Narrative:

During the day at brown field, I did some practice autorotations on taxiway 'D.' I had to share with an astra helicopter, and heard all of his xmissions to the tower. However, later on that afternoon, I had to share with 2 military helicopters. I never heard any of the xmissions to the tower from them. I returned to the ramp and waited for departure. As I sat on the ramp, I observed an INS helicopter go through its routine before patrol, and again I heard no radio communication to the tower. At approximately XA45 hours I started my aircraft turned on avionics, did my checks and called the tower. I received no response. All throughout my warmup checks, I heard no radio chatter. Again I called the tower with no response. I spooled up to takeoff power and lifted to a hover. I made a 90 degree right turn to look down the taxiway for traffic. I noticed no traffic and no lights in the control tower. I reported I was departing from the taxiway, and got no response. I departed to the west and as I was ready to turn northbound, I observed a set of aircraft lights above and to my right. As I could see there was separation I continued my turn. Shortly after I completed my turn, the tower called me to say that a coast guard aircraft had just departed. I asked if the tower had heard any of my xmissions, and he responded that he heard something, but it was garbled. I continued my flight through lindbergh's airspace and up the coast, with no radio problems. I don't understand how we could not have been heard, and not heard any xmissions, unless tower was on military frequency and not heard us. Callback conversation with reporter revealed the following information: reporter states there were no problems found with his radios. He has no idea why he was not heard. There has been no follow up of any kind.

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Original NASA ASRS Text

Title: HELI PLT HAVING COM DIFFICULTY DEPARTS WITHOUT CLRNC.

Narrative: DURING THE DAY AT BROWN FIELD, I DID SOME PRACTICE AUTOROTATIONS ON TXWY 'D.' I HAD TO SHARE WITH AN ASTRA HELI, AND HEARD ALL OF HIS XMISSIONS TO THE TWR. HOWEVER, LATER ON THAT AFTERNOON, I HAD TO SHARE WITH 2 MIL HELIS. I NEVER HEARD ANY OF THE XMISSIONS TO THE TWR FROM THEM. I RETURNED TO THE RAMP AND WAITED FOR DEP. AS I SAT ON THE RAMP, I OBSERVED AN INS HELI GO THROUGH ITS ROUTINE BEFORE PATROL, AND AGAIN I HEARD NO RADIO COM TO THE TWR. AT APPROX XA45 HRS I STARTED MY ACFT TURNED ON AVIONICS, DID MY CHKS AND CALLED THE TWR. I RECEIVED NO RESPONSE. ALL THROUGHOUT MY WARMUP CHKS, I HEARD NO RADIO CHATTER. AGAIN I CALLED THE TWR WITH NO RESPONSE. I SPOOLED UP TO TKOF PWR AND LIFTED TO A HOVER. I MADE A 90 DEG R TURN TO LOOK DOWN THE TXWY FOR TFC. I NOTICED NO TFC AND NO LIGHTS IN THE CTL TWR. I RPTED I WAS DEPARTING FROM THE TXWY, AND GOT NO RESPONSE. I DEPARTED TO THE WEST AND AS I WAS READY TO TURN NBOUND, I OBSERVED A SET OF ACFT LIGHTS ABOVE AND TO MY R. AS I COULD SEE THERE WAS SEPARATION I CONTINUED MY TURN. SHORTLY AFTER I COMPLETED MY TURN, THE TWR CALLED ME TO SAY THAT A COAST GUARD ACFT HAD JUST DEPARTED. I ASKED IF THE TWR HAD HEARD ANY OF MY XMISSIONS, AND HE RESPONDED THAT HE HEARD SOMETHING, BUT IT WAS GARBLED. I CONTINUED MY FLT THROUGH LINDBERGH'S AIRSPACE AND UP THE COAST, WITH NO RADIO PROBS. I DON'T UNDERSTAND HOW WE COULD NOT HAVE BEEN HEARD, AND NOT HEARD ANY XMISSIONS, UNLESS TWR WAS ON MIL FREQ AND NOT HEARD US. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR STATES THERE WERE NO PROBS FOUND WITH HIS RADIOS. HE HAS NO IDEA WHY HE WAS NOT HEARD. THERE HAS BEEN NO FOLLOW UP OF ANY KIND.

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