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An emb-500 flight crew reported their crew alerting system (cas) alerted GPS outage at which time the autopilot reverted to pitch and roll. The crew misunderstood ATC and mistakenly began a descent to FL350 while dealing with the autopilot but TCAS alerted RA at which point they returned to FL350. Shortly thereafter; GPS returned to normal.
| Attributes | |
| ACN | 1444830 |
| Time | |
| Date | 201704 |
| Local Time Of Day | 1201-1800 |
| Place | |
| Locale Reference | ZZZ.ARTCC |
| State Reference | US |
| Environment | |
| Flight Conditions | VMC |
| Light | Daylight |
| Aircraft 1 | |
| Make Model Name | Embraer Phenom 100 |
| Flight Phase | Descent |
| Flight Plan | IFR |
| Component | |
| Aircraft Component | GPS & Other Satellite Navigation |
| Person 1 | |
| Function | Captain Pilot Flying |
| Qualification | Flight Crew Air Transport Pilot (ATP) Flight Crew Instrument Flight Crew Multiengine |
| Person 2 | |
| Function | First Officer Pilot Not Flying |
| Qualification | Flight Crew Multiengine Flight Crew Instrument Flight Crew Flight Instructor Flight Crew Air Transport Pilot (ATP) |
| Experience | Flight Crew Last 90 Days 40 Flight Crew Total 1800 Flight Crew Type 150 |
| Events | |
| Anomaly | Aircraft Equipment Problem Less Severe Conflict Airborne Conflict Deviation - Altitude Excursion From Assigned Altitude Deviation - Procedural Clearance Inflight Event / Encounter Other / Unknown |
| Miss Distance | Horizontal 5000 Vertical 600 |
Narrative:
On a flight to ZZZ we had been cleared to descend from FL380 to FL360. As soon as we leveled at FL360 we began to have GPS issues. The cas message displayed 'both on GPS 1'. Shortly thereafter we completely lost GPS signal. The autopilot reverted to pitch and roll mode. As the pilot flying (PF) was resetting the autopilot to altitude hold and heading mode ATC gave us a traffic call. The call was; 'traffic at 12 o'clock at FL370 and FL350'. The PF (busy resetting the autopilot) did not hear the full radio call; only the altitudes. The pilot monitoring (pm) thought he heard; 'traffic at 12 o'clock at FL370; descend to FL350'. The pm told the PF to start the descent to FL350. A descent was initiated and almost immediately the PF spotted the traffic at FL350. The PF immediately commanded the autopilot to climb back to FL360. As we leveled at FL360 the B737 at FL350 reported that they received a TCAS RA; and reported that they showed that we were 400' low. ATC asked us to verify our altitude. We told them that we were level at FL360; but that we were having some GPS/autopilot issues we were working on. Controller advised us that they never saw us leave FL360. Several minutes later GPS signal was restored; and the rest of the flight was completed without incident.moving forward; more attention will be given to verifying clearances during high workload times. Additionally; any time both crew members do not hear the full clearance; we will ask ATC for clarification.
Original NASA ASRS Text
Title: An EMB-500 flight crew reported their Crew Alerting System (CAS) alerted GPS OUTAGE at which time the autopilot reverted to PITCH and ROLL. The crew misunderstood ATC and mistakenly began a descent to FL350 while dealing with the autopilot but TCAS alerted RA at which point they returned to FL350. Shortly thereafter; GPS returned to normal.
Narrative: On a flight to ZZZ we had been cleared to descend from FL380 to FL360. As soon as we leveled at FL360 we began to have GPS issues. The CAS message displayed 'both on GPS 1'. Shortly thereafter we completely lost GPS signal. The autopilot reverted to pitch and roll mode. As the Pilot Flying (PF) was resetting the autopilot to altitude hold and heading mode ATC gave us a traffic call. The call was; 'Traffic at 12 o'clock at FL370 and FL350'. The PF (busy resetting the autopilot) did not hear the full radio call; only the altitudes. The Pilot monitoring (PM) thought he heard; 'Traffic at 12 o'clock at FL370; descend to FL350'. The PM told the PF to start the descent to FL350. A descent was initiated and almost immediately the PF spotted the traffic at FL350. The PF immediately commanded the autopilot to climb back to FL360. As we leveled at FL360 the B737 at FL350 reported that they received a TCAS RA; and reported that they showed that we were 400' low. ATC asked us to verify our altitude. We told them that we were level at FL360; but that we were having some GPS/autopilot issues we were working on. Controller advised us that they never saw us leave FL360. Several minutes later GPS signal was restored; and the rest of the flight was completed without incident.Moving forward; more attention will be given to verifying clearances during high workload times. Additionally; any time both crew members do not hear the full clearance; we will ask ATC for clarification.
Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.