AD 2008-05-14

This AD becomes effective on April 16, 2008.

On April 16, 2008, the Director of the Federal Register approved the incorporation by reference of certain publications listed in this AD.

To get the service information identified in this AD, contact the following:

—For Sierra Hotel Aero, Inc. service information contact: Sierra Hotel Aero, 1690 Aeronca Lane, South St. Paul, MN 55075; phone: (651) 306-1456; fax: (612) 677-3171; Internet: http://www.navion.com/servicebulletins.html; e-mail: servicebulletinsupport@navion.com.

—For American Navion Society (ANS) service information contact: American Navion Society, Ltd., PMB 335, 16420 SE McGillivray #103, Vancouver, WA 98683-3461; telephone: (360) 833-9921; fax: (360) 833-1074; e-mail: flynavion@yahoo.com.

To view the AD docket, go to U.S. Department of Transportation, Docket Operations, M-30, West Building Ground Floor, Room W12-140, 1200 New Jersey Avenue, SE., Washington, DC 20590, or on the Internet at http://www.regulations.gov. The docket number is FAA-2007-27611; Directorate Identifier 2007-CE-024-AD.

Tim Smyth, Aerospace Engineer, Chicago Aircraft Certification Office (ACO), 2300 East Devon Avenue, Room 107, Des Plaines, Illinois 60018; telephone: (847) 294-7132; fax: (847) 294-7834.

On April 6, 2007, we issued a proposal to amend part 39 of the Federal Aviation Regulations (14 CFR part 39) to include an AD that would apply to all Sierra Hotel Aero, Inc. Models Navion (L-17A), Navion A (L-17B), (L-17C), Navion B, Navion D, Navion E, Navion F, Navion G, and Navion H airplanes. This proposal was published in the Federal Register as a notice of proposed rulemaking (NPRM) on April 12, 2007 (72 FR 18413). The NPRM proposed to detect and correct fuel system leaks or improperly operating fuel selector valves, which could result in the disruption of fuel flow to the engine.

We provided the public the opportunity to participate in developing this AD. The FAA has reviewed 111 public comments submitted to the docket pertaining to the proposed rulemaking activity which would impose a mandatory airworthiness inspection on all Navion airplane fuel systems. This proposed action includes testing of the fuel system selector valve for proper operation and replacement with a serviceable unit if necessary. The public responded to this published notice with significant personal and technical information. The FAA appreciates the detailed technical information submitted for consideration in addressing this important airworthiness issue. Many commenters spent a considerable amount of time researching and organizing extensive data to support their positions and to help the FAA address this unsafe condition. In addition, several commenters provided their Navion airplane system knowledge and expertise by proposing alternative corrective actions that will benefit all Navion owners and operators. This is one of the benefits of the rulemaking process.

It became clear that the majority of commenters were presenting similar points or positions. Because of this, we have grouped and categorized similar statements or positions. A total of 19 categories have been developed with a statement that summarizes the viewpoints, information, or position(s) submitted by the commenters. The FAA has addressed each summarized statement below.

The following presents the comments received on the proposal and FAA's response to each comment:

Comment Issue No. 1: Data Does Not Support Issuance of an AD

Richard W. Crapse and 38 other commenters believe the accident database information and other service difficulty reporting data does not support the issuance of an AD and requests the NPRM be withdrawn.

The FAA does not agree. There have been a number of Navion accident investigations where it has been determined that the fuel selector valve condition contributed to the cause of the accident. The overall number of accidents is small (nine accidents generally related to the fuel system with three of those reported accidents directly citing the fuel valve in the preliminary NTSB reports as a potential cause in the accidents). However, these reports have highlighted the fact that some selector valves may be reaching the limit of their serviceable life (many over 50 years old) and require additional inspections, checks, maintenance, or replacement to help address continued airworthiness.

We are not changing the final rule AD action based on this comment.

Comment Issue No. 2: The Corrective Action Could Create Safety Problems

John B. Conklin and 18 other commenters state the proposed service information corrective action could create more safety problems than it would solve. We infer that they think the corrective actions should be modified to eliminate potential problems the current proposed corrective actions would cause.

The FAA partially agrees. The FAA is always cognizant that inspections, checks, or modifications can potentially create maintenance induced errors that can affect continued airworthiness. However, the FAA believes the procedures in the service information minimize this potential concern. We believe this action addresses the unsafe condition for these airplanes while minimizing the risk of introducing new safety hazards.

We are not changing the final rule AD action based on this comment.

Comment Issue No. 3: There Are Other Fuel System Related Safety Issues

Ripley Quinby and 12 other commenters cite that there are potentially more fuel system related safety issues than just the selector valve (e.g., engine primer system, gascolator, flexible fuel lines, etc.). We infer the commenters believe we should take additional AD action.

Based on the submitted comments and data, it has been shown that a comprehensive fuel system inspection or check would enhance the continued airworthiness of the Navion airplane. The FAA appreciates the commenter's input regarding other potential safety issues and will monitor the continued airworthiness of the Navion airplanes. The FAA may take additional rulemaking action on these airplanes.

We are not changing the final rule AD action based on this comment.

Comment Issue No. 4: The Vacuum Test Is Too Severe

William Wade and 17 other commenters state the proposed 24 inches of mercury vacuum test is too severe and will potentially fail good fuel selector valves. The type certificate (TC) holder's published procedure does not have a calibration standard to ensure accurate testing results and at high altitude locations 24 inches of mercury vacuum may be impossible to obtain. The commenters request we decrease the mercury vacuum test to less than the 24 inches required in the TC holder's service bulletin.

The FAA partially agrees. The FAA accepted the TC holder's 24 inches of mercury vacuum test as the proper value to ensure fuel selector integrity. Because of the rigorous standard cited by the TC holder, it is not necessary to have a calibration standard procedure to compare against. The published service bulletin procedure is conservative enough to account for some deviation in the testing procedure and still address the continued airworthiness of the fuel selector valve.

In regards to high altitude vacuum testing, we have changed the AD to allow for a 1 inch of mercury reduction from the 24 inches of mercury standard for every 1,000 feet of pressure altitude over sea level testing conditions. We have also added the ANS Field Service Bulletin No. 1001, dated April 30, 2007, as an option to comply with this AD. The public stated and FAA recognizes that the Navion fuel system actually creates a fuel system vacuum of less than 10 inches of mercury. The FAA will consider an alternative method of compliance (AMOC) to this requirement. The public is encouraged to submit substantiating data to support an alternative approach.

Comment Issue No. 5: Add AMOCs

Aircraft Owners and Pilots Association (AOPA) and ANS along with 49 other commenters request that the FAA consider AMOCs to the published service documentation cited in the NPRM.

The FAA agrees. The FAA has reviewed the ANS Field Service Bulletin No. 1001, dated April 30, 2007, and has added this option to the AD. In addition, several commenters submitted documentation showing that certain manufactured fuel selector valves can be serviced in the field by airframe and powerplant (A&P) mechanics or other appropriately rated facilities. Finally, several commenters cite other airplane manufacturer (TC holder) service information that describes simplified testing methods to ascertain the continued airworthiness of the entire fuel system. If the commenters formalize and tailor these methods for the Navion airplane, the FAA will review and consider all AMOC requests we receive provided they follow the procedures in 14 CFR 39.19 and this AD.

We are changing the final rule AD action by adding ANS Field Service Bulletin No. 1001, dated April 30, 2007, as an option to comply with this AD.

Comment Issue No. 6: The Replacement Fuel Selector Valve Orifice Is Undersized

Richard E. Holmes and 11 other commenters question the replacement fuel selector valve orifice size to provide adequate fuel flow for larger engine installations. They question whether the required fuel selector outlet orifice size needs to be larger than what is currently specified in the TC holder's service documentation.

The FAA researched this issue and found that the replacement fuel selector valve that is specified in the AD provides adequate flow requirements for the larger engine installations and satisfies 14 CFR part 23 fuel flow compliance requirements. Several commenters also submitted extensive service experience showing acceptable fuel flow rates for the valves installed in Navion airplanes.

We are not changing the final rule AD action based on this comment.

Comment Issue No. 7: Delron Parts

Richard B. Olwin and four other commenters question the TC holder's position that Delron (“Plastic”) parts in certain fuel selector valve designs cause a safety issue. They request that the FAA allow the use of fuel selector valves that have plastic parts.

The FAA agrees with this comment. We have looked into this issue and found that FAA-approved parts manufacturer approval (PMA) fuel selector valves with plastic parts in their design exist. No service difficulty reports directly related to this issue were found. We will continue to monitor these parts, but at this time we find no unsafe condition.

The fuel selector valves required in the service information for this AD do not contain plastic parts. If someone wants to use a fuel selector valve with plastic parts, the FAA will review and consider all AMOC requests we receive provided they follow the procedures in 14 CFR 39.19 and this AD.

We are not changing the final rule AD action based on this comment.

Comment Issue No. 8: Navion Fuel System Is An Unsafe Condition

Richard E. Holmes cites a Navion Fuel system accumulator tank issue, and he thinks we infer that this tank needs replacing. He requests that we clarify whether this issue is part of our AD actions.

We agree that the accumulator tank is part of the fuel system, and we require a one-time inspection of the entire fuel system. However, this AD action is not focused on the accumulator tank but on the fuel selector valve. Although the fuel system accumulator tank is outside the scope of this rulemaking effort, we researched this issue and found no service difficulty data to show this to be an unsafe condition.

We are not changing the final rule AD action based on this comment.

Comment Issue No. 9: Reference Documents

Richard E. Holmes requests we provide the referenced documentation cited in the NPRM.

This information is available in the AD docket file and can be accessed by the public. The street address for the Docket Office (telephone (800) 647-5527) is in the ADDRESSES section. In addition, the TC holder has this information available at their Web site http://www.sierrahotelaero.com.

Comment Issue No. 10: Lack of Proper Maintenance

Andrew B. Woodside and eight other commenters believe the fuel system problems can be traced back to lack of proper maintenance. They request the AD action be withdrawn.

The FAA agrees that maintenance has contributed to the unsafe condition. If proper maintenance is being performed, the likelihood of having air introduced into the engine, which may cause loss of power, is minimized. In one instance, the owner had maintenance performed on his fuel selector valve to fix a leaking problem, but it appears this repair caused a power loss on takeoff. However, because of the actual reported accidents and their associated cause, the FAA has determined that the existing continued airworthiness instructions are inadequate and additional fuel system inspections and corrective actions are needed to help maintain the continued airworthiness of the Navion airplanes.

We are not changing the final rule AD action based on this comment.

Comment Issue No. 11: Unclear AD

Matt Hunsaker and six other commenters state the AD is not well thought out. They request we withdraw the proposed AD action.

The FAA disagrees. Service history and the NPRM published on April 12, 2007, substantiate why we should take corrective action to address this unsafe condition. The TC holder has developed and published what they believe is the proper corrective action to address the unsafe condition.

We have changed the final rule AD action to include another compliance action as an option based on the response to the NPRM. Moreover, the public may always propose AMOCs to show compliance to the corrective action requirements cited in the AD. The FAA will review and consider all AMOC requests we receive provided they follow the procedures in 14 CFR 39.19 and this AD.

Comment Issue No. 12: AD Will Make Money for TC Holder

Leo Burke and 15 other commenters state the TC holder is using the AD process to make money for the TC holder. They request the AD be revised to allow other methods of compliance.

The FAA disagrees that the AD process is being used for monetary gain. We issue ADs when an unsafe condition has been identified and the condition is likely to exist or develop in other products of the same type design (14 CFR 39.5). Service history and the NPRM published on April 12, 2007, substantiate why we should take corrective action to address this unsafe condition. Our regulatory responsibility does not address whether the TC holder's service bulletins are profitable, only whether they fully address the identified unsafe condition.

We have reviewed and added another option for addressing the unsafe condition in this final rule AD action. We will also review other AMOC requests we receive provided they follow the procedures in 14 CFR 39.19 and this AD.

Comment Issue No. 13: Add Sierra Hotel Aero, Inc. Service Bulletin 101A

Sierra Hotel Aero, Inc. and one other commenter suggest we add Sierra Hotel Aero, Inc. Navion Service Bulletin No. 106A, dated May 1, 2007, to the final rule AD.

FAA agrees to add this service bulletin, which provides instructions to replace the fuel selector valve.

Comment Issue No. 14: Difference in Fuel Selector Valve Operation

Ron Natalie and four other commenters cite that the replacement fuel selector valves may operate differently causing pilot confusion and fuel mismanagement accidents. They request that the AD address potential changes in the fuel selector operation.

The FAA agrees there are several valve options to replace a defective valve and not all these valve options operate exactly the same way. One valve design has a mechanical lockout stop that prevents the pilot from selecting the fuel shutoff position without a separate and distinct action. The valve placard labeling may be somewhat different. There can be 3-position or as many as a 5-position valve design installed. There may be more than one fuel selector in the fuel system. Because of field-approved and supplemental type certificate (STC) fuel system modifications, there are variations in the field. It is the responsibility of the pilot to understand the fuel system he or she is operating and be well versed in the fuel management procedures for that particular airplane.

We are not changing the final rule AD action based on this comment.

Comment Issue No. 15: Continued Airworthiness Information

Andrew B. Woodside suggests that Navion owners have access to the continued airworthiness information, acquire it, and use it.

The FAA agrees. We provide the contact information for obtaining additional information from both Sierra Hotel Aero (TC Holder) and the American Navion Society in paragraph (h)(2) of this final rule AD action.

Comment Issue No. 16: Modified Fuel Systems

Tony B. Russell and six other commenters state the NPRM does not address modified Navion fuel systems accomplished by field approval, STC, or other appropriate methods.

The FAA partially agrees. The FAA recognizes that many Navion airplanes have modified fuel systems that can include auxiliary fuel and wing tip fuel tanks. However, we have no way of determining which airplanes have modified fuel systems that could include auxiliary fuel and wing tip fuel tanks, and therefore, we cannot exempt these airplanes from the AD.

We are not changing the final rule AD action based on this comment. The FAA will consider AMOC requests to satisfy the AD compliance requirements. This can be accomplished on a case-by-case basis, or in the case of an STC holder they can submit an AMOC proposal for their STC design approval provided they follow the procedures in 14 CFR 39.19 and this AD.

Comment Issue No. 17: Different Testing Acceptance Criteria

Maynard Keith Franklin and three other commenters cite that other Navion service documentation defines different (higher) leak rates for other fuel system components (e.g., gascolator) than what is defined in the fuel selector valve testing requirements. They request that we standardize the leakage rates for the fuel system inspection.

The FAA partially agrees. The FAA determined that there are other acceptable leak rates that might be lower than the rate cited in the TC holder's service bulletin. Those previous Navion maintenance publications for fuel system components include the fuel system gascolator. For this final rule action, we are using the TC holder's requirements cited in the current service bulletin to address the test and acceptance criteria for the fuel selector. However, if someone submits substantiating data, the FAA will review and consider all AMOC requests we receive provided they follow the procedures in 14 CFR 39.19 and this AD to show compliance with the TC holder's published service documentation.

We are not changing the final rule AD action based on this comment.

Comment Issue No. 18: Unsafe Installation of Replacement Fuel Selector Valve

Ron Judy and six other commenters state that the proposed replacement valve may cause installation safety issues. They request that we or the TC holder provide instructions that address installation fit problems for all aircraft.

The FAA disagrees. After discussing with the TC holder, we have confirmed the proposed replacement valve can be properly installed. We have also confirmed with a representative of ANS that a replacement valve can be properly installed. Any discrepancy that is found during installation must be handled on a case-by-case basis and documented using FAA Form 337.

We are not changing the final rule AD action based on this comment.

Comment Issue No. 19: Repair of Fuel Selector Valve

Mike Pettaway and three other commenters state that an A&P mechanic can repair a fuel selector valve since that type of repair is cited in the (A&P) practical testing standards.

The FAA partially agrees. It is true that an A&P mechanic is trained to disassemble, repair, and re-assemble various components and assemblies; however, even when this type of work is performed in the field, the work must be accomplished with some form of FAA accepted or approved data (e.g. manufacturer service instruction(s), manufacturer's service bulletins, maintenance manuals, etc.). The mechanic does not have the authority to perform repairs on the fuel selector valve itself without the manufacturer's supporting continued airworthiness data or an FAA-approved or accepted procedure.

We are not changing this final rule AD action based on this comment.

We have carefully reviewed the available data and determined that air safety and the public interest require adopting the AD as proposed except for the changes previously discussed and minor editorial corrections. We have determined that these minor corrections:

• Are consistent with the intent that was proposed in the NPRM for correcting the unsafe condition; and

• Do not add any additional burden upon the public than was already proposed in the NPRM.

We estimate that this AD affects 1,500 airplanes in the U.S. registry.

We estimate the following costs to do the inspection:

We estimate the following costs to do any necessary replacements that would be required based on the results of the inspection. We have no way of determining the number of airplanes that may need this repair/replacement:

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 AD.

We have determined that this AD will not have federalism implications under Executive Order 13132. This AD will 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 this AD:

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 summary of the costs to comply with this AD (and other information as included in the Regulatory Evaluation) and placed it in the AD Docket. You may get a copy of this summary by sending a request to us at the address listed under ADDRESSES. Include “Docket No. FAA-2007-27611; Directorate Identifier 2007-CE-024-AD” in your request.

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

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

2. FAA amends § 39.13 by adding a new AD to read as follows: