AD 97-20-04

This amendment adopts a new airworthiness directive (AD) that is applicable to Enstrom Helicopter Corporation (Enstrom) Model F-28A, 280 and certain serial-numbered F-28C and 280C helicopters. This action requires an inspection of the voltage control system and an owner/operator (pilot) cockpit check of the amperage of the electrical system. If certain Prestolite- manufactured components are installed, additional tests and actions are required before further flight and at each pre-flight run-up and annual inspection thereafter. A terminating action is provided by replacing the existing voltage control system with a transistorized system. This amendment is prompted by 14 reports of voltage control system problems, including one incident in which smoke emanated from the radio panel during flight, forcing the pilot to make an emergency landing. The actions specified in this AD are intended to prevent an electrical overload and a failure of the voltage regulator and over-voltage relay, that could result in an inflight fire, and subsequent forced landing of the helicopter.

Final rule; request for comments

97-20-04 ENSTROM HELICOPTER CORPORATION: Amendment 39-10142. Docket No. 96-SW- 31-AD.

Applicability: Model F-28A; 280; F-28C helicopters, with a serial number (S/N) less than S/N 745; and Model 280C helicopters, with a S/N less than S/N 1502, certificated in any category.

NOTE 1: This AD applies to each helicopter 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 helicopters that have been modified, altered, or repaired so that the performance of the requirements of this AD is affected, the owner/operator must use the authority provided in paragraph (e) to request approval from the FAA. This approval may address either no action, if the current configuration eliminates the unsafe condition, or different actions necessary to address the unsafe condition described in this AD. Such a request should include an assessment of the effect of the changed configuration on the unsafe condition addressed by this AD. In no case does the presence of any modification, alteration, or repair remove any helicopter from the applicability of this AD.

Compliance: Required as indicated, unless accomplished previously.

To prevent an electrical overload and a failure of the voltage regulator and over-voltage relay, that could result in an inflight fire, and subsequent forced landing of the helicopter:

(a) Within the next five hours time-in-service (TIS) after the effective date of this AD, determine if a Prestolite-manufactured voltage regulator, part number (P/N) VSF7203, or Prestolite- manufactured over-voltage relay, P/N X16799, P/N X17621, or P/N FOC-4002A, is installed.

(1) If any of these parts are installed, perform the following:

(i) Determine if the alternator output is within the proper output voltage range (14.2 + .2 to -.4 volts). If the alternator output voltage is not within the proper voltage range, adjust or replace the voltage regulator.

(ii) Conduct an operational test of the over-voltage relay, and replace any over-voltage relay that fails the operational test with an airworthy over-voltage relay. Accomplish both the operational test and the over-voltage relay replacement in accordance with paragraph 6.3.3 of Enstrom Helicopter Corporation SDB No. 0086, dated March 31, 1996.

(2) If no over-voltage relay is installed, before further flight, install an airworthy relay, P/N FOC-4002A, in accordance with paragraph 6.3.4. of Enstrom Helicopter Corporation Service Directive Bulletin (SDB) No. 0086, dated March 31, 1996, or complete the terminating action described in paragraph (c).

(b) After compliance with paragraph (a) of this AD, thereafter, before each flight, check the amp meter for readings within the normal operating range while the helicopter engine is operating at 2,200 revolutions-per-minute (RPM). This check may be performed by the owner/operator (pilot)holding at least a private pilot certificate, and must be entered into the aircraft records showing compliance with this paragraph in accordance with sections 43.9 and 91.417(a)(2)(v) of the Federal Aviation Regulations (14 CFR 43.9 and 91.417(a)(2)(v)).

(c) After compliance with paragraph (a) of this AD, thereafter, at each annual inspection or 100 hour time-in-service (TIS) inspection, whichever occurs first, perform the following:

(1) Determine if the alternator output is within the proper output voltage range, and if the alternator output voltage is not within the proper voltage range, adjust or replace the voltage regulator.

(2) Conduct an operational test of the over-voltage relay, and replace any over-voltage relay that fails the operational test with an airworthy over-voltage relay in accordance with paragraph 6.3.3 of Enstrom Helicopter Corporation SDB No. 0086, dated March 31, 1996.

(d) Replacement of the existing voltage control system with a transistorized voltage controller, P/N ECD-069-11, and modifying the wiring in accordance with paragraph 6.4 of Enstrom Helicopter Corporation SDB No. 0086, dated March 31, 1996, is considered a terminating action for the requirements of this AD.

(e) 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, Chicago Aircraft Certification Office, FAA. Operators shall submit their requests through an FAA Principal Maintenance Inspector, who may concur or comment and then send it to the Manager, Chicago Aircraft Certification Office.

NOTE 2: Information concerning the existence of approved alternative methods of compliance with this AD, if any, may be obtained from the Chicago Aircraft Certification Office.

(f) The check, test, and replacement, if necessary, shall be done in accordance with Enstrom Helicopter Corporation Service Directive Bulletin No. 0086, dated March 31, 1996. Thisincorporation 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 Enstrom Helicopter Corporation, Twin County Airport, P.O. Box 490, Menominee, Michigan 49858. Copies may be inspected at the FAA, Office of the Assistant Chief Counsel, 2601 Meacham Blvd., Room 663, Fort Worth, Texas; or at the Office of the Federal Register, 800 North Capitol Street, NW., suite 700, Washington, DC.

(g) This amendment becomes effective on October 7, 1997.

This amendment adopts a new AD that is applicable to Enstrom Model F-28A, 280 and certain serial-numbered Model F-28C and 280C helicopters. This action requires a determination of whether a Prestolite-manufactured voltage regulator, part number (P/N) VSF7203, or a Prestolite-manufactured over-voltage relay, P/N X16799, X17621, or FOC-4002A is installed, and if installed, within 5 hours time-in-service (TIS), an inspection of the alternator output voltage system for proper operation and an operational test of the over-voltage relay; after the initial inspection, before each flight, a pilot check to determine that the amp meter is reading within the normal range while the engine is operating at 2,200 revolutions-per-minute (RPM); and thereafter, at each annual inspection or 100 hour TIS inspection, whichever occurs first, a test to determine if the alternator output voltage is within normal limits and a test of the over-voltage relay. The checks required bythis AD may be performed by the owner/operator holding at least a private pilot certificate, and must be entered into the aircraft records showing compliance with the applicable sections of this AD in accordance with sections 43.9 and 91.417(a)(2)(v) (14 CFR 43.9 and 91.417(a)(2)(v)) of the Federal Aviation Regulations. This amendment is prompted by 14 reports of these helicopters having electrical system problems, including one incident in which smoke came from the radio panel during flight, forcing the pilot to make an emergency landing. An investigation conducted by the rotorcraft manufacturer, with FAA participation, revealed that the Prestolite- manufactured voltage regulator, P/N VSF7203, failed, which resulted in a massive voltage increase. A subsequent failure of the over-voltage protection device resulted in overheating of the system wiring and components. The investigation revealed that at least four of the 14 helicopters did not have over-voltage protection installed. This condition, if not corrected, could result in an electrical overload and a failure of the voltage regulator and over-voltage relay, that could result in an inflight fire, and subsequent forced landing of the helicopter.

The FAA has reviewed and approved the technical contents of Enstrom Helicopter Corporation Service Directive Bulletin No. 0086, dated March 31, 1996, which describes procedures for inspecting the voltage control system, testing the components, and replacing the voltage regulator and over-voltage relay as necessary.

Since an unsafe condition has been identified that is likely to exist or develop on other Enstrom Model F-28A, F-28C, 280 and 280C helicopters of the same type design, this AD is being issued to prevent failure of the voltage regulator and over-voltage relay, resulting in an over-voltage and possible fire. This AD requires, within the next five hours time-in-service (TIS), an inspection to determine if the Prestolite-manufactured voltage regulator, part number (P/N) VSF7203, or Prestolite-manufactured over-voltage relays, P/N X16799, X17621, or FOC-4002A, are installed, and an inspection of the alternator output voltage and an operational test of the over-voltage relay. If any of these components are installed, the AD further requires, before each flight, a pilot check of the amp meter for readings within the normal operating range. Thereafter, at each annual inspection or 100 hour TIS inspection (whichever occurs first), a test is required to determine if the alternator output voltage is within tolerance, and if the alternator output voltage is not within the specified range, an adjustment to the voltage regulator, or replacement of the voltage regulator with an airworthy voltage regulator if the voltage regulator cannot be adjusted within the specified range. An operational test of the over-voltage relay is required to determine if the relay operates at the correct voltage, and replacement of any over-voltage relay that fails the operational test with an airworthy over-voltage relay. Any aircraft found without over-voltage relay protection must have an airworthy over-voltage relay installed. A terminating action is provided for in the AD by modifying the wiring and replacing the existing voltage control system with a transistorized voltage controller, P/N ECD-069-11, with built-in over-voltage protection. The actions are required to be accomplished in accordance with the Compliance section of the service bulletin described previously.

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 should identify 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 No. 96-SW-31-AD." The postcard will be date stamped and returned to the commenter.

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 USC 106(g), 40113, 44701.

39.13 - [Amended]
2. Section 39.13 is amended by adding a new airworthiness directive to read as follows: