Date: 202102
Local time of day: 0601-1200
Location: ZZZ.Airport, US
Flight conditions: VMC
Weather elements / visibility: Rain; 5
Light: Daylight
Aircraft: Skyhawk 172/Cutlass 172
Operator: FBO
Operating under: Part 91
Flight plan: IFR
Mission: Training
Flight phase: Initial Approach
Airspace: Class D ZZZ
ATC / advisory: Tower ZZZ
Aircraft component: Communication Systems
Component problem: Failed
Reporter organization: Personal
Reporter function: Instructor; Pilot Flying
Reporter qualification: Flight Crew Commercial; Flight Crew Flight Instructor; Flight Crew Multiengine; Flight Crew Instrument
Human factors: Human-Machine Interface; Troubleshooting
Anomaly: Aircraft Equipment Problem Critical; Inflight Event / Encounter Weather / Turbulence
Detector: Person Flight Crew
When detected: In-flight
Result: Air Traffic Control Provided Assistance; Flight Crew Diverted; Flight Crew Requested ATC Assistance / Clarification; General Maintenance Action
Contributing factors: Aircraft
Primary problem: Aircraft

Narrative: Upon reaching clearance for ILS XX circle Runway XY at ZZZ from Approach; we were switched over to ZZZ Tower frequency. Established on the approach between the IAF and FAF; I keyed the mic to establish contact with Tower inbound. The entire avionics turned off completely; losing intercom; transponder; GPS/Nav/Comm 1; and Nav/Comm 2. ZZZ was currently under IFR due to 2SM visibility; but we were in visual conditions on the approach course. I broke off from the approach and turned to the south; since we were no longer receiving navigational guidance along the approach; and I had no communications to contact Tower or Approach. I knew the weather towards the south was looking clearer so the plan was to continue south towards ZZZ1 or ZZZ2. We troubleshot the avionics; checking circuit breakers and cycling the avionics switch to no avail. No indications of ammeter discharge or low voltage illuminated; and the turn coordinator was still operable as well as engine instruments; so I presumed that the failure was based solely on avionics and not complete electrical failure. We descended lower; maintaining VFR so that we could receive cell signal; and I contacted ZZZ Tower via cellphone; since they gave us instructors their phone number another time when they had an ATC/instructor meeting. I told them we were okay; and had complete avionics failure. I asked for the phone number for ZZZ1 Tower so I could communicate with them if I decided to continue south to ZZZ1. At that time; the visibility and clouds around ZZZ began to clear up and we could start to see towards ZZZ. I asked ZZZ Tower if the field was still IFR; and they replied that it just went VFR. We proceeded inbound toward ZZZ; maintaining VFR; and were able to receive landing and taxi clearances for our aircraft through the cell phone. The aircraft was repaired; with the problem being a short-circuited avionics switch.




Synopsis: C172 flight instructor reported a complete failure of communication and navigation equipment while on an instrument approach and in reduced visibility. The instructor broke off the approach; remaining in visual conditions; and was eventually able to contact ATC on a cell phone and make a successful approach and landing.