A321
Flight Crew Air Transport Pilot (ATP)
Distraction; Situational Awareness
ATC Issue All Types; Conflict Airborne Conflict; Deviation - Speed All Types; Inflight Event / Encounter Unstabilized Approach
Flight Crew Became Reoriented
Human Factors; Procedure
This event occurred on arrival/approach going into SAN RWY 27. We had set up and briefed an RNAV approach to RWY 27. The Captain was the PF (Pilot Flying). ATC left us high and fast to prepare us for the imminent slam dunk. To further complicate the approach they vectored us in tight to the airport and close to preceding traffic. As we approached the final approach course; ATC finally gave us descent clearance and told us to slow from 250 to 210 to 170 in about the same time frame that it has taken me to type this sentence. With all automation engaged; the aircraft would not slow down to a slow enough speed with the speed brakes extended to configure the flaps; and descending was out of the question. I had to disengage the autothrottle to get the aircraft to slow to flaps extend minus 10 knots; a speed about ten knots into the 'foot' when the speedbrakes were extended beyond half. The entire time this was going on; we were getting higher above the arrival's recommended vertical path; but we were still at 4000-5000 feet MSL and AFL; so we still had time to achieve a stabilized approach. Once slowdown was achieved; and we were able to configure; locate and get adequate spacing on our preceding traffic; we were able to re-acquire the vertical path by around 3000 MSL. Everything was getting back to normal. We were configured with gear; full flaps on a level flight path with autopilot on and autothrottle off. I was about to re-engage the autothrottle and call for the landing checklist; when we received a TCAS ALERT with an amber dot 300 feet below us. We started trying to locate the traffic in the high terrain area east of SAN and I got distracted. When I looked back inside at my PFD; we were about 10-15 knots into the amber airspeed foot. I realized that I had been distracted away from re-engaging the autothrottle. I immediately advanced the thrust levers and re-engaged the autothrottle; and the engines advanced to full power and then pulled back to a normal thrust level once normal speed was achieved. No altitude was lost. We continued the stabilized approach to a normal; uneventful landing. To reiterate; there was no lateral or vertical deviation from flight path. The approach speed we were attempting to fly was approximately 141 knots. According to the FOQA (data); we slowed to 126 knots for about 10 seconds and advanced to full power and flew back to normal speed in about 10 seconds. He also stated that VStall for our weight and configuration was calculated to be 116 knots.I flew the MD-80 and the B-757 for a lot of years; and in those years I heard countless times about how difficult it was to get those aircraft to slow down and go down. Compared to the A321S or H; they are a dream. The A321S/H is difficult to slow below flaps extend speed let alone get ten knots below so that you don't over speed in a gust. If you have to slow quickly to fit in behind traffic; or descend while slowing; and you extend the speedbrakes; the top of the 'foot' is; a lot of times; above your flaps extend speed. The autothrottle will not allow you to go below the top of the foot. You have to disengage the autothrottle in this instance; or maintain level flight until you slow below flaps extend speed; and hope you can make up for the late descent. ATC seems to be completely oblivious to this issue; nor do I expect that they'll ever understand. So; I must adapt my technique to keep us out of the yellow/red. Henceforth; if I have to disengage the autothrottle; I intend to have my right hand on the thrust levers as a constant reminder that I am now the autothrottle. This is not the normal Airbus MO of setting the thrust levers to climb on departure and not touching them again until they are moved to idle in the flare. The downside to this technique is that it takes my right hand out of the picture; and I'll have to direct the PM to do actions thus distracting him/her. Once airspeed issues are overcome; I will re-engage the autothrottle; especially in a high threat environment such as SAN.
A321 Captain reported a low speed event when the aircraft slowed with autothrottles off.