02-21356. Airworthiness Directives; Pilatus Britten-Norman Limited BN-2, BN-2A, BN-2B, BN-2T, and BN2A MK. III Series Airplanes

AGENCY:

Federal Aviation Administration, DOT.

ACTION:

Notice of proposed rulemaking (NPRM).

SUMMARY:

This document proposes to adopt a new airworthiness directive (AD) that would apply to all Pilatus Britten-Norman Limited (Pilatus Britten-Norman) BN-2, BN-2A, BN-2B, BN-2T, BN2A MK. III series airplanes. This proposed AD would require you to repetitively inspect the bottom corner of the engine mount bracket for cracks and replace any cracked bracket with a new one. This proposed AD is the result of mandatory continuing airworthiness information (MCAI) issued by the airworthiness authority for the United Kingdom. The actions specified by this proposed AD are intended to detect and correct cracks in the engine mount bracket. Such a condition could cause the engine mount assembly to fail, which could result in the engine separating from the airplane and lead to loss of control of the airplane.

DATES:

The Federal Aviation Administration (FAA) must receive any comments on this proposed rule on or before September 27, 2002.

ADDRESSES:

Submit comments to FAA, Central Region, Office of the Regional Counsel, Attention: Rules Docket No. 2002-CE-21-AD, 901 Locust, Room 506, Kansas City, Missouri 64106. You may view any comments at this location between 8 a.m. and 4 p.m., Monday through Friday, except Federal holidays. You may also send comments electronically to the following address: [e-mail]. Comments sent electronically must contain “Docket No. 2002-CE-21-AD” in the subject line. If you send comments electronically as attached electronic files, the files must be formatted in Microsoft Word 97 for Windows or ASCII text.

You may get service information that applies to this proposed AD from B-N Group Limited, Bembridge, Isle of Wight, United Kingdom PO35 5PR; telephone: [phone]; facsimile: [phone]. You may also view this information at the Rules Docket at the address above.

FOR FURTHER INFORMATION CONTACT:

Doug Rudolph, Aerospace Engineer, FAA, Small Airplane Directorate, 901 Locust, Room 301, Kansas City, Missouri 64106; telephone: [phone]; facsimile: [phone].

SUPPLEMENTARY INFORMATION:

Comments Invited

How Do I Comment on This Proposed AD?

The FAA invites comments on this proposed rule. You may submit whatever written data, views, or arguments you choose. You need to include the rule's docket number and submit your comments to the address specified under the caption ADDRESSES. We will consider all comments received on or before the closing date. We may amend this proposed rule in light of comments received. Factual information that supports your ideas and suggestions is extremely helpful in evaluating the effectiveness of this proposed AD action and determining whether we need to take additional rulemaking action.

Are There Any Specific Portions of This Proposed AD I Should Pay Attention To?

The FAA specifically invites comments on the overall regulatory, economic, environmental, and energy aspects of this proposed rule that might suggest a need to modify the rule. You may view all comments we receive before and after the closing date of the rule in the Rules Docket. We will file a report in the Rules Docket that summarizes each contact we have with the public that concerns the substantive parts of this proposed AD.

How Can I Be Sure FAA Receives My Comment?

If you want FAA to acknowledge the receipt of your mailed comments, you must include a self-addressed, stamped postcard. On the postcard, write “Comments to Docket No. 2002-CE-21-AD.” We will date stamp and mail the postcard back to you.

Discussion

What Events Have Caused This Proposed AD?

The Civil Aviation Authority (CAA), which is the airworthiness authority for the United Kingdom, recently notified FAA that an unsafe condition may exist on all Pilatus Britten-Norman BN-2, BN-2A, BN-2B, BN-2T, and BN2A MK. III series airplanes. The CAA reports two occurrences of extensive cracks being found on the bottom corner of the engine mount bracket between the attachment flange and the main bracket. The cracks were found during regular scheduled maintenance.

The manufacturer has determined that this condition is a result of the reinforcing doubler being too close to the flange.

What Are the Consequences if the Condition Is Not Corrected?

This condition, if not detected and corrected, could result in failure of the engine mount. Such failure could result in the engine separating from the airplane and lead to loss of control of the airplane.

Is There Service Information That Applies to This Subject?

Pilatus Britten-Norman has issued Service Bulletin SB 275, Issue 1, dated November 30, 2001.

What Are the Provisions of This Service Information?

The service bulletin includes procedures for inspecting the engine mount bracket for cracks and specifies replacing any cracked bracket.

What Action Did the CAA Take?

The CAA classified this service bulletin as mandatory and issued CAA AD Number 005-11-2001, not dated, in order to ensure the continued airworthiness of these airplanes in the United Kingdom.

Was This in Accordance With the Bilateral Airworthiness Agreement?

These airplane models are manufactured in the United Kingdom and are type certificated for operation in the United States under the provisions of section 21.29 of the Federal Aviation Regulations (14 CFR 21.29) and the applicable bilateral airworthiness agreement.

Pursuant to this bilateral airworthiness agreement, the CAA has kept FAA informed of the situation described above.

Are There Differences Between This Proposed AD, the Service Information, and the CAA AD?

The CAA AD and the service information allows continued flight if cracks are found in the engine mount bracket that do not exceed certain limits. The applicable service bulletin specifies replacement of the engine mount bracket only if cracks are found exceeding this limit, as does CAA AD 005-11-2001. This proposed AD, if adopted, would not allow continued flight if any crack is found. FAA policy is to disallow airplane operation when known cracks exist in primary structure, unless the ability to sustain ultimate load with these cracks is proven. The engine mount bracket is considered primary structure, and the FAA has not received any analysis to prove that ultimate load can be sustained with cracks in this area.

Is There a Modification I Can Incorporate Instead of Repetitively Inspecting the Engine Mount Brackets?

The FAA has determined that long-term continued operational safety would be better assured by design changes that remove the source of the problem rather than by performing repetitive inspections. With this in mind, we will continue to work with Pilatus Britten-Norman in collecting information to determine whether a future design change may be necessary.

The FAA's Determination and an Explanation of the Provisions of this Proposed AD

What Has FAA Decided?

The FAA has examined the findings of the CAA; reviewed all available information, including the service information referenced above; and determined that:

—the unsafe condition referenced in this document exists or could develop on other Pilatus Britten-Norman BN-2, BN-2A, BN-2B, BN-2T, and BN2A MK. III series airplanes of the same type design that are on the U.S. registry;

—the actions specified in the previously-referenced service information should be accomplished on the affected airplanes; and

—AD action should be taken in order to correct this unsafe condition.

What Would This Proposed AD Require?

This proposed AD would require you to repetitively inspect the bottom corner of the engine mount bracket for cracks, replace any cracked bracket, return the removed bracket(s) to Pilatus Britten-Norman, and report the return to FAA.

Cost Impact

How Many Airplanes Would This Proposed AD Impact?

We estimate that this proposed AD affects 126 airplanes in the U.S. registry.

What Would Be the Cost Impact of This Proposed AD on Owners/Operators of the Affected Airplanes?

We estimate the following costs to accomplish the proposed inspection for BN-2, BN-2A, and BN-2B, and BN2A MK. III series airplanes:

Labor cost	Parts cost	Total cost per airplane
4 workhours x $60 per hour = $240	$10	$250

We estimate the following costs to accomplish the proposed inspection for BN-2T series airplanes:

Labor cost	Parts cost	Total cost per airplane
8 workhours x $60 per hour = $480	$10	$490

We estimate the following costs to accomplish any necessary replacements for BN-2, BN-2A, BN-2B, and BN-2T series airplanes that would be required based on the results of the proposed inspection. We have no way of determining the number of airplanes that may need such replacement:

Labor cost	Parts cost per bracket	Total cost per bracket per engine
48 workhours x $60 per hour = $2,880 per engine (2 engines per airplane)	$1,295 (2 brackets per engine)	$2,880 + $1,295 = $4,175

We estimate the following costs to accomplish any necessary replacements for BN2A MK. III series airplanes that would be required based on the results of the proposed inspection. We have no way of determining the number of airplanes that may need such replacement:

Labor cost	Parts cost per bracket	Total cost per bracket per engine
48 workhours x $60 per hour = $2,880 per engine (2 engines per airplane)	$714	$2,880 + $714 = $3.594

What Would Be the Compliance Time of This Proposed AD?

The compliance time of this proposed AD is “within the next 500 hours time-in-service (TIS) or within the next 24 calendar months after the effective date of this AD, whichever occurs first.”

Why Is the Compliance Time of This Proposed AD Presented in Both Hours TIS and Calendar Time?

We have established the compliance time of this proposed AD in both hours TIS and calendar time. The unsafe condition is dependent upon repetitive airplane operation. However, the recommended maintenance program specifies other actions in this area at intervals not to exceed 2 years. Therefore, the compliance time will ensure that high-time airplanes are inspected within a certain amount of hours TIS and the lower time airplanes would be inspected at the next maintenance event in the affected area. We have determined that this compliance time:

—Will ensure that the unsafe condition is addressed in a timely manner on all affected airplanes; and

—Will not inadvertently ground any of the affected airplanes.

Regulatory Impact

Would This Proposed AD Impact Various Entities?

The regulations proposed herein would 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. Therefore, it is determined that this proposed rule would not have federalism implications under Executive Order 13132.

Would This Proposed AD Involve a Significant Rule or Regulatory Action?

For the reasons discussed above, I certify that this proposed 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) if promulgated, 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 draft regulatory evaluation prepared for this action has been placed 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
• Safety

The Proposed Amendment

Accordingly, under the authority delegated to me by the Administrator, the Federal Aviation Administration proposes to amend 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 U.S.C. 106(g), 40113, 44701.

§ 39.13

[Amended]

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

Pilatus Britten-Norman Limited: Docket No. 2002-CE-21-AD.

(a) What airplanes are affected by this AD? This AD affects the following airplane models, all serial numbers, that are certificated in any category:

Models

BN-2, BN-2A, BN-2A-2, BN-2A-3, BN-2A-6, BN-2A-8, BN-2A-9, BN-2A-20, BN-2A-21, BN-2A-26, BN-2A-27, BN-2B-20, BN-2B-21, BN-2B-26, BN-2B-27, BN-2T, BN-2T-4R, BN2A MK. III, BN2A MK. III-2, BN2A MK. III-3

(b) Who must comply with this AD? Anyone who wishes to operate any of the airplanes identified in paragraph (a) of this AD must comply with this AD.

(c) What problem does this AD address? The actions specified by this AD are intended to detect and correct cracks in the engine mount bracket. Such a condition could cause the engine mount assembly to fail, which could result in the engine separating from the airplane and lead to loss of control of the airplane.

(d) What actions must I accomplish to address this problem? To address this problem, you must accomplish the following:

Actions	Compliance	Procedures
(1) Inspect the bottom corner of the engine mounting bracket between the attachment flange and the main part of the bracket for cracks (i) If cracks are found during any inspection, replace the bracket with a new bracket and continue with the repetitive inspection requirements of this AD (ii) If no cracks are found during any inspection, continue with the repetitive inspection requirements of this AD	Initially insect within the next 500 hours time-in-service (TIS) or within the next 24 calendar months after the effective date of this AD, whichever occurs first, and repetitively inspect thereafter at intervals not-to-exceed 500 hours TIS or 1,000 landings, whichever occurs first. Replace cracked bracket prior to further flight after the inspection in which the crack is found	In accordance with Pilatus Britten Norman Service Bulletin SB 275, Issue 1, dated November 30, 2001.
(2) Send the removed brackets to the Engineering and Design Authority, B-N Group Ltd. and report the return to FAA. The Office Management and Budget (OMB) approved the information collection requirements contained in this regulation under the provisions of the Paperwork Reduction Act of 1980 (44 U.S.C. the 3501 et seq.) and assigned OMB Control Number 2120-0056	Within 10 days after removing the bracket or within 10 days after the effective date of this AD, whichever occurs later	Send the removed brackets to B-N Group Limited, Bembridge, Isle of Wight, United Kingdom PO35 5PR, and report the return to Doug Rudolph, FAA, at the address in paragraph (f) of this AD.

(e) Can I comply with this AD in any other way? You may use an alternative method of compliance or adjust the compliance time if:

(1) Your alternative method of compliance provides an equivalent level of safety; and

(2) The Standards Office Manager, Small Airplane Directorate, approves your alternative. Submit your request through an FAA Principal Maintenance Inspector, who may add comments and then send it to the Standards Office Manager.

Note 1:

This AD applies to each airplane identified in paragraph (a) of this AD, 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 you have not eliminated the unsafe condition, specific actions you propose to address it.

(f) Where can I get information about any already-approved alternative methods of compliance? Contact Doug Rudolph, Aerospace Engineer, FAA, Small Airplane Directorate, 901 Locust, Room 301, Kansas City, Missouri 64106; telephone: [phone]; facsimile: [phone].

(g) What if I need to fly the airplane to another location to comply with this AD? The FAA can issue a special flight permit under sections 21.197 and 21.199 of the Federal Aviation Regulations (14 CFR 21.197 and 21.199) to operate your airplane to a location where you can accomplish the requirements of this AD.

(h) How do I get copies of the documents referenced in this AD? You may get copies of the documents referenced in this AD from B-N Group Limited, Bembridge, Isle of Wight, United Kingdom PO35 5PR; telephone: [phone]; facsimile: [phone]. You may view these documents at FAA, Central Region, Office of the Regional Counsel, 901 Locust, Room 506, Kansas City, Missouri 64106.

Note 2:

The subject of this AD is addressed in the United Kingdom CAA AD Number 005-11-2001, not dated.

Issued in Kansas City, Missouri, on August 14, 2002.

Michael Gallagher,

Manager, Small Airplane Directorate, Aircraft Certification Service.