Narrative:

We experienced an unusual and potentially hazardous avionics failure in our challenger 300. The incident involved a complete loss of tuning capability for communication and navigation radios including the transponder codes accompanied by a failure of the copilot's mfd. All attempts at radio tuning failed and the avionics began changing frequencys and transponder codes without pilot inputs. The events developed as follows: during cruise flight; we noticed fluctuations in the navigation display on the copilot's mfd. This involved rapid flickering of the course line display. Within 1 min; the same thing began to occur on the pilot's mfd. We received a frequency change and I noted that I was not able to input the new frequency either through the FMS or mfd radio tuning functions. All frequency displays except for HF turned amber (including transponder code display). Within 60 seconds of the amber display indications; the frequencys and transponder code began changing without pilot input. We attempted to use the reversionary tuning feature by independently selecting FMS or mfd only tuning. This had no effect. We selected the communication #1 121.5 option on the reversionary panel. This feature worked as advertised and allowed us to regain communications on 121.5 only. Approximately 10-15 mins into the event; the copilot's mfd failed completely with a blank screen. We were not able to display electronic approach charts. Given the conditions; we elected not to make further attempts at changing switch position on the reversionary panel -- we did not attempt to display charts on the pilot's mfd and I don't know if this would have worked. Over the next 30 mins we were asked repeatedly by ATC to either maintain our assigned transponder code or squawk 7600. We were not able to do either because the transponder code along with communication and navigation frequencys continued to change without pilot inputs. After selecting the transponder to standby and then back on; it seemed to hold 7600 for several mins at a time. We were able to confirm with ATC that the transponder codes were in fact changing so the problem wasn't just limited to a display issue. We landed with 121.5 on communication #1 as our only means of communication. The mdc recorded a total of 9 events associated with various types of avionics and stall protection failures during the event. All were recorded within a few mins of each other. We took photographs of the mdc entries and sent them to maintenance for recording. After a power-down and re-start; all avionics returned to normal functioning. The FMS remained functional for navigation with GPS capability only. RNAV was lost due to lack of VOR tuning capability. The ILS approach for the landing airport had been selected in the FMS prior to the failure. Despite the loss of manual tuning capability; the navigation-to-navigation xfer did occur when intercepting the ILS.

Related reports:

Google
 

Original NASA ASRS Text

Title: A CL30 FLT CREW EXPERIENCED FAILURE OF ALL NAV AND COM TUNING CAPABILITY; AS WELL AS LOSS OF FO'S MFD. THEY WERE ABLE TO COMMUNICATE ON GUARD USING THE REVERSION FEATURE.

Narrative: WE EXPERIENCED AN UNUSUAL AND POTENTIALLY HAZARDOUS AVIONICS FAILURE IN OUR CHALLENGER 300. THE INCIDENT INVOLVED A COMPLETE LOSS OF TUNING CAPABILITY FOR COM AND NAV RADIOS INCLUDING THE XPONDER CODES ACCOMPANIED BY A FAILURE OF THE COPLT'S MFD. ALL ATTEMPTS AT RADIO TUNING FAILED AND THE AVIONICS BEGAN CHANGING FREQS AND XPONDER CODES WITHOUT PLT INPUTS. THE EVENTS DEVELOPED AS FOLLOWS: DURING CRUISE FLT; WE NOTICED FLUCTUATIONS IN THE NAV DISPLAY ON THE COPLT'S MFD. THIS INVOLVED RAPID FLICKERING OF THE COURSE LINE DISPLAY. WITHIN 1 MIN; THE SAME THING BEGAN TO OCCUR ON THE PLT'S MFD. WE RECEIVED A FREQ CHANGE AND I NOTED THAT I WAS NOT ABLE TO INPUT THE NEW FREQ EITHER THROUGH THE FMS OR MFD RADIO TUNING FUNCTIONS. ALL FREQ DISPLAYS EXCEPT FOR HF TURNED AMBER (INCLUDING XPONDER CODE DISPLAY). WITHIN 60 SECONDS OF THE AMBER DISPLAY INDICATIONS; THE FREQS AND XPONDER CODE BEGAN CHANGING WITHOUT PLT INPUT. WE ATTEMPTED TO USE THE REVERSIONARY TUNING FEATURE BY INDEPENDENTLY SELECTING FMS OR MFD ONLY TUNING. THIS HAD NO EFFECT. WE SELECTED THE COM #1 121.5 OPTION ON THE REVERSIONARY PANEL. THIS FEATURE WORKED AS ADVERTISED AND ALLOWED US TO REGAIN COMS ON 121.5 ONLY. APPROX 10-15 MINS INTO THE EVENT; THE COPLT'S MFD FAILED COMPLETELY WITH A BLANK SCREEN. WE WERE NOT ABLE TO DISPLAY ELECTRONIC APCH CHARTS. GIVEN THE CONDITIONS; WE ELECTED NOT TO MAKE FURTHER ATTEMPTS AT CHANGING SWITCH POS ON THE REVERSIONARY PANEL -- WE DID NOT ATTEMPT TO DISPLAY CHARTS ON THE PLT'S MFD AND I DON'T KNOW IF THIS WOULD HAVE WORKED. OVER THE NEXT 30 MINS WE WERE ASKED REPEATEDLY BY ATC TO EITHER MAINTAIN OUR ASSIGNED XPONDER CODE OR SQUAWK 7600. WE WERE NOT ABLE TO DO EITHER BECAUSE THE XPONDER CODE ALONG WITH COM AND NAV FREQS CONTINUED TO CHANGE WITHOUT PLT INPUTS. AFTER SELECTING THE XPONDER TO STANDBY AND THEN BACK ON; IT SEEMED TO HOLD 7600 FOR SEVERAL MINS AT A TIME. WE WERE ABLE TO CONFIRM WITH ATC THAT THE XPONDER CODES WERE IN FACT CHANGING SO THE PROB WASN'T JUST LIMITED TO A DISPLAY ISSUE. WE LANDED WITH 121.5 ON COM #1 AS OUR ONLY MEANS OF COM. THE MDC RECORDED A TOTAL OF 9 EVENTS ASSOCIATED WITH VARIOUS TYPES OF AVIONICS AND STALL PROTECTION FAILURES DURING THE EVENT. ALL WERE RECORDED WITHIN A FEW MINS OF EACH OTHER. WE TOOK PHOTOGRAPHS OF THE MDC ENTRIES AND SENT THEM TO MAINT FOR RECORDING. AFTER A PWR-DOWN AND RE-START; ALL AVIONICS RETURNED TO NORMAL FUNCTIONING. THE FMS REMAINED FUNCTIONAL FOR NAV WITH GPS CAPABILITY ONLY. RNAV WAS LOST DUE TO LACK OF VOR TUNING CAPABILITY. THE ILS APCH FOR THE LNDG ARPT HAD BEEN SELECTED IN THE FMS PRIOR TO THE FAILURE. DESPITE THE LOSS OF MANUAL TUNING CAPABILITY; THE NAV-TO-NAV XFER DID OCCUR WHEN INTERCEPTING THE ILS.

Data retrieved from NASA's ASRS site as of May 2009 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.