PA-31 instructor pilot reported an altitude deviation occurred following a wake turbulence encounter...

Attributes
ACN	1678371
Time
Date	201908
Local Time Of Day	0601-1200
Place
Locale Reference	ZJX.ARTCC
State Reference	FL
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Make Model Name	PA-31 Navajo/Chieftan/Mojave/T1040
Operating Under FAR Part	Part 91
Flight Phase	Climb
Route In Use	Direct
Flight Plan	IFR
Aircraft 2
Make Model Name	Any Unknown or Unlisted Aircraft Manufacturer
Flight Phase	Climb
Component
Aircraft Component	Autopilot
Person 1
Function	Pilot Not Flying Instructor
Qualification	Flight Crew Instrument Flight Crew Multiengine Flight Crew Air Transport Pilot (ATP) Flight Crew Flight Instructor
Experience	Flight Crew Last 90 Days 150 Flight Crew Total 12500 Flight Crew Type 150
Events
Anomaly	Deviation - Altitude Excursion From Assigned Altitude Deviation - Procedural Clearance Inflight Event / Encounter Wake Vortex Encounter

Narrative:

During level off at FL250; wake turbulence was encountered at 24;900 feet. The autopilot was engaged and commanded to level off at 25;000 MSL. At 24;900 feet the aircraft encountered its only turbulence for the entire flight and seemed similar to other wake turbulence encounters. During the turbulence encounter it seemed the autopilot was not going to achieve FL250 and it seemed prudent to disconnect the autopilot. It became evident that during the wake turbulence event the autopilot trimmed the aircraft in a nose up condition because when the autopilot was disengaged the aircraft pitched up; and nose down trim was initiated; by the time the aircraft was trimmed; the aircraft ascended 250 feet above FL250. It seemed as though the aircraft was in a nose up trim condition but the servo was holding the nose down until the autopilot was disconnected.

Original NASA ASRS Text

Title: PA-31 Instructor Pilot reported an altitude deviation occurred following a wake turbulence encounter at FL250.

Narrative: During level off at FL250; wake turbulence was encountered at 24;900 feet. The autopilot was engaged and commanded to level off at 25;000 MSL. At 24;900 feet the aircraft encountered its only turbulence for the entire flight and seemed similar to other wake turbulence encounters. During the turbulence encounter it seemed the autopilot was not going to achieve FL250 and it seemed prudent to disconnect the autopilot. It became evident that during the wake turbulence event the autopilot trimmed the aircraft in a nose up condition because when the autopilot was disengaged the aircraft pitched up; and nose down trim was initiated; by the time the aircraft was trimmed; the aircraft ascended 250 feet above FL250. It seemed as though the aircraft was in a nose up trim condition but the servo was holding the nose down until the autopilot was disconnected.

Data retrieved from NASA's ASRS site 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.

PA-31 instructor pilot reported an altitude deviation occurred following a wake turbulence encounter at FL250.