Goodbye, Mode-C

The Federal Aviation Administration has released details of its plans to mandate Mode-S transponders on all new aircraft certified under Parts 121 or 135, and to phase in the new technology on older aircraft when the Mode-C (or even older Mode-A) transponders on those airplanes wear out.

Mode-S transponders have actually been around since 1975, but only recently has the industry been able to benefit by differences over the more common Mode-C technology. Mode-S -- for "Select Beacon System" -- transponders constantly transmit an aircraft's location (including whether the airplane is on the ground, or in the air) and altitude to ATC, with greater precision (within 25-foot increments with some systems) than Mode-C. This precision is better suited to today's multi-function displays (MFDs) and traffic collision avoidance systems (TCAS).

Mode-S transponders also transmit an aircraft's N-number.

Below is the text of an Aircraft Electronics Association (AEA) Regulatory Update outlining the FAA's plan.

SUBJECT: FAA PROPOSES TO TERMINATE MODE S TRANSPONDER EXEMPTIONS FOR PART 135 OPERATORS

REFERENCE: Federal Register dated October 7, 2005, Page 58967

SUMMARY: The FAA proposes that all FAA authorized exemptions of 14 CFR 121.345(c) and 135.143(c) terminate no later than March 1, 2007. The FAA will not be granting any new exemptions after March 1, 2007.

MAJOR HIGHLIGHTS: The FAA proposes that all existing FAA authorized exemptions of 14 CFR 121.345(c) and 135.143(c) terminate no later than March 1, 2007. The FAA will not be granting any new exemptions after March 1, 2007.

This proposed date would provide affected operators with approximately 18 months to install a Mode S transponder if necessary under Sec. Sec.  121.345(c) and 135.143(c).

Under paragraphs (c) of Sec. Sec.  121.345 and 135.143, after January 1, 1992, only Mode S transponders may be newly installed in U.S. registered civil aircraft. Under these regulations, the term "installation" does not include: (1) Temporary installation of a Mode C transponder or substitute equipment as appropriate, during maintenance of the permanent equipment; (2) reinstallation of equipment after temporary removal for maintenance; or (3) for fleet operations, installation of equipment in a fleet aircraft after removal of the equipment for maintenance from another aircraft in the same operator's fleet.

Consequently, the FAA proposes that effective March 1, 2007, if a transponder needs to be permanently replaced it must be replaced with a Mode S transponder.

The FAA notes that if the operator was issued an exemption before March 1, 2007, allowing them to install a Mode C transponder on their aircraft, they may continue to use that transponder until it no longer can be repaired and must be replaced with a Mode S. Therefore, if they hold an exemption, any Mode A or C transponder that is installed on or before March 1, 2007, may remain in their aircraft and may continue to be repaired after March 1, 2007. When that Mode A or C transponder can no longer be repaired, it must be replaced with a Mode S transponder.

Comments must be filed no later than November 7, 2005.

FMI: www.aea.net, www.faa.gov