Sunday, May 3, 2015

Hike #31: Hole-in-the-Rock

Tuesday, 2015-04-21
Hole-in-the-Rock, at Papago Park
½ hour
First time at Hole-in-the-Rock

Once again I met my wife at Papago after work. This time we started from the parking lot across the road, at the short trail that leads to Hole-in-the-Rock.

From the Hole, one has a good view of the downtowns of Phoenix and Tempe, as well as that region in between, the one most people call Sky Harbor International Airport. Phoenix is somewhat unusual for a big American city in that its airport is only a few miles away from its downtown.

This afternoon the planes were taking off towards the west and landing from the east. This is, I believe, typical. Also typical, I believe, is that these directions are flipped in the morning, with planes taking off towards the east and landing from the west. Why is this, I wonder? I suspect it's due to the shifting wind direction in the Valley, with the gentle morning breeze typically blowing from the east, and the afternoon wind blowing from the west. The daily wind-flip phenomenon is apparent to anyone who commutes to work by bike everyday—at least, after a few years of that person biking westward in the mornings and eastward in the afternoons and giving up that prevailing omni-tailwind to change jobs and residences and consequently to bike into an omni-headwind almost every day, twice a day. Anyway, pilots who are taking off or landing prefer, unlike cyclists, a headwind because it means the plane's relative speed to the ground is slower than if the wind is a tailwind.

Another possibility for the airplane flight patterns flipping midday is that the airlines take advantage of the efficiencies of an airport that's west of most other airports in the country. Most flights leaving Sky Harbor, I presume, are going eastward, and most flights arriving are coming westward. Furthermore, there probably are more departing flights in the morning and more arriving flights in the evening—excluding red-eyes, every flight departs earlier in the day than it arrives—so it might make sense to adjust the take-off and landing directions to facilitate this: i.e., in the morning take off towards the east and in the evening land from the east.

But the flight paths don't flip everyday, and that makes me think the main cause is something inconsistent and transient, something like wind direction.

Nevertheless, until I'm told by someone who knows what they're talking about, this is an open question here at Just Enough Craig.


L said...

The takeoff pattern is based predominantly on the wind direction. If the wind is light enough then the takeoff direction can be based on noise or directional concerns. -Nelson

Craig Brandenburg said...

L— Thank you! And thanks to Nelson!