The bulletin
Text extracted from the PDF.
FAA Aviation Safety
SPECIAL AIRWORTHINESS
INFORMATION BULLETIN SUBJ: NAVIGATION - Traffic Advisory System - Misleading Intruder Aircraft Vertical Trend SAIB: NE-17-26 Date: September 25, 2017 This is information only. Recommendations aren’t mandatory.
Introduction
This Special Airworthiness Information Bulletin alerts you, owners and operators of aircraft equipped with an Avidyne TAS600A, TAS600, and 9900BX Traffic Advisory System (TAS) of an airworthiness concern regarding the display of intruder aircraft vertical trend indications. At this time, this airworthiness concern is not an unsafe condition that would warrant airworthiness directive (AD) action under Title 14 of the Code of Federal Aviation Regulations (14 CFR) part 39.
Background
Avidyne has identified a defect in TAS units that may prevent the TAS from updating intruder aircraft vertical trend when rapidly changing ownship altitude updates are received. This problem is particularly pronounced when the TAS receives ownship altitude updates from an ARINC-429 altitude source providing 1 ft. resolution. However, there is the potential that the problem may be observed regardless of the source of ownship altitude updates. This issue does not affect traffic alerting because aircraft vertical trend is not used in the alerting algorithm. This issue also does not affect intruder range, altitude, and bearing indications.
Avidyne has released Service Information Letter 606-00161-005, regarding this issue. Avidyne has also released Service Bulletin (SB) 601-00185-009, which updates the software in the TAS600A processor to provide a solution to this behavior. Avidyne does not plan to release a software update to address this issue in TAS600 or 9900BX TAS series systems.
Recommendations
• The FAA recommends that owners and operators of TAS600 or 9900BX series TASs remain aware that those TASs have a defect and that they cannot rely on the display of intruder aircraft vertical trend indications.
• The FAA recommends that owners and operators of TAS600A series TASs remain aware that those TASs have a defect and that they cannot rely on the intruder display of vertical trend indications until the TAS600A series TAS has complied with Avidyne SB 601-00185-009.
For Further Information Contact
Nick Rediess, Aerospace Engineer, FAA, Boston ACO Branch, 1200 District Avenue, Burlington, MA 01803; phone: 781-238-7159; email: nicholas.rediess@faa.gov.
For Related Service Information Contact
Avidyne Corporation, 710 North Drive, Melbourne, FL 32934; phone: 888-723-7592, (Toll Free US) or, 781-402-7592 (International Direct Dial); fax: 781-402-7599; Internet:
http://www.avidyne.com/support/index.asp.