SAIB NE-20-11

FAA Aviation Safety

SPECIAL AIRWORTHINESS

INFORMATION BULLETIN SUBJ: 568F Propeller Blades – Inspection Under the Compression Wrap SAIB: NE-20-11 Date: April 30, 2020 This is information only. Recommendations aren’t mandatory.

Introduction

This Special Airworthiness Information Bulletin (SAIB) alerts owners, operators and maintenance facilities of Hamilton Sundstrand Corporation (Hamilton Sundstrand) 568F-1, 568F-5, 568F-7, and 568F-11 model propellers that certain maintenance facilities may be misinterpreting the instructions in the Hamilton Sundstrand Component Maintenance Manual (CMM) 61-13-12, including revisions issued through Action Items, such that they are not removing and replacing the propeller blade’s compression wrap at each Major Inspection of a blade.

At this time, the implications of this oversight are still being evaluated and it has not been determined whether the airworthiness concern reaches the level where it is considered an unsafe condition that would warrant airworthiness directive (AD) action under Title 14 of the Code of Federal Regulations (14 CFR) part 39 for mandatory corrective action.

Background

The FAA was notified that a few maintenance facilities were performing a Major Propeller Inspection, as required by the Airworthiness Limitations section, but did not interpret that the CMM requires the compression wrap to be removed from the blade at each of its Major Inspections. These maintenance facilities performed the tasks in the CHECK/General section of the CMM, but failed to remove the compression wrap and inspect the blade tulip section, which is required during the Major Inspection of a blade regardless if the compression wrap exhibited no evidence of surface visual damage. To clarify, the Major Propeller Inspection includes the tasks in the CHECK/General section, including the visual and dimensional inspection requirements identified in the Table 503 of the CMM, and then further identifies other additional inspection requirements that, in combination, form the complete Major Propeller Inspection workscope. The specific instructions for this inspection are contained in Repair 4-15 of the CMM.

The FAA believes it is necessary to ensure proper interpretation of the CMM and to reinforce the need to remove the compression wrap during the blade’s Major Inspection. This is based on known instances in which corrosion has been found under the compression wrap even with no visible evidence of damage to the compression wrap. The FAA, therefore, is reminding maintenance facilities that the CMM requires removal and replacement of the compression wrap when conducting the Major Propeller Inspection, regardless if it exhibited no surface damage. Hamilton Sundstrand is planning to revise CMM 61-13-12 to prevent misinterpretation on the tasks in the CHECK/General and the CHECK/Major Propeller Inspection sections of the CMM.

Recommendations

The FAA recommends that all owners, operators, and maintenance facilities of the affected Hamilton Sundstrand propellers listed in the introduction of this SAIB do the following:

1. Perform all the tasks in the CHECK/Major Propeller Inspection section of Hamilton Sundstrand CMM 61-13-12 when a propeller is in the shop for a major inspection. Specifically, it is required that the compression wrap be removed and replaced (in order to perform the tulip inspection) during the Major Propeller Inspection.

2. Contact the engineer on this SAIB for any known propellers that did not receive the complete Major Inspection.

For Further Information Contact

Michael Schwetz, Aerospace Engineer, 1200 District Avenue, Burlington, MA 01803, United States;

phone: (781) 238-7761; email: michael.schwetz@faa.gov.

(Optional) For Related Service Information Contact

Hamilton Sundstrand, 1 Hamilton Road, Windsor Locks, CT 06096-1010, United States;

phone: (877) 808-7575; email: CRC@collins.com.