Hanscom Field Advisory Commission ~ Transponder Ponderation

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Residents raised several transponder issues during the Citizen Comments period for the October 2019 HFAC meeting:  the potential danger of turning transponders off while flying in busy airspace; absence of transponder signals from aircraft idling on the runway; and the approaching FAA deadline for installation of ADS-B (Automatic Dependent Surveillance-Broadcast) transponders on all aircraft.  Note: ADS-B transponders continuously broadcast an aircraft’s GPS location and identification information to receivers on other aircraft and on the ground.

General Aviation Pilots Can Turn off ADS-B Transponders in the Air, But Should They?

In response to a question about whether or not transponders can be turned off during flight, Commission member and Hanscom Pilots Association representative Thomas Hirsch explained that there are a number of ways for general aviation pilots to temporarily turn off transponders. When asked if that could be unsafe in the busy airspace surrounding Hanscom Field (which averages 10,000-11,000 flight operations/month), Hirsch explained, “It would be unsafe to the extent that if people are using ADS-B and other traffic collision avoidance [equipment], right, you wouldn’t see nearby aircraft. So it’s not in your best interest to turn it off.”

Ayer resident Amy McCoy wondered if turning off aircraft transponders during flights within the 30 nautical mile radius of Logan Airport could be a violation of federal regulation, and Hirsch, Commission Chair Christopher Eliot, and Mark Wimmer, Massport Airport Data Specialist for Hanscom, all agreed pilots should leave transponders on within that airspace.

Local Aircraft Transponders “Squawk” at Take-off, Not Before

Describing the extremely loud noise generated by some jets while still sitting on the runway, Bedford resident Patty Dahlgren lamented, “My ability to associate that sound volume with a given plane doesn’t exist.”  She was referring to the inability of her Airnoise button (a small wifi device that allows one touch filing of air noise reports to Massport) to identify noisy jets idling on the runway before take-off.  Because the button relies upon ID information from the FlightAware flight tracking app, which in turn relies upon aircraft transponder signals, it can’t ID aircraft unless transponders are turned on and transmitting.

Hirsch explained that aircraft transponders in use at Hanscom Field typically don’t begin to broadcast or “squawk” GPS and ID signals until planes reach take-off speed, which varies by aircraft size and type.  He also noted that some busy airports such as Logan prefer that pilots leave transponders on even when aircraft are on the ground to help track runway/taxiway traffic.  He and Amber Goodspeed, Massport Airport Administrative Manager for Hanscom, agreed that such a system is too sophisticated for use at Hanscom Field.

Flight Schools Face Deadline for FAA Mandated Installation of ADS-B Transponders

When the Commission was asked if there is a sense of how many local flight school planes are already equipped with ADS-B transponders, Hirsch said it is doubtful that all local flight school planes will have transponders installed in time to meet the FAA mandated deadline of January 1, 2020.  Goodspeed noted that in the past, the deadline has been pushed back by the FAA to allow aircraft owners additional time for the installations.

Questioned about what would happen to aircraft which don’t meet the FAA deadline, Hirsch explained that owners could be granted an exemption to fly out of the airfield to another location to have an ADS-B transponder installed.  He added that the East Coast Aero Club Flight School does have a maintenance facility which has begun installing transponders.