AD 97-14-01

This amendment supersedes Airworthiness Directive (AD) 75-24-07 R1, which currently requires repetitively inspecting the left-hand (LH) rudder bar assembly for cracks and loose fasteners on certain Pilatus Britten-Norman Ltd. BN-2A and BN-2A Mk 111 series airplanes, and replacing any cracked part. The superseding action requires inspecting the LH rudder bar assembly and determining the wall thickness of the slider tube unit. This action also would require modifying the rudder bar assembly by replacing the LH slider tube with a new strengthened slider tube unit as terminating action for the repetitive inspections currently required by AD 75-24-07 R1. The development of a modification to the rudder bar assembly, which terminates the repetitive inspections required by AD 75-24-07 R1, prompted this AD. The actions specified by this AD are intended to prevent failure of the pilot s rudder bar assembly, which could result in loss of control of the airplane during landing operations.

Final rule.

97-14-01 PILATUS BRITTEN-NORMAN, LTD.: Amendment 39-10058; Docket No. 96-CE-24-AD. Supersedes AD 75-24-07 R1, Amendment 39-4571.

Applicability: BN-2A and BN-2A Mk 111 Series airplanes (all serial numbers), certificated in any category.

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 (f) 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 after the effective date of this AD, unless already accomplished.

To prevent failure of the left-hand (LH) rudder bar assembly, which, if not detected and corrected, could result in loss of control of the airplane during landing operations, accomplish the following:

(a) Within the next 500 landings after the effective date of this AD, inspect the LH rudder bar unit for cracks (using a dye penetrant method), and measure the thickness/gauge of the LH slider tube in accordance with paragraph 1 of the ACTION Inspection section of Pilatus Britten-Norman (PBN) Service Bulletin (SB) No. BN-2/SB.111, Issue 1, dated October 25, 1977, and paragraphs 1 through 3 in the ACTION section of PBN SB No. BN-2/SB.56, Issue 2, dated February 13, 1978.

NOTE 2: For operators who have not kept records of the landings of the airplane, use 3 landings per 1 hour time-in-service (TIS).

(b) If no cracks are visible, accomplish the following in accordance with paragraph 3a. and 3b. of the ACTION Inspection section of PBN SB No. BN-2/SB.111, dated October 25, 1977:

(1) For airplanes that have slider tubes with 17 gauge metal (.056-inch thick),

(i) Continue to inspect the LH rudder bar assembly for cracks every 500 landings and,

(ii) Upon the total accumulation of 5,000 landings or within the next 500 landings after the effective date of this AD, whichever occurs later, accomplish Modification NB/M/948 by installing a new, strengthened slider tube unit, part number (P/N) NB-45-A1-2975 in accordance with the ACTION Rectification section of PBN SB No. BN-2/SB.111, dated October 25, 1977.

(2) For airplanes that have slider tubes with 20 gauge metal (.036-inch thick),

(i) Continue to inspect the LH rudder bar assembly for cracks every 250 landings and,

(ii) Upon the total accumulation of 2,500 landings or within the next 500 landings after the effective date of this AD, whichever occurs later, accomplish Modification NB/M/948 by installing a new, strengthened slider tube unit, P/N NB-45-A1-2975 in accordance with the ACTION Rectification section of PBN SB No. BN-2/SB.111, dated October 25, 1977.

(c) If cracks are visible during any inspection required by this AD, prior to further flight, accomplish Modification NB/M/948 in accordance with the ACTION Rectification section of PBN SB No. BN-2/SB.111, dated October 25, 1977.

(d) Accomplishing Modification NB/M/948 using P/N NB-45-A1-2975 at any time prior to the required number of accumulated landings in paragraphs (b)(1)(ii) and (b)(2)(ii) of this AD is a terminating action for the repetitive inspections required by this AD.

(e) 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.

(f) 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, Small Airplane Directorate, Aircraft Certification Service, FAA, 1201 Walnut, suite 900, Kansas City, Missouri 64106. The request shall be forwarded through an appropriate FAA Maintenance Inspector, who may add comments and then send it to the Manager, Small Airplane Directorate.

NOTE 3: Information concerning the existence of approved alternative methods of compliance with this AD, if any, may be obtained from Small Airplane Directorate.

(g) The inspections and modifications required by this AD shall be done in accordance Pilatus Britten-Norman Service Bulletin No. BN-2/SB.111, Issue 1, dated October 25, 1977, or Pilatus Britten-Norman Service Bulletin No. BN-2/SB.56, Issue 2, dated February 13, 1978, whichever is applicable. This incorporation by reference was approved by the Director of the Federal Register in accordance with 5 U.S.C. 552(a) and 1 CFR part 51. Copies may be obtained from Pilatus Britten-Norman Ltd., Bembridge, Isle of Wight, United Kingdom PO35 5PR. 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., suite 700, Washington, DC.

(h) This amendment (39-10058) supersedes AD 75-24-07 R1, Amendment 39-4571.

(i) This amendment becomes effective on August 18, 1997.

Events Leading to the Issuance of This AD
A proposal to amend part 39 of the Federal Aviation Regulations (14 CFR part 39) to include an AD that would apply to Pilatus Britten-Norman Ltd. BN-2A and BN-2A Mk 111 series airplanes was published in the Federal Register on March 3, 1997 (62 FR 9390). The action proposed to require:

(1) Inspecting for cracks in the LH rudder bar assembly using a dye penetrant method, and measuring the thickness of the slider tube to determine the applicability of the proposed action, either .056-inch (17 gauge), or .036-inch (20 gauge),

(2) Repetitively inspecting for cracks until the accumulation of a determined number of landings, then accomplishing Modification NB/M/948 by installing a new, strengthened central piller/slider tube assembly, part number (P/N) NB-45-A1-2975, and

(3) If cracks are found during any inspection, accomplishing Modification NB/M/948 by installing P/N NB-45-A1-2975.

Accomplishmentof the proposed action would be in accordance with Pilatus Britten-Norman Service Bulletin No. BN-2/SB.111, Issue 1, dated October 25, 1977 or Pilatus Britten-Norman Service Bulletin No. BN-2/SB.56, Issue 2, dated February 13, 1978, whichever is applicable.

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.

The FAA's Determination
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.

FAA s Aging Aircraft Commuter Class Policy
The actions required by this AD are consistentwith the FAA's aging commuter aircraft policy, which briefly states that, when a modification exists that could eliminate or reduce the number of required critical inspections, the modification should be incorporated. This policy is based on the FAA's determination that reliance on critical repetitive inspections on airplanes utilized in commuter service carries an unnecessary safety risk when a design change exists that could eliminate or, in certain instances, reduce the number of those critical inspections. In determining what inspections are critical, the FAA considers (1) the safety consequences of the airplane if the known problem is not detected by the inspection; (2) the reliability of the inspection such as the probability of not detecting the known problem; (3) whether the inspection area is difficult to access; and (4) the possibility of damage to an adjacent structure as a result of the problem.

Compliance Time
The compliance time for this AD is based on number of landings rather than hours time-in-service. The reason for this type of compliance is that the area that is showing fatigue is the pilot s rudder bar assembly and pillar/slider tube unit. This area of the airplane is used during the landing operation; furthermore, the stress and fatigue is greater in this thinner gauged metal slider tube unit upon landing. Therefore, it has been determined to use the number of landings rather than hours time-in-service as the compliance time for this AD.

For airplanes equipped with the thinner (20 gauge) slider tubes, the AD requires accomplishing the modification upon the total accumulation of 2,500 landings, or within the next 500 landings after the effective date of the action, whichever occurs later; and for airplanes equipped with the thicker (17 gauge) slider tubes, the AD requires accomplishing the modification within the next 500 landings after the effective date of the action or upon the total accumulation of 5,000 landings, whichever occurs later.

(NOTE: If the operators have not recorded the number of landings, the landings can be calculated by multiplying 3 landings per 1 hour time-in-service.)

Cost Impact
The FAA estimates that 109 airplanes in the U.S. registry will be affected by this AD, that it will take approximately 15 workhours per airplane to accomplish this action, and that the average labor rate is approximately $60 an hour. Parts cost approximately $560 per airplane. Based on these figures, the total cost impact of this AD on U.S. operators is estimated to be $159,140 or $1,460 per airplane. In addition, the cost figures referenced above are based on the presumption that no affected airplane operator has incorporated the inspection-terminating installation. Pilatus Britten-Norman does not know the number of parts distributed to the affected airplane owners/operators. Numerous sets of parts were sent out to the owners/operators of the affected airplanes, but over the years Pilatus Britten-Norman has not retained these records.

The AD's Impact Utilizing the FAA's Aging Commuter Class Aircraft Policy
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 109 airplanes in the U.S. registry that will be affected by this AD, the FAA has determined that approximately 30 percent are operated in scheduled passenger service by 11 different operators. A significant number of the remaining 70 percent are operating in other forms of air transportation such as air cargo and air taxi.

The average utilization of the fleet for those airplanes in commercial commuter service is approximately 20 to 40 landings per week with approximately 3 landings per 1 hour TIS per week. Based on these figures, operators of commuter-class airplanes involved in commercial operation will have to accomplish the modification within approximately 3 to 5 calendar months after the AD becomes effective. For private owners, who typically operate their airplanes between 100 to 200 landings per year, this will allow 12 to 25 years before the modification will be mandatory.

Regulatory Impact
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), 40113, 44701.

39.13 [Amended]
2. Section 39.13 is amended by removing airworthiness directive (AD) 75-24-07 R1, Amendment 39-4571 and by adding a new AD to read as follows: