A P180 first officer reported accidentally striking the pitch trim switch with the efb; disconnectin...

Narrative:

I was the non-flying pilot on the flight. After a scheduled crew swap; this was our first leg as a crew. It was also the last leg of a scheduled 14-hour duty day for me. During the flight we experienced an inadvertent disengagement of the autopilot and a momentary departure from our cruise altitude of FL340. The weather at the time of the incident was night VMC with some scattered thunderstorms to the west of our route. We were enjoying a mostly smooth flight and our passengers seemed to be content. About half way into the flight at FL340 we noticed that the thunderstorms to our west had grown significantly. We discussed whether our current routing would be out of the weather; along with a possible climb to FL360 for fuel management purposes. I had just finished working with the efb (electronic flight bag) and had turned to observe the numerous lightning strikes that were occurring to our west. While observing the lightning out the right side of the aircraft I turned back to check my instrument panel and noticed the aircraft was in a left descending turn (20-25 degree left bank and 3-4 degree nose down pitch attitude) and the altimeter read about 250 ft low. I also noticed that the captain (flying pilot) was looking down at our FMS updating the fuel numbers. I quickly looked at his eadi and then the autopilot panel and determined that the autopilot had disengaged. I immediately brought this to his attention and he then initiated an aggressive recovery to our assigned heading and altitude. Once we were stabilized and established back on course; he had me reengage the autopilot. ATC did query us about our change in heading; but after my response that we were correcting they did not require any further explanation or make any reference to an altitude deviation. After the incident the captain and I discussed what had happened and we concluded that I had inadvertently hit the pitch trim switch (the piaggio is equipped with an electronic barrel type trim switch) with the efb or my elbow as I turned around to observe the lighting out my window. We did not hear any aural tone that would have indicated the autopilot disengaged and did not hear the pitch trim clacker; which could have also given us an indication.

Original NASA ASRS Text

Title: A P180 First Officer reported accidentally striking the pitch trim switch with the EFB; disconnecting the autopilot and initiating a heading and altitude deviation.

Narrative: I was the non-flying pilot on the flight. After a scheduled crew swap; this was our first leg as a crew. It was also the last leg of a scheduled 14-hour duty day for me. During the flight we experienced an inadvertent disengagement of the autopilot and a momentary departure from our cruise altitude of FL340. The weather at the time of the incident was night VMC with some scattered thunderstorms to the west of our route. We were enjoying a mostly smooth flight and our passengers seemed to be content. About half way into the flight at FL340 we noticed that the thunderstorms to our west had grown significantly. We discussed whether our current routing would be out of the weather; along with a possible climb to FL360 for fuel management purposes. I had just finished working with the EFB (Electronic Flight Bag) and had turned to observe the numerous lightning strikes that were occurring to our west. While observing the lightning out the right side of the aircraft I turned back to check my instrument panel and noticed the aircraft was in a left descending turn (20-25 degree left bank and 3-4 degree nose down pitch attitude) and the altimeter read about 250 FT low. I also noticed that the Captain (Flying Pilot) was looking down at our FMS updating the fuel numbers. I quickly looked at his EADI and then the autopilot panel and determined that the autopilot had disengaged. I immediately brought this to his attention and he then initiated an aggressive recovery to our assigned heading and altitude. Once we were stabilized and established back on course; he had me reengage the autopilot. ATC did query us about our change in heading; but after my response that we were correcting they did not require any further explanation or make any reference to an altitude deviation. After the incident the Captain and I discussed what had happened and we concluded that I had inadvertently hit the pitch trim switch (the Piaggio is equipped with an Electronic Barrel Type Trim switch) with the EFB or my elbow as I turned around to observe the lighting out my window. We did not hear any aural tone that would have indicated the autopilot disengaged and did not hear the pitch trim clacker; which could have also given us an indication.

Data retrieved from NASA's ASRS site as of April 2012 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.

Attributes
ACN	849729
Time
Date	200908
Local Time Of Day	0601-1200
Place
Locale Reference	RZC.VORTAC
State Reference	AR
Environment
Flight Conditions	VMC
Light	Night
Aircraft 1
Make Model Name	P180 Avanti
Operating Under FAR Part	Part 91
Flight Phase	Cruise
Route In Use	Direct
Flight Plan	IFR
Person 1
Function	Pilot Not Flying First Officer
Qualification	Flight Crew Air Transport Pilot (ATP) Flight Crew Multiengine
Experience	Flight Crew Last 90 Days 180 Flight Crew Total 4800 Flight Crew Type 800
Events
Anomaly	Deviation - Altitude Excursion From Assigned Altitude Deviation - Procedural Clearance Deviation - Track / Heading All Types

A P180 first officer reported accidentally striking the pitch trim switch with the efb; disconnecting the autopilot and initiating a heading and altitude deviation.