Regulatory Flexibility Determination

The Regulatory Flexibility Act of 1980 (RFA) establishes “as a principle of regulatory issuance 

that agencies shall endeavor, consistent with the objective of the rule and of applicable statutes, 

to fit regulatory and informational requirements to the scale of the business, organizations, and 

governmental jurisdictions subject to regulation.” To achieve that principle, the RFA requires 

agencies to solicit and consider flexible regulatory proposals and to explain the rationale for their 

actions. The RFA covers a wide range of small entities, including small businesses, not-forprofit organizations and small governmental jurisdictions.

Agencies must perform a review to determine whether a proposed or final 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 Act.

This proposed rule would impact part 135 operators and smaller air services businesses.

Part 135 Operators

The U.S. Small Business Administration (SBA) classifies businesses as small based on size 

standards, typically expressed as number of employees. The FAA identified 609 part 135

operators that meet the Small Business Administration definition of a small entity (entities with 

1,500 or fewer employees) out of the 610 part 135 operators affected by this proposed rule. We 

consider this a substantial number of small entities.

For the 609 part 135 small operators, we estimate costs that range between $14 thousand and

$1.2 million for adopting this airworthiness directive. We also estimated the value of their
aircraft, which ranges between $22 thousand and $21 million. Using the preceding information, 

the FAA estimates that their ratio of annualized cost to asset value are higher than 5 percent for

432 part 135 operators.

Smaller air services businesses

We estimate that more than 5,000 smaller air services businesses would be affected by this 

proposed rule. We consider this a substantial number of small entities. For each of these entities 

we estimated costs of about $14 thousand although we were unable to estimate their asset value. 

The FAA decided that the rule would have a significant economic impact on a substantial 

number of entities. Therefore, we have performed a regulatory flexibility analysis for these

small entities.

Initial Regulatory Flexibility Analysis

Under Section 603(b) of the RFA, the initial analysis must address: 

 Description of reasons the agency is considering the action

 Statement of the legal basis and objectives for the proposed rule

 Description of the record keeping and other compliance requirements of the proposed 

rule

 All federal rules that may duplicate, overlap, or conflict with the proposed rule

 Description and an estimated number of small entities to which the proposed rule will 

apply

 Describe alternatives considered
Description of reasons the agency is considering the action

This proposed AD was prompted by failure reports of multiple cylinder head-to-barrel 

separations and cracked and leaking aluminum cylinder heads.

Statement of the legal basis and objectives for the proposed 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.

Description of the record keeping and other compliance requirements of the proposed 

rule

Public reporting for this collection of information is estimated to be approximately 5 minutes per 

response, including the time for reviewing instructions, completing and reviewing the collection 

of information. Total paperwork costs range between $7 and $623 per small entity.

All federal rules that may duplicate, overlap, or conflict with the proposed rule

The FAA is unaware of any Federal rules that duplicate, overlap, or conflict with this 

rule.
Description and an estimated number of small entities to which the proposed rule will 

apply

The FAA identified 432 small part 135 operators on which the rule will have a significant 

economic impact. We estimate that the small part 135 operators have assets valued

between $22 thousand and $21 million.

Describe alternatives considered

We have considered the following alternatives:

• Do nothing - This option is not acceptable due to the number of failures of ECi cylinder 

head assemblies and the consequences of the failures.

• Periodic inspections only (no forced removals) - Though the NTSB recommends this 

option, we do not find it acceptable. The rate of crack growth to failure is unknown, but 

has shown that it can be more rapid than the intervals of Part 43 mandated inspections. 

Further, failure events tend to group in both low time (<500 hr) failure events and high 

time (>1000 hr) failure events.

• Forced removals only (no periodic inspections) - We do not find that this option is 

acceptable. Failure events may still occur at times other than the low and high times 

groups described above, and periodic inspections may find impending failures.