Citation Excel (C560XL)
Flight Crew Instrument; Flight Crew Multiengine
Troubleshooting; Workload
Aircraft Equipment Problem Less Severe; Conflict Airborne Conflict; Inflight Event / Encounter Unstabilized Approach; Inflight Event / Encounter Weather / Turbulence
Air Traffic Control Provided Assistance; Flight Crew Executed Go Around / Missed Approach; Flight Crew Took Evasive Action; Flight Crew Requested ATC Assistance / Clarification; Flight Crew Regained Aircraft Control; Flight Crew Overcame Equipment Problem; Flight Crew FLC Overrode Automation
Aircraft
While downwind on approach to XXL; GPS failed and Approach reported that radio was garbled and scratchy; after I called and reported loss of my primary navigational aids. I continued turning my #2 radio then the GPS (Garmin 430) came back on line. As I started the approach needles swayed back and forth then settled down. Glide slope needle centered on glide path and after a few a few seconds needle and aircraft nosed down violently at 3000 fpm. I grabbed the controls and abandoned the approach. Approach asked if I needed assistance. I stated that I had navigational problems but wanted to try again. During 2nd approach I slowed aircraft too early from 170kts as requested; because needles were less erratic; but trailing traffic was closing on me and tower told me to abandon the approach. On 3rd attempt I flew the approach manually and maintained centerline averaging the heading because localizer needle and flight director swayed left and right.
C560XL pilot reported GPS malfunction that caused the aircraft to pitch down violently on the approach.