Narrative:

While on an IFR flight plan and in cruise confign level at my assigned altitude of 5000 ft; I encountered moderate to severe turbulence. The aircraft began a descent. I applied full power and pitched up for best climb. The aircraft continued descent at about 500 FPM to 4500 ft. At this point ATC asked for verification that I was level at 5000 ft. I replied that I was unable to maintain 5000 ft and that I was in moderate to severe turbulence. ATC responded that they understood. At this point; I was in a full power climb slowly climbing back to 5000 ft with turbulence that was likely to get worse before it got better; so I asked ATC for cancellation of my IFR flight plan and VFR following back to my departure airport. ATC politely approved my request. I filed a PIREP with FSS to advise them of the turbulence. I believe that this problem was caused by unusual WX conditions. During my WX briefing; the specialist noted that there was a NOTAM for turbulence; but that is fairly common. There were no PIREPS to support the NOTAM. The turbulence lasted for a few hours and then subsided. To help prevent situations like this; I believe it would be helpful if more pilots made PIREPS more frequently. ATC was very helpful and understanding of my situation.

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Original NASA ASRS Text

Title: THE PLT OF A GRUMMAN AA-1 ENCOUNTERS SEVERE TURB 14 MI W OF VNY AND IS UNABLE TO MAINTAIN ALT.

Narrative: WHILE ON AN IFR FLT PLAN AND IN CRUISE CONFIGN LEVEL AT MY ASSIGNED ALT OF 5000 FT; I ENCOUNTERED MODERATE TO SEVERE TURB. THE ACFT BEGAN A DSCNT. I APPLIED FULL PWR AND PITCHED UP FOR BEST CLB. THE ACFT CONTINUED DSCNT AT ABOUT 500 FPM TO 4500 FT. AT THIS POINT ATC ASKED FOR VERIFICATION THAT I WAS LEVEL AT 5000 FT. I REPLIED THAT I WAS UNABLE TO MAINTAIN 5000 FT AND THAT I WAS IN MODERATE TO SEVERE TURB. ATC RESPONDED THAT THEY UNDERSTOOD. AT THIS POINT; I WAS IN A FULL PWR CLB SLOWLY CLBING BACK TO 5000 FT WITH TURB THAT WAS LIKELY TO GET WORSE BEFORE IT GOT BETTER; SO I ASKED ATC FOR CANCELLATION OF MY IFR FLT PLAN AND VFR FOLLOWING BACK TO MY DEP ARPT. ATC POLITELY APPROVED MY REQUEST. I FILED A PIREP WITH FSS TO ADVISE THEM OF THE TURB. I BELIEVE THAT THIS PROB WAS CAUSED BY UNUSUAL WX CONDITIONS. DURING MY WX BRIEFING; THE SPECIALIST NOTED THAT THERE WAS A NOTAM FOR TURB; BUT THAT IS FAIRLY COMMON. THERE WERE NO PIREPS TO SUPPORT THE NOTAM. THE TURB LASTED FOR A FEW HRS AND THEN SUBSIDED. TO HELP PREVENT SITUATIONS LIKE THIS; I BELIEVE IT WOULD BE HELPFUL IF MORE PLTS MADE PIREPS MORE FREQUENTLY. ATC WAS VERY HELPFUL AND UNDERSTANDING OF MY SITUATION.

Data retrieved from NASA's ASRS site as of January 2009 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.