Narrative:

ATC advised precipitation at 12 O'clock position, in 10 mi. Our radar showed a small area of lowest intensity return in that area when we lowered the radar units scale (distance). We were at FL310, cleared to descend, and were on a vector direct to destination. The flight encountered an approximately medium to severe level of intensity of turbulence and moderate to heavy precipitation for approximately 30 seconds to 1 min. The controller did not offer an intensity but merely stated precipitation and our radar showed lowest level of intensity of return. When in the clear on the other side of the narrow cell, we looked back to see a twring anvil above us. The aircraft suffered hail damage and was grounded for repair, before further flight, upon landing. The radar did not accurately depict the intensity of the WX and the IMC conditions obscured our vision (ability to see the thunderstorm). WX reports, forecasts and PIREPS had (printed out) indicated no significant WX and turbulence (neg) in that area. The radar unit in this particular plane has a history of write-up's that we were not aware of. ATC should advise of intensity. Maintenance should calibrate or replace the radar unit.

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Original NASA ASRS Text

Title: A DC20 FALCON FREIGHTER ENTERS A TSTM AT FL310 AND EXPERIENCES SEVERE TURB. FO SAID THAT THE ACFT'S RADAR SHOWED 'A SMALL AREA OF LOWEST INTENSITY.'

Narrative: ATC ADVISED PRECIP AT 12 O'CLOCK POS, IN 10 MI. OUR RADAR SHOWED A SMALL AREA OF LOWEST INTENSITY RETURN IN THAT AREA WHEN WE LOWERED THE RADAR UNITS SCALE (DISTANCE). WE WERE AT FL310, CLRED TO DSND, AND WERE ON A VECTOR DIRECT TO DEST. THE FLT ENCOUNTERED AN APPROX MEDIUM TO SEVERE LEVEL OF INTENSITY OF TURB AND MODERATE TO HVY PRECIP FOR APPROX 30 SECONDS TO 1 MIN. THE CTLR DID NOT OFFER AN INTENSITY BUT MERELY STATED PRECIP AND OUR RADAR SHOWED LOWEST LEVEL OF INTENSITY OF RETURN. WHEN IN THE CLR ON THE OTHER SIDE OF THE NARROW CELL, WE LOOKED BACK TO SEE A TWRING ANVIL ABOVE US. THE ACFT SUFFERED HAIL DAMAGE AND WAS GNDED FOR REPAIR, BEFORE FURTHER FLT, UPON LNDG. THE RADAR DID NOT ACCURATELY DEPICT THE INTENSITY OF THE WX AND THE IMC CONDITIONS OBSCURED OUR VISION (ABILITY TO SEE THE TSTM). WX RPTS, FORECASTS AND PIREPS HAD (PRINTED OUT) INDICATED NO SIGNIFICANT WX AND TURB (NEG) IN THAT AREA. THE RADAR UNIT IN THIS PARTICULAR PLANE HAS A HISTORY OF WRITE-UP'S THAT WE WERE NOT AWARE OF. ATC SHOULD ADVISE OF INTENSITY. MAINT SHOULD CALIBRATE OR REPLACE THE RADAR UNIT.

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.