Narrative:

Chain of events. Flying into guc while encountering severe turbulence I heard other aircraft reporting severe turbulence and asking for block altitude, saying they were ballooning 1000 ft or more. I only had 8 hours in the AC69, flying it as a single pilot in turbulence, icing, IMC and entering a holding pattern to climb in and going thru checklists at the same time. Even for an 11000 hour pilot it is a hard workload. ATC then gave me a new altitude of FL200 which I repeated back as FL200 they tell me, and they have the recordings so I'm sure they're right. However, I rolled in FL220 in my altitude alert and continued to climb in hold to FL125 from then to FL220. I flew for about 50 miles at FL220 when they gave me a 40 degree turn for traffic and asked me my assigned altitude. They told me to climb to FL250 and I was assigned FL200. Then ATC said they had lost radar contact with a C130 because I was at wrong altitude. Clearly my fault. I heard 200 said 200, but being under heavy workload, and just a little bit scared my brain heard FL220 and tuned it in my altitude alert. I know you want to know how ATC can help. Remember I screwed up. The only thing they could do is watch closely in severe WX, monitor more closely and give us idiots all the help they can. This is the first time in 31 yrs I missed an altitude.

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Original NASA ASRS Text

Title: AN AC69 PLT WHILE ENCOUNTERING WX AND TURB, RECEIVES AN ALT CLRNC AND READS IT BACK, BUT CLBS TO ANOTHER ALT.

Narrative: CHAIN OF EVENTS. FLYING INTO GUC WHILE ENCOUNTERING SEVERE TURB I HEARD OTHER ACFT RPTING SEVERE TURB AND ASKING FOR BLOCK ALT, SAYING THEY WERE BALLOONING 1000 FT OR MORE. I ONLY HAD 8 HRS IN THE AC69, FLYING IT AS A SINGLE PLT IN TURB, ICING, IMC AND ENTERING A HOLDING PATTERN TO CLB IN AND GOING THRU CHKLISTS AT THE SAME TIME. EVEN FOR AN 11000 HR PLT IT IS A HARD WORKLOAD. ATC THEN GAVE ME A NEW ALT OF FL200 WHICH I REPEATED BACK AS FL200 THEY TELL ME, AND THEY HAVE THE RECORDINGS SO I'M SURE THEY'RE RIGHT. HOWEVER, I ROLLED IN FL220 IN MY ALT ALERT AND CONTINUED TO CLB IN HOLD TO FL125 FROM THEN TO FL220. I FLEW FOR ABOUT 50 MILES AT FL220 WHEN THEY GAVE ME A 40 DEG TURN FOR TFC AND ASKED ME MY ASSIGNED ALT. THEY TOLD ME TO CLB TO FL250 AND I WAS ASSIGNED FL200. THEN ATC SAID THEY HAD LOST RADAR CONTACT WITH A C130 BECAUSE I WAS AT WRONG ALT. CLEARLY MY FAULT. I HEARD 200 SAID 200, BUT BEING UNDER HEAVY WORKLOAD, AND JUST A LITTLE BIT SCARED MY BRAIN HEARD FL220 AND TUNED IT IN MY ALT ALERT. I KNOW YOU WANT TO KNOW HOW ATC CAN HELP. REMEMBER I SCREWED UP. THE ONLY THING THEY COULD DO IS WATCH CLOSELY IN SEVERE WX, MONITOR MORE CLOSELY AND GIVE US IDIOTS ALL THE HELP THEY CAN. THIS IS THE FIRST TIME IN 31 YRS I MISSED AN ALT.

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.