Regulatory Flexibility Determination

Airworthiness Directive – Twin Commander Aircraft LLC Airplanes

The Regulatory Flexibility Act of 1980 (Public Law 96-354) (RFA) establishes 

“as a principle of regulatory issuance that agencies shall endeavor, consistent with the 

objectives of the rule and of applicable statutes, to fit regulatory and informational 

requirements to the scale of the businesses, organizations, and governmental jurisdictions 

subject to regulation.” To achieve this principle, agencies are required to solicit and 

consider flexible regulatory proposals and to explain the rationale for their actions to 

assure that such proposals are given serious consideration.” The RFA covers a widerange of small entities, including small businesses, not-for-profit organizations, and small 

governmental jurisdictions.

Agencies must perform a review to determine whether a rule will have a 

significant economic impact on a substantial number of small entities. If the agency 

determines that it will, the agency must prepare a regulatory flexibility analysis as 

described in the RFA.

A. Reason for Agency Action

We are adopting a new airworthiness directive (AD) for certain Twin Commander 

Aircraft LLC Models 690, 690A, and 690B airplanes. This AD requires inspection for 

cracking of the outer fuselage attachments, the lower wing main spar, the vertical 

channels, the upper picture window channels, aft cabin pressure web, external wing to 

fuselage fillets, and fasteners; repair or replacement of damaged parts as necessary; and 
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modification of the structure with reinforced parts. This AD was prompted by cracks 

found in the upper picture window frame channels, left- and right-hand wing main spar 

frame support channels, and aft pressure bulkhead web. This condition, if not corrected, 

could result in structural failure of the airplane. We are issuing the AD to correct the 

unsafe condition on these products.

B. Legal Basis and Objectives of the Final Rule

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.

C. Recordkeeping and Other Compliance Requirements of the Rule

Compliance

Compliance with the AD must occur within the times specified, unless already 

done.
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Inspection 

(1) Inspect the airplane structural components, at the compliance times specified 

in paragraphs (g)(1)(i) through (g)(1)(iv) of the AD following Part I of Twin Commander 

Aircraft LLC Service Bulletin 241, September 26, 2012:

(i) For airplanes with 10,000 or more hours time-in-service (TIS), inspect within 

the next 30 days after the effective date of the AD.

(ii) For airplanes with 7,500 through 9,999 hours TIS, inspect within the next 60 

days after the effective date of the AD.

(iii) For airplanes with 5,000 through 7,499 hours TIS, inspect within the next 6 

months after the effective date of the AD.

(iv) For airplanes with less than 5,000 hours TIS, inspect when the airplane 

accumulates a total of 5,000 hours TIS or within the next 12 months after the effective 

date of the AD, whichever occurs later.

Repair

If any damage, cracks, and/or cracks that exceed the allowable limits specified in 

the service bulletin are found during the inspection required in paragraph (g)(1) of the

AD, before further flight, repair or replace parts as necessary following Twin 

Commander Aircraft LLC Service Bulletin 241, dated, September 26, 2012. If Twin 

Commander Aircraft LLC Service Bulletin 241, dated, September 26, 2012, does not give 

procedures for repair of the damaged area, before further flight, you must contact Twin 

Commander Aircraft LLC to obtain repair instructions approved by the Seattle Aircraft 

Certification Office (ACO) specifically for compliance with this AD and incorporate

those instructions. You can find contact information for Twin Commander Aircraft LLC 

in paragraph (l)(2) of the AD.

Modification and Reassembly

(1) Before further flight after completing the actions in paragraphs (g) and (h) of 

the AD, modify and reassemble the airplane using the modification and reassembly 
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procedures in Part II of Twin Commander Aircraft LLC Service Bulletin 241, dated, 

September 26, 2012.

(2) Although Twin Commander Aircraft LLC Service Bulletin 241, dated 

September 26, 2012, states that at least one person on the modification team must have 

completed the Twin Commander Aircraft LLC approved training, the FAA does not 

require that a mechanic complete this specialized training to do the modification work 

required in the AD. Regulations 14 CFR 65.81(a) and 14 CFR 65.81(b) provide criteria 

about qualifications of those performing maintenance; in this case, the requirements of 

the AD. 

D. Federal Rules that May Duplicate, Overlap, or Conflict with the Proposed Rule

There are no rules that duplicate, overlap or conflict with the Airworthiness 

Directive.

E. Description and estimation of the number of Small Entities Affected by Rule 

Under the RFA, the FAA must determine whether a proposed rule significantly 

affects a substantial number of small entities. This determination is typically based on 

small entity size and revenue thresholds that vary depending on the affected industry.1

 

To determine the number of small entities affected by the airworthiness directive, we 

searched the FAA Aircraft Registry database.

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 The database provides ownership 

information for 175 of the airplanes affected by the AD, and average airplane values for 

these aircraft are available in the Aircraft Bluebook Price Digest. 

 1 Thresholds are based on the North American Industry Classification System (NAICS). The NAICS is the 

standard used by Federal statistical agencies in classifying business establishments for the purpose of 

collecting, analyzing, and publishing statistical data related to the U.S. business economy.
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The FAA aircraft registry categorizes owners of affected airplanes as individuals, 

co-owners, corporations, and governments. A review of the corporations shows that an 

overwhelming majority are privately held. In most cases, the information about these

corporations cannot be determined because financial and employment data for privately 

held entities is sparse. Nevertheless, the FAA believes the number of small business 

entities affected by this AD is substantial. 

The serial numbers for the 175 affected airplanes that we have information on

was used to look up average retail values in the Aircraft Bluebook Price Digest.

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 The 

“Digest” provides average retail values by model, year, and serial number. It is only a 

guide since the actual condition and upgrades to individual airplanes are not known. The 

value range for the 175 affected airplanes is between $225,000 and $555,000 per 

airplane. The range is primarily due to age (i.e., the older an airplane the lower its retail 

value versus a newer model of the same airplane). The total retail value of the affected 

airplanes is equal to the sum of the retail value for each individual airplane. This 

summation equals $78.9 million (or an average of about $451,000 per airplane). 

The economic impact on small entities due to the AD is significant. This 

determination is based on the percentage of the cost of compliance per airplane ($58,090) 

to the average retail value per airplane ($451,000), which is estimated to be 12.9 percent. 

Based on the discussion above, complying with this AD is determined to be 

significant economic impact on a substantial number of small entities. 

 2 FAA Aircraft Registry Database by Make and Model of Aircraft as of June 2013. These aircraft were 

manufactured by Aero Commander and Rockwell. 3 Winter 2011 Edition.
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F. Alternatives Considered

Given the immediate safety problem, the FAA had to act immediately which resulted 

in our rejection of extending compliance time. If an unsafe condition is not found in the 

inspection no repair expense will occur.

International Trade Impact Assessment

The Trade Agreements Act of 1979 (Public Law 96-39), as amended by the 

Uruguay Round Agreements Act (Public Law 103-465), prohibits Federal agencies from 

establishing standards or engaging in related activities that create unnecessary obstacles 

to the foreign commerce of the United States. Pursuant to these Acts, the establishment 

of standards is not considered an unnecessary obstacle to the foreign commerce of the 

United States, so long as the standard has a legitimate domestic objective, such as the 

protection of safety, and does not operate in a manner that excludes imports that meet this 

objective. The statute also requires consideration of international standards and, where 

appropriate, that they be the basis for U.S. standards. The FAA has assessed the potential 

effect of this final rule and determined that because it addresses an immediate safety issue 

this rule is not considered an unnecessary obstacle to the foreign commerce of the United 

States. 

Unfunded Mandates Assessment

Title II of the Unfunded Mandates Reform Act of 1995 (Public Law 104-4) 

requires each Federal agency to prepare a written statement assessing the effects of any 

Federal mandate in a proposed or final agency rule that may result in an expenditure of 
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$100 million or more (in 1995 dollars) in any one year by State, local, and tribal 

governments, in the aggregate, or by the private sector; such a mandate is deemed to be a 

"significant regulatory action." The FAA currently uses an inflation-adjusted value of 

$143.1 million in lieu of $100 million. This final rule does not contain such a mandate; 

therefore, the requirements of Title II of the Act do not apply.