An official website of the United States government
Here's how you know
A .mil website belongs to an official U.S. Department of Defense organization in the United States.
A lock (lock ) or https:// means you’ve safely connected to the .mil website. Share sensitive information only on official, secure websites.

Home : Articles
Would you stake your life, right now, on the condition of your equipment?
NEWS | Sept. 1, 2021

HOT ITEM - Rotary-Wing Aircraft: Configure Mode S / ADS-B Out Properly

A Tobyhanna Army Depot electronics mechanic repairs the transponder on an AH-64D Apache Attack Helicopter
Photo by Thomas Robbins


During maintenance on the APX-123/APX-123A Mode 5 transponder, the aircraft-assigned default Mode S can be zeroized or “set to factory default.” Units are subsequently not ensuring that the default Mode S address is reloaded into the APX-123/APX-123A. As a result, the FAA detects an invalid address, which is flagged and reported to the Army as non-compliance. In some instances, the FAA could restrict access to airspace for non-compliant aircraft. Worse still, unless this ongoing problem is corrected, the FAA could cause HQ DA to exact penalties from units that fail to comply with the guidance in this article.

The attached PDF spells out what you need to know. It explains the following:
  • The difference between the aircraft-assigned default Mode S and the factory default.
  • The difference between default Mode S and operational Mode S.
  • The need to reload the aircraft-assigned default Mode S any time the aircraft system processors are replaced or a new aircraft OFP software is loaded.
  • The difference between the Mode S address and the Mode S Flight ID.
  • The fact that the APX-123/APX-123A does not retain the aircraft-assigned and loaded default Mode S address in the transponder; it is retained in the aircraft system processors.
  • Avoiding the use of duplicate Mode S among aircraft.
If you have questions, the POCs are listed at the end of the PDF and can be reached through the Outlook global address list.

To access the PDF, click on the image below:

Mode S / ADS-B Out PDF
Click on image above to view and download PDF
Want to get better search results faster? 
Click the link below to access our "how to" guide
After entering a keyword, you must hit or click the Search bar/box below for the function to work.
Simply hitting Return won't yield results.
Note about links to archive articles

If you come across a link to a pre-2014 PS Magazine issue or article that uses LOGSA in the web address (URL), use this link instead:
For issues/articles from 2014 and after, click on the Archive/Index tab in the top menu of this website.

BE ADVISED: With the migration to Army365, emails in older articles may still reflect an address. To update, change the domain to