EMB ERJ 170/175 ER/LR
Flight Crew Multiengine; Flight Crew Instrument; Flight Crew Air Transport Pilot (ATP)
Flight Crew Total 4500; Flight Crew Type 2500
Situational Awareness
Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Published Material / Policy; Inflight Event / Encounter Wake Vortex Encounter
General None Reported / Taken
Environment - Non Weather Related; Human Factors; Procedure
While on approach to Runway 25L in LAX we encountered significant wake turbulence. We intercepted the LOC and GS outside of LIMMA and were already flaps 2. We further configured to flaps 3. Approaching LIMMA we started to get GS oscillations and the First Officer (FO) elected to turn off the autopilot and hand fly. He also called for gear down. Passing LIMMA I switched to Tower frequency. As the aircraft slowed the FO called for flaps 5. Shortly after selecting flaps 5 the aircraft began to buffet and bank 20 degrees to each side. The FO applied power and bank to control the uncommanded bank. By the time we were through the wake turbulence we were about 155kts and flaps 5. The FO called for Vapp and landing check. I set Vapp and checked in with Tower for the landing clearance and advised we had experienced wake turbulence. He advised the proceeding aircraft was an A321 and cleared us to land. During this exchange with the Tower the master caution illuminated and we received caution messages; AOA LIMIT FAIL; WINDSHEAR FAIL and SHAKER ANTICIPATED on the EICAS. Other than the caution messages the aircraft indications were normal and the aircraft was handling normally and we elected to continue with the approach and landing. With only about 300 feet before the stable approach altitude I completed the landing check. At the 1000 feet AFE we were stable and I called '1000 feet instruments normal' and got a 'checks' response from the FO and a normal landing proceeded. On roll out the three caution messages disappeared and ADS PROBE 1;2; & 4 FAIL crew advisory messages appeared on the EICAS. We contacted the Maintenance radio frequency on taxi in and advised them of the messages. Upon parking we called Dispatch and Maintenance Control and advised them of the messages and filled out the logbook. We then looked at the QRH for the 3 caution messages and while the AOA LIMIT FAIL and WINDSHEAR FAIL were just to heighten the crew's awareness to the environment and aircraft condition; The SHAKER ANTICIPATED message required a crew action including changing the landing configuration; which we did not perform. It was at that moment that we realized we should have performed a go around and worked the messages prior to landing. Both the FO and I were very surprised by the wake turbulence since we were at least 5nm behind the A321; in fact the aircraft had already touched down when we hit the wake. There was a slight tailwind which could have contributed to the wake staying in the glide path. We briefly discussed the messages in flight and decided since the plane was stable and we were fully configured it was best to land and look into the messages on the ground. I had a similar situation happen a few years prior but at an altitude of about 4000 feet on a long straight in approach to SEA. In that instance we did do a go around and went through the messages in the QRH however I don't remember the SHAKER ANTICIPATED message and checklist. It's possible that message didn't appear in that instance. But I had in the back of my mind that previously when I had this happen they were just awareness type cautions and that basically be extra vigilant as you configure and land. This previous experience bias and our lower altitude gave me the sense that it was best to just land the aircraft. Task saturation at the time the wake and messages occurred also contributed to not fully thinking trough the possible issues. However; on look back and reading the SHAKER ANTICIPATED checklist and thinking about it more critically we should have gone around; performed the checklist and been flaps full as prescribed by the checklist for landing.
EMB-175 Captain reported system anomalies were annunciated after encountering wake turbulence 5 nm in trail of an A321 on approach to LAX.