Narrative:

IFR training flight. IFR flight plan. Assigned 2500 MSL vectoring for approach VOR-24 lou bowman by standiford approach control. We were in VFR conditions at the time under a 3000 MSL overcast. As we were turning and slowing down, we flew from under the overcast to clear sky conditions. At this point the aircraft was pulled down, slowing 1500 FPM descent on vsi, and occupants were violently thrown against the ceiling of aircraft with such force that headsets/glasses, etc were pulled from occupants' heads. Immediate full throttle and 10 degree nose up pitch only slowed the descent somewhat. Severe turbulence (CAT) persisted approximately 30 second. (Seemed a lot longer.) during which time ATC advised of low altitude alert for our aircraft. When asked for altitude report, the altimeter showed 2200' with 1200 FPM descent on vsi. This was relayed to ATC. As soon as the turbulence abated some we regained 2500' level immediately. The WX for the flight was 20 scattered 30 overcast visibility 10 mi surface wind 180-15 30 wind 240/36. Condition existed for shear, however, the previous 12 hours of apches and vectors in and out of clouds had been relatively smooth. There was no reason to suspect severe CAT in good VFR conditions. After the initial bump on the head, pulling seat belt uncomfortably tight helped considerably. The ensuing approach and landing were uneventful and the aircraft was undamaged. Callback conversation with reporter revealed the following: a callback was initiated by the analyst to provide information not included on the old NASA reporting form. Licensing and experience of the instructor and student was obtained. The reporter reiterated that the downdraft was encountered at the precise point that the cloud cover ended. A cold front was transiting the area, and the reporter feels that the abrupt boundary of the cloud deck marked the position of the front. There are no terrain features at the point where turbulence was encountered that would suggest turbulence created by orthographic effect. Upon reflection, the reporter suggests that an altitude as low as 2000' was reached. The student's head hit the roof with sufficient force to cause headaches to persist for 4 days, indicating the possibility of a concussion. In subsequent flight training, the student exhibits nervousness in the vicinity of cloud, and is now experiencing difficulty in this phase of his flight training.

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Original NASA ASRS Text

Title: INSTRUCTOR AND STUDENT ON IFR TRAINING FLT EXPERIENCE MOMENTARY LOSS OF ACFT CONTROL UPON ENCOUNTERING SEVERE AND SUDDEN DOWNDRAFT.

Narrative: IFR TRAINING FLT. IFR FLT PLAN. ASSIGNED 2500 MSL VECTORING FOR APCH VOR-24 LOU BOWMAN BY STANDIFORD APCH CTL. WE WERE IN VFR CONDITIONS AT THE TIME UNDER A 3000 MSL OVERCAST. AS WE WERE TURNING AND SLOWING DOWN, WE FLEW FROM UNDER THE OVERCAST TO CLEAR SKY CONDITIONS. AT THIS POINT THE ACFT WAS PULLED DOWN, SLOWING 1500 FPM DSCNT ON VSI, AND OCCUPANTS WERE VIOLENTLY THROWN AGAINST THE CEILING OF ACFT WITH SUCH FORCE THAT HEADSETS/GLASSES, ETC WERE PULLED FROM OCCUPANTS' HEADS. IMMEDIATE FULL THROTTLE AND 10 DEG NOSE UP PITCH ONLY SLOWED THE DSCNT SOMEWHAT. SEVERE TURBULENCE (CAT) PERSISTED APPROX 30 SEC. (SEEMED A LOT LONGER.) DURING WHICH TIME ATC ADVISED OF LOW ALT ALERT FOR OUR ACFT. WHEN ASKED FOR ALT REPORT, THE ALTIMETER SHOWED 2200' WITH 1200 FPM DSCNT ON VSI. THIS WAS RELAYED TO ATC. AS SOON AS THE TURBULENCE ABATED SOME WE REGAINED 2500' LEVEL IMMEDIATELY. THE WX FOR THE FLT WAS 20 SCATTERED 30 OVERCAST VISIBILITY 10 MI SURFACE WIND 180-15 30 WIND 240/36. CONDITION EXISTED FOR SHEAR, HOWEVER, THE PREVIOUS 12 HRS OF APCHES AND VECTORS IN AND OUT OF CLOUDS HAD BEEN RELATIVELY SMOOTH. THERE WAS NO REASON TO SUSPECT SEVERE CAT IN GOOD VFR CONDITIONS. AFTER THE INITIAL BUMP ON THE HEAD, PULLING SEAT BELT UNCOMFORTABLY TIGHT HELPED CONSIDERABLY. THE ENSUING APCH AND LNDG WERE UNEVENTFUL AND THE ACFT WAS UNDAMAGED. CALLBACK CONVERSATION WITH REPORTER REVEALED THE FOLLOWING: A CALLBACK WAS INITIATED BY THE ANALYST TO PROVIDE INFO NOT INCLUDED ON THE OLD NASA REPORTING FORM. LICENSING AND EXPERIENCE OF THE INSTRUCTOR AND STUDENT WAS OBTAINED. THE REPORTER REITERATED THAT THE DOWNDRAFT WAS ENCOUNTERED AT THE PRECISE POINT THAT THE CLOUD COVER ENDED. A COLD FRONT WAS TRANSITING THE AREA, AND THE REPORTER FEELS THAT THE ABRUPT BOUNDARY OF THE CLOUD DECK MARKED THE POSITION OF THE FRONT. THERE ARE NO TERRAIN FEATURES AT THE POINT WHERE TURBULENCE WAS ENCOUNTERED THAT WOULD SUGGEST TURBULENCE CREATED BY ORTHOGRAPHIC EFFECT. UPON REFLECTION, THE REPORTER SUGGESTS THAT AN ALT AS LOW AS 2000' WAS REACHED. THE STUDENT'S HEAD HIT THE ROOF WITH SUFFICIENT FORCE TO CAUSE HEADACHES TO PERSIST FOR 4 DAYS, INDICATING THE POSSIBILITY OF A CONCUSSION. IN SUBSEQUENT FLT TRAINING, THE STUDENT EXHIBITS NERVOUSNESS IN THE VICINITY OF CLOUD, AND IS NOW EXPERIENCING DIFFICULTY IN THIS PHASE OF HIS FLT TRAINING.

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.