King air pilot reports using xm nexrad and onboard radar to avoid heavy weather but still encounteri...

Narrative:

I was flying under an IFR flight plan and requested deviation 30 degrees left/right for weather. I proceeded and chose the best route according to xm and the onboard aircraft radar. I ended up flying through clouds that appeared safer than the rest. I proceeded to go through the clouds but inadvertently ended up losing altitude and heading due to what I learned a few moments later was a developing storm cell. After I recovered from the altitude loss and proceeded back on course; the xm painted the area I just flew through as a developed cell. My corrective action for the future would be understanding xm and onboard radar as tools that may be delayed by a few moments and not give me actual time relevant weather info. I have also learned how to decipher my onboard radar with more accuracy to avoid problems in the future. Flying through the clouds; my autopilot kicked off and I had to manually take the controls to maintain the aircraft and I did not expect the autopilot to disengage as early as it did. In the future I will be more diligent about the autopilot disengage as to not lose as much altitude and/or heading. This was a learning experience that I will use in the future as to refrain from deviated altitude and heading.

Original NASA ASRS Text

Title: King Air pilot reports using XM Nexrad and onboard Radar to avoid heavy weather but still encountering turbulence that causes the autopilot to disengage with resulting altitude and heading deviations. Both systems show the area as a developed cell shortly after passing through.

Narrative: I was flying under an IFR flight plan and requested deviation 30 degrees left/right for weather. I proceeded and chose the best route according to XM and the onboard aircraft radar. I ended up flying through clouds that appeared safer than the rest. I proceeded to go through the clouds but inadvertently ended up losing altitude and heading due to what I learned a few moments later was a developing storm cell. After I recovered from the altitude loss and proceeded back on course; the XM painted the area I just flew through as a developed cell. My corrective action for the future would be understanding XM and onboard radar as tools that may be delayed by a few moments and not give me actual time relevant weather info. I have also learned how to decipher my onboard radar with more accuracy to avoid problems in the future. Flying through the clouds; my autopilot kicked off and I had to manually take the controls to maintain the aircraft and I did not expect the autopilot to disengage as early as it did. In the future I will be more diligent about the autopilot disengage as to not lose as much altitude and/or heading. This was a learning experience that I will use in the future as to refrain from deviated altitude and heading.

Data retrieved from NASA's ASRS site as of July 2013 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	1101699
Time
Date	201307
Local Time Of Day	1201-1800
Place
Locale Reference	ZFW.ARTCC
State Reference	TX
Environment
Flight Conditions	Mixed
Light	Daylight
Aircraft 1
Make Model Name	Beech F90
Operating Under FAR Part	Part 91
Flight Phase	Cruise
Route In Use	Vectors Visual Approach
Flight Plan	IFR
Person 1
Function	Pilot Flying
Qualification	Flight Crew Instrument Flight Crew Commercial Flight Crew Flight Instructor Flight Crew Multiengine
Experience	Flight Crew Last 90 Days 50 Flight Crew Total 1650 Flight Crew Type 170
Events
Anomaly	Aircraft Equipment Problem Less Severe Deviation - Altitude Excursion From Assigned Altitude Deviation - Track / Heading All Types Inflight Event / Encounter Weather / Turbulence

King air pilot reports using xm nexrad and onboard radar to avoid heavy weather but still encountering turbulence that causes the autopilot to disengage with resulting altitude and heading deviations. Both systems show the area as a developed cell shortly after passing through.