SAIB ACE-96-12

SPECIAL

AIRWORTHINESS

INFORMATION

BULLETIN

AIRCRAFT CERTIFICATION SERVICE 800 INDEPENDENCE AVENUE, S.W.

WASHINGTON, DC 20591

U.S. Department of Transportation Federal Aviation Administration

No. ACE-96-12 December 20, 1996

Published by: FAA, AFS-610, P.O. Box 26460, Oklahoma City, OK 73125 This is issued for informational purposes only and any recommendation for corrective action is not mandatory.

INTRODUCTION:

The purpose of this Special Airworthiness Informa tion Bulletin is to advise operators of Cessna Model 401, 401A, 401B, 402, 402A and 402B airplanes that the Federal Aviation Administration is strongly advising accomplishing the provisions of Cessna Service Letter ME72-4.

BACKGROUND:

As part of the Aging Commuter Airplane Program , the Federal Aviation Administration (FAA) has reviewed existing Airworthiness Directives ( ADs) on airplanes commonly used in scheduled service. The purpose of the review was to identify cases where critical repetitive inspections could be eliminated by mandating installation of improve d parts that do not require such inspections.

These “terminating actions” are accomplished by issuance of a superseding AD.

Specifically, an AD superseding AD 70-03-04 Revisi on 1 was contemplated. This would have required the installation of steel turbocharger heat shields in place of the turbocharger insulation blankets originally installed on these airpla nes. Currently, AD 70-03-04 Revision 1 requires repetitive inspections of the existing turbocha rger insulation blankets and acknowledges the installation of the steel turbocharger heat shield as terminating action for the inspection; but does not mandate installation of the steel turbocharger heat shield.

While investigating the feasibility of supersed ing AD 70-03-04 Revision 1 to mandate installation of the steel turbocharger heat shield, Cessna informed the FAA that parts to accomplish the proposed terminating action were not available and that the tooling required to fabricate the parts was no longer in existence. It was not deemed feasible to mandate AD action which would require parts which were not available from the manufactur er. Therefore, it was decided to issue this Special Airworthiness Information Bulletin. Th e FAA notes that compliance with the repetitive inspections mandated by AD 70-03-04 Revision 1 continues to assure safety, but recognizes the improvement in safety provided by the elimination of critical repetitive inspections.

Based on the number of spares sales, it is reasonable to conclude that most of the affected airplanes have already installed the steel turbocharger heat shields, and that there will not be a substantial impact on the fleet.

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RECOMMENDATION:

As soon as practical, for Cessna Model 401, 401A , 401B, 402, 402A and 402B airplanes, comply with the provisions of Cessna Service Letter ME72-4. Complying with this Service Letter is terminating action for AD 70-03-04 Re vision 1. The FAA realizes that parts are not available from the manufacturer and suggests that utilizing serviceable salvage parts is an acceptable alternative to new parts for this application. The FAA strongly recommends that any airplane not incorporating the provisions of Cessna Service Letter ME72-4 be modified as soon as practical.

FOR FURTHER INFORMATION CONTACT:

Paul Pendleton, Aerospace Safety Engineer, Fede ral Aviation Administration, Wichita Aircraft Certification Office, 1801 Airport Road, Room 100, Mid-Continent Airport Wichita, KS 67209,

(316) 946-4143, or Karl Schletzbaum, Aerospace Safe ty Engineer, at the same address, (316) 946-4146.