation described above.

FAA's Determination and Requirements of the Proposed AD

We are proposing this AD because we have examined the FOCA's findings, evaluated all information and determined the unsafe condition described previously is likely to exist or develop on other products of the same type design that are certificated for operation in the United States.

This proposed AD would require you to do repetitive eddy-current, non-destructive inspections of the nose skin and adjacent structure above the left and right main landing gear bay and repetitive visual inspections of the forward support structure of the floor panel for crack damage. If you find any crack damage, this proposed AD would require you to contact Pilatus to obtain a repair solution and incorporate the repair.

Differences Between the FOCA AD, the Service Information, and This Proposed AD

FOCA AD HB-2006-374, effective date August 2, 2006, allows continued flight if cracks are found in the nose skin that do not exceed certain limits. The applicable service bulletin specifies repair of the nose skin only if cracks are found exceeding limits illustrated in Pilatus PC-7 Service Bulletin No. 57-009, dated January 29, 2004, as does FOCA AD HB-2006-374, effective date August 2, 2006. This proposed AD, if adopted, does not allow continued flight if any crack is found. FAA policy is to disallow airplane operation when known cracks exist in primary structure, unless the ability to sustain ultimate load with these cracks is proven. The nose skin is considered primary structure, and the FAA has not received any analysis to prove that ultimate load can be sustained with cracks in this area.

The requirements of this proposed AD, if adopted as a final rule, would take precedence over the provisions in the service information.

Costs of Compliance

We estimate that this proposed AD would affect 10 airplanes in the U.S. registry.

We estimate the following costs to do the proposed inspection:

Labor cost	Parts cost	Total cost per airplane	Total cost on U.S. operators
3 work-hours × $80 per hour = $240	No parts required	$240	$2,400

Any required “upon-condition” repairs would vary depending upon the damage found. Based on this, we have no way of determining the potential repair costs for each airplane or the number of airplanes that would need the repairs based on the result of the proposed inspections.

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.

Regulatory Findings

We have 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 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 regulatory evaluation of the estimated costs to comply with this proposed AD and placed it in the AD docket.

Examining the AD Docket

You may examine the AD docket that contains the proposed AD, the regulatory evaluation, any comments received, and other information on the Internet at http://dms.dot.gov;​; or in person at the Docket Management Facility between 9 a.m. and 5 p.m., Monday through Friday, except Federal holidays. The Docket Office (telephone [phone]) is located at the street address stated in the ADDRESSES section. Comments will be available in the AD docket shortly after receipt.

List of Subjects in 14 CFR Part 39

• Air transportation
• Aircraft
• Aviation safety
• 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:

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

§ 39.13

[Amended]

2. The FAA amends § 39.13 by adding the following new AD:

Pilatus Aircraft Ltd.: Docket No. FAA-2006-25582; Directorate Identifier 2006-CE-42-AD.

Comments Due Date

(a) We must receive comments on this airworthiness directive (AD) action by October 16, 2006.

Affected ADs

(b) None.

Applicability

(c) This AD applies to Model PC-7 airplanes, manufacturer serial numbers 101 through 618 inclusive, that are certificated in any category.

Unsafe Condition

(d) This AD results from mandatory continuing airworthiness information (MCAI) issued by the airworthiness authority for Switzerland. We are issuing this AD to detect and correct cracks in the nose skin and adjacent structure above the left and right main landing gear bay and in the forward support structure of the floor panel. Crack propagation in certain areas could lead to failure of the main wing torsion box. This failure could result in loss of control.

Compliance

(e) To address this problem, you must do the following:

Actions	Compliance	Procedures
(1) Inspect: (i) The forward area of the floor panel and the related structure for cracks using magnified, visual methods. (ii) The nose skin and adjacent structure above the left and right main landing gear bay for cracks using eddy-current, non-destructive methods.	Initially inspect within the next 150 hours time-in-service or 6 calendar months, whichever occurs first, after the effective date of this AD, unless already done. Repetitively inspect thereafter at intervals specified in paragraph 2. B. of Pilatus PC-7 Aircraft Maintenance Manual (AMM) 05-10-00, dated March 4, 2005	Do the initial inspection following Pilatus PC-7 Service Bulletin No. 57-009, dated January 29, 2004. Do the repetitive inspections following the procedures in AMM 57-10-03, dated March 4, 2005, and AMM 05-30-05, dated February 28, 2006.
(2) If crack damage is found during any inspection required by paragraph (e)(1) of this AD, obtain an FAA-approved repair solution from the manufacturer through the FAA at the address specified in paragraph (f) of this AD and incorporate the repair	Before further flight after any inspection in which crack damage is found. Further flight with crack damage is not permitted. After incorporating the repair, repetitively inspect as specified in paragraph (e)(1) of this AD	Obtain an FAA-approved repair solution from the manufacturer through the FAA at the address specified in paragraph (f) of this AD and incorporate the repair.

Alternative Methods of Compliance (AMOCs)

(f) The Manager, Standards Staff, FAA, ATTN: Doug Rudolph, Aerospace Engineer, FAA, Small Airplane Directorate, 901 Locust, Room 301, Kansas City, Missouri 64106; telephone: [phone]; facsimile: [phone], has the authority to approve AMOCs for this AD, if requested using the procedures found in 14 CFR 39.19.

Related Information

(g) The Federal Office for Civil Aviation Swiss AD HB-2006-374, effective date August 2, 2006, also addresses the subject of this AD. To get copies of the service information referenced in this AD, contact Pilatus Aircraft Ltd., Customer Liaison Manager, CH-6371 Stans, Switzerland; telephone: [phone]; fax: [phone]. To view the AD docket, go to the Docket Management Facility; U.S. Department of Transportation, 400 Seventh Street, SW., Nassif Building, Room PL-401, Washington, DC, or on the Internet at http://dms.dot.gov. The docket number is Docket No. FAA-2006-25582; Directorate Identifier 2006-CE-42-AD.

Issued in Kansas City, Missouri, on September 11, 2006.

John R. Colomy,

Acting Manager, Small Airplane Directorate, Aircraft Certification Service.