Smaller airport control towers that the U.S. government will begin closing April 7 haven’t reduced aircraft accidents, according to a federal analysis of crashes before and after the towers opened.
A study of more than 200 airports by the U.S. Federal Aviation Administration obtained by Bloomberg contradicts previous agency findings and adds new fuel to the debate over the shutdown of 149 towers run by private contractors.
The FAA found almost identical numbers of accidents occurred near airports in the five-year period before a tower was opened compared with a five-year span afterward. The study examined accidents that occurred near more than 200 of the 251 airports operated by private firms under contract to FAA.
“I wouldn’t expect to see a big safety difference between controlled and uncontrolled airports,” John Hansman, an aeronautics professor at the Massachusetts Institute of Technology in Cambridge, said in an interview.
While having a controller on duty may help prevent accidents including mid-air collisions, those types of crashes are so rare that it would be difficult to spot in accident data, Hansman said.
“In general, towers that have low traffic levels should be able to go to uncontrolled procedures without any difficulty or increase in risk,” he said.
Shutting down a tower doesn’t close an airport. Pilots use a common radio frequency to speak with each other and coordinate landings, takeoffs and taxiing.
The FAA announced March 22 that it would close 149 towers because of mandatory budget cuts known as sequestration, setting off a wave of lawsuits and objections from lawmakers seeking to halt the shutdowns. The FAA must cut $637 million from its $16 billion budget by Sept. 30, according to an agency release.
“The FAA determined that the agency’s long-standing procedures for ceasing operations of towers and the transfer of airspace between facilities will maintain safety at the airports that will no longer receive federal funding for on-site air traffic services,” Laura Brown, an agency spokeswoman, said in an e-mail yesterday.
Groups representing private pilots and the contract towers have denounced the closings as a threat to safety and the economic well-being of communities near airports.
Spencer Dickerson, executive director of the Alexandria, Virginia-based Contract Tower Association, declined to comment on the FAA safety analysis because he hadn’t seen it.
The group is convinced that having controllers improves safety because they can guide a lost pilot or act as a traffic cop if skies become too congested, Dickerson said in an interview.
An analysis posted online by the group estimated that closing the towers for the six months remaining in this fiscal year may cause as many as 216 deaths from increased accidents.
That total is about half of annual deaths in private-flight accidents, according to U.S. National Transportation Safety Board data.
Those additional accidents combined with a loss of efficiency at the airports would cost an estimated $2.5 billion, the analysis found. It was based on a 1990 study by the FAA that accidents would be about twice as likely at airports without a control tower.
A March 26 report by the non-partisan Congressional Research Service concluded there would be a “relatively small” reduction in safety if towers closed, based on the 1990 FAA study. Because crash rates have declined since then, the 1990 report may overstate the risks, the CRS study said.
The more recent FAA study casts doubt on whether adding a tower has the safety benefits that the agency originally thought and may influence debate over the contract tower program’s $150 million annual funding.
The new FAA study found 615 crashes occurred near airports in the five years before a contract tower was opened, compared with 618 in the same period afterward.
When only accidents that may be linked to a controller -- such as mid-air collisions and runway mishaps -- were considered, the results were similar. There were 94 such accidents before a tower and 99 afterward, according to the data.
More fatalities occurred prior to the opening of a contract tower, 21 deaths compared with two in the five-year period after towers began, according to FAA and NTSB data. Two accidents accounted for 15 of the 21 deaths.
“The data doesn’t seem surprising to me,” Kevin Hiatt, president of the non-profit Flight Safety Foundation in Alexandria, Virgina, said in an interview.
Many towers are at airports with declining flight levels, where the safety may not be significantly altered by having a controller to guide planes, Hiatt said.
At the same time, the study didn’t shake Hiatt’s belief that towers bring order and safety at busier, more complex airports, he said.
“Are there some towers that could close down and safety wouldn’t be compromised? Absolutely,” Russell Mills, a political science professor at Bowling Green State University in Ohio who studies aviation policy, said in an e-mail.
“But there are also a number of towers where there needs to be a deeper, site-specific look at the efficiency, operational, and safety impacts of closing a tower,” Mills said.
Just as a stop light can reduce the risk of collisions at a busy intersection, towers protect planes at the busiest airports with contract facilities, Bruce Landsberg, president of the Aircraft Owners and Pilots Association’s Air Safety Institute, said in an interview. AOPA is an advocacy group for private pilots based in Frederick, Maryland, and has criticized the tower closings.
Contract towers were created in the early 1980s as the FAA struggled to staff its air-traffic control system after President Ronald Reagan fired 11,000 striking controllers in 1981, according to the CRS report.
They are located at small- and mid-sized airports that typically cater to private pilots, with smaller numbers of charter and military flights. Of the 149 that will lose FAA funding, 13 averaged at least one scheduled airline arrival and departure per day in 2011, according to FAA data.
Towers operated by private firms cost an average of $1.5 million less per year than if the FAA staffed them, according to a 2012 report by the Transportation Department’s Inspector General.