AD 96-13-09

This amendment adopts a new airworthiness directive (AD) that is applicable to all Jetstream Model 4101 airplanes. This action requires a review of maintenance records to determine the time-in-service (TIS) of the bearings in the starter/generators of both engines. This action also establishes a new TIS limit for the bearings, and requires replacement of the starter/generator unit with a serviceable unit, if necessary. This amendment is prompted by reports of controlled in-flight engine shutdowns resulting from failure of the bearings in the starter/generator unit. The actions specified in this AD are intended to prevent such failure of the bearings of the starter/generator, which could cause severe vibrations and resultant in-flight shutdown of one or both engines.

Final rule; request for comments

96-13-09 JETSTREAM AIRCRAFT LIMITED: Amendment 39-9677. Docket 96-NM-129-AD.
Applicability: All Model 4101 airplanes, 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 (c) 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, unless accomplished previously.

To prevent severe vibrationof one or both engines, which could cause in-flight engine shutdown, accomplish the following:

(a) Within 7 days after the effective date of this AD, review the airplane maintenance records to determine the hours time-in-service (TIS) accumulated on the bearings in the starter/generator units of both engines, in accordance with Jetstream Alert Service Bulletin J41-A24-036, dated February 26, 1996.

(1) If the bearings on both of the starter/generator units have accumulated 300 or more hours TIS: Prior to further flight, replace at least one of the starter/generator units with a unit having bearings with less than 300 hours TIS, in accordance with the alert service bulletin.

(2) If the bearings on one or both starter/generator units have bearings with less than 300 hours TIS: Prior to the accumulation of 300 hours TIS on the bearings on both starter/generator units, remove at least one of the units and replace it with a unit having bearings with less than 300 hoursTIS, in accordance with the alert service bulletin.

(b) As a continuing requirement thereafter: Prior to the accumulation of 300 hours TIS on the bearings on both of the starter/generator units on the airplane, remove at least one of the units and replace it with a unit having bearings with less than 300 hours TIS, in accordance with Jetstream Alert Service Bulletin J41-A24-036, dated February 26, 1996.

(c) An alternative method of compliance or adjustment of the compliance time that provides an acceptable level of safety may be used if approved by the Manager, Standardization Branch, ANM-113, FAA, Transport Airplane Directorate. Operators shall submit their requests through an appropriate FAA Principal Maintenance Inspector, who may add comments and then send it to the Manager, Standardization Branch, ANM-113.

NOTE 2: Information concerning the existence of approved alternative methods of compliance with this AD, if any, may be obtained from the Standardization Branch, ANM-113.

(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) The actions shall be done in accordance with Jetstream Alert Service Bulletin J41-A24-036, dated February 26, 1996. 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 Jetstream Aircraft, Inc., P.O. Box 16029, Dulles International Airport, Washington, DC 20041-6029. Copies may be inspected at the FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington; or at the Office of the Federal Register, 800 North Capitol Street, NW., suite 700, Washington, DC.

(f) This amendment becomes effective on July 15, 1996.

The Civil Aviation Authority (CAA), which is the airworthiness authority for the United Kingdom, recently notified the FAA that an unsafe condition may exist on all Jetstream Model 4101 airplanes. The CAA advises that it has received reports of controlled in-flight engine shutdowns. Investigation has revealed that the bearings of the direct current (DC) starter/generator failed, which resulted in severe vibration. The bearing failures that resulted in engine shutdown occurred at 409, 433, and 470 hours time-in-service (TIS). These conditions, if not corrected, could result in an in-flight engine shutdown.

Explanation of Relevant Service Information
Jetstream has issued Alert Service Bulletin J41-A24-036, dated February 26, 1996, which describes procedures for reviewing the airplane maintenance records to determine the number of hours TIS that the bearings of the DC starter/generator have accumulated. The alert service bulletin also describes procedures to remove and replace the starter/generator units with serviceable units when the bearings have reached a certain (reduced) TIS limit. Such replacement of one of the starter/generator units (per airplane) when the bearings have reached a certain reduced TIS limit, reduces the possibility of the bearings failing in both of the starter/generator units on any one airplane during the same flight. The CAA classified this service bulletin as mandatory and issued United Kingdom airworthiness directive 002-02-96, dated March 1, 1996, in order to assure the continued airworthiness of these airplanes in the United Kingdom.

FAA's Conclusions
This airplane model is manufactured in the United Kingdom and is 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 the FAA informed of the situation described above. The FAA has examined the findings of the CAA, reviewed all available information, and determined that AD action is necessary for products of this type design that are certificated for operation in the United States.

Explanation of Requirements of Rule
Since an unsafe condition has been identified that is likely to exist or develop on other airplanes of the same type design registered in the United States, this AD is being issued to prevent in-flight engine shutdown of both engines on the same flight due to failure of the bearings of the starter/generators of the engines and resultant severe vibration. This AD requires a review of maintenance records to determine the TIS of the bearings in the starter/generators of both engines. This action also establishes a new TIS limit for the bearings in one of the two starter/generator units on each airplane, and requires replacement of the unit with a serviceable unit. The actions are required to be accomplished in accordance with the service bulletin described previously.

Differences Between Service Bulletin and AD
Operators should note that the requirements of this AD differ from certain TIS recommendations in the referenced alert service bulletin. Specifically, this AD establishes a new limit of 300 hours TIS for the bearings of one of the starter/generators of each airplane, rather than specifying replacement of the unit when 300 hours "remain" on the unit before scheduled bearing replacement, as indicated in the alert service bulletin. The FAA considers that replacement of a unit with 300 hours "remaining" on the unit could permit a unit to operate significantly longer than 300 hours TIS if the TIS limit for the unit had previously been extended. The FAA finds that specifying a 300-hour TIS limit for the bearings of one of the starter/generator units per airplane will ensure that, at no one time, will an airplane be operating with both starter/generator units having more than 300 hours TIS on the bearings. A review of starter/generator unit failure reports and consideration of probability of failure requirements in the type certification basis for Jetstream Model 4101 airplanes support the establishment of a 300-hour TIS limit for the bearings of one of the starter/generator units on each airplane. This limit will ensure an acceptable level of safety, as related to continued availability of power from both engines on Jetstream Model 4101 airplanes. Additionally, the manufacturer has notified the FAA that the availability of ample parts may be a problem should the AD require both starter/generator units to be replaced if their bearings exceed the TIS limit. The FAA has determined that limiting the bearings to 300 hours TIS on at least one of the starter/generator units on the airplane provides an adequate level of safety; therefore, this AD establishes a 300-hour TIS limit for the bearings of only one of the two starter/generator units of the airplane.Interim Action
This is considered to be interim action. The manufacturer has advised that it currently is developing a modification that will positively address the unsafe condition addressed by this AD. Once the modification is developed, approved, and available, the FAA may consider further rulemaking.

Determination of Rule's Effective Date
Since a situation exists that requires the immediate adoption of this regulation, it is found that notice and opportunity for prior public comment hereon are impracticable, and that good cause exists for making this amendment effective in less than 30 days.

Comments Invited
Although this action is in the form of a final rule that involves requirements affecting flight safety and, thus, was not preceded by notice and an opportunity for public comment, comments are invited on this rule. Interested persons are invited to comment on this rule by submitting such written data, views, or arguments as they may desire. Communications shallidentify the Rules Docket number and be submitted in triplicate to the address specified under the caption "ADDRESSES." All communications received on or before the closing date for comments will be considered, and this rule may be amended in light of the comments received. Factual information that supports the commenter's ideas and suggestions is extremely helpful in evaluating the effectiveness of the AD action and determining whether additional rulemaking action would be needed.

Comments are specifically invited on the overall regulatory, economic, environmental, and energy aspects of the rule that might suggest a need to modify the rule. All comments submitted will be available, both before and after the closing date for comments, in the Rules Docket for examination by interested persons. A report that summarizes each FAA-public contact concerned with the substance of this AD will be filed in the Rules Docket.

Commenters wishing the FAA to acknowledge receipt of their comments submitted in response to this rule must submit a self-addressed, stamped postcard on which the following statement is made: "Comments to Docket Number 96-NM-129-AD." The postcard will be date stamped and returned to the commenter.

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.

The FAA has determined that this regulation is an emergency regulation that must be issued immediately to correct an unsafe condition in aircraft, and that it is not a "significant regulatory action" under Executive Order 12866. It has been determined further that this action involves an emergency regulation under DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979). If it is determined that this emergency regulation otherwise would be significant under DOT Regulatory Policies and Procedures, a final regulatory evaluation will be prepared and placed in the Rules Docket. A copy of it, if filed, may be obtained from 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 U.S.C. 106(g), 40113, 44701.

39.13 - [Amended]
2. Section 39.13 is amended by adding the following new airworthiness directive: