Losing Remote Autonomous Integrity Monitoring (RAIM) and thus GPS reliability, particularly in Instrument Meteorological Conditions (IMC) or at night, is a critical flight safety issue that can lead to a loss of situational awareness and terrain collision.
A preliminary NTSB report on a fatal air ambulance crash in New Mexico highlighted the dangers, where the crew repeatedly lost GPS due to military jamming (which was noted in a NOTAM) and subsequently impacted mountainous terrain after attempting a visual approach in dark conditions.
Pilots are advised to check RAIM availability pre-flight, have backup navigation approaches, and if GPS reliability is lost during an approach, the immediate and safest action is to climb to avoid obstacles.
Losing situational awareness on any flight is a bad thing, but it’s particularly bad in IMC.
When you can’t see the horizon because of clouds or darkness, it can become a potentially deadly situation. This is why instrument flight candidates are taught to fly by “partial panel,” which means the instructor “fails” an instrument, often the attitude indicator, by covering it up.
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Meg Godlewski has been an aviation journalist for more than 24 years and a CFI for more than 20 years. If she is not flying or teaching aviation, she is writing about it. Meg is a founding member of the Pilot Proficiency Center at EAA AirVenture and excels at the application of simulation technology to flatten the learning curve. Follow Meg on Twitter @2Lewski.
