Narrative:

Departed cma airport. VFR for flight to ccb airport. Contacted pt mugu for VFR flight following. Was then handed off to burbank approach. Crossed the burbank arsa at 5500 ft per VFR arrival chart for upland, ca, cable VFR arrs. It became apparent that an IFR approach to ccb would be necessary due to a fairly solid undercast. Contacted ontario approach and requested radar vectors for the VOR runway 6 at ccb. Was given a vector of 'right heading 180 maintain VFR.' I complied and began a slight climb to 6000 ft to maintain VFR separation from some isolated cumulus below. At this time I noticed an medium large transport climbing through the undercast at our 10 O'clock position, heading approximately 260. At this time I was approximately 5700 ft. I maintained heading for about 15-30 seconds and then determined that wake turbulence would be likely if the medium large transport continued its climb and heading. I then turned left 20-30 degrees and began a descent. Almost simultaneously, ontario approach requested the medium large transport to continue its climb to 6000 ft. (I'm not sure of the altitude.) the medium large transport then appeared to level off and the pilot responded 'negative we have a TCASII alert' or something to that effect. Ontario approach then made a couple of calls to us using just our north number. While we heard them and attempted to assure them that the traffic was no longer a factor, we were either 'stepped on' or had a momentary microphone problem. This momentary loss/miscom contributed to the anxiety of all concerned as I'm sure that the medium large transport never saw us. We were then vectored to 360, descend to 4000 ft to pomona VOR where we picked up the approach to ccb. The remainder of the flight was without incident.

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Original NASA ASRS Text

Title: SMA REQUESTS POP UP IFR CLRNC. SIGHTS MLG CLBING THROUGH OVCST. DEVIATES HDG TO AVOID WAKE TURB.

Narrative: DEPARTED CMA ARPT. VFR FOR FLT TO CCB ARPT. CONTACTED PT MUGU FOR VFR FLT FOLLOWING. WAS THEN HANDED OFF TO BURBANK APCH. CROSSED THE BURBANK ARSA AT 5500 FT PER VFR ARR CHART FOR UPLAND, CA, CABLE VFR ARRS. IT BECAME APPARENT THAT AN IFR APCH TO CCB WOULD BE NECESSARY DUE TO A FAIRLY SOLID UNDERCAST. CONTACTED ONTARIO APCH AND REQUESTED RADAR VECTORS FOR THE VOR RWY 6 AT CCB. WAS GIVEN A VECTOR OF 'R HDG 180 MAINTAIN VFR.' I COMPLIED AND BEGAN A SLIGHT CLB TO 6000 FT TO MAINTAIN VFR SEPARATION FROM SOME ISOLATED CUMULUS BELOW. AT THIS TIME I NOTICED AN MLG CLBING THROUGH THE UNDERCAST AT OUR 10 O'CLOCK POS, HDG APPROX 260. AT THIS TIME I WAS APPROX 5700 FT. I MAINTAINED HDG FOR ABOUT 15-30 SECONDS AND THEN DETERMINED THAT WAKE TURB WOULD BE LIKELY IF THE MLG CONTINUED ITS CLB AND HDG. I THEN TURNED L 20-30 DEGS AND BEGAN A DSCNT. ALMOST SIMULTANEOUSLY, ONTARIO APCH REQUESTED THE MLG TO CONTINUE ITS CLB TO 6000 FT. (I'M NOT SURE OF THE ALT.) THE MLG THEN APPEARED TO LEVEL OFF AND THE PLT RESPONDED 'NEGATIVE WE HAVE A TCASII ALERT' OR SOMETHING TO THAT EFFECT. ONTARIO APCH THEN MADE A COUPLE OF CALLS TO US USING JUST OUR N NUMBER. WHILE WE HEARD THEM AND ATTEMPTED TO ASSURE THEM THAT THE TFC WAS NO LONGER A FACTOR, WE WERE EITHER 'STEPPED ON' OR HAD A MOMENTARY MICROPHONE PROBLEM. THIS MOMENTARY LOSS/MISCOM CONTRIBUTED TO THE ANXIETY OF ALL CONCERNED AS I'M SURE THAT THE MLG NEVER SAW US. WE WERE THEN VECTORED TO 360, DSND TO 4000 FT TO POMONA VOR WHERE WE PICKED UP THE APCH TO CCB. THE REMAINDER OF THE FLT WAS WITHOUT INCIDENT.

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.