B737-900 flight crew reported encountering wake turbulence on approach into SEA 3 miles in trail of an A320.
Synopsis
B737-900 flight crew reported encountering wake turbulence on approach into SEA 3 miles in trail of an A320.
Narrative
We were tracking the localizer to 16R. ATC cleared us down to 3000 ft. The FO (First Officer) was the Pilot Flying; and I was Pilot Monitoring. The FO was doing a shallow descent about 500 FPM to maintain at or near glide slope. ATC said he needed us to increase to 'standard rate descent'. The FO increased to 1000 FPM. We were expecting ATC to clear us for the approach (it was visual conditions and we had reported the airport in sight); but he instead cleared us to 2100 ft. and at 2100 ft.; cleared for the approach. We assumed he still needed the higher rate of descent; so we continued. Just before FINKA; the FAF; we experienced wake turbulence and approximately a 40 degree left bank with an aural warning. The FO did a great job recovering and recovered by FINKA. At FINKA; Approach switched us over to Tower; and I informed him we had some significant wake turbulence. He replied; 'from who' in a somewhat condescending tone. I said 'from the preceding aircraft'. He said; 'that would be an A320 3 miles ahead' again in a somewhat condescending tone. I was not too appreciative of the way he spoke to us like an A320 wouldn't produce enough wake to roll us; but it did. We were merely reporting it.I believe we should clarify with ATC why they need us below preceding aircraft on approach even if it is a narrow body and clarify the clearance. Also; ATC should be made aware that it can cause wake turbulence events. We experienced it.
Second reporter narrative
We were on vectors to intercept the localizer for ILS 16R. After being cleared down to 3000 ft.; ATC reminded us to maintain a standard rate of descent. As PF (Pilot Flying); I had only been descending at about 500 FPM so we wouldn't go too far below glide slope with traffic 3 miles ahead and potential wake turbulence. I increased our descent rate to 1000 FPM. Just before we reached 3000 ft. we were cleared to '2100 ft.; then cleared the visual 16R'. It was clear to me that the Controller wanted us down at 2100 ft. before intercepting the glide slope. I made sure to maintain 1000 FPM descent; but at about 2400 ft. we hit wake turbulence strong enough to roll the aircraft momentarily to about a 40 degree left bank. I recovered and leveled off at about 2300 ft. until intercepting glide slope and then continued the visual approach. The Captain advised the Controller that we had a 'pretty significant wake turbulence event'. The Controller asked 'from what?' The Captain said 'preceding traffic'. The Controller said that would be an A320; 3 miles ahead; and to contact Tower. I was a little distracted and got a few kts. slow on short final; but recovered for a normal landing.I am not sure why the Controller needed us that low before we intercepted glide slope. I haven't seen that kind of requirement before in SEA. We had 3 miles separation behind a narrow-body aircraft so it was a valid clearance; but it still imposed some risk. I hope there was a greater risk of some kind that justified this unusual clearance.
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Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.