GA small aircraft altitude deviation excursion from clearance altitude.

Attributes
ACN	148799
Time
Date	199006
Day	Sun
Local Time Of Day	0601 To 1200
Place
Locale Reference	atc facility : sgd
State Reference	CA
Altitude	msl bound lower : 2900 msl bound upper : 4000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zoa artcc : zob
Operator	general aviation : personal
Make Model Name	Small Aircraft, High Wing, 1 Eng, Fixed Gear
Flight Phase	cruise other descent : approach descent other
Flight Plan	IFR
Person 1
Affiliation	Other
Function	flight crew : single pilot
Qualification	pilot : atp
Experience	flight time last 90 days : 30 flight time total : 1670 flight time type : 900
ASRS Report	148799
Person 2
Affiliation	government : faa
Function	controller : radar
Qualification	controller : radar
Events
Anomaly	altitude deviation : excursion from assigned altitude non adherence : clearance
Independent Detector	other controllera
Resolutory Action	flight crew : returned to intended course or assigned course other
Consequence	Other
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

The problem arose due to my misunderstanding of a clearance. I was flying from truckee, ca, to napa, ca, where sky conditions were reported to be 800' overcast. I decided to request an IFR clearance just northeast of sacramento and was cleared direct to napa. The final controller was ZOA who initially gave me a vector and told me to maintain 5000'. I was then cleared to 4000' and direct to scaggs island VOR. Next I was told to go outbnd on the 230 degree right of the VOR and I understood that I was cleared for the approach. I might add I was not getting reception on either communication radio, and should have verified that I had understood 'cleared for the approach.' upon reaching the VOR I started my descent to 2900' which is the altitude for the outbnd leg of the procedure turn. Upon reaching 2900' I was asked if I was at 4000' and replied that I was at 2900' and was instructed to climb and maintain 4000'. It was at that time I knew I had misunderstood the clearance. The only contributing factor as to the misunderstanding of the clearance was that particular frequency was unclr on both communication radios. The fact that I didn't read the clearance back and particularly that I didn't state 'cleared for the approach' was the main contributing factor to the miscom. As far as prevention measure to preclude this type of problem in the future I can strive to be more diligent in always reading back my clearance.

Original NASA ASRS Text

Title: GA SMA ALT DEVIATION EXCURSION FROM CLRNC ALT.

Narrative: THE PROB AROSE DUE TO MY MISUNDERSTANDING OF A CLRNC. I WAS FLYING FROM TRUCKEE, CA, TO NAPA, CA, WHERE SKY CONDITIONS WERE RPTED TO BE 800' OVCST. I DECIDED TO REQUEST AN IFR CLRNC JUST NE OF SACRAMENTO AND WAS CLRED DIRECT TO NAPA. THE FINAL CTLR WAS ZOA WHO INITIALLY GAVE ME A VECTOR AND TOLD ME TO MAINTAIN 5000'. I WAS THEN CLRED TO 4000' AND DIRECT TO SCAGGS ISLAND VOR. NEXT I WAS TOLD TO GO OUTBND ON THE 230 DEG R OF THE VOR AND I UNDERSTOOD THAT I WAS CLRED FOR THE APCH. I MIGHT ADD I WAS NOT GETTING RECEPTION ON EITHER COM RADIO, AND SHOULD HAVE VERIFIED THAT I HAD UNDERSTOOD 'CLRED FOR THE APCH.' UPON REACHING THE VOR I STARTED MY DSNT TO 2900' WHICH IS THE ALT FOR THE OUTBND LEG OF THE PROC TURN. UPON REACHING 2900' I WAS ASKED IF I WAS AT 4000' AND REPLIED THAT I WAS AT 2900' AND WAS INSTRUCTED TO CLB AND MAINTAIN 4000'. IT WAS AT THAT TIME I KNEW I HAD MISUNDERSTOOD THE CLRNC. THE ONLY CONTRIBUTING FACTOR AS TO THE MISUNDERSTANDING OF THE CLRNC WAS THAT PARTICULAR FREQ WAS UNCLR ON BOTH COM RADIOS. THE FACT THAT I DIDN'T READ THE CLRNC BACK AND PARTICULARLY THAT I DIDN'T STATE 'CLRED FOR THE APCH' WAS THE MAIN CONTRIBUTING FACTOR TO THE MISCOM. AS FAR AS PREVENTION MEASURE TO PRECLUDE THIS TYPE OF PROB IN THE FUTURE I CAN STRIVE TO BE MORE DILIGENT IN ALWAYS READING BACK MY CLRNC.

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.