Date: 202009
Local time of day: 0601-1200
Location: ZZZ.Airport, US
Weather elements / visibility: VFR on top of cloud deck; 15
Light: Daylight
Aircraft: Medium Large Transport; Low Wing; 2 Turbojet Eng
Operator: Corporate
Operating under: Part 125
Flight plan: IFR
Mission: Training
Flight phase: Final Approach
Airspace: Class C ZZZ
ATC / advisory: Tower ZZZ
Aircraft component: GPS & Other Satellite Navigation
Component problem: Malfunctioning
Reporter organization: Corporate
Reporter function: Check Pilot; Pilot Not Flying
Reporter qualification: Flight Crew Air Transport Pilot (ATP); Flight Crew Flight Engineer; Flight Crew Flight Instructor; Flight Crew Instrument; Flight Crew Multiengine
Human factors: Situational Awareness
Anomaly: Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Published Material / Policy; Inflight Event / Encounter CFTT / CFIT
Detector: Automation Aircraft Terrain Warning; Person Air Traffic Control
When detected: Other On Approach
Result: Flight Crew Executed Go Around / Missed Approach
Contributing factors: Aircraft; Human Factors; ATC Equipment / Nav Facility / Buildings
Primary problem: Aircraft

Narrative: On practice ZZZ LOC XX; approximately 4 miles from the end of the runway; flight in VFR conditions above an undercast we received a low altitude alert from ZZZ Tower. We advised Tower were VFR and leveling at the MDA (900 MSL) and; at the same time; while cross checking our position on the LOC both pilots noted that the GPS had not updated from the Final Approach Fix (ZZZZZ) to the end of the runway. After cross checking position on the EFB display we elected to execute a missed approach at the end of the runway.The reason for this report is both systems and human factors related. Both pilots were concentrating on the descent and level off from FAF altitude to MDA using a 'dive and drive procedure' which is no longer commonly used in heavy jet aircraft. Concentrating on the altitude an equipment error to update the next waypoint automatically was missed and the low altitude alert from Tower compounded the 'startle factor'. The startle factor was amplified by the fact we were VFR above an overcast with no terrain in sight.  Based on training; we executed a missed approach to create time and regain situational awareness; from a personal perspective when an unexpected event occurs; even in seasoned pilots; it takes a few minutes to understand what happened; not second guess yourself and reset situational awareness.As a follow-up to the event; I contacted ZZZ Tower who related that they have issued numerous low altitude alerts on this approach; for aircraft at the correct altitude; usually involving a high descent rate approach to MDA. I reviewed the approach with the PF (Pilot Flying)and confirmed that he had set an excessive rate (1500 feet/min) when our company procedure calls for less than 1;000 feet/min within 1;000 feet of the terrain.A better briefing on use of automation during the crew brief may have mitigated the high descent rate; and as Pilot Not Flying validating the waypoint switch over at FAF should have been accomplished. Although we were given missed approach instructions ahead of time from approach control (practice approach); if we were relying on GPS for the published missed; it would have been difficult to reprogram the GPS (during the missed approach) to fly the published missed approach (our aircraft does not have TACAN (Tactical Air Navigation system) (raw data) capability and in this situation would require GPS to fly the published missed). As a final observation; we did not receive any onboard GPWS (Ground Proximity Warning System) or TAWS (Terrain Avoidance and Warning System) warning with respect to terrain and have asked company maintenance to verify proper operation of both systems.




Synopsis: Corporate flight crew report aircraft navigation equipment anomalies on approach.