Narrative:

Aircraft unable to maintain assigned altitude of 7000' due to extremely strong downdrafts in moderate turbulence over hilly terrain approaching mountainous terrain. Requested lower altitude, ATC advised they were unable to issue lower altitude. Advised ATC we would have to declare an emergency because we were unable to maintain 7000'. ATC replied 7000' was MEA for that area. Requested and received VFR on top clearance.* ATC said there had been other reports of turbulence below 10000' and asked if we wanted to climb. We replied we were unable. Requested about 30 degree right turn to get away from approaching mountainous terrain and downdraft. ATC granted request. ATC then asked if we were still in emergency condition and we advised we were ok and able to maintain 6500'. Frequency change to sba approach and we advised ATC we were again able to climb to 7000'. We were cleared to that altitude and continued on course. *We were vectored on a route east of route we were originally cleared on and it took us closer to mountainous terrain. Received preflight briefing from compuserve (EMI) there were 2 PIREPS about turbulence near gvo VOR, so on arrival at airport I called hawthorne FSS and asked for update on turbulence. Briefer's remarks indicated that turbulence wouldn't be a significant factor (see enclosed printout). Flight was planned for roundtrip sna-sbp-sna. Ground time in sbp was 1 hour, so didn't get new briefing for return flight due to smooth flight from sna-sbp (which did not include flying over mountainous terrain). Route clearance received for return leg was east of intended flight planned route and that route flows to sbp.

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Original NASA ASRS Text

Title: SMA ENCOUNTERED DOWNDRAFTS AND WAS UNABLE TO MAINTAIN ASSIGNED ALT.

Narrative: ACFT UNABLE TO MAINTAIN ASSIGNED ALT OF 7000' DUE TO EXTREMELY STRONG DOWNDRAFTS IN MODERATE TURB OVER HILLY TERRAIN APCHING MOUNTAINOUS TERRAIN. REQUESTED LOWER ALT, ATC ADVISED THEY WERE UNABLE TO ISSUE LOWER ALT. ADVISED ATC WE WOULD HAVE TO DECLARE AN EMER BECAUSE WE WERE UNABLE TO MAINTAIN 7000'. ATC REPLIED 7000' WAS MEA FOR THAT AREA. REQUESTED AND RECEIVED VFR ON TOP CLRNC.* ATC SAID THERE HAD BEEN OTHER RPTS OF TURB BELOW 10000' AND ASKED IF WE WANTED TO CLB. WE REPLIED WE WERE UNABLE. REQUESTED ABOUT 30 DEG RIGHT TURN TO GET AWAY FROM APCHING MOUNTAINOUS TERRAIN AND DOWNDRAFT. ATC GRANTED REQUEST. ATC THEN ASKED IF WE WERE STILL IN EMER CONDITION AND WE ADVISED WE WERE OK AND ABLE TO MAINTAIN 6500'. FREQ CHANGE TO SBA APCH AND WE ADVISED ATC WE WERE AGAIN ABLE TO CLB TO 7000'. WE WERE CLRED TO THAT ALT AND CONTINUED ON COURSE. *WE WERE VECTORED ON A ROUTE E OF ROUTE WE WERE ORIGINALLY CLRED ON AND IT TOOK US CLOSER TO MOUNTAINOUS TERRAIN. RECEIVED PREFLT BRIEFING FROM COMPUSERVE (EMI) THERE WERE 2 PIREPS ABOUT TURB NEAR GVO VOR, SO ON ARR AT ARPT I CALLED HAWTHORNE FSS AND ASKED FOR UPDATE ON TURB. BRIEFER'S REMARKS INDICATED THAT TURB WOULDN'T BE A SIGNIFICANT FACTOR (SEE ENCLOSED PRINTOUT). FLT WAS PLANNED FOR ROUNDTRIP SNA-SBP-SNA. GND TIME IN SBP WAS 1 HR, SO DIDN'T GET NEW BRIEFING FOR RETURN FLT DUE TO SMOOTH FLT FROM SNA-SBP (WHICH DID NOT INCLUDE FLYING OVER MOUNTAINOUS TERRAIN). ROUTE CLRNC RECEIVED FOR RETURN LEG WAS E OF INTENDED FLT PLANNED ROUTE AND THAT ROUTE FLOWS TO SBP.

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.