Corp pilot has altitude deviation at level off to assigned altitude.

Attributes
ACN	194465
Time
Date	199111
Day	Sun
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : hec
State Reference	CA
Altitude	msl bound lower : 20000 msl bound upper : 21300
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zla
Operator	general aviation : corporate
Make Model Name	Light Transport, Low Wing, 2 Turbojet Eng
Navigation In Use	Other
Flight Phase	climbout : intermediate altitude
Route In Use	enroute : direct
Flight Plan	IFR
Person 1
Affiliation	Other
Function	flight crew : single pilot
Qualification	pilot : atp
Experience	flight time last 90 days : 125 flight time total : 10000 flight time type : 1000
ASRS Report	194465
Person 2
Affiliation	government : faa
Function	controller : radar
Qualification	controller : radar
Events
Anomaly	altitude deviation : overshoot non adherence : clearance
Independent Detector	other controllera other other : unspecified cockpit
Resolutory Action	flight crew : returned to intended course or assigned course
Consequence	Other
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

Picked up IFR clearance from lax center 126.35 at 17500 MSL. Was cleared direct hector VOR to maintain FL200. When called by center, climb had continued to approximately 21300. Center did not indicate if there was a traffic conflict. We fly this light transport with a single pilot waiver. I was the sole occupant of the aircraft, returning to las after a drop off. I was using FMS to go direct to hec. Autoplt was on and altitude preselect was set to assigned altitude FL200. Autoplt trim wheel is very sensitive. If touched even slightly it can cancel altitude preselect mode. While my attention was diverted by some paperwork I must have accidently bumped the autoplt trim wheel. There is no aural warning for this. Only when the entire autoplt is disabled is there a warning. Prevention: be more vigilant, monitor autoplt very carefully especially in climb/descent modes. Install a guard to prevent accidental touching of trim wheel.

Original NASA ASRS Text

Title: CORP PLT HAS ALTDEV AT LEVEL OFF TO ASSIGNED ALT.

Narrative: PICKED UP IFR CLRNC FROM LAX CENTER 126.35 AT 17500 MSL. WAS CLRED DIRECT HECTOR VOR TO MAINTAIN FL200. WHEN CALLED BY CENTER, CLB HAD CONTINUED TO APPROX 21300. CENTER DID NOT INDICATE IF THERE WAS A TFC CONFLICT. WE FLY THIS LTT WITH A SINGLE PLT WAIVER. I WAS THE SOLE OCCUPANT OF THE ACFT, RETURNING TO LAS AFTER A DROP OFF. I WAS USING FMS TO GO DIRECT TO HEC. AUTOPLT WAS ON AND ALT PRESELECT WAS SET TO ASSIGNED ALT FL200. AUTOPLT TRIM WHEEL IS VERY SENSITIVE. IF TOUCHED EVEN SLIGHTLY IT CAN CANCEL ALT PRESELECT MODE. WHILE MY ATTN WAS DIVERTED BY SOME PAPERWORK I MUST HAVE ACCIDENTLY BUMPED THE AUTOPLT TRIM WHEEL. THERE IS NO AURAL WARNING FOR THIS. ONLY WHEN THE ENTIRE AUTOPLT IS DISABLED IS THERE A WARNING. PREVENTION: BE MORE VIGILANT, MONITOR AUTOPLT VERY CAREFULLY ESPECIALLY IN CLB/DSCNT MODES. INSTALL A GUARD TO PREVENT ACCIDENTAL TOUCHING OF TRIM WHEEL.

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.