Narrative:

11/89 en route from oak to medford on a 135 cargo flight in VFR conditions (sky clear, received traffic advisories from center), received mfr ATIS (sky obscured/RVR fluctuating from 2600 to 6000' RVR, fog and haze). 25 NM from mfr VOR, requested and received an IFR clearance to mfr from ZSE. Was cleared to oed VOR V23 at 10000'. Shortly thereafter was switched to mfr approach. Received clearance from mfr approach to proceed direct mfr VOR, then to samie with an expect further clearance time. Shortly thereafter was switched to mfr tower. Tower asked for position report. Tower asked to confirm level at 10000'. Replied with a confirmation of level flight at 10000' approximately 3 DME from the oed VOR. On tower frequency was listening to communication between mfr tower and a departing flight which had been given instructions to 9500'. Was given instructions to hold southeast of the oed VOR, right turns with an efc time. Entering hold at 10000', was cleared to samie with instructions to report samie inbound. From the oed VOR, began a descent out of 10000' toward samie. Mfr tower completed the approach as published, landed. I was instructed to contact the tower. Contacted the tower via phone and talked to the supervisor. The supervisor stated that since a flight was departing, and mfr was a non radar environment, he had contacted ZSE for confirmation of position of my plane. ZSE's radar readout showed my altitude to be at 6500', thus he was questioning as to whether there was a misunderstanding on my part as to altitude instructions. I stated that I had maintained 10000' until reaching the mfr VOR and began a descent after leaving the VOR for samie. The supervisor stated that sometimes it was possible to get an erroneous readout from a faulty transponder. I stated that I had been listening to communication between the tower and the departing flight which had been instructed to climb to 9500'. (Tops of ground fog was approximately 2500' MSL with clear skies above.) the tower supervisor stated that his paperwork showed that my flight had descended to 6500' and that he was basically confirming that I had not received instructions to descend from 10000' while approaching the mfr VOR. The conversation was then cordially terminated. Prevention/correction: better communication between ATC and flight crew, especially in a non radar environment.

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Original NASA ASRS Text

Title: ATX SMT ALT DEVIATION BEGAN DESCENT WITHOUT CLRNC. SKY WAS CLEAR ABOVE FOG LAYER WITH ANOTHER ACFT IN CLIMB IFR TO ON-TOP.

Narrative: 11/89 ENRTE FROM OAK TO MEDFORD ON A 135 CARGO FLT IN VFR CONDITIONS (SKY CLEAR, RECEIVED TFC ADVISORIES FROM CENTER), RECEIVED MFR ATIS (SKY OBSCURED/RVR FLUCTUATING FROM 2600 TO 6000' RVR, FOG AND HAZE). 25 NM FROM MFR VOR, REQUESTED AND RECEIVED AN IFR CLRNC TO MFR FROM ZSE. WAS CLRED TO OED VOR V23 AT 10000'. SHORTLY THEREAFTER WAS SWITCHED TO MFR APCH. RECEIVED CLRNC FROM MFR APCH TO PROCEED DIRECT MFR VOR, THEN TO SAMIE WITH AN EXPECT FURTHER CLRNC TIME. SHORTLY THEREAFTER WAS SWITCHED TO MFR TWR. TWR ASKED FOR POS RPT. TWR ASKED TO CONFIRM LEVEL AT 10000'. REPLIED WITH A CONFIRMATION OF LEVEL FLT AT 10000' APPROX 3 DME FROM THE OED VOR. ON TWR FREQ WAS LISTENING TO COM BTWN MFR TWR AND A DEPARTING FLT WHICH HAD BEEN GIVEN INSTRUCTIONS TO 9500'. WAS GIVEN INSTRUCTIONS TO HOLD SE OF THE OED VOR, RIGHT TURNS WITH AN EFC TIME. ENTERING HOLD AT 10000', WAS CLRED TO SAMIE WITH INSTRUCTIONS TO RPT SAMIE INBND. FROM THE OED VOR, BEGAN A DSCNT OUT OF 10000' TOWARD SAMIE. MFR TWR COMPLETED THE APCH AS PUBLISHED, LANDED. I WAS INSTRUCTED TO CONTACT THE TWR. CONTACTED THE TWR VIA PHONE AND TALKED TO THE SUPVR. THE SUPVR STATED THAT SINCE A FLT WAS DEPARTING, AND MFR WAS A NON RADAR ENVIRONMENT, HE HAD CONTACTED ZSE FOR CONFIRMATION OF POS OF MY PLANE. ZSE'S RADAR READOUT SHOWED MY ALT TO BE AT 6500', THUS HE WAS QUESTIONING AS TO WHETHER THERE WAS A MISUNDERSTANDING ON MY PART AS TO ALT INSTRUCTIONS. I STATED THAT I HAD MAINTAINED 10000' UNTIL REACHING THE MFR VOR AND BEGAN A DSCNT AFTER LEAVING THE VOR FOR SAMIE. THE SUPVR STATED THAT SOMETIMES IT WAS POSSIBLE TO GET AN ERRONEOUS READOUT FROM A FAULTY XPONDER. I STATED THAT I HAD BEEN LISTENING TO COM BTWN THE TWR AND THE DEPARTING FLT WHICH HAD BEEN INSTRUCTED TO CLB TO 9500'. (TOPS OF GND FOG WAS APPROX 2500' MSL WITH CLEAR SKIES ABOVE.) THE TWR SUPVR STATED THAT HIS PAPERWORK SHOWED THAT MY FLT HAD DSNDED TO 6500' AND THAT HE WAS BASICALLY CONFIRMING THAT I HAD NOT RECEIVED INSTRUCTIONS TO DSND FROM 10000' WHILE APCHING THE MFR VOR. THE CONVERSATION WAS THEN CORDIALLY TERMINATED. PREVENTION/CORRECTION: BETTER COM BTWN ATC AND FLT CREW, ESPECIALLY IN A NON RADAR ENVIRONMENT.

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.