Narrative:

On my airplane the avionics master switch is adjacent to the fuel boost pump switch. Both are located to the left of the yoke. Though it was VMC and I was not on a flight plan; I was using the ILS for reference as I approached rdu. The ILS indicator was driven by a garmin GNS480. As I flew down the final; I reached to turn on the boost pump and accidentally turned off the avionics master. Since I usually fly with my left hand on the yoke; I reached across with my right hand for the boost pump switch. I may have hit a little turbulence; or may just have been inattentive; I'm not sure which. Of course; when the GNS480 loses power; it takes at least several seconds before it is operational again; and there is no navigation guidance in the meantime. When it does re-initialize; it is no longer programmed to track the ILS. Fortunately; 1) it was VMC; and 2) the #2 navigation receiver; a king kx-155; was also tuned and idented. The #2 receiver immediately provided navigation guidance as soon as power was restored. Corrective actions: 1) develop the habit of operating the fuel boost pump switch with my left hand; with which I can more accurately locate the switch. 2) be aware that when flying with digital avionics like the GNS480; a momentary loss of power can lead to an extended navigation outage. 3) keep the #2 navigation (the kx-155) tuned and ready. 4) perhaps the tso for digital navigation C129; C145; C146 should specify that when power is restored they should resume operation in the same mode (tuned to ILS; in my case) as when power was lost; or should specify a maximum time to become operational after a power loss.

Related reports:

Google
 

Original NASA ASRS Text

Title: M20 PLT SWITCHES OFF THE AVIONICS MASTER WHEN REACHING FOR THE FUEL BOOST PUMP.

Narrative: ON MY AIRPLANE THE AVIONICS MASTER SWITCH IS ADJACENT TO THE FUEL BOOST PUMP SWITCH. BOTH ARE LOCATED TO THE L OF THE YOKE. THOUGH IT WAS VMC AND I WAS NOT ON A FLT PLAN; I WAS USING THE ILS FOR REF AS I APCHED RDU. THE ILS INDICATOR WAS DRIVEN BY A GARMIN GNS480. AS I FLEW DOWN THE FINAL; I REACHED TO TURN ON THE BOOST PUMP AND ACCIDENTALLY TURNED OFF THE AVIONICS MASTER. SINCE I USUALLY FLY WITH MY L HAND ON THE YOKE; I REACHED ACROSS WITH MY R HAND FOR THE BOOST PUMP SWITCH. I MAY HAVE HIT A LITTLE TURB; OR MAY JUST HAVE BEEN INATTENTIVE; I'M NOT SURE WHICH. OF COURSE; WHEN THE GNS480 LOSES PWR; IT TAKES AT LEAST SEVERAL SECONDS BEFORE IT IS OPERATIONAL AGAIN; AND THERE IS NO NAV GUIDANCE IN THE MEANTIME. WHEN IT DOES RE-INITIALIZE; IT IS NO LONGER PROGRAMMED TO TRACK THE ILS. FORTUNATELY; 1) IT WAS VMC; AND 2) THE #2 NAV RECEIVER; A KING KX-155; WAS ALSO TUNED AND IDENTED. THE #2 RECEIVER IMMEDIATELY PROVIDED NAV GUIDANCE AS SOON AS PWR WAS RESTORED. CORRECTIVE ACTIONS: 1) DEVELOP THE HABIT OF OPERATING THE FUEL BOOST PUMP SWITCH WITH MY L HAND; WITH WHICH I CAN MORE ACCURATELY LOCATE THE SWITCH. 2) BE AWARE THAT WHEN FLYING WITH DIGITAL AVIONICS LIKE THE GNS480; A MOMENTARY LOSS OF PWR CAN LEAD TO AN EXTENDED NAV OUTAGE. 3) KEEP THE #2 NAV (THE KX-155) TUNED AND READY. 4) PERHAPS THE TSO FOR DIGITAL NAV C129; C145; C146 SHOULD SPECIFY THAT WHEN PWR IS RESTORED THEY SHOULD RESUME OP IN THE SAME MODE (TUNED TO ILS; IN MY CASE) AS WHEN PWR WAS LOST; OR SHOULD SPECIFY A MAX TIME TO BECOME OPERATIONAL AFTER A PWR LOSS.

Data retrieved from NASA's ASRS site as of January 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.