Date: 202108
Local time of day: 0601-1200
Location: OAK.Airport, CA
Flight conditions: IMC
Weather elements / visibility: Turbulence; 10
Light: Daylight
Aircraft: Light Transport; Low Wing; 2 Turbojet Eng
Operator: Corporate
Operating under: Part 91
Flight plan: IFR
Mission: Passenger
Flight phase: Initial Climb
Airspace: Class C OAK
ATC / advisory: Tower OAK
Second aircraft: A321
Reporter organization: Corporate
Reporter function: Single Pilot; Pilot Flying
Reporter qualification: Flight Crew Instrument; Flight Crew Air Transport Pilot (ATP); Flight Crew Multiengine; Other Commercial Rotorcraft
Human factors: Situational Awareness
Anomaly: ATC Issue All Types; Deviation - Altitude Crossing Restriction Not Met; Deviation - Altitude Overshoot; Deviation / Discrepancy - Procedural Clearance; Inflight Event / Encounter Weather / Turbulence; Inflight Event / Encounter Loss Of Aircraft Control
Detector: Person Flight Crew
When detected: In-flight
Result: Air Traffic Control Issued New Clearance; Flight Crew Became Reoriented; Flight Crew Regained Aircraft Control
Contributing factors: Environment - Non Weather Related; Procedure; Human Factors
Primary problem: Ambiguous

Narrative: I was preparing to conduct a Part 91 IFR flight from OAK. My clearance was Runway 30; CNDEL4 Departure EBAYE AVE EHF and to climb via the SID. Upon reaching Runway 30; I was holding on Taxiway Whiskey behind an A321. After the A321 started its takeoff roll; I watched and noted the point at which it lifted off. At the same time I was instructed to 'Line up and wait'. After what I thought to be a very short time; less than a minute from lining up; I was cleared for takeoff with a caution warning for wake turbulence. Upon reaching Vr and prior to the A321's rotation point; I rotated and began my initial climb. I had 1900 ft set in my Altitude Select as I was to cross LECHE at or below 2;000 ft; on a heading of 296 degrees which I had set on my DG's bug. At approximately 600 ft I engaged the autopilot. Almost immediately after entering IMC conditions at approximately 700 ft; I entered very heavy turbulence. I disengaged the autopilot at which time the plane entered an un-commanded roll to the left. I tried to recover but the plane was shaking very violently and kept wanting to violently roll to the left between 35 to 40 degrees of bank angle. The plane was really not responding to my control inputs; at least not according to my flight director. I really had no idea what was happening at the time and was very startled. At first I thought I might have a control surface failure. Then I realized that I must have flown through and was now within the A321 wake vortices.  I had a very hard time controlling the aircraft. I was worried if I could not keep the plane out of an upset condition; I was way too low for a successful recovery. I could also hear that my passengers were very uncomfortable.  At this point; I just reverted to flying 101; aviate; navigate; communicate. I hit my Takeoff/Go-Around switch which also disengaged the yaw damper and put my command bars at a 10 degree nose up and wings level command. At that point I was just trying to concentrate on putting the airplane symbol into the command bars and just keep wings level. All the while keeping my eye on my TCAS for any aircraft near or around me. (I never got one traffic warning or alert during this whole event). At some point a controller came on and began giving me vectors. I had not yet talked to the controllers or advised them of my situation as I had not gotten to the communicate" part yet. I was also told to squawk my assigned transponder code. I had selected the code prior to taxi but failed to enter it. At approximately 1800 feet I began to try to level the airplane but was having a hard time doing so. I did not want to push down too hard and put the plane in an excessive negative G situation. I think I passed the max altitude by 150 ft but; immediately corrected to 1800 ft. When I was switched to the next frequency I was still attempting to regain my composure and just follow the controller's instructions. The turbulence completely disappeared out of about 2;500 feet. Out of 10;000 feet; I cancelled IFR and continued VFR with flight following. The rest of the flight was uneventful until I was advised by NorCal of a possible pilot deviation and was given a phone number to call upon landing.  How the problem arose: Inadvertent flight into wake turbulence. Contributing Factors: Too early release behind a heavy aircraft. IMC Conditions. Failure to ask for a possible short delay to my takeoff clearance due to wake turbulence. How it was discovered: Difficulty in controlling the aircraft due to violent and uncommanded aircraft attitudes. Corrective Actions: Maintain wings level attitude. Follow ATC Instructions. Perceptions: Fear of possible loss of control in IMC conditions and very low altitude for recovery. Judgements: Just fly the plane. Aviate; Navigate; Communicate. Decisions: Do whatever it takes to keep wings level attitude. Factors affecting the quality of human performance: The startle effect. Actions or Inactions: Have hand written; 'Enter Squawk Code';in my Pre-Taxi Checklist. Just did what I could to fly my plane out of an inadvertent but bad situation."




Synopsis: Light Transport Corporate Pilot reported encountering wake turbulence departing OAK in trail of an A321.