Aircraft encounters turbulence, pilot unable to maintain altitude.

Attributes
ACN	545542
Time
Date	200204
Day	Sun
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : zab.artcc
State Reference	NM
Altitude	msl single value : 11000
Environment
Flight Conditions	VMC
Weather Elements	Turbulence
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zab.artcc
Operator	general aviation : personal
Make Model Name	Turbo-Viking
Operating Under FAR Part	Part 91
Flight Phase	cruise : level
Flight Plan	IFR
Aircraft 2
Controlling Facilities	artcc : zab.artcc
Operator	general aviation : personal
Make Model Name	PA-34-200 Seneca I
Flight Phase	cruise : level
Flight Plan	IFR
Person 1
Affiliation	other
Function	flight crew : single pilot
Qualification	pilot : multi engine pilot : instrument
Experience	flight time last 90 days : 10 flight time total : 494 flight time type : 288
ASRS Report	545542
Person 2
Affiliation	government : faa
Function	controller : radar
Events
Anomaly	altitude deviation : excursion from assigned altitude inflight encounter : turbulence non adherence : far
Independent Detector	other controllera
Resolutory Action	controller : issued advisory flight crew : returned to assigned altitude
Consequence	faa : reviewed incident with flight crew
Supplementary
Problem Areas	Flight Crew Human Performance Environmental Factor Weather
Primary Problem	Weather
Air Traffic Incident	Pilot Deviation

Narrative:

Flying at 10000 ft from lubbock to taos via santa flight engineer the ride was smooth outside of lubbock. As we neared santa flight engineer the ride became very turbulent. I was told to climb to 11000 ft. The ride at 11000 ft was more turbulent and altitude was very hard to hold. The autoplt on the aircraft was unable to hold the altitude and the 1000 ft within 5 mi of the 2 IFR aircraft was broken. The controller communicated this to me. Separation was never compromised as we, the 3 on board, had visual identify of the seneca. We watched it as its wings violently rocked up and down as it flew a 30-45 degree crab to its ground path. At one point I made a comment that it was rough for us and the seneca looked like it was also experiencing some turbulence. The pilot of the seneca said 'that is an understatement'.

Original NASA ASRS Text

Title: ACFT ENCOUNTERS TURB, PLT UNABLE TO MAINTAIN ALT.

Narrative: FLYING AT 10000 FT FROM LUBBOCK TO TAOS VIA SANTA FE THE RIDE WAS SMOOTH OUTSIDE OF LUBBOCK. AS WE NEARED SANTA FE THE RIDE BECAME VERY TURBULENT. I WAS TOLD TO CLB TO 11000 FT. THE RIDE AT 11000 FT WAS MORE TURBULENT AND ALT WAS VERY HARD TO HOLD. THE AUTOPLT ON THE ACFT WAS UNABLE TO HOLD THE ALT AND THE 1000 FT WITHIN 5 MI OF THE 2 IFR ACFT WAS BROKEN. THE CTLR COMMUNICATED THIS TO ME. SEPARATION WAS NEVER COMPROMISED AS WE, THE 3 ON BOARD, HAD VISUAL IDENT OF THE SENECA. WE WATCHED IT AS ITS WINGS VIOLENTLY ROCKED UP AND DOWN AS IT FLEW A 30-45 DEG CRAB TO ITS GROUND PATH. AT ONE POINT I MADE A COMMENT THAT IT WAS ROUGH FOR US AND THE SENECA LOOKED LIKE IT WAS ALSO EXPERIENCING SOME TURB. THE PLT OF THE SENECA SAID 'THAT IS AN UNDERSTATEMENT'.

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.