WW24 experiences altitude deviation when the altitude capture function of the autoplt is disengaged.

Attributes
ACN	697408
Time
Date	200605
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : zdc.artcc
State Reference	VA
Altitude	msl single value : 32000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zdc.artcc
Operator	general aviation : corporate
Make Model Name	IAI1124/1124A/Westwind
Operating Under FAR Part	Part 91
Navigation In Use	Other
Flight Phase	climbout : intermediate altitude
Flight Plan	IFR
Person 1
Affiliation	company : corporate
Function	flight crew : captain oversight : pic
Qualification	pilot : commercial pilot : multi engine pilot : instrument pilot : atp
Experience	flight time last 90 days : 25 flight time total : 9000 flight time type : 500
ASRS Report	697408
Person 2
Affiliation	company : corporate
Function	flight crew : first officer
Qualification	pilot : multi engine pilot : instrument pilot : commercial
Experience	flight time last 90 days : 100 flight time total : 1300 flight time type : 50
ASRS Report	697586
Events
Anomaly	aircraft equipment problem : less severe altitude deviation : overshoot non adherence : clearance
Independent Detector	other flight crewa other flight crewb
Resolutory Action	controller : issued alert flight crew : returned to assigned altitude
Consequence	other
Supplementary
Problem Areas	Aircraft Flight Crew Human Performance
Primary Problem	Aircraft
Air Traffic Incident	Pilot Deviation

Narrative:

We were in the climb phase of the flight and the aircraft was being flown by the autoplt. ZDC cleared us to climb to FL320. In the cockpit; FL320 was set in the altitude select window. Altitude select (capture) was selected on the flight director. Upon reaching FL320; the autoplt did not capture and hold the altitude selected. We (crew) noticed and started corrective action at FL324. By the time climb was stopped and a descent was started the aircraft had reached about FL325. We (crew) descended the aircraft back to FL320. Around FL323 in the descent the controller asked us our altitude. We replied we were leveling at FL320. Upon reaching FL320 the controller again asked us our altitude. We (crew) replied level at FL320. Shortly afterwards the controller cleared us to our cruise altitude of FL360. This aircraft has recently gone through an exterior and interior refurbishment; dec/05. In the cockpit the pilot seats were completely overhauled with new foam inside and leather and sheepskin exterior. The flight director control module is on the left side of the center pedestal. The pilot eat overhangs that side of the pedestal directly over the control module. I believe that in moving about in the seat the overhang portion of the seat cushion deselected the altitude select mode. At this time we are changing the pilot seats design and repositioning the flight director control module in the center pedestal.

Original NASA ASRS Text

Title: WW24 EXPERIENCES ALTDEV WHEN THE ALT CAPTURE FUNCTION OF THE AUTOPLT IS DISENGAGED.

Narrative: WE WERE IN THE CLB PHASE OF THE FLT AND THE ACFT WAS BEING FLOWN BY THE AUTOPLT. ZDC CLRED US TO CLB TO FL320. IN THE COCKPIT; FL320 WAS SET IN THE ALT SELECT WINDOW. ALT SELECT (CAPTURE) WAS SELECTED ON THE FLT DIRECTOR. UPON REACHING FL320; THE AUTOPLT DID NOT CAPTURE AND HOLD THE ALT SELECTED. WE (CREW) NOTICED AND STARTED CORRECTIVE ACTION AT FL324. BY THE TIME CLB WAS STOPPED AND A DSCNT WAS STARTED THE ACFT HAD REACHED ABOUT FL325. WE (CREW) DSNDED THE ACFT BACK TO FL320. AROUND FL323 IN THE DSCNT THE CTLR ASKED US OUR ALT. WE REPLIED WE WERE LEVELING AT FL320. UPON REACHING FL320 THE CTLR AGAIN ASKED US OUR ALT. WE (CREW) REPLIED LEVEL AT FL320. SHORTLY AFTERWARDS THE CTLR CLRED US TO OUR CRUISE ALT OF FL360. THIS ACFT HAS RECENTLY GONE THROUGH AN EXTERIOR AND INTERIOR REFURBISHMENT; DEC/05. IN THE COCKPIT THE PLT SEATS WERE COMPLETELY OVERHAULED WITH NEW FOAM INSIDE AND LEATHER AND SHEEPSKIN EXTERIOR. THE FLT DIRECTOR CTL MODULE IS ON THE L SIDE OF THE CTR PEDESTAL. THE PLT EAT OVERHANGS THAT SIDE OF THE PEDESTAL DIRECTLY OVER THE CTL MODULE. I BELIEVE THAT IN MOVING ABOUT IN THE SEAT THE OVERHANG PORTION OF THE SEAT CUSHION DESELECTED THE ALT SELECT MODE. AT THIS TIME WE ARE CHANGING THE PLT SEATS DESIGN AND REPOSITIONING THE FLT DIRECTOR CTL MODULE IN THE CTR PEDESTAL.

Data retrieved from NASA's ASRS site as of January 2009 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.