AD 95-21-14 ACTIVE

This amendment supersedes Airworthiness Directive (AD) 83-18-03, which currently requires repetitively inspecting the tailplane outboard hinge assembly on certain de Havilland DHC-6 series airplanes, and replacing any cracked tailplane outboard hinge assembly. The Federal Aviation Administration's policy on aging commuter-class aircraft is to eliminate or, in certain instances, reduce the number of certain repetitive short-interval inspections when improved parts or modifications are available. This action requires eventually modifying the tailplane outboard hinge arm and tailplane hinge plate with parts of improved design (Modification No. 6/1799) as terminating action for the currently required repetitive inspections. The actions specified by this AD are intended to prevent tailplane failure caused by cracks in either outboard hinge arm or the hinge plate, which, if not detected and corrected, could result in loss of control of the airplane.

Final rule.

95-21-14 DE HAVILLAND: Amendment 39-9401; Docket No. 91-CE-46-AD. Supersedes AD 83-18-03, Amendment 39-4719.

Applicability: Models DHC-6-1, DHC-6-100, DHC-6-200 and DHC-300 airplanes (serial numbers 1 to 810), certificated in any category, that do not have Modification 6/1799 incorporated in accordance with the ACCOMPLISHMENT INSTRUCTIONS, Replacement, section of de Havilland Service Bulletin (SB) No. 6/421, Revision B, dated November 11, 1983.

NOTE 1: This AD applies to each airplane identified in the preceding applicability provision, regardless of whether it has been modified, altered, or repaired in the area subject to the requirements of this AD. For airplanes that have been modified, altered, or repaired so that the performance of the requirements of this AD is affected, the owner/operator must request approval for an alternative method of compliance in accordance with paragraph (e) of this AD. The request should include an assessment of the effect of the modification, alteration, or repair on the unsafe condition addressed by this AD; and, if the unsafe condition has not been eliminated, the request should include specific proposed actions to address it.

Compliance: Required as indicated in the body of this AD, unless already accomplished.

To prevent tailplane failure caused by cracks in either the outboard hinge arm or the hinge plate, which, if not detected and corrected, could result in loss of control of the airplane, accomplish the following:

(a) Within the next 50 hours time-in-service (TIS) after the effective date of this AD or within the next 1,200 hours TIS after the last inspection accomplished in accordance with superseded AD 83-18-03, Amendment 39-4719, whichever occurs later, inspect the tailplane outboard hinge arm assembly for cracks in accordance with the ACCOMPLISHMENT INSTRUCTIONS, Inspection, section of de Havilland SB No. 6/421, Revision B, dated November 11, 1983.

(1) If cracks are not found, reinspect every 1,200 hours TIS until Modification 6/1799 (tailplane outboard hinge arm and tailplane hinge plate) is installed as required by paragraph (b) of this AD.

(2) If cracks are found, prior to further flight, replace the tailplane outboard hinge arm assembly with Modification 6/1799 in accordance with the ACCOMPLISHMENT INSTRUCTIONS, Replacement, section of de Havilland SB No. 6/421, Revision B, dated November 11, 1983.

(b) Within 2,400 hours TIS after the effective date of this AD, replace the tailplane outboard hinge arm assembly with Modification 6/1799 in accordance with the ACCOMPLISHMENT INSTRUCTIONS, Replacement, section of de Havilland SB No. 6/421, Revision B, dated November 11, 1983, unless already accomplished in accordance with paragraph (a)(2) of this AD.

(c) Compliance with paragraph (a)(2) or (b) of this AD is considered terminating action for the inspection requirements of this AD.

(d) Special flight permits may be issued in accordance with sections 21.197 and 21.199 of the Federal Aviation Regulations (14 CFR 21.197 and 21.199) to operate the airplane to a location where the requirements of this AD can be accomplished.

(e) An alternative method of compliance or adjustment of the initial or repetitive compliance times that provides an equivalent level of safety may be approved by the Manager, New York Aircraft Certification Office (ACO), FAA, 10 Fifth Street, 3rd Floor, Valley Stream, New York 11581. The request shall be forwarded through an appropriate FAA Maintenance Inspector, who may add comments and then send it to the Manager, New York ACO.

NOTE 2: Information concerning the existence of approved alternative methods of compliance with this AD, if any, may be obtained from the New York ACO.

(f) The inspections and modification required by this AD shall be done in accordance with de Havilland Service Bulletin No. 6/421, Revision B, dated November 11, 1983. This incorporation by reference was approved bythe Director of the Federal Register in accordance with 5 U.S.C. 552(a) and 1 CFR part 51. Copies may be obtained from de Havilland, Inc., 123 Garratt Boulevard, Downsview, Ontario M3K 1Y5 Canada. Copies may be inspected at the FAA, Central Region, Office of the Assistant Chief Counsel, Room 1558, 601 E. 12th Street, Kansas City, Missouri, or at the Office of the Federal Register, 800 North Capitol Street, NW., 7th Floor, suite 700, Washington, DC.

(g) This amendment (39-9401) supersedes AD 83-18-03, Amendment 39-4719.

(h) This amendment becomes effective on December 4, 1995.

A proposal to amend part 39 of the Federal Aviation Regulations (14 CFR part 39) to include an AD that would apply to certain de Havilland DHC-6 series airplanes without Modification No. 6/1799 incorporated was published in the Federal Register on October 31, 1994 (59 FR 54410). The action proposed to supersede AD 83-18-03 with a new AD that would (1) initially retain the requirement of repetitively inspecting the tailplane outboard hinge assembly for cracks, and replacing any cracked part; and (2) eventually require modifying the tailplane outboard hinge arm and tailplane hinge plate with parts of improved design (Modification No. 6/1799) as terminating action for the currently required repetitive inspections. Accomplishment of the proposed actions would be in accordance with de Havilland Service Bulletin No. 6/421, Revision B, dated November 11, 1983.

Interested persons have been afforded an opportunity to participate in the making of this amendment.No comments were received on the proposed rule or the FAA's determination of the cost to the public.

After careful review of all available information related to the subject presented above, the FAA has determined that air safety and the public interest require the adoption of the rule as proposed except for minor editorial corrections. The FAA has determined that these minor corrections will not change the meaning of the AD and will not add any additional burden upon the public than was already proposed.

The FAA estimates that 141 airplanes in the U.S. registry will be affected by this AD, that it will take approximately 35 workhours per airplane to accomplish the required action, and that the average labor rate is approximately $60 an hour. Parts cost approximately $4,400 per airplane. Based on these figures, the total cost impact of this AD on U.S. operators is estimated to be $916,500. This figure is based on the assumption that no affected airplane owner/operator hasaccomplished the required modification.

The intent of the FAA's aging commuter airplane program is to ensure safe operation of commuter-class airplanes that are in commercial service without adversely impacting private operators. Of the approximately 141 airplanes in the U.S. registry that are affected by this AD, the FAA has determined that approximately 40 percent are operated in scheduled passenger service. A significant number of the remaining 60 percent are operated in other forms of air transportation such as air cargo and air taxi.

This AD allows 2,400 hours time-in-service (TIS) after the effective date of this AD before mandatory accomplishment of the design modification. The average utilization of the fleet for those airplanes in commercial commuter service is approximately 25 to 50 hours TIS per week. Based on these figures, operators of commuter-class airplanes involved in commercial operation will have to accomplish the required modification within 12 to 24 calendar months after this AD becomes effective. For private owners, who typically operate between 100 to 200 hours TIS per year, this allows 12 to 24 years before the required modification is mandatory.

The following paragraphs present cost scenarios for airplanes where no cracks are found and where cracks are found during the inspections, and where the remaining airplane life is 15 years with an average annual utilization rate of 1,600 hours TIS. A copy of the full Cost Analysis and Regulatory Flexibility Determination for this AD may be examined at the FAA, Central Region, Office of the Assistant Chief Counsel, Attention: Rules Docket No. 91-CE-46-AD, Room 1558, 601 E. 12th Street, Kansas City, Missouri.

- No Cracks Scenario: Under the provisions of AD 83-18-03, an owner/operator of a de Havilland DHC-6 series airplane in scheduled service who operates an average of 1,600 hours TIS annually will inspect every 1,200 hours TIS. This amounts to a remaining airplane life (estimated 15 years) amount of $4,769; this figure is based on the assumption that no cracks are found during the inspections. This AD requires the same 1,200-hour TIS inspection until 2,400 hours TIS after the effective date of the AD when the operator has to replace the tailplane outboard hinge arm assembly (eliminating the need for further repetitive inspections), which results in a present value cost of $6,574. The incremental cost of this AD for such an airplane is $1,805 ($6,574 - $4,769) or $1,309 annualized over the 1.5 years it will take to accumulate 2,400 hours TIS. An owner of a general aviation airplane who operates 800 hours TIS annually without finding any cracks during the 1,200-hour TIS inspections will incur a present value incremental cost of $3,483 ($5,990 - $2,507). This amounts to a per year amount of $1,327 over the three years it takes to accumulate 2,400 hours TIS.

- Cracks Found Scenario: Under the provisions of AD 83-18-03, an owner/operator of a de Havilland DHC-6 series airplane who finds cracks during an inspection will repair the crack prior to further flight and resume inspections every 1,200 hours TIS. This AD requires immediate replacement of the arm assembly if cracks are found during an inspection as terminating action for the repetitive inspection requirement. The repair cost is the same as the replacement except that the repair does not terminate the inspection requirement. For this reason, this AD results in present-day cost savings, which will continue to grow over the remaining life of the airplane since repetitive inspections are not required. Using the assumed 15-year remaining life, the cost savings for incorporating Modification 6/1799 will be $4,409 for scheduled service airplane owners/operators and $2,149 for general aviation airplane owners/operators.

The Regulatory Flexibility Act of 1980 (RFA) was enacted by Congress to ensure that small entities are not unnecessarily or disproportionally burdened by government regulations. The RFA requires government agencies to determine whether rules could have a "significant economic impact on a substantial number of small entities," and, in cases where they could, conduct a Regulatory Flexibility Analysis in which alternatives to the rule are considered. FAA Order 2100.14A, Regulatory Flexibility Criteria and Guidance, outlines FAA procedures and criteria for complying with the RFA. Small entities are defined as small businesses and small not-for-profit organizations that are independently owned and operated or airports operated by small governmental jurisdictions. A "substantial number" is defined as a number that is not less than 11 and that is more than one-third of the small entities subject to a rule, or any number of small entities judged to be substantial by the rulemaking official. A "significant economic impact" is defined by an annualized net compliance cost, adjusted for inflation, which is greater than a threshold cost level fordefined entity types. FAA Order 2100.14A sets the size threshold for small entities operating aircraft for hire at 9 aircraft owned and the annualized cost thresholds, adjusted to 1994 dollars, at $69,000 for scheduled operators and $5,000 for unscheduled operators.

Of the 141 U.S.-registered airplanes affected by this AD, 6 airplanes are owned by the federal government. Of the other 135, one business owns 26 airplanes, one business owns 9 airplanes, one business owns 8 airplanes, one business owns 7 airplanes, one business owns 4 airplanes, two businesses own 3 airplanes each, thirteen businesses own 2 airplanes each, and forty-nine businesses each own 1 airplane.

Because the FAA has no readily available means of obtaining data on sizes of these entities, the economic analysis for this AD utilizes the worst case scenario using the lower annualized cost threshold of $5,000 for operators in unscheduled service instead of $69,000 for operators in scheduled service. With this in mind and based on the above ownership distribution, the 64 entities owning 3 or fewer airplanes will not experience a "significant economic impact" as defined by FAA Order 2100.14A. Since the remaining five entities do not constitute a "substantial number" as defined in the Order, this AD will not have a "significant economic impact on a substantial number of small entities."

The regulations adopted herein will not have substantial direct effects 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. Therefore, in accordance with Executive Order 12612, it is determined that this final rule does not have sufficient federalism implications to warrant the preparation of a Federalism Assessment.

For the reasons discussed above, I certify that this action (1) is not a "significant regulatory action" under Executive Order 12866; (2) is not a "significant rule"under 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. A copy of the final evaluation prepared for this action is contained in the Rules Docket. A copy of it may be obtained by contacting the Rules Docket at the location provided under the caption "ADDRESSES".

List of Subjects in 14 CFR Part 39
Air transportation, Aircraft, Aviation safety, Incorporation by reference, Safety.

Adoption of the Amendment
Accordingly, pursuant to 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:

PART 39 - AIRWORTHINESS DIRECTIVES
1. The authority citation for part 39 continues to read as follows:
Authority: 49 USC 106(g), 40101, 40113, 44701.

Section 39.13 - [AMENDED]
2. Section 39.13 is amended by removing Airworthiness Directive (AD) 83-18-03, Amendment 39-4719, and adding a new AD to read as follows:

Service information that applies to this AD may be obtained from de Havilland, Inc., 123 Garratt Boulevard, Downsview, Ontario, Canada, M3K 1Y5. This information may also be examined at the Federal Aviation Administration (FAA), Central Region, Office of the Assistant Chief Counsel, Attention: Rules Docket 91-CE-46-AD, Room 1558, 601 E. 12th Street, Kansas City, Missouri 64106; or at the Office of the Federal Register, 800 North Capitol Street, NW., suite 700, Washington, DC.

Jon Hjelm, Aerospace Engineer, FAA, New York Aircraft Certification Office, 10 Fifth Street, 3rd Floor, Valley Stream, New York 11581; telephone (516) 256-7523; facsimile (516) 568-2716.