Small aircraft had transmitter failure while on an IFR flight plan in VMC.

Attributes
ACN	86399
Time
Date	198804
Day	Sat
Local Time Of Day	0601 To 1200
Place
Locale Reference	atc facility : sli
State Reference	CA
Altitude	msl bound lower : 1600 msl bound upper : 1600
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : sna
Operator	general aviation : instructional
Make Model Name	Small Aircraft, High Wing, 1 Eng, Fixed Gear
Flight Phase	cruise other descent other
Route In Use	enroute : on vectors
Flight Plan	IFR
Person 1
Affiliation	Other
Function	instruction : instructor
Qualification	pilot : atp pilot : cfi
Experience	flight time last 90 days : 90 flight time total : 3200 flight time type : 1200
ASRS Report	86399
Person 2
Function	controller : approach
Qualification	controller : radar
Events
Anomaly	aircraft equipment problem : less severe non adherence : far
Independent Detector	other flight crewa
Resolutory Action	controller : issued new clearance
Consequence	Other
Supplementary
Primary Problem	Aircraft
Air Traffic Incident	other

Narrative:

While trying to transmit over VHF communication radio to ATC discovered transmitters were not transmitting. Since occurrence was in VMC, I was about to squawk 1200 and proceed to an uncontrolled airport in VMC. As ATC had assigned 1600' MSL and heading 180 degrees, which was taking us beyond power off gliding distance of land (over pacific ocean). Then ATC assigned vector to bring us back toward land so I continued as assigned by ATC. When they discovered that I could not transmit, they told me to respond with identify when xmissions received, which I did. After landing investigation revealed nothing as the radios would then transmit, but I suspect microphone defect possible. Suggest carrying spare microphone/headset for possible supplemental use in these situations.

Original NASA ASRS Text

Title: SMA HAD TRANSMITTER FAILURE WHILE ON AN IFR FLT PLAN IN VMC.

Narrative: WHILE TRYING TO XMIT OVER VHF COM RADIO TO ATC DISCOVERED XMITTERS WERE NOT XMITTING. SINCE OCCURRENCE WAS IN VMC, I WAS ABOUT TO SQUAWK 1200 AND PROCEED TO AN UNCTLED ARPT IN VMC. AS ATC HAD ASSIGNED 1600' MSL AND HDG 180 DEGS, WHICH WAS TAKING US BEYOND PWR OFF GLIDING DISTANCE OF LAND (OVER PACIFIC OCEAN). THEN ATC ASSIGNED VECTOR TO BRING US BACK TOWARD LAND SO I CONTINUED AS ASSIGNED BY ATC. WHEN THEY DISCOVERED THAT I COULD NOT XMIT, THEY TOLD ME TO RESPOND WITH IDENT WHEN XMISSIONS RECEIVED, WHICH I DID. AFTER LNDG INVESTIGATION REVEALED NOTHING AS THE RADIOS WOULD THEN XMIT, BUT I SUSPECT MICROPHONE DEFECT POSSIBLE. SUGGEST CARRYING SPARE MIC/HEADSET FOR POSSIBLE SUPPLEMENTAL USE IN THESE SITUATIONS.

Data retrieved from NASA's ASRS site as of August 2007 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.