Charter ferry flight encounters turbulence. Altitude deviation.

Attributes
ACN	179240
Time
Date	199105
Day	Tue
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : slc
State Reference	UT
Altitude	msl bound lower : 10500 msl bound upper : 11000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : slc
Operator	general aviation : instructional
Make Model Name	Small Transport
Flight Phase	descent other
Route In Use	arrival other
Flight Plan	IFR
Person 1
Affiliation	Other
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 50 flight time total : 3100 flight time type : 125
ASRS Report	179240
Person 2
Affiliation	Other
Function	flight crew : first officer
Qualification	pilot : instrument pilot : commercial
Events
Anomaly	altitude deviation : excursion from assigned altitude inflight encounter : weather non adherence : clearance other anomaly
Independent Detector	other controllera other flight crewa
Resolutory Action	flight crew : returned to intended course or assigned course flight crew : regained aircraft control
Consequence	Other
Supplementary
Primary Problem	Weather
Air Traffic Incident	Pilot Deviation other

Narrative:

On arrival from san-slc, center requested that we keep our speed up to 250 KIAS. I was PNF and told center that we were unable because of moderate turbulence. We reduced from 220 KTS to 180 KIAS while descending to 11000'. While I was getting INS approach plates out for slc, center asked, 'say altitude.' when I looked up at altimeter, I saw 10700' and climbing, as copilot struggled for control in turbulence. Copilot said deviation from assigned altitude was unavoidable due to control loss. I took controls, advised ATC of turbulence and altitude. Correction immediately followed. I am not convinced altitude deviation was unavoidable, but we had endured moderate turbulence for previous 30 mi. Since I was observing the panel only after recovery was initiated, I cannot attest to aircraft performance capability during the infraction. (I was getting charts out of cabinet.)

Original NASA ASRS Text

Title: CHARTER FERRY FLT ENCOUNTERS TURBULENCE. ALT DEVIATION.

Narrative: ON ARR FROM SAN-SLC, CENTER REQUESTED THAT WE KEEP OUR SPD UP TO 250 KIAS. I WAS PNF AND TOLD CENTER THAT WE WERE UNABLE BECAUSE OF MODERATE TURB. WE REDUCED FROM 220 KTS TO 180 KIAS WHILE DSNDING TO 11000'. WHILE I WAS GETTING INS APCH PLATES OUT FOR SLC, CENTER ASKED, 'SAY ALT.' WHEN I LOOKED UP AT ALTIMETER, I SAW 10700' AND CLBING, AS COPLT STRUGGLED FOR CTL IN TURB. COPLT SAID DEVIATION FROM ASSIGNED ALT WAS UNAVOIDABLE DUE TO CTL LOSS. I TOOK CTLS, ADVISED ATC OF TURB AND ALT. CORRECTION IMMEDIATELY FOLLOWED. I AM NOT CONVINCED ALT DEVIATION WAS UNAVOIDABLE, BUT WE HAD ENDURED MODERATE TURB FOR PREVIOUS 30 MI. SINCE I WAS OBSERVING THE PANEL ONLY AFTER RECOVERY WAS INITIATED, I CANNOT ATTEST TO ACFT PERFORMANCE CAPABILITY DURING THE INFRACTION. (I WAS GETTING CHARTS OUT OF CABINET.)

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.