Starting March 30, San Francisco Airport (SFO) saw a reduction in its permitted hourly arrival rate from 54 arrivals/hour to 36 arrivals/hour. The Engine Cowl looks at what impact this has had on SFO’s operation in the first week under the new rules.
What has changed?
Two factors have caused the drop in the hourly arrival rate at SFO.
First, the two north-south runways will be closed for maintenance until October. This has reduced the arrival rate by nine arrivals/hour.
Second, the FAA will no longer allow “side-by-side” parallel arrivals at SFO given the close proximity of the two east-west runways which are separated by only 750 feet. This has further reduced the arrival rate by another nine arrivals/hour.
Together, these two factors have reduced the permitted arrival rate from 54 arrivals/hour to 36 arrivals/hour.
When the two north-south runways reopen in October, the maximum arrival rate will increase to 45 arrivals/hour.
What impact has this had on SFO’s operation?
Using ADS-B satellite data supplied by GOscore, we look at the operational impact of the reduction in arrival rate at SFO.
The chart above shows the distribution of hourly arrivals at SFO, comparing the week before the change to the week after the change.
For example, in the week before the change, five one-hour periods saw 34 arrivals. After the change, 15 one-hour periods saw 34 arrivals.
Overall, 14% of one-hour periods in the week before the change would have exceeded the new limit of 36 arrivals/hour. However, none of the hours exceeded 44 arrivals/hour so once the cap increases to 45 arrivals/hour in October, this should be sufficient to cover most periods.
After the change, fewer one-hour periods exceed 36 arrivals/hour. However, there is now a concentration of one-hour periods which see between 34 and 37 arrivals/hour.
We also look at what impact this has had on aircraft ground-time at SFO.
Perhaps surprisingly, average ground-time was slightly lower in the week after the change than in the week before the change.
While the full impact of the new arrivals limit remains to be seen, SFO’s operation seems to have been relatively resilient so far.
Visit goscore.aero to try out GOscore's data and dashboard for yourself.
Or listen to The Airline Tech Podcast to hear firsthand from GOscore's founder, Eli Masinter.
Garth Lund
