IFR Fix: Rude reception

“The missed approach segment is GPS based so I would have been unable to execute the published missed approach,” the pilot noted. “The fact that a failure like this occurred, while hopefully very rare, exposes some potential problems with widely utilized and heavily relied upon GPS navigation for critical phases of flight.”

Once on the ramp, the pilot began checking avionics alerts and found multiple warning messages. Another pilot reported losing GPS while taxiing. “No NOTAM's for GPS outages were in effect at the time,” the Cessna pilot added in a filing with the Aviation Safety Reporting System.

Will such reports remain rare? The Defense Department operates the GPS system, and some GPS outages are planned events associated with security exercises. They are increasing in number and scope, and for several years, AOPA has pressed the FAA to address the potential impact on general aviation and the problem of obscure means of pilot notification.

GPS has become the heart of the NextGen modernization program, engineered into everything from RNAV instrument approaches to Automatic Dependent Surveillance-Broadcast (ADS-B) for traffic separation. With the mandated deadline less than a year hence to equip aircraft with ADS-B Out to operate where a transponder is now required, GPS dependence is growing.

Pilots have documented similar experiences via the Aviation Safety Reporting System. When a Boeing flight crew lost both GPS receivers five minutes after hearing another aircraft report losing guidance, they sought answers in their quick reference handbook but only reached Step 2 before the procedure for transitioning to an alternate navigation source grew unclear.

That did not stop the captain—who surmised that military activity was blocking the GPS reception—from activating the alternate system.

“The crew needs more QRH information regarding this procedure,” the captain told the Aviation Safety Reporting System.

Back to that Cessna. A less-well-known component of the NextGen transformation is the VOR MON, for minimum operational network, composed of “geographically situated VORs in the contiguous United States” needed “to provide coverage at and above 5,000 feet above ground level.”

The MON is designed to get you to an airport within 100 nautical miles to fly an instrument approach “without the necessity of GPS, DME, ADF, or Surveillance,” so keep your legacy instrument flying skills sharp for the day the screens go dark.