EMB-170 flight crew reported encountering light wake turbulence during approach into SFO.
Synopsis
EMB-170 flight crew reported encountering light wake turbulence during approach into SFO.
Narrative
During cruise we noted that SFO was indicating that clouds were moving through the San Bruno gap over the airport; but that the approach area was still VFR supporting charted visuals tip toe 28L and FMS bridge visual 28R. We loaded the FMS Bridge Visual 28R into the active flight plan; and used secondary flight plan 1 (with ZFW removed) to load the ILS 28L approach. We reviewed the way points for both; and I briefed both approaches; with 28L being briefed as a visual backed up by the ILS. I fully briefed the ILS in case; given the weather; we needed to fall back on the full instrument approach. We obtained landing data for both runways; noting that the speeds were the same and briefed distances for each runway. During descent on the BDEGA4 we were told to expect a visual approach 28L; after which we swapped the active and secondary 1 flight plans and confirmed Frequency; Course; and Minimums (not set expecting the visual). Approach vectored us onto base and asked if we had pairing traffic for 28R in sight at one o'clock; which we did. Approach instructed us to maintain visual separation; and vectored us on a 310 heading in a descent to 3;000 feet; with a caution for a heavy ahead of us also for 28L. I was focused on maintaining a path slightly above the path of the heavy; and monitoring separation from pairing traffic. As we neared intercepting the localizer for 28L; the heavy ahead of us reported they didn't have the runway in sight. We were not issued any further instructions. I became worried about possible loss of separation from the paired aircraft; and so armed LNAV to intercept the 28L localizer. I judged that were we to cross the 28L localizer; we would no longer be safely separated from the paired aircraft landing 28R. As we neared intercepting the localizer for 28L; Approach began several interactions with the heavy ahead of us; such that there was no opportunity for us to communicate our intentions to Approach. After we had turned to intercept the localizer; Approach called noting that we had done so; and asked if we had the airport in sight. We replied that we did not; after which approach cleared us for the ILS 28R approach; noting our distance from that approach's FAF. The FO responded that we were on the 28L localizer; after which approach cleared us for the ILS 28L. We set minimums and continued to configure for the approach. Approach queried our pairing traffic for 28R; asking if they had us in sight. They reported they did not have us in sight; mostly likely due to our brief IMC encounter into the clouds which prevented us from seeing the airport. Approach then instructed us to commence a missed approach; which we did. We were then vectored by approach; who initially told us to expect 28R; and then changed the instruction to 28L. We performed the required tasks to set up for the second attempt of the ILS 28L approach; which was successful. The heavy we were previously behind was cleared for the ILS 28R ahead of us; and during the approach; we encountered occasional very light wake turbulence. I flew the approach slightly high as needed to avoid worse wake encounters. We landed in the touch down zone; and the remainder was uneventful.The primary cause of this event is the physical layout of SFO; with two parallel runways 28L and 28R which do not have the required separation to allow for simultaneous instrument approaches. Contributing to this was a change in weather near the airport; which prevented the continued use of visual approaches. The level of traffic at SFO during this time also was a contributing factor.Suggestions: Construct new runways at SFO which do allow for simultaneous instrument approaches. Explore improved automated weather reporting along the existing approach paths which would enable ATC to have a better idea of when visuals are likely to become untenable; and thus enable ATC to be more proactive in planning for a transition to instrument approaches.
Second reporter narrative
Initially got vectors for the visual 28L ; visibility got lower as we got closer to final ; ATC cleared us for the ILS 28L. Not enough space between aircrafts ATC instructed us to go around.Cause: ATC was busy coordinating aircrafts while we were being vectored to final visual 28L. We couldn't see airport in sight. At that moment; the ATC meant to say Cleared for the ILS 28L;" but mistakenly said "Cleared for the ILS 28R." He corrected himself to "Cleared for the ILS 28L;" but by then we were already getting closer to the aircraft on the 28R approach. To avoid the conflict; the captain intercepted the 28L localizer. It was because we were also being told to maintain visual separation with the traffic for the 28R. In the end; due to the deteriorating weather; all the aircraft were unable to continue with a visual approach; and because of the spacing with other aircraft; we had to go around.Suggestions: Better weather reporting service would help atc coordination. Construct new runways that could prevent the loss of separation."
Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.