Aircraft flew into severe turbulence and descended 600 ft below cleared altitude.

Attributes
ACN	274300
Time
Date	199406
Day	Mon
Local Time Of Day	1801 To 2400
Place
Locale Reference	atc facility : avp
State Reference	PA
Altitude	msl bound lower : 8400 msl bound upper : 10000
Environment
Flight Conditions	IMC
Light	Daylight
Aircraft 1
Operator	general aviation : personal
Make Model Name	Commercial Fixed Wing
Operating Under FAR Part	Part 91
Flight Phase	cruise other
Route In Use	enroute airway : zny
Flight Plan	IFR
Person 1
Affiliation	Other
Function	flight crew : single pilot
Qualification	pilot : atp
Experience	flight time last 90 days : 60 flight time total : 2100 flight time type : 850
ASRS Report	274300
Person 2
Affiliation	government : faa
Function	controller : radar
Qualification	controller : radar
Events
Anomaly	altitude deviation : excursion from assigned altitude inflight encounter : weather non adherence : clearance other anomaly other spatial deviation
Independent Detector	other controllera other other : unspecified cockpit
Resolutory Action	controller : issued new clearance flight crew : regained aircraft control
Consequence	Other
Supplementary
Primary Problem	Weather
Air Traffic Incident	Pilot Deviation

Narrative:

En route at 9000 ft with both radar and stormscope operative. The radar (black and white) was not showing any contours and stormscope was showing WX on either side of course about 20 mi out. I was feeling pretty good that we would not have to divert around thunderstorms when we entered moderate rain. The ride was smooth when suddenly lightning developed and the stormscope lit up like a christmas tree. At this point, we had been in the rain for about 1 min so I decided the best course of action was to make a 180 degree turn. I informed ATC of my intentions and was cleared to 10000 ft. As I entered the turn, I encountered severe turbulence. Although the aircraft was set for climb, I lost 600 ft of altitude. ATC questioned altitude loss as I again started my climb to 10000 ft and I explained to him that I was in a thunderstorm and could not maintain altitude. Entire encounter was over in about 2 mins. I assume I entered a developing thunderstorm and that is why it did not show up on the stormscope. Although I took what I thought to be the best course of action, the 180 degree turn, the encounter with turbulence was unavoidable and therefore the loss of altitude was unavoidable. If I was I the same situation again, I would do the same thing.

Original NASA ASRS Text

Title: ACFT FLEW INTO SEVERE TURB AND DSNDED 600 FT BELOW CLRED ALT.

Narrative: ENRTE AT 9000 FT WITH BOTH RADAR AND STORMSCOPE OPERATIVE. THE RADAR (BLACK AND WHITE) WAS NOT SHOWING ANY CONTOURS AND STORMSCOPE WAS SHOWING WX ON EITHER SIDE OF COURSE ABOUT 20 MI OUT. I WAS FEELING PRETTY GOOD THAT WE WOULD NOT HAVE TO DIVERT AROUND TSTMS WHEN WE ENTERED MODERATE RAIN. THE RIDE WAS SMOOTH WHEN SUDDENLY LIGHTNING DEVELOPED AND THE STORMSCOPE LIT UP LIKE A CHRISTMAS TREE. AT THIS POINT, WE HAD BEEN IN THE RAIN FOR ABOUT 1 MIN SO I DECIDED THE BEST COURSE OF ACTION WAS TO MAKE A 180 DEG TURN. I INFORMED ATC OF MY INTENTIONS AND WAS CLRED TO 10000 FT. AS I ENTERED THE TURN, I ENCOUNTERED SEVERE TURB. ALTHOUGH THE ACFT WAS SET FOR CLB, I LOST 600 FT OF ALT. ATC QUESTIONED ALT LOSS AS I AGAIN STARTED MY CLB TO 10000 FT AND I EXPLAINED TO HIM THAT I WAS IN A TSTM AND COULD NOT MAINTAIN ALT. ENTIRE ENCOUNTER WAS OVER IN ABOUT 2 MINS. I ASSUME I ENTERED A DEVELOPING TSTM AND THAT IS WHY IT DID NOT SHOW UP ON THE STORMSCOPE. ALTHOUGH I TOOK WHAT I THOUGHT TO BE THE BEST COURSE OF ACTION, THE 180 DEG TURN, THE ENCOUNTER WITH TURB WAS UNAVOIDABLE AND THEREFORE THE LOSS OF ALT WAS UNAVOIDABLE. IF I WAS I THE SAME SIT AGAIN, I WOULD DO THE SAME THING.

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.