Large Transport
Flight Crew Last 90 Days 126; Flight Crew Type 15000
Fatigue; Communication Breakdown; Distraction
ATC Issue All Types; Deviation - Speed All Types; Deviation / Discrepancy - Procedural Clearance
Flight Crew Returned To Clearance; Flight Crew FLC complied w / Automation / Advisory
Human Factors
Flight was third of four on day two of three. Previous day started with 1.5 hour ground. Day one of trip was four legs with first three flown in an [older model]. Heat in [throughout the trip] made for tiring day since ground air in each location would slowly fall behind cabin cooling needs. We pulled ground air and used marginally more effective APU air when cabin cooling fell off at each location. Fourth leg in an [newer model] and was first time we felt cool since reporting for duty.Late arrival made for shorter overnight; but got eight hours in bed; exercised; called home; and caught van feeling adequately rested. First leg included a TCAS descend RA due to a VFR aircraft at 13;500 ft that had us in sight descending toward our altitude (level at 13;000 ft after departure stopped our climb for the VFR aircraft). We disengaged the A/P and A/T; and complied with RA guidance until clear of conflict; notifying Departure of TCAS descent to around 12;500 ft; then continued climb out; notifying Dispatch via ACARS of the RA. I did not feel fatigued throughout day two of the trip; but it was a busy day. We took a slight delay [on departure] to increase our fuel load to address Dispatch concerns about possible lingering storms in ATL. Once we determined the final ZFW (Zero Fuel Weight); we were able to add 2000 pounds while still staying around 1000 pounds below our landing limited ATOG (Allowable Takeoff Gross Weight). Event was on ATL leg. We noted and briefed ATL airspeed compliance issues during preflight briefings and were well aware of need to maintain assigned air speeds. During descent into ATL Approach switched us from Runway 28 to Runway 27L and held us fairly high on downwind; then directed us to slow from 240 to 210 and to descend from (if I recall correctly) 12;000 ft to 7000 ft and to expedite descent. I remember noting a bit of a sharp tone from the Controller on that call; and thinking it odd; both because we had been carefully and precisely following his instructions; and because it is impossible to both slow and expedite descent at the same time. The downwind position and heavy traffic load implied by radio chatter and TCAS targets maneuvering toward final made me anticipate an extended final so I set the lower altitude and airspeed on the control panel; selected Level Change; and deployed speed brakes rather than flaps so as to expedite while avoiding a drug in final with flaps extended. Shortly thereafter; we were given a vector north for a base leg and further descent and directed to slow to 180. I set 180 in the Speed window and (IIRC) 4000 ft in the Altitude window. I decided to continue the descent with speed brakes extended until the airspeed had bled off through flaps up maneuver speed; and then retract the speed brakes and extend the flaps. However; I allowed myself to get distracted from this by traffic calls; accepting the PM's (Pilot Monitoring) offer of updating the final approach active waypoint to one inside of our base leg for accurate profile guidance; and attempting to acquire both the field and final traffic thru a scattered to broken deck between us and the field. The aircraft had slowed as programmed to 180 and I had failed to close the speed brakes or extend the flaps. As the aircraft leveled at 4000 ft; I noted the A/T moving up followed shortly by an 'AIRSPEED TOO LOW' audible warning. As I scanned the instruments; I disengaged the autopilot and auto throttles; closed the speed brakes; and advanced the throttles. When I pulled the yoke back a bit to maintain altitude the stick shaker activated so I pushed the power to a setting near max; relaxed aft control wheel; and called for flaps 5. The stick shaker stopped and did not reactivate; altitude did not go below 3950 ft. Precise airspeed during this sequence is hard to be sure of; but went no higher than 190 during the initial transition to manual control and stick shaker recovery.  Either during the last few seconds ofthe recovery or a few seconds later; we were given a vector to final and traffic to follow point out. Controller then adjusted clearance to direct DEPOT to intercept. We broke out of clouds and acquired and called the field and traffic to follow. We were cleared visual approach to follow traffic. The last airspeed assignment we had heard was 180 on the base leg. If 180 to the marker was assigned we did not hear it. (I'd have replied we could give him 170 only to the marker if we had heard such a call since we were a 127K jet at that point and an unstable approach would have been likely.)Once cleared for the visual; we began to slow since clearance on the preceding 767 was already just inside three NM. About two to three NM prior to DEPOT; Controller queried us on our airspeed in a very aggressive tone. PM replied we were slowing to final speed for traffic. Controller; to be polite; was rather upset. We were told we'd been assigned 180 to the marker and had failed to comply. We reported DEPOT and asked for clearance to Tower without response from Controller. He eventually responded to a subsequent request and cleared us to Tower. We maintained just inside three NM spacing to touchdown and preceding traffic clearing the runway with us on short final. There was no apparent loss of spacing between us and any following traffic. After clearing the runway; Ground notified us of a possible Pilot Deviation with a number for TRACON. After reaching the gate; I contacted Dispatch and had them notify our Company ATC liaison. I then called the TRACON number and told that gentleman we had never heard a direction to maintain 180 to the marker; and that when we were cleared the visual we slowed to maintain safe landing spacing; which he agreed was proper if there had been no 180 to the marker instruction. Back to basics. Fly the jet and keep crosscheck going. Always believed stuff could happen to me; and have always used that to motivate myself to keep checking on things so as to make a positive difference. In this case; I allowed myself to be distracted from a very basic task without even realizing I was in the Yellow let alone the Red. Thankfully we responded correctly to the airspeed warning properly once it sounded.  PM was also distracted with FMC programming and radio chatter; but might have questioned having speed brakes out and selecting Level Change/180. After the flight; we were sure we hadn't heard a 180 to the marker instruction. A possible technique to use when coming back from a Yellow/Red excursion might be to query Controller to confirm latest clearance. If a 180 to the marker instruction was given during our low airspeed recovery and we didn't hear it; a confirm clearance call to the Controller might have been a nuisance to him given the traffic/radio congestion; but would have gotten us solidly back in the Green. Late runway changes happen as do congested patterns; but the aggressive and angry calls made by our Final Approach Controller were not helpful and an additive condition complicating the safe conclusion of the flight.
[Report narrative contained no additional information.]
During a busy arrival and vector to final at ATL; the crew did not hear an assigned airspeed to the outer marker.