Back in October, Chicago O'Hare International Airport opened its fourth east-west runway and promptly switched most operations to east-west from the diagonal pattern they'd used before. Chicago Tribune transportation writer Jon Hilkevich, a private pilot, explains the implications:
Today taxi times to the gate are generally longer than they were several months ago because of a longer route that takes arrivals an extra mile or more around the airfield. The purpose is to have the planes taxi behind other planes waiting to take off so as to reduce the possibility of collisions, airline and FAA air traffic officials said. The taxiing time and distance vary, based on the runway and the gate involved.
Any time saved in the air can be canceled out by the additional time spent on the ground.
"It is a longer taxi route, designed to keep you from taxiing across active runways," said Halli Mulei, a Chicago-based first officer who has flown for United Airlines for 17 years. "But we are flying a shorter final (approach) into O'Hare, saving fuel and about 10 minutes."
From the Oct. 17 opening through Dec. 11, O'Hare has been able to accommodate 112 or more landings per hour on average on 68 percent of the days, according to the FAA.
That compares to a rate of 112 or more arrivals per hour only 20 percent of days in November 2012, FAA data show.
The airlines, in other words, love this new configuration, because fuel use while airborne is quite a lot more than fuel use on the ground. Of course, if there are stiff crosswinds, it's a different story:
During winter, when winds often howl out of the north, wet or icy runways are another condition pilots confront.
"The combination of an icy runway and high wind gusts is where we can have a problem," said Mulei, the United first officer and also a spokeswoman for the United chapter of the Air Line Pilots Association. "If braking action is poor, my crosswind limit on a Boeing 767 could go down to 17 knots" from a norm of up to a 40-knot crosswind on a dry runway, she said.