Embraer Legacy 450/500
Flight Crew Air Transport Pilot (ATP); Flight Crew Flight Instructor; Flight Crew Multiengine; Flight Crew Instrument
Flight Crew Last 90 Days 15; Flight Crew Total 9300; Flight Crew Type 500
Deviation - Altitude Excursion From Assigned Altitude; Deviation - Speed All Types; Inflight Event / Encounter Wake Vortex Encounter; Inflight Event / Encounter Weather / Turbulence
Flight Crew Returned To Clearance
Environment - Non Weather Related; Weather
While in level cruise at FL400 in smooth conditions; we evidently hit a wake or wind gust that caused the aircraft to rapidly accelerate to red line. The autopilot pitched up abruptly and before we could intervene we were off our altitude by about 300 feet.I often leave some room between red line and the target speed in turbulent conditions. In this incident; I was running close to red line since it had been smooth. We reported deviation to ATC but there was no issue.
Embraer 500 Captain reported speed and altitude excursions after encountering either wake turbulence or wind gust in cruise flight at FL400.