Flight Crew Air Transport Pilot (ATP)
Fatigue
ATC Issue All Types; Inflight Event / Encounter Unstabilized Approach; Inflight Event / Encounter Wake Vortex Encounter
Flight Crew Executed Go Around / Missed Approach
Human Factors; Procedure
In the flare after an ILS approach to Runway 35C at DFW I initiated a go-around due to wake turbulence from the preceding arrival. On glide path at about the 50 ft radio altimeter call out the wings started rocking. I attempted to slightly flatten out the descent angle to rise above the turbulence but the oscillation continued for another cycle. At around 20-30 feet and nowhere near stable due to the buffeting I initiated an autopilot-off go-around. We followed ATC instructions and returned to land uneventfully on runway 35R.In my opinion the event occurred due to poor spacing by the DFW approach facility. We had followed this aircraft on the arrival and in fact were kept 1000 ft higher than normal at SILER due to our tight lateral separation. The ATIS had advertised visual approaches with a 1500 ft reported ceiling but were told to expect the ILS by the Controller. As we joined final we were instructed to maintain 170 knots to a five mile final. The next transmission we received informed us that we had a 40 knot overtake on the aircraft in front of us yet there was no amendment to our previous speed assignment by the Controller. Based on that information I put the gear down with landing flaps and asked the FO to query the Controller whether he still wanted that 170 knots given our closure rate. Of course I knew the answer but when the FO finally got the question out the Controller responded by telling us to reduce to final approach speed; which I was already doing. Basically what happened is the Controller treated us like we were a visual instead of an ILS; even though we were IMC until after passing the FAF. We were never informed what type of aircraft we were following. At some point in the radio exchanges subsequent to our go-around the FO was able to glean that the preceding aircraft whose wake we hit was a B757. By the way this was the return leg of an all-nighter; the second consecutive night in a row for me.It would have helped to have known the type aircraft whose heels we were nipping on final approach. The '170 to five mile final' instruction was unrealistic given our separation and the weather. Not exactly how you want to end an all-night duty period.
A321 Captain reported executing a go-around after encountering wake turbulence during their landing flare in trail of a B757 to DFW airport.