Date: 201307
Local time of day: 0601-1200
Location: ZZZ.Airport, US
Flight conditions: IMC
Weather elements / visibility: Rain
Light: Daylight
Aircraft: Cheetah; Tiger; Traveler AA5 Series
Operator: Personal
Operating under: Part 91
Flight plan: IFR
Mission: Personal
Flight phase: Cruise
Airspace: Class E ZZZ
ATC / advisory: Center ZZZ
Aircraft component: Flight Dynamics
Component problem: Failed
Reporter organization: Personal
Reporter function: Single Pilot
Reporter qualification: Flight Crew Instrument; Flight Crew Private
Anomaly: Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Flight Crew
When detected: In-flight
Result: Air Traffic Control Provided Assistance; Flight Crew Requested ATC Assistance / Clarification; General Declared Emergency; General Maintenance Action
Contributing factors: Aircraft
Primary problem: Aircraft

Narrative: I was flying IFR and experienced a total loss of all on-board avionics electrical power while in IMC. The only avionics that remained powered was the Garmin 496 portable GPS that is mounted in the panel (it is battery powered when not powered by the aircraft electrical system). I also had a handheld transceiver which I used to restore radio communications with Approach. I declared an emergency and proceeded to the airport in mixed IMC conditions for a safe landing. The aircraft I was flying uses an 'Avionics Master Switch' to cycle power on/off for all the avionics. I suspected this switch was at fault for the failure; and after the local FBO troubleshot the system; they agreed with that assessment. The switch (which is actually a circuit breaker with a toggle; and not just a 'switch') was replaced; restoring normal operation. The 'switch' used in the panel is a Tyco model W31X2M1G35 Toggle Thermal Circuit Breaker; which upon tripping; cannot be reset by the pilot. So effectively; the breaker is actually a non-replaceable fuse. I do not know if the breaker tripped as a result of a valid electrical anomaly; or whether it just 'failed' to the off position. Additionally; I am unsure of the certification basis of the AA5-B; but the current amendment 14 CFR Part 23 regulations state that (23.1357): '(d) If the ability to reset a circuit breaker or replace a fuse is essential to safety in flight; that circuit breaker or fuse must be so located and identified that it can be readily reset or replaced in flight.' I would contend that the radios; GPS; transponder; etc; failing in IMC conditions constitutes a safety of flight issue; thus the use of this switch does not meet the current Part 23 regulations. The use of an 'Avionics Master Switch' is not depicted in the standard POH; so I can presume that it was added at some point in the past upgrade of the aircrafts instrument panel. Obviously a single-point failure such as this is undesirable; but I believe the use of a non-resetting CB for the purpose of provided non-redundant power to all on-board avionics is not an airworthy configuration (at least for IFR flight). I am unsure as to the exact responsibility/burden on the PIC to determine airworthiness of the aircraft system design and architecture; hence my submission of this ASRS report. I believe that the aircraft is 'airworthy' in terms of the 14 CFR Part 91 requirements for IFR flight; but the installation design/approval of whatever past panel upgrade should not have been approved/installed as it is. If someone were to question whether I had adequately determined the airworthiness of the aircraft; I am uncertain if I could do so other than to provide evidence of a current airworthiness certificate; up-to-date annual inspection; etc. So I believe that the aircraft is airworthy 'on paper'; but from a design architecture and approval viewpoint; I am uncertain if the avionics power system design should have been approved as installed. My situation is unique because I have a much more thorough knowledge of aircraft systems; design; architecture and certification than the average private pilot; so I do not know if that burden of knowledge applies a higher requirement for determining aircraft airworthiness from a PIC responsibility per the 14 CFR part 91 regs. Prior to the in-flight failure; I did not have any reason to suspect that anything may be unairworthy regarding the system design for IFR flight; or else I would not have departed IFR knowing of a potential dangerous failure mode of the aircraft I was flying. My revelation only came after the failure and upon investigation of the design of the system and the overarching design requirements. Going forward; I will be inspecting the aircraft logbooks; records; etc; in hopes to better understand the past avionics work and determine an appropriate fix to reduce the likelihood of future total avionics system failures. I believe the installation of an emergency bus or other alternate power source is the ideal scenario; as this would likely have changed my in-flight emergency to merely an inconvenience and a minor increase in workload as I would have to reset the transponder code; frequencies; etc upon restoration of electrical power to the avionics. I believe that the field approval process for instrument panel/avionics installations is probably not as thorough as the approvals necessary to obtain initial FAA type certification (this is based on my experience in my career in aircraft design & certification). Further; I believe less ambiguity is warranted; as sorting through exactly what constitutes minor/major alterations for in-service changes is confusing; and probably increases the likelihood that an A&P; avionics shop; or other provided of aircraft maintenance services would buy-off marginally airworthy systems under the guise of 'minor' alterations. Or; put another way; it is a lot easier to skirt around the 14 CFR part 23 design requirements in a minor/major/STC alteration manner than it was to originally design and certify the systems of the aircraft.

Callback: Reporter states that the aircraft still possessed basic flight instruments after the switch failure; but navigation and communication would have been impossible without the Garmin 496 and handheld VHF.



Synopsis: Grumman AA5 pilot experienced a total loss of all onboard avionics electrical power while in IMC when avionics master switch failed. A battery powered Garmin 496 and hand held transceiver were used to land safely. Reporter asserts that this switch; a Toggle Thermal Circuit Breaker; which; upon tripping; cannot be reset by the pilot may violate FAR 23.1357 (d).