Service Bulletins

SB 23-4175, Rev.1, Communications – Audio Storage and Playback Unit (ASPU) Configuration Change

Issued: Original, July 14, 2017
Revision 1, January 17, 2019

Note: This revision replaces the original issue of SB 23-4175 in its entirety and was revised to:

  • Add clarity to the Effectivity section as to which aircraft this kit is compatible with
  • Update the aircraft serial number effectivity for kits 434-3018-0003 and 434-3018-0009

Revision Compliance: NO EFFECT. Airplanes previously modified by this service bulletin are not affected by this revision.

Effectivity: Super King Air Model B300, Serial Numbers FL-954, FL-967 thru FL-1096; Super King Air Model B300C, Serial Numbers FM-58 thru FM-71; Super King Air Model B200GT, Serial Numbers BY-229 thru BY-293; Super King Air Model B200CGT, Serial Number BZ-1; King Air C90CTi, Serial Numbers LJ-2122 thru LJ-2136.

The equivalent of this service document has been incorporated on production airplanes FL-1097 and on, FM-72 and on, BY-294 and on, BZ-2 and on, and LJ-2137 and on.

Note: Do not install the 434-3018-003 kit if any aircraft has a 434-3014, 434-3017 or 434-3019 Fusion Phase 2 Upgrade Kit installed on the aircraft. The Fusion Phase 2 upgrade kit installs the most recent production ASPU software, thus eliminating the need for the 434-3018 ASPU kit.

Note: Textron Aviation-owned or Textron Aviation-authorized Service Centers are the only facilities that can complete this service document.

Reason: The aural warning system may give a false failure call-out during startup.

Description: This service document provides parts and instructions to install Recommended Field Service Kit 434-3018-0001, 434-3018-0003, or 434-3018-0009. This kit should be installed to prevent the aural warning system from annunciating a test failure when a failure does not exist on a Mod 3A ASPU. This kit eliminates the aural warning system test false failure that may occur during startup.

Compliance Recommended: This service document should be accomplished at a scheduled maintenance period or inspection.

A service document published by Textron Aviation may be recorded as completed in an aircraft log only when the following requirements are satisfied:

  1. The mechanic must complete all of the instructions in the service document, including the intent therein.
  2. The mechanic must correctly use and install all applicable parts supplied with the service document kit. Only with written authorization from Textron Aviation can substitute parts or rebuilt parts be used to replace new parts.
  3. The mechanic or airplane owner must use the technical data in the service document only as approved and published.
  4. The mechanic or airplane owner must apply the information in the service document only to aircraft serial numbers identified in the Effectivity section of the document.
  5. The mechanic or airplane owner must use maintenance practices that are identified as acceptable standard practices in the aviation industry and governmental regulations.

No individual or corporate organization other than Textron Aviation is authorized to make or apply any changes to a Textron Aviation-issued service document or flight manual supplement without prior written consent from Textron Aviation.

Textron Aviation is not responsible for the quality of maintenance performed to comply with this document, unless the maintenance is accomplished at a Textron Aviation-owned Service Center.

The above information may be abbreviated for space purposes. For the entire communication, go to

About the Author

Leave a Reply