Flight crew of C500 experience inadvertent autoplt disconnect. Momentary loss of control results.

Attributes
ACN	609237
Time
Date	200402
Day	Tue
Local Time Of Day	0601 To 1200
Place
Locale Reference	navaid : act.vortac
State Reference	TX
Altitude	msl single value : 16000
Environment
Flight Conditions	IMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zhu.artcc
Operator	general aviation : corporate
Make Model Name	Citation I
Operating Under FAR Part	Part 91
Flight Phase	cruise : level
Route In Use	enroute : direct
Flight Plan	IFR
Person 1
Affiliation	company : corporate
Function	flight crew : first officer
Qualification	pilot : atp
Experience	flight time last 90 days : 50 flight time total : 15000 flight time type : 6000
ASRS Report	609237
Person 2
Affiliation	company : corporate
Function	flight crew : captain oversight : pic
Events
Anomaly	aircraft equipment problem : critical other anomaly
Independent Detector	other flight crewa
Resolutory Action	flight crew : overcame equipment problem flight crew : regained aircraft control
Consequence	other
Supplementary
Problem Areas	Aircraft Flight Crew Human Performance
Primary Problem	Aircraft

Narrative:

We were on a routine IFR flight from hou to cnw. We were in solid IFR conditions at 16000 ft. As the PNF in the right seat, I had just turned in the ASOS and was in the process of copying it when we received an instruction from ZHU to go direct to destination. Although I have more than 6000 hours in CE550 and 560 aircraft, we were in an older CE500 which I have flown several times. In reconstructing what took place, it appears that I inadvertently disconnected the autoplt while attempting to answer ATC without either pilot being aware of it. The PF was looking at the approach plate and I was copying the ASOS information when the PF realized that the airplane was rolling into a steep bank. He immediately initiated corrective action, then contacted ATC and informed them that we had had an autoplt problem. The flight was continued without further incident. There was no traffic conflict. The main problem is the location of the autoplt disconnect switch on this airplane, coupled with the lack of an 'autoplt disconnected' warning. The switch is above and behind the radio transmit switch on the right side of the copilot's yoke and it is easy to confuse the two. Although this in itself is not a problem, that there either is no warning to the pilot that the autoplt has been disconnected, or that it was not working properly was the major contributor to this potentially serious incident. The roll apparently occurred because the airplane was in a turn when the autoplt disconnected. That both pilots were performing other tasks at the time was also a factor, although this particular airplane is certified for single-pilot operation. Callback conversation with reporter revealed the following information: a phone discussion with the reporter revealed the following. This older aircraft apparently has had a variety of after market modifications including the autoplt. The reporter is unsure as to the confign as compared to new. In addition, he noted that a logbook write-up regarding the incident resulted in the replacement of the 'autoplt controller' so he is now uncertain whether the actual incident resulted from an inadvertent disconnect or an autoplt malfunction.

Original NASA ASRS Text

Title: FLT CREW OF C500 EXPERIENCE INADVERTENT AUTOPLT DISCONNECT. MOMENTARY LOSS OF CTL RESULTS.

Narrative: WE WERE ON A ROUTINE IFR FLT FROM HOU TO CNW. WE WERE IN SOLID IFR CONDITIONS AT 16000 FT. AS THE PNF IN THE R SEAT, I HAD JUST TURNED IN THE ASOS AND WAS IN THE PROCESS OF COPYING IT WHEN WE RECEIVED AN INSTRUCTION FROM ZHU TO GO DIRECT TO DEST. ALTHOUGH I HAVE MORE THAN 6000 HRS IN CE550 AND 560 ACFT, WE WERE IN AN OLDER CE500 WHICH I HAVE FLOWN SEVERAL TIMES. IN RECONSTRUCTING WHAT TOOK PLACE, IT APPEARS THAT I INADVERTENTLY DISCONNECTED THE AUTOPLT WHILE ATTEMPTING TO ANSWER ATC WITHOUT EITHER PLT BEING AWARE OF IT. THE PF WAS LOOKING AT THE APCH PLATE AND I WAS COPYING THE ASOS INFO WHEN THE PF REALIZED THAT THE AIRPLANE WAS ROLLING INTO A STEEP BANK. HE IMMEDIATELY INITIATED CORRECTIVE ACTION, THEN CONTACTED ATC AND INFORMED THEM THAT WE HAD HAD AN AUTOPLT PROB. THE FLT WAS CONTINUED WITHOUT FURTHER INCIDENT. THERE WAS NO TFC CONFLICT. THE MAIN PROB IS THE LOCATION OF THE AUTOPLT DISCONNECT SWITCH ON THIS AIRPLANE, COUPLED WITH THE LACK OF AN 'AUTOPLT DISCONNECTED' WARNING. THE SWITCH IS ABOVE AND BEHIND THE RADIO XMIT SWITCH ON THE R SIDE OF THE COPLT'S YOKE AND IT IS EASY TO CONFUSE THE TWO. ALTHOUGH THIS IN ITSELF IS NOT A PROB, THAT THERE EITHER IS NO WARNING TO THE PLT THAT THE AUTOPLT HAS BEEN DISCONNECTED, OR THAT IT WAS NOT WORKING PROPERLY WAS THE MAJOR CONTRIBUTOR TO THIS POTENTIALLY SERIOUS INCIDENT. THE ROLL APPARENTLY OCCURRED BECAUSE THE AIRPLANE WAS IN A TURN WHEN THE AUTOPLT DISCONNECTED. THAT BOTH PLTS WERE PERFORMING OTHER TASKS AT THE TIME WAS ALSO A FACTOR, ALTHOUGH THIS PARTICULAR AIRPLANE IS CERTIFIED FOR SINGLE-PLT OP. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: A PHONE DISCUSSION WITH THE RPTR REVEALED THE FOLLOWING. THIS OLDER ACFT APPARENTLY HAS HAD A VARIETY OF AFTER MARKET MODIFICATIONS INCLUDING THE AUTOPLT. THE RPTR IS UNSURE AS TO THE CONFIGN AS COMPARED TO NEW. IN ADDITION, HE NOTED THAT A LOGBOOK WRITE-UP REGARDING THE INCIDENT RESULTED IN THE REPLACEMENT OF THE 'AUTOPLT CTLR' SO HE IS NOW UNCERTAIN WHETHER THE ACTUAL INCIDENT RESULTED FROM AN INADVERTENT DISCONNECT OR AN AUTOPLT MALFUNCTION.

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.