Small aircraft deviates from IFR clearance due to thunderstorm buildups.

Attributes
ACN	151041
Time
Date	199007
Day	Sun
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : sdz
State Reference	NC
Altitude	msl bound lower : 3000 msl bound upper : 11000
Environment
Flight Conditions	Mixed
Light	Daylight
Aircraft 1
Operator	general aviation : personal
Make Model Name	Small Aircraft, High Wing, 1 Eng, Fixed Gear
Flight Phase	cruise other
Route In Use	enroute airway : v66
Flight Plan	IFR
Person 1
Affiliation	Other
Function	flight crew : single pilot
Qualification	pilot : instrument pilot : private
Experience	flight time last 90 days : 40 flight time total : 580 flight time type : 150
ASRS Report	151041
Person 2
Affiliation	government : faa
Function	controller : radar
Qualification	controller : radar
Events
Anomaly	altitude deviation : excursion from assigned altitude non adherence : far non adherence : clearance
Independent Detector	other controllera other flight crewa
Resolutory Action	controller : issued new clearance
Consequence	faa : reviewed incident with flight crew
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

While on an IFR flight plan from anderson, sc, to raleigh, nc, I encountered an increasing number of scattered clouds which began to build above my altitude of 9000'. I was able to divert around them for awhile and requested a new altitude of 11000'. I was cleared to 10000' and within a min to 11000'. The clouds became more dense and seemed to be building much faster. I requested raleigh WX at about mid day and got 1 hour old WX which was approximately 3000 brn 5 mi some scattered rain southwest. I continued toward sdz and had increasing difficulty steering around buildups which were probably approximately 15000. I asked the controller if he saw any activity, but his response was that his radar was not really WX radar but he did not believe he saw any activity. I would have contacted 'flight watch' which I am familiar with, however, things were happening rather quickly. The controller gave me permission to divert left or right as necessary. I asked for raleigh WX again thinking they would have present WX but they still only had hour old WX. About this time I came upon a very large hole and requested a lower altitude. It is this time that the exact correct sequence of events is uncertain as I was convinced in my own mind that I wanted down. I told the controller 'I had to come down' as I could not avoid the buildups. I began to circle and requested a descent. The controller asked me if I wanted an IFR or VFR descent. I responded I wanted a VFR descent while on my IFR plan as I was in VMC in a large hole. It is at this time that I may have started my descent before actually being cleared to do so. The response from the controller was to ask me what altitude I was going to level off at. I responded 3000' as I approached 3000', and continued on to raleigh. While continuing on to raleigh I was asked to contact mr X at washington center after landing, which I did. Mr X had me talk with mr Y, a controller. Mr Y said he was not the person controling me at the time of the incident but that mr Z who was the controller was unavailable. Mr Y tried to put me at ease and told me that he only wanted to talk to me and assured me that they intended no further action. I was and I am sure I seemed surprised as I asked him at least twice as we talked 'this is the end of this?' and he assured me repeatedly 'yes!'

Original NASA ASRS Text

Title: SMA DEVIATES FROM IFR CLRNC DUE TO TSTM BUILDUPS.

Narrative: WHILE ON AN IFR FLT PLAN FROM ANDERSON, SC, TO RALEIGH, NC, I ENCOUNTERED AN INCREASING NUMBER OF SCATTERED CLOUDS WHICH BEGAN TO BUILD ABOVE MY ALT OF 9000'. I WAS ABLE TO DIVERT AROUND THEM FOR AWHILE AND REQUESTED A NEW ALT OF 11000'. I WAS CLRED TO 10000' AND WITHIN A MIN TO 11000'. THE CLOUDS BECAME MORE DENSE AND SEEMED TO BE BUILDING MUCH FASTER. I REQUESTED RALEIGH WX AT ABOUT MID DAY AND GOT 1 HR OLD WX WHICH WAS APPROX 3000 BRN 5 MI SOME SCATTERED RAIN SW. I CONTINUED TOWARD SDZ AND HAD INCREASING DIFFICULTY STEERING AROUND BUILDUPS WHICH WERE PROBABLY APPROX 15000. I ASKED THE CTLR IF HE SAW ANY ACTIVITY, BUT HIS RESPONSE WAS THAT HIS RADAR WAS NOT REALLY WX RADAR BUT HE DID NOT BELIEVE HE SAW ANY ACTIVITY. I WOULD HAVE CONTACTED 'FLT WATCH' WHICH I AM FAMILIAR WITH, HOWEVER, THINGS WERE HAPPENING RATHER QUICKLY. THE CTLR GAVE ME PERMISSION TO DIVERT L OR R AS NECESSARY. I ASKED FOR RALEIGH WX AGAIN THINKING THEY WOULD HAVE PRESENT WX BUT THEY STILL ONLY HAD HR OLD WX. ABOUT THIS TIME I CAME UPON A VERY LARGE HOLE AND REQUESTED A LOWER ALT. IT IS THIS TIME THAT THE EXACT CORRECT SEQUENCE OF EVENTS IS UNCERTAIN AS I WAS CONVINCED IN MY OWN MIND THAT I WANTED DOWN. I TOLD THE CTLR 'I HAD TO COME DOWN' AS I COULD NOT AVOID THE BUILDUPS. I BEGAN TO CIRCLE AND REQUESTED A DSNT. THE CTLR ASKED ME IF I WANTED AN IFR OR VFR DSNT. I RESPONDED I WANTED A VFR DSNT WHILE ON MY IFR PLAN AS I WAS IN VMC IN A LARGE HOLE. IT IS AT THIS TIME THAT I MAY HAVE STARTED MY DSNT BEFORE ACTUALLY BEING CLRED TO DO SO. THE RESPONSE FROM THE CTLR WAS TO ASK ME WHAT ALT I WAS GOING TO LEVEL OFF AT. I RESPONDED 3000' AS I APCHED 3000', AND CONTINUED ON TO RALEIGH. WHILE CONTINUING ON TO RALEIGH I WAS ASKED TO CONTACT MR X AT WASHINGTON CTR AFTER LNDG, WHICH I DID. MR X HAD ME TALK WITH MR Y, A CTLR. MR Y SAID HE WAS NOT THE PERSON CTLING ME AT THE TIME OF THE INCIDENT BUT THAT MR Z WHO WAS THE CTLR WAS UNAVAILABLE. MR Y TRIED TO PUT ME AT EASE AND TOLD ME THAT HE ONLY WANTED TO TALK TO ME AND ASSURED ME THAT THEY INTENDED NO FURTHER ACTION. I WAS AND I AM SURE I SEEMED SURPRISED AS I ASKED HIM AT LEAST TWICE AS WE TALKED 'THIS IS THE END OF THIS?' AND HE ASSURED ME REPEATEDLY 'YES!'

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.