The Department of Defense is conducting more GPS interference tests in the western United States through October. AOPA reports that will cause GPS navigation to be unreliable at times near the test centers. The areas affected center on the Bonneville (BVL) Vortac in Utah, Truth or Consequences (TCS) Vortac in New Mexico, and Sierra Vista Municipal Airport in Arizona. Smaller scale tests will also be conducted near Patuxent River Naval Air Station in Maryland. In the west, the area of unreliability can start within 160 nm of the test center at 4,000 feet agl and expand with altitude to a radius of 400 nm at 40,000 feet msl. AOPA is also asking for pilot reports on GPS reception problems.
"These 'denial-of-service' tests are fairly common," said AOPA Director of Advanced Technology Randy Kenagy. "The government is preparing to transition to a satellite-based navigation system. It has to be tested for both accidental and deliberate interference. And with approval imminent to use GPS-based technology in lieu of VOR, the federal government needs to understand the increased impact of these tests on our operations. That's why we've established an e-mail address to solicit members' help."
The FAA publishes outages as GPS notams. Pilots should be sure to ask a preflight briefer about any outages along their route of flight if they're planning to use GPS navigation. GPS notams are included in a standard DUATS briefing.
AOPA provides an advance schedule of GPS tests, listing dates, times, and areas affected. However, the military can cancel or add additional tests. Pilots are reminded to obtain a briefing, including a request for GPS notams, immediately prior to flight.
AOPA would also appreciate pilot reports of problems with GPS reception in the vicinity of these tests. E-mail the report to email@example.com, and include whether you received a GPS notam.