A charter B727 enters a thunderstorm when their radar failed to show the hazards ahead.

Attributes
ACN	407517
Time
Date	199807
Day	Wed
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : elw
State Reference	SC
Altitude	msl bound lower : 28000 msl bound upper : 28000
Environment
Flight Conditions	IMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : ztl
Operator	common carrier : air carrier
Make Model Name	B727-200
Operating Under FAR Part	other : other
Flight Phase	cruise other
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp pilot : flight engineer
Experience	flight time last 90 days : 205 flight time total : 6500 flight time type : 3500
ASRS Report	407517
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : commercial pilot : instrument
Events
Anomaly	aircraft equipment problem : less severe altitude deviation : excursion from assigned altitude inflight encounter : weather inflight encounter other non adherence : clearance other anomaly
Independent Detector	other flight crewa
Resolutory Action	controller : issued new clearance flight crew : exited adverse environment flight crew : regained aircraft control
Consequence	Other
Supplementary
Primary Problem	Aircraft
Air Traffic Incident	other

Narrative:

In cruise/descent into knoxville, tn, the flight encountered unexpected and unrpted severe turbulence, heavy precipitation, and hail. The aircraft suffered at least two observed lightning strikes to the nose. Airborne WX radar (honeywell primus-90) showed only light to moderate precipitation in the general vicinity. The flight was unable to hold assigned altitude, and immediately contacted ATC for a block altitude and right-of-course deviation. After 30-60 seconds, the aircraft was in the clear. There were no reported injuries to crew or passenger, and no immediate sign of damage to the aircraft or its system. The aircraft's onboard WX radar has a history of maintenance problems, including failure to show areas of known precipitation. The aircraft was flown to a maintenance facility for inspection. Callback conversation with reporter revealed the following information: the reporter said that he has had some experiences with other aircraft with this type radar but feels that it is a 'company maintenance' problem. He says that their maintenance department doesn't have the expertise to fix the radar return problems. Other air carrier's have this system without showing any problems with it. The owner of this part 129 carrier has issued a 'blank check' to maintenance in order for them to fix the radars.

Original NASA ASRS Text

Title: A CHARTER B727 ENTERS A TSTM WHEN THEIR RADAR FAILED TO SHOW THE HAZARDS AHEAD.

Narrative: IN CRUISE/DSCNT INTO KNOXVILLE, TN, THE FLT ENCOUNTERED UNEXPECTED AND UNRPTED SEVERE TURB, HVY PRECIPITATION, AND HAIL. THE ACFT SUFFERED AT LEAST TWO OBSERVED LIGHTNING STRIKES TO THE NOSE. AIRBORNE WX RADAR (HONEYWELL PRIMUS-90) SHOWED ONLY LIGHT TO MODERATE PRECIPITATION IN THE GENERAL VICINITY. THE FLT WAS UNABLE TO HOLD ASSIGNED ALT, AND IMMEDIATELY CONTACTED ATC FOR A BLOCK ALT AND RIGHT-OF-COURSE DEV. AFTER 30-60 SECONDS, THE ACFT WAS IN THE CLR. THERE WERE NO RPTED INJURIES TO CREW OR PAX, AND NO IMMEDIATE SIGN OF DAMAGE TO THE ACFT OR ITS SYS. THE ACFT'S ONBOARD WX RADAR HAS A HISTORY OF MAINT PROBS, INCLUDING FAILURE TO SHOW AREAS OF KNOWN PRECIPITATION. THE ACFT WAS FLOWN TO A MAINT FACILITY FOR INSPECTION. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR SAID THAT HE HAS HAD SOME EXPERIENCES WITH OTHER ACFT WITH THIS TYPE RADAR BUT FEELS THAT IT IS A 'COMPANY MAINT' PROB. HE SAYS THAT THEIR MAINT DEPT DOESN'T HAVE THE EXPERTISE TO FIX THE RADAR RETURN PROBS. OTHER ACR'S HAVE THIS SYS WITHOUT SHOWING ANY PROBS WITH IT. THE OWNER OF THIS PART 129 CARRIER HAS ISSUED A 'BLANK CHK' TO MAINT IN ORDER FOR THEM TO FIX THE RADARS.

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.