Narrative:

On dec/sat/94 I was returning to the oak airport fr OM a currency/pleasure flight in my cessna 182 skylane. At approximately 27 NM DME northwest of the airport, I contacted bay approach. I advised I was VFR at 3500 ft but requested an IFR clearance to execute the ILS 27R approach at oak. Oak was reporting 2700 ft overcast, 15 mi visibility and light rain showers. WX to the northwest of the field was 6000 ft VFR, a slow-moving front was entering the bay area. Bay approach initially provided me a 140 degree heading and asked if I could maintain VFR. I advised that I could but would soon need the IFR clearance closer in at 3500 ft. The controller shortly thereafter advised me to climb and maintain 4000 ft, and that I was cleared to the oak airport via radar vectors for the ILS runway 24R. Approximately 8-10 mi north of the airport, the controller advised of crossing traffic, a heavy 747. I advised I was IMC, and no contact. I then saw the B747 emerge from a layer ahead and to my left. I requested an immediate vector for wake turbulence. Bay TRACON advised me to 'turn right to 140 degrees.' after a period of time (probably about 1 min), TRACON advised me to 'turn left to 100 degrees.' shortly after completing the heading change, I flew through what I believe was wake turbulence from the B747. My aircraft was strongly jolted causing approach plate binders to be lifted from the center console between the 2 front seats and deposited in the back seat. Other pieces of pilot equipment (flashlights, sectional charts, a hand-held GPS, pens, etc) were thrown about the cabin. I received a bruise to my left upper thigh from the seat belt, and a strain to my lower back. I would characterize this turbulence as severe, as control of the aircraft was momentarily lost. I brought this aircraft back to straight and level and turned right to avoid what I thought could potentially be more turbulence from the other wingtip. I then advised bay TRACON of what happened. Breaking into an area of VFR WX I canceled my IFR clearance, descended and landed at oak. No damage to the aircraft was evident. I contacted bay TRACON after landing. The supervisor advised me that the crossing traffic had been a 747-400, heavily loaded for its non-stop sfo-london flight. She advised that I had crossed behind the B747, but could not tell me how far. I would suggest that appropriate authority/authorized determine what is a safe crossing distance between light aircraft and such heavy aircraft and ATC be aware of the significance of allowing these types of aircraft to come too close. I have been a pilot for 21 yrs, flying light aircraft, helicopters through business jets. I have never had an experience like this.

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Original NASA ASRS Text

Title: SEVERE WAKE TURB.

Narrative: ON DEC/SAT/94 I WAS RETURNING TO THE OAK ARPT FR OM A CURRENCY/PLEASURE FLT IN MY CESSNA 182 SKYLANE. AT APPROX 27 NM DME NW OF THE ARPT, I CONTACTED BAY APCH. I ADVISED I WAS VFR AT 3500 FT BUT REQUESTED AN IFR CLRNC TO EXECUTE THE ILS 27R APCH AT OAK. OAK WAS RPTING 2700 FT OVCST, 15 MI VISIBILITY AND LIGHT RAIN SHOWERS. WX TO THE NW OF THE FIELD WAS 6000 FT VFR, A SLOW-MOVING FRONT WAS ENTERING THE BAY AREA. BAY APCH INITIALLY PROVIDED ME A 140 DEG HDG AND ASKED IF I COULD MAINTAIN VFR. I ADVISED THAT I COULD BUT WOULD SOON NEED THE IFR CLRNC CLOSER IN AT 3500 FT. THE CTLR SHORTLY THEREAFTER ADVISED ME TO CLB AND MAINTAIN 4000 FT, AND THAT I WAS CLRED TO THE OAK ARPT VIA RADAR VECTORS FOR THE ILS RWY 24R. APPROX 8-10 MI N OF THE ARPT, THE CTLR ADVISED OF XING TFC, A HVY 747. I ADVISED I WAS IMC, AND NO CONTACT. I THEN SAW THE B747 EMERGE FROM A LAYER AHEAD AND TO MY L. I REQUESTED AN IMMEDIATE VECTOR FOR WAKE TURB. BAY TRACON ADVISED ME TO 'TURN R TO 140 DEGS.' AFTER A PERIOD OF TIME (PROBABLY ABOUT 1 MIN), TRACON ADVISED ME TO 'TURN L TO 100 DEGS.' SHORTLY AFTER COMPLETING THE HDG CHANGE, I FLEW THROUGH WHAT I BELIEVE WAS WAKE TURB FROM THE B747. MY ACFT WAS STRONGLY JOLTED CAUSING APCH PLATE BINDERS TO BE LIFTED FROM THE CTR CONSOLE BTWN THE 2 FRONT SEATS AND DEPOSITED IN THE BACK SEAT. OTHER PIECES OF PLT EQUIP (FLASHLIGHTS, SECTIONAL CHARTS, A HAND-HELD GPS, PENS, ETC) WERE THROWN ABOUT THE CABIN. I RECEIVED A BRUISE TO MY L UPPER THIGH FROM THE SEAT BELT, AND A STRAIN TO MY LOWER BACK. I WOULD CHARACTERIZE THIS TURB AS SEVERE, AS CTL OF THE ACFT WAS MOMENTARILY LOST. I BROUGHT THIS ACFT BACK TO STRAIGHT AND LEVEL AND TURNED R TO AVOID WHAT I THOUGHT COULD POTENTIALLY BE MORE TURB FROM THE OTHER WINGTIP. I THEN ADVISED BAY TRACON OF WHAT HAPPENED. BREAKING INTO AN AREA OF VFR WX I CANCELED MY IFR CLRNC, DSNDED AND LANDED AT OAK. NO DAMAGE TO THE ACFT WAS EVIDENT. I CONTACTED BAY TRACON AFTER LNDG. THE SUPVR ADVISED ME THAT THE XING TFC HAD BEEN A 747-400, HEAVILY LOADED FOR ITS NON-STOP SFO-LONDON FLT. SHE ADVISED THAT I HAD CROSSED BEHIND THE B747, BUT COULD NOT TELL ME HOW FAR. I WOULD SUGGEST THAT APPROPRIATE AUTH DETERMINE WHAT IS A SAFE XING DISTANCE BTWN LIGHT ACFT AND SUCH HVY ACFT AND ATC BE AWARE OF THE SIGNIFICANCE OF ALLOWING THESE TYPES OF ACFT TO COME TOO CLOSE. I HAVE BEEN A PLT FOR 21 YRS, FLYING LIGHT ACFT, HELIS THROUGH BUSINESS JETS. I HAVE NEVER HAD AN EXPERIENCE LIKE THIS.

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.