Date: 201810
Local time of day: 1801-2400
Location: ZNY.ARTCC, NY
Flight conditions: VMC
Aircraft: B767 Undifferentiated or Other Model
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Climb
ATC / advisory: Center ZNY
Second aircraft: Any Unknown or Unlisted Aircraft Manufacturer
Reporter organization: Air Carrier
Reporter function: First Officer; Pilot Not Flying
Reporter qualification: Flight Crew Multiengine; Flight Crew Instrument; Flight Crew Air Transport Pilot (ATP)
Second reporter function: Captain; Pilot Flying
Anomaly: Aircraft Equipment Problem Less Severe; Flight Deck / Cabin / Aircraft Event Illness / Injury; Inflight Event / Encounter Wake Vortex Encounter; Inflight Event / Encounter Weather / Turbulence; Inflight Event / Encounter Bird / Animal
Detector: Person Flight Crew
When detected: In-flight
Result: Flight Crew Returned To Departure Airport; Flight Crew Landed As Precaution; General Maintenance Action; General Physical Injury / Incapacitation
Contributing factors: Environment - Non Weather Related
Primary problem: Environment - Non Weather Related

Narrative: During climb out passing approximately 25;000 feet we encountered a brief moment of severe turbulence somewhere between 25;000-26;000 feet. Possibly wake turbulence from another aircraft. The turbulence started and ended after 2-3 seconds. There was no time to command 'flight attendants be seated immediately' as the event was over before I could even pick up the cabin interphone. We checked in with the cabin and initially were told one of the flight attendants in the aft galley had sustained a wrist injury. The flight attendants in the mid and aft galleys also indicated a loud bang was heard and that the tail shook violently with the turbulence encounter. We continued the climb to 31;000 feet. At level off we evaluated the EICAS; STAT; F/CTRL and GEAR pages on the MFDs. Nothing abnormal was noted. Additionally; we could not make contact with New York Oceanic on the L HF radio. Upon successful contact with New York Oceanic on the R HF radio we could not receive a successful SELCAL check on either radio. We contacted dispatch via SATCOM and conducted a conference call with [Maintenance] and the [Chief Pilot]. We came to a collaborative decision after describing the incident that in the interest of safety we should air return to [departure airport] to have the aircraft inspected. I called back to have the relief pilot woken up. He returned to the cockpit and before making the final call to turn around we consulted one last time with all three of us on the flight deck. He agreed with all of the above. We received a clearance from New York Oceanic and initiated the return to [departure airport]. We coordinated with Dispatch and New York Oceanic to dump the remaining fuel in our center tank to be under max landing weight. During the descent we experience a partial failure of the L autopilot. We lost pitch mode of the L autopilot and switched to the R autopilot without further issue. On downwind approach at 4000 feet we struck a bird with the radome. Configuration and approach was normal. Touchdown was normal. No other anomalies were felt during the approach and landing.


Second narrative: [Report narrative contained no additional information.]


Synopsis: B767 flight crew reported returning to departure airport after experiencing multiple system anomalies following a severe wake turbulence encounter climbing through FL250.