San Francisco - Loupe One Departure from SJC - How Much Fuel does it Waste?

I understand the rationale of ATC for the Loupe One departure out of SJC for flights going north or east - to get them above inbound traffic to SFO and OAK. However, I wonder how much fuel is wasted every day with the departure to the north, turn back to the south, and finally turning back to the north to cross over the airport.

I appreciate how complicated it is to coordinate traffic among three airports, but I bet someday someone will come up with a better plan.

And seriously (not sarcastically), what would that plan be?

First, the extra fuel burn is not that much. Assume a 737-400 is at 12000 feet when it crosses back over the top of SJC on the loop departure. Compare that to a similar flight doing a straight-out departure. If it takes 5 minutes to 12,000 feet, at 250 knots groundspeed it covers 24 statute miles. Both flights will hit top of climb (TOC) at the same time, still 24SM apart. The flight that did the loop departure burns extra fuel making up the 24SM gap but that's at efficient cruising altitude and airspeeds and takes less than 3 minutes. Assuming cruise fuel burn of 5500 pounds/hour that's 275 pounds or 45 gallons. (This is a highly simplistic analysis with lots of assumptions but in the ballpark).

SJC departures can't turn to the west due to terrain, or to the east due to even higher terrain.

A left turn above 10-12000 feet at OSI conflicts with traffic climbing out of SFO.

Offsetting to the east along the middle of the bay conflicts with SFO arrivals from the north and OAK departures. OAK and SFO are even more hemmed in by terrain and proximity. Don't forget there are several GA and military airports in the area too.

Unfortunately ATC in any urban area is a complex jigsaw puzzle...worse in the BA due to topography, lots of airports in a fairly small area, weather, and politics.

So again, what would you propose that doesn't cause a net increase in total fuel burned over the BA?

And seriously (not sarcastically), what would that plan be?



And seriously, I wish I had a computer program that could figure it out. Your calculations are interesting and suggest it's not as much of a problem as I thought. It just bugs me every time I'm on a flight that does the loop - it just seems like such a waste.

There was a time a number of years ago where flights heading east did not do the loop. I didn't know enough about flight patterns then to understand how they did it. Maybe there were more delays and ground holds waiting for an opening - which probably was just as inefficient, if not more so.

I thought the looping was to get high enough to get over the hills, at least when heading east.

I thought the looping was to get high enough to get over the hills, at least when heading east.

The requirement to cross back over the airport at 12,000 feet is a lot higher than needed to get over the hills.

Back about 20 years ago the FAA invented Airport Radar Service Areas (ARSAs) which I believe are now "Class C" airspace. The general configuration is a "stepped cone" or "inverted wedding cake". In their usual wisdom, the one FAA designed for San Jose had parts of the ARSA going underground where it ran into nearby hills! They quickly issued a revision.

Normal Bay Traffic (http://photos.palal.net/v/aviation/tfcflow-west.jpg.html)
Reversed Bay Traffic (http://photos.palal.net/v/aviation/tfcflow-east.jpg.html)

Thanks, Palal, for the links to those interesting diagrams.
I'm wondering if there might be a different departure route (not "Loupe One") for Hawaii and Asia-bound flights from SJC. I say this because, over the years, I have observed ascending widebodies over Palo Alto (that clearly had departed SJC - HA 767s, and, back in the day, AA 777s).

Normal Bay Traffic (http://photos.palal.net/v/aviation/tfcflow-west.jpg.html)
Reversed Bay Traffic (http://photos.palal.net/v/aviation/tfcflow-east.jpg.html)

Nice general diagram, except the 3d airport on there is SJO :eek:

Normal Bay Traffic (http://photos.palal.net/v/aviation/tfcflow-west.jpg.html)
Reversed Bay Traffic (http://photos.palal.net/v/aviation/tfcflow-east.jpg.html)

These diagrams are great, very informative!

Do you know if something similar exists for NYC airspace? That would be interesting to look at in comparison, since you also have 3 major airports in close proximity.

These diagrams are great, very informative!

Do you know if something similar exists for NYC airspace? That would be interesting to look at in comparison, since you also have 3 major airports in close proximity.

I remember seeing something similar for NYC, but I can't find what I'm looking for. This may be a good start (http://www.faa.gov/air_traffic/nas_redesign/regional_guidance/eastern_reg/nynjphl_redesign/)

Nice general diagram, except the 3d airport on there is SJO :eek:

Yea.... these are not my diagrams, I just posted them on my site.