We may not yet be able to power large airplanes sustainably with biofuels, but there are still ways that the airline industry can easily cut down on its fuel use and CO2 emissions. One ultra-simple solution: Keep planes at the gate longer with their engines turned off instead of having them idle on the runway.
The idea comes courtesy of Hamsa Balakrishnan, an MIT professor specializing in airspace efficiency, in a paper published in the MIT Technical Report (PDF). Balakrishnan received funding from the FAA to find ways for aircraft to slash CO2 emissions at airports. So in 2008, Balakrishnan and her team set about analyzing Boston’s Logan International Airport, looking at the make and model of departing planes as well as historical data.
“We wanted to see if we could reduce the amount of time spent taxiing and swap that for a little
extra time spent at the gate with engines off,” explains Balakrishnan. “The challenge is to do this
in a way that you’re still maintaining pressure on runways and keeping
utilization up. A naive strategy would be to let one aircraft taxi at a
time. There would be no congestion, but it’s not being efficient in terms of throughput.”
The FAA wouldn’t let the team actually speak with air traffic controllers to change flight taxiing patterns, so the MIT researchers instead communicated their suggestions for gate pushback rates with color-coded cards given to air traffic controllers (see above). A sample communication from air traffic control to a flight deck might sound something like this: “AAL123, please hold push for 3 min. Time is now 2332, expect clearance at 2335. Remain on my frequency, I will contact you.”
Air traffic controllers used different color-coded cards over the course of a month. In the end, the MIT researchers discovered that planes held longer at the gate experienced a decrease in taxiing time on the runway. Each gate-held flight also saved 16 to 20 gallons of fuel on its journey. And, with fuel use being a primary driver of ticket cost as well as carbon emissions, saving 20 gallons helps both the environment and consumer wallets.
Balakrishnan and her team plan to continue research on gate taxiing in the hopes that the FAA will eventually adopt something similar to their fuel and CO2-saving strategy.