Flight crew reported a seemingly erroneous GPWS alert while being vectored for an approach into the BUR airport.
Synopsis
Flight crew reported a seemingly erroneous GPWS alert while being vectored for an approach into the BUR airport.
Narrative
As we were descending on the arrival (JANNY5); just before being vectored for the approach (just past WABBIT) we were instructed by SoCal approach TRACON to descend and maintain 5000 ft. which we complied to. While passing mountains near the Santa Susana pass; we received a 'terrain; terrain; pull up'; 'landing gear' warning from our GPWS system. Pilot-flying (Capt) then reacted and began climbing; we reached about 5400 ft. until the alert cleared. After which; we reported to ATC that we were responding to a terrain warning which is why we climbed even though not instructed to. We then requested for next instruction which we were given 'descend and maintain 4000 ft.' and intercept BUR ILS 8 localizer to which we complied. Rest of the flight was uneventful. This could have had to do with RA (radio altimeter) equipment malfunction or perhaps 5G interference. We could not ascertain what would cause the alert. We have descended many times to 5000 ft. in this exact sector with no issues but this time; alert came on inexplicably. Unable to come up with suggestion but we did write up the aircraft for maintenance to check the GPWS system.
Second reporter narrative
During the approach into BUR we were level at 5000 ft. and got a GPWS call 'terrain terrain pull up; landing gear.' We were not near terrain and were on a STAR at the published altitude. We notified SoCal approach of what happened and they told us that they recommend we get our equipment checked. Faulty equipment.
Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.