Interpretation 15

This is in response to a request for interpretation submitted by the Kansas City Air Route Traffic Control Center (ZKC) dated January 23, 2015 concerning the January 8, 2015 change to FAA JO 7110.65, Chapter 4, Section 8, Paragraph 1, Subparagraphs ‘j’ and ‘k’.

1. Why did the language change from GPS UNRELIABLE NOTAMS to GPS TESTING NOTAMS?

2. Why did the language change from “inform pilots that GPS is unreliable” to “inform pilots that GPS may not be available”?

3. During testing, if a pilot indicates that they wish to proceed with a GPS instrument approach, can a controller clear them to do so?

4. Is a pilot report sufficient to indicate that GPS interference is no longer a factor?

5. Shouldn’t the restriction only apply to GPS approaches [sic GPS-dependent]?

1. The titling of GPS Testing NOTAMS was a joint decision between Flight Standards, the Spectrum Engineering and Policy Office, the US NOTAM Office and Air Traffic. The primary reason for removing “unreliable” in favor of “may not be available” was because unreliable was considered confusing and repetitive. The Aeronautical Information Manual (AIM) and Pilot Controller Glossary define unreliable as meaning “may not be available”. Although “GPS Testing” does not appear in the NOTAM, the term is an all-inclusive moniker for any number of events the Department of Defense (DoD) chooses to enhance or interfere with the system.

2. The group, indicated above, determined “may not be available” better described the effect on the system than “unreliable”. The language changed because, during times of GPS testing, the GPS signal is either on or off. If a pilot is receiving a GPS signal during testing times, it is a usable signal for navigation.

3. Yes. If the pilot has determined that he/she is receiving a GPS signal and requests a GPS-dependent RNAV approach, the controller may issue it.

4. Yes, if the question is in reference to second report for a reported anomaly outside of published testing times.

However, if it is during NOTAM’d testing times, then the answer is no. A report of positive GPS reception during testing times is only an indication that at that time that aircraft is receiving a signal and thus is not experiencing interference. As indicated above, the signal is either on or off. Interference could happen at any time during the testing period. Continue to advise aircraft that GPS may not be available and request intentions until advised that the testing organization has terminated its testing or until the testing times have expired.

5. Yes, the restriction only applies to GPS-dependent RNAV approaches.