Date: 201309
Local time of day: 1801-2400
Location: SFO.Tower, CA
Flight conditions: Marginal
Light: Night
Aircraft: A320
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Initial Approach
Airspace: Class B SFO
ATC / advisory: Tower SFO
Aircraft component: Flap Control (Trailing & Leading Edge)
Component problem: Improperly Operated
Reporter organization: Air Carrier
Reporter function: First Officer; Pilot Flying
Human factors: Workload; Distraction; Time Pressure
Second reporter function: Captain; Pilot Not Flying
Anomaly: ATC Issue All Types; Deviation / Discrepancy - Procedural Published Material / Policy; Inflight Event / Encounter Fuel Issue; Inflight Event / Encounter Weather / Turbulence
Detector: Person Flight Crew
When detected: In-flight
Result: Air Traffic Control Issued Advisory / Alert; Air Traffic Control Issued New Clearance; Flight Crew Became Reoriented
Contributing factors: Environment - Non Weather Related; Weather; Procedure; Aircraft
Primary problem: Ambiguous

Narrative: On final approach to 28L; while configuring the for landing; the 'GPWS' master caution came on while the gear was in transit. The delay in configuration was cause by: crew high work load; last minute runway change; non-standard ATC instructions; out of sequence configuration due to slow traffic ahead and low fuel condition (extended hold/eminent diversion).While enroute to SFO ATC started issuing extended holding patterns due to a marine layer moving in over the Bay Area. Even though we had opted to add extra 1;000 LBS of fuel and flew very efficient profiles; we advised ATC of a possible diversion to SJC 12 minutes from our agreed 'bingo fuel.' Approximately 11 minutes later; we were given vectors for approach to Runway 28R at SFO. ATC issued us a fair amount of delay vectors putting us on a very long final for Runway 28R. With our fuel now being 4;800 LBS; we verbally agreed on changing our alternate from SJC to OAK. ATC had also vectored a slower moving traffic in front of us; and began issuing us very low approach speeds on long final; so considering our distance from the airport; and fuel situation; I elected to extend 'Flaps 3' (out of sequence) and wait on the gear.  As we approached the FAF; I called for: 'Gear Down; Flaps Full; and Landing Checklist.' As the Captain reached for the gear handle; ATC issued a 'go-around'; which they recanted immediately and called us in sight (we had broken out of the layer seconds prior to ATC calling for the 'go-around'). With the slower traffic ahead and airport now insight; we requested the visual to Runway 28L. ATC cleared us for both the visual; and for landing Runway 28L.  As I maneuvered for Runway 28L; I called for: 'flaps full.' Captain was entering the new runway in the FMS; after selecting flaps full; he reached for the gear lever while looking at me; and I nodded in agreement. He selected gear down and started to read the 'Landing Checklist'. Seconds later; with the gear still in transit; the 'GPWS' master activated. We both signaled to each other that we were comfortable continuing with the landing given we still had plenty of altitude; were stable; and now fully configured as the gear was now indicating down and locked. We proceeded to land uneventfully on Runway 28L I suggest better dispatch fuel planning on evening flights to SFO. Marine layers seem to happen frequently even when not forecasted.  More leeway on Captain discretion to add fuel: (1;000 LBS) does not go very far on an A320. A go-around is at very best 2;000-2;500 LBS of burn.  ATC avoiding to vector slower traffic in front of larger planes when holding has been issued and/or ATC has been made aware of light fuel load.


Second narrative: First Officer then elected to extend 'Flaps 3' (out of sequence) before deploying landing gear; due to position; ATC spacing assessment and low fuel observation. As spacing improved; First Officer called for 'gear down.' As I reached for the gear handle to select landing gear down; ATC immediately issued a 'go-around' instruction to us--so I did not put the gear down. I held my hand up to the First Officer to signal that gear must now wait (because of the new go-around clearance). This action may have confused him; as he paused before initiating a 'go-around.' Just before he initiated the assigned 'go-around;' ATC then cancelled the 'go-around' clearance; saying; 'Tower has you in sight;' and where we were now told to continue approach (even though we had just over 2 miles separation from the preceding slowing aircraft). I was certain that another 'go-around' was going to be issued behind the slowing aircraft ahead; and very cognizant of our low fuel situation; so I initiated a request for Runway 28L while above 1;000 feet. ATC cleared us to land on Runway 28L and I began to activate the new runway in the FMS for accurate glide slope and an unexpected go-around into clouds. First Officer quickly called for 'flaps full' while he aligned the aircraft; where I was already looking down. I selected flaps full; verified the runway was clear; and then looked at the First Officer while reaching to select landing gear down. He nodded in agreement and said 'gear down' while I selected the gear down; and I attempted to read the landing checklist. While the gear was in transit; the GPWS master warning activated. Perhaps an earlier call to ATC for advising of our TIME UNTIL DIVERSION (i.e.; at 15 mins. vs. at 12 mins.) would have alleviated the stresses; and prompted ATC to sequence us before the slower aircraft--essentially eliminating out of sequence flap selection and erroneous 'go-around' directives. Following SOP 'to the T' despite major distractions. Another suggestion would be to allow for more holding fuel; above the Captain's 1;000 lb. limit; to alleviate fuel concerns and accommodate overwhelmed ATC facilities.


Synopsis: ATC put slower traffic ahead of an A320 on a Runway 28L ILS and while slowing for that traffic; Flaps 3 were selected causing an EGPWS warning because the gear was still up as ATC issued; then canceled a go-around.