Date: 201912
Local time of day: 1201-1800
Location: LAX.Airport, CA
Flight conditions: Marginal
Aircraft: EMB ERJ 170/175 ER/LR
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Initial Approach
Airspace: Class B LAX
ATC / advisory: TRACON SCT
Second aircraft: A320
Aircraft component: Air Data Computer
Component problem: Failed
Reporter organization: Air Carrier
Reporter function: First Officer; Pilot Not Flying
Reporter qualification: Flight Crew Instrument; Flight Crew Air Transport Pilot (ATP); Flight Crew Multiengine
Anomaly: Aircraft Equipment Problem Less Severe; Inflight Event / Encounter Wake Vortex Encounter
Detector: Person Flight Crew
When detected: In-flight
Result: General None Reported / Taken
Contributing factors: Aircraft; Environment - Non Weather Related; Human Factors; Procedure
Primary problem: Human Factors

Narrative: While flying the IRNMN into LAX; assigned Runway 24R. We were on vectors joining final and cleared the ILS 24R when we encountered wake turbulence from the aircraft we were following. I would consider it a light to moderate wake encounter based on my experience with wake; I've had worse wake but this was enough to draw our attention. We hit the wake shortly after leveling at 2;200 feet on a heading to join the final with 160 kts assigned and AP/AT engaged. As we hit the wake the aircraft banked in both directions; the AT/AP disengaged; and the following amber EICAS messages posted: 'WINDSHEAR FAIL' 'AT FAIL' 'STALL PROT FAIL' 'AOA LIMIT FAIL.' We had flown through the wake and had the runway in sight with the aircraft under control. The Captain and I discussed running the QRH for the associated messages and both agreed that under the current conditions it would be best to continue for a visual landing on Runway 24R. After a normal landing the four amber messages extinguished and the following cyan messages posted: 'ADS PROBE 4 FAIL' 'ADS PROBE 3 FAIL' 'ADS PROBE 2 FAIL' 'ADS PROBE 1 FAIL.' After reporting the wake encounter to Tower they advised we had been 4 miles in trail of an A320. We exited the runway; crossed the parallel Runway 24L and began taxiing. Our gate was occupied and while we were stopped and waiting we began looking up the EICAS messages we had before and after landing. When looking over the 'STALL PROT FAIL' amber message we had after the wake we saw that with this EICAS message we should have adjusted our Vref and required landing distance per the QRH. We debriefed this at the gate and agreed it would be prudent to file a report.When in doubt; slow down and run the QRH. We knew the messages we had after the wake encounter were associated with the wake but we still should have gone around to review the QRH for the messages. We had enough fuel to do this safely and although it would have been inconvenient to go around; in hindsight it would have been the correct thing to do. During the arrival we were initially given descend maintain 2;600 feet on the downwind leg. The Pilot Flying correctly recognized that this would be a long downwind based on the traffic to follow and so elected to descend slowly as to stay above their flight path. As we were turning base; Approach instructed us to descend maintain 2;200 feet and expedite descent and join the localizer 24R. Although we both thought the expedited descent instruction was unusual we complied and doing so put us below the flight path of the aircraft we were following. There may be a reason for the expedited descent instruction that we didn't see; but we both thought it was unnecessary to expedite a 400 feet descent which we knew would put us in the wake of the aircraft we were following. I think following up with the SCT Final Controller who was managing our arrival during the wake encounter and understanding why the 'expedite descent' instruction was given may help shed some light on this event. Had we received a 'descend maintain' instruction while joining final I believe we would have planned our descent to remain above the wake of the aircraft we were following.




Synopsis: EMB-175 FO reported encountering wake turbulence on approach to LAX in trail of an A320 that resulted in multiple system failures.