Upon exiting IMC and seeing no change in the display; a B737-300 captain was concerned that his weat...

Narrative:

At cruise altitude we were traveling in an area of IMC where turbulence was reported by ATC. The weather radar was being used to detect any possible embedded convective activity. Once we entered an area where we were clear of the weather and we could see the ocean surface below; I observed that the radar depiction did not change. I raised the tilt angle to see if pointing the radar to a known area free of reflective precipitation would change the returns; but the depiction of returns remained. I ran the radar in 'test' mode to check the integrity of the system which it passed and returned it to WX mode. The returns then looked normal and it appeared regular function was restored. My concern is; while I was in the weather; was the radar giving me valid data or was it somehow malfunctioning without me knowing it. It obviously performed differently from before the test function was performed and after.

Original NASA ASRS Text

Title: Upon exiting IMC and seeing no change in the display; a B737-300 Captain was concerned that his weather radar was providing invalid convective weather returns. This concern was reinforced when operating in the 'Test' mode for a short period resulted in appropriate returns.

Narrative: At cruise altitude we were traveling in an area of IMC where turbulence was reported by ATC. The weather radar was being used to detect any possible embedded convective activity. Once we entered an area where we were clear of the weather and we could see the ocean surface below; I observed that the radar depiction did not change. I raised the tilt angle to see if pointing the radar to a known area free of reflective precipitation would change the returns; but the depiction of returns remained. I ran the radar in 'Test' mode to check the integrity of the system which it passed and returned it to WX mode. The returns then looked normal and it appeared regular function was restored. My concern is; while I was in the weather; was the radar giving me valid data or was it somehow malfunctioning without me knowing it. It obviously performed differently from before the test function was performed and after.

Data retrieved from NASA's ASRS site as of April 2012 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.

Attributes
ACN	880931
Time
Date	201003
Local Time Of Day	1201-1800
Place
Locale Reference	ZDC.ARTCC
State Reference	VA
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Make Model Name	B737-300
Operating Under FAR Part	Part 121
Flight Phase	Cruise
Component
Aircraft Component	Weather Radar
Person 1
Function	Captain
Qualification	Flight Crew Air Transport Pilot (ATP)
Experience	Flight Crew Last 90 Days 162 Flight Crew Type 162
Events
Anomaly	Aircraft Equipment Problem Critical

Upon exiting IMC and seeing no change in the display; a B737-300 captain was concerned that his weather radar was providing invalid convective weather returns. This concern was reinforced when operating in the 'test' mode for a short period resulted in appropriate returns.