Narrative:

Picked up the IFR clearance from ZME while on the ground at glh. Since local WX was VFR, center was notified of departure after the aircraft was airborne. Radar identify was established and the aircraft was given clearance to climb to 9000' and continue on own navigation (RNAV) to bhm. The aircraft continued a normal cruise climb toward the assigned altitude. I noted some activity on the on board stormscope, approximately 35-40 mi away near my route of flight. I requested and received clearance from center to deviate to the south to avoid this area. While in VFR WX with no indications of any storm activity within 35-40 mi, I encountered sudden extremely severe turbulence. Within 1-2 seconds, the aircraft inverted and entered a spin. While in this condition the aircraft encountered IMC while falling through a cloud. The pilot determined that he was inverted and spinning and initiated corrective action. After power was reduced to retard airspeed, the wings were leveled, spin stopped and the aircraft was transitioned to normal flight. The aircraft remained in the green arc (below vne) at all times. I estimate that in less than 30 seconds the aircraft dropped from approximately 9000' to 3000'. During this episode, I estimate that I may have pulled about 3 G's positive. I heard the vertical seat adjustment fail and noted that the compass mounting bracket had been broken. I attribute the compass mounting bracket breakage to being struck by an approach plate binder. I also noted a vacuum warning light and activated my backup source. This warning was not on prior to the excursion. I called center to notify them as to what had happened and to inform them that I was all right. Center cleared me to 4000' and asked me if I wanted to return to glh. I declined the glh return due to strong surface winds encountered on departure and possible damage to the aircraft. Center informed me that jan was VFR and I elected to divert to there. I started to track center's vector to jan, but after several mins discovered that my track was to the west instead of southeast. Center then gave me no gyro turns while I reslaved my HSI 2 times and got a line of flight on my dg that agreed with center's estimate of my track. I also found the compass on the cabin floor and placed it in my lap in case the HSI would not stay slaved. After I broke out of the clouds and could see jan, center attempted to hand me off to jan approach. I could not get all of the new frequency due to radio interference and proceeded to look up the appropriate frequency from my approach plate. The next morning several mechanics examined the aircraft and determined that no damage to the airframe or skin was evident. The compass bracket was repaired, pilot and copilot seats exchanged, and both the vacuum pump and a landing light were replaced.

Related reports:

Google
 

Original NASA ASRS Text

Title: PLT LOSES CONTROL OF GA SMA DUE TO TURBULENCE.

Narrative: PICKED UP THE IFR CLRNC FROM ZME WHILE ON THE GND AT GLH. SINCE LCL WX WAS VFR, CENTER WAS NOTIFIED OF DEP AFTER THE ACFT WAS AIRBORNE. RADAR IDENT WAS ESTABLISHED AND THE ACFT WAS GIVEN CLRNC TO CLB TO 9000' AND CONTINUE ON OWN NAV (RNAV) TO BHM. THE ACFT CONTINUED A NORMAL CRUISE CLB TOWARD THE ASSIGNED ALT. I NOTED SOME ACTIVITY ON THE ON BOARD STORMSCOPE, APPROX 35-40 MI AWAY NEAR MY ROUTE OF FLT. I REQUESTED AND RECEIVED CLRNC FROM CENTER TO DEVIATE TO THE S TO AVOID THIS AREA. WHILE IN VFR WX WITH NO INDICATIONS OF ANY STORM ACTIVITY WITHIN 35-40 MI, I ENCOUNTERED SUDDEN EXTREMELY SEVERE TURB. WITHIN 1-2 SECS, THE ACFT INVERTED AND ENTERED A SPIN. WHILE IN THIS CONDITION THE ACFT ENCOUNTERED IMC WHILE FALLING THROUGH A CLOUD. THE PLT DETERMINED THAT HE WAS INVERTED AND SPINNING AND INITIATED CORRECTIVE ACTION. AFTER PWR WAS REDUCED TO RETARD AIRSPD, THE WINGS WERE LEVELED, SPIN STOPPED AND THE ACFT WAS TRANSITIONED TO NORMAL FLT. THE ACFT REMAINED IN THE GREEN ARC (BELOW VNE) AT ALL TIMES. I ESTIMATE THAT IN LESS THAN 30 SECS THE ACFT DROPPED FROM APPROX 9000' TO 3000'. DURING THIS EPISODE, I ESTIMATE THAT I MAY HAVE PULLED ABOUT 3 G'S POSITIVE. I HEARD THE VERT SEAT ADJUSTMENT FAIL AND NOTED THAT THE COMPASS MOUNTING BRACKET HAD BEEN BROKEN. I ATTRIBUTE THE COMPASS MOUNTING BRACKET BREAKAGE TO BEING STRUCK BY AN APCH PLATE BINDER. I ALSO NOTED A VACUUM WARNING LIGHT AND ACTIVATED MY BACKUP SOURCE. THIS WARNING WAS NOT ON PRIOR TO THE EXCURSION. I CALLED CENTER TO NOTIFY THEM AS TO WHAT HAD HAPPENED AND TO INFORM THEM THAT I WAS ALL RIGHT. CENTER CLRED ME TO 4000' AND ASKED ME IF I WANTED TO RETURN TO GLH. I DECLINED THE GLH RETURN DUE TO STRONG SURFACE WINDS ENCOUNTERED ON DEP AND POSSIBLE DAMAGE TO THE ACFT. CENTER INFORMED ME THAT JAN WAS VFR AND I ELECTED TO DIVERT TO THERE. I STARTED TO TRACK CENTER'S VECTOR TO JAN, BUT AFTER SEVERAL MINS DISCOVERED THAT MY TRACK WAS TO THE W INSTEAD OF SE. CENTER THEN GAVE ME NO GYRO TURNS WHILE I RESLAVED MY HSI 2 TIMES AND GOT A LINE OF FLT ON MY DG THAT AGREED WITH CENTER'S ESTIMATE OF MY TRACK. I ALSO FOUND THE COMPASS ON THE CABIN FLOOR AND PLACED IT IN MY LAP IN CASE THE HSI WOULD NOT STAY SLAVED. AFTER I BROKE OUT OF THE CLOUDS AND COULD SEE JAN, CENTER ATTEMPTED TO HAND ME OFF TO JAN APCH. I COULD NOT GET ALL OF THE NEW FREQ DUE TO RADIO INTERFERENCE AND PROCEEDED TO LOOK UP THE APPROPRIATE FREQ FROM MY APCH PLATE. THE NEXT MORNING SEVERAL MECHS EXAMINED THE ACFT AND DETERMINED THAT NO DAMAGE TO THE AIRFRAME OR SKIN WAS EVIDENT. THE COMPASS BRACKET WAS REPAIRED, PLT AND COPLT SEATS EXCHANGED, AND BOTH THE VACUUM PUMP AND A LNDG LIGHT WERE REPLACED.

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.