Narrative:

On oct/xx/95 I was assigned as the captain operating phl-den in an A320 airbus, equipped with a bendix rdr-4B color WX radar unit. The WX in the northeast united states was dominated by the remains of hurricane opal which was producing continuous moderate rain showers in the philadelphia area at the time of our am departure. During the taxi out with rain showers pouring down on the aircraft, I turned on the WX radar unit and adjusted the tilt to 15 degrees up and selected the range to 40 mi in an attempt to scan the terminal area for the presence of WX echo returns. The WX radar display indicated what is euphemistically termed a 'bloom' condition. This condition of severe radar attenuation is documented in the flight manual on page 6-52. This flight manual states, 'at lower altitudes in the presence of precipitation, the radar display may turn mostly or completely red or green. This 'bloom' condition may obscure definition of cells. The condition may be alleviated by manually adjusting the gain knob. A recommended technique prior to entering the approach environment or at low altitude is to select the 1 O'clock position manually. Small adjustments may have to be made to define specific cells. When gain is no longer needed, return gain knob to automatic.' with the radar gain control in the automatic position, the radar display indicated a continuous attentuation arc from the radome out to 10-15 mi. This arc was 90 percent red radar display and 10 percent amber. No radar returns were visible in the area beyond this attenuation arc. I then selected manual gain control as recommended, with the only display change being the color changed to 90 percent green and 10 percent amber returns in the attenuation arc. Since other aircraft were departing the airport in front of us and no thunderstorms were forecast in the area for 4 hours, we departed. While airborne between 5000 ft and FL200 we flew through an area of rain showers for 5- 10 mins in which the intensity of the rain pounding on the windshield was consistent with moderate showers. These showers should have been visible on any properly functioning airborne WX radar unit. But no radar returns were displayed on our radar unit beyond the continuous attenuation arc. Once out of the low altitude structure and at cruising flight level for 2 hours, the radar unit operated properly. This known anomaly is going to be a contributing factor to a future WX related accident involving this radar unit being flown at low altitudes in visible moisture. This problem needs to be fixed now!

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Original NASA ASRS Text

Title: ACFT EQUIP PROB. WX RADAR.

Narrative: ON OCT/XX/95 I WAS ASSIGNED AS THE CAPT OPERATING PHL-DEN IN AN A320 AIRBUS, EQUIPPED WITH A BENDIX RDR-4B COLOR WX RADAR UNIT. THE WX IN THE NE UNITED STATES WAS DOMINATED BY THE REMAINS OF HURRICANE OPAL WHICH WAS PRODUCING CONTINUOUS MODERATE RAIN SHOWERS IN THE PHILADELPHIA AREA AT THE TIME OF OUR AM DEP. DURING THE TAXI OUT WITH RAIN SHOWERS POURING DOWN ON THE ACFT, I TURNED ON THE WX RADAR UNIT AND ADJUSTED THE TILT TO 15 DEGS UP AND SELECTED THE RANGE TO 40 MI IN AN ATTEMPT TO SCAN THE TERMINAL AREA FOR THE PRESENCE OF WX ECHO RETURNS. THE WX RADAR DISPLAY INDICATED WHAT IS EUPHEMISTICALLY TERMED A 'BLOOM' CONDITION. THIS CONDITION OF SEVERE RADAR ATTENUATION IS DOCUMENTED IN THE FLT MANUAL ON PAGE 6-52. THIS FLT MANUAL STATES, 'AT LOWER ALTS IN THE PRESENCE OF PRECIPITATION, THE RADAR DISPLAY MAY TURN MOSTLY OR COMPLETELY RED OR GREEN. THIS 'BLOOM' CONDITION MAY OBSCURE DEFINITION OF CELLS. THE CONDITION MAY BE ALLEVIATED BY MANUALLY ADJUSTING THE GAIN KNOB. A RECOMMENDED TECHNIQUE PRIOR TO ENTERING THE APCH ENVIRONMENT OR AT LOW ALT IS TO SELECT THE 1 O'CLOCK POS MANUALLY. SMALL ADJUSTMENTS MAY HAVE TO BE MADE TO DEFINE SPECIFIC CELLS. WHEN GAIN IS NO LONGER NEEDED, RETURN GAIN KNOB TO AUTO.' WITH THE RADAR GAIN CTL IN THE AUTO POS, THE RADAR DISPLAY INDICATED A CONTINUOUS ATTENTUATION ARC FROM THE RADOME OUT TO 10-15 MI. THIS ARC WAS 90 PERCENT RED RADAR DISPLAY AND 10 PERCENT AMBER. NO RADAR RETURNS WERE VISIBLE IN THE AREA BEYOND THIS ATTENUATION ARC. I THEN SELECTED MANUAL GAIN CTL AS RECOMMENDED, WITH THE ONLY DISPLAY CHANGE BEING THE COLOR CHANGED TO 90 PERCENT GREEN AND 10 PERCENT AMBER RETURNS IN THE ATTENUATION ARC. SINCE OTHER ACFT WERE DEPARTING THE ARPT IN FRONT OF US AND NO TSTMS WERE FORECAST IN THE AREA FOR 4 HRS, WE DEPARTED. WHILE AIRBORNE BTWN 5000 FT AND FL200 WE FLEW THROUGH AN AREA OF RAIN SHOWERS FOR 5- 10 MINS IN WHICH THE INTENSITY OF THE RAIN POUNDING ON THE WINDSHIELD WAS CONSISTENT WITH MODERATE SHOWERS. THESE SHOWERS SHOULD HAVE BEEN VISIBLE ON ANY PROPERLY FUNCTIONING AIRBORNE WX RADAR UNIT. BUT NO RADAR RETURNS WERE DISPLAYED ON OUR RADAR UNIT BEYOND THE CONTINUOUS ATTENUATION ARC. ONCE OUT OF THE LOW ALT STRUCTURE AND AT CRUISING FLT LEVEL FOR 2 HRS, THE RADAR UNIT OPERATED PROPERLY. THIS KNOWN ANOMALY IS GOING TO BE A CONTRIBUTING FACTOR TO A FUTURE WX RELATED ACCIDENT INVOLVING THIS RADAR UNIT BEING FLOWN AT LOW ALTS IN VISIBLE MOISTURE. THIS PROB NEEDS TO BE FIXED NOW!

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.