Wanted: A Methodical Means to Close Towers

Discussion surrounding FAA Control Tower closures as a result of sequestration has dominated the transportation community recently. Some of the concerns and opinions are valid, while others could be characterized as fear-mongering. In any case, sequestration cuts will likely result in at least temporary tower closures. This isn’t the doing of the FAA, but that doesn’t necessarily mean the FAA is choosing which towers will close in a manner that best serves long term aviation community need or safety. I am hopeful that any permanent closures will be evaluated using more thorough methodology.

I can’t say that all control towers should stay open. In fact, I can personally think of a few where the level of enplanements, traffic volume, or the types of activity that once justified a tower changed long ago, and should probably be closed. But I also know that there are places where towers do a great deal to help pilots and their aircraft avoid tragedy.

After doing some research, methodology to do this already exists. The FAA has a document, “Establishment and Discontinuance Criteria for Airport Traffic Control Towers” (http://www.faa.gov/regulations_policies/policy_guidance/investment_criteria/media/establish_atct.pdf). This document sets policy justification for control tower actions.

Updated in 1990, this document represented a change in policy from previous standards of justification. Until 1974, air carrier airports needed a minimum of 24,000 annual itinerant operations, while general aviation airports need at least 50,000 annual itinerant operations to establish a tower. In 1975, this baseline was revised to incorporate a benefit-cost analysis model that considered accident risk, reduction of flying time, mix of aircraft types, percentage of passengers injured and percent of aircraft damaged.

In the FAA’s document, the foremost benefit of having an FAA Control Tower is cited as safety. According to the FAA, safety benefits of having a tower include reduction of the frequency of midair collisions, fewer and less frequent instances of aircraft damaged in landing accidents, and assistance to pilots in avoiding accidents. There is no doubt that the level of traffic and the benefit of having a tower directly correspond.

Towers are established with consideration given to site-specific activity forecasts, other prevented accidents, and reduced flying time. After evaluation of these criteria and the costs associated with operation, an airport is “eligible for a tower establishment when the benefits which derive from operating the tower exceed the installation and operating costs…A tower meets discontinuance criteria when the costs of the continued operation exceed the benefits.” It is math that dictates when a tower is established.

This document even indicates that “explicit dollar values are assigned to the prevention of fatalities and injuries, and time saved.” In 1990, when this report was written, a single fatality was valued at $1.5 million and even a serious injury at $640,000. Adjusted to today’s dollar value, this would be approximately equivalent to $2.59 million and $1.1 million, respectively. Yes, we actually assign a value to a life. I know that is hard to stomach, but for objective analysis, we have to do the math.

But alas, we are not talking about the establishment of new towers; we are discussing the discontinuance of tower operations. The FAA addresses this too, as follows:

When considering discontinuance of a tower, a site-specific analysis will be performed that would include consideration of:
• Assurance that factors unique to the location such as weather and topography, are properly accounted for;
• Potential use of the site to provide capacity and training relief for a hub airport;
• Impact on adjacent facilities;
• Operational factors otherwise accounted for by the benefit-cost analysis;
• The possibility of significant changes in traffic activity attributable to local conditions;
• and Military requirements.

But the FAA does acknowledge that “for tower discontinuance, however, we do not normally know, nor can we ascertain the site specific likelihood of collision occurrence in the absence of the tower.” This is more difficult to calculate but one could imagine it would not be too dissimilar to the establishment criteria.

Control towers exist to increase safety in high traffic density areas. Put bluntly, “airport traffic control towers are effective in preventing collision between aircraft.” The FAA and NTSB have evaluated accidents and incidents over time and have statistically proven that they occur with lower frequency at towered airports.

There are many services a tower can provide to help aircraft and flight crews mitigate the risk associated with operating in the terminal area, in close proximity to other aircraft. During daylight hours a simple call from the tower to remind a pilot to put their gear down can save, if not a life, at least a great deal of aircraft damage.

Towered airports help pilots make sure they are choosing a runway that is in alignment with the prevailing wind by establishing, and by establishing an active runway, provide order to the flow of arrivals from many different directions and departures destined similarly. Ground controllers help avoid incursions. At busy airports, a tower controller limits overall traffic pattern volume, helping to avoid conditions that are more likely to increase the risk of an accident. On the ground, tower controllers manage taxiing aircraft, helping them avoid runway incursions with aircraft landing or taking off. Tower controllers update weather on ATIS reports more frequently than may occur in hourly AWOS or ASOS reports, allowing pilots more accurate weather information when challenging conditions occur.

Despite all the discussion about tower closures, there has been little mention of the “upstream” effects of a tower closure. Towers don’t just interact with the aircraft in their airspace, but they also help coordinate traffic with neighboring and overlaying airspace controllers. Airline and IFR traffic volumes are unlikely to decrease just because of the tower closures, and these are two groups that must use controllers’ services. This doesn’t mean they need a control tower, but control towers do allow better coordination with radar controller facilities.

In a closure, the coordination these tower controllers offer will need to be managed by the upstream facilities, something that takes time and will likely reduce the number of IFR departures able to operate during IFR conditions at airports with previously operating control towers. Clearing an aircraft in IFR conditions without a tower requires blocking of the airspace for a designated period of time or until the controller is able to receive communication and radar tracking of the aircraft. No other aircraft can be cleared for takeoff or landing until this is established.

If the other facilities see their workload increase, another effect may be that they may not always be able to provide optional traffic separation services to VFR traffic, leaving previously monitored traffic to do it on their own and no longer be monitored (or to receive traffic advisories). Coordination with upstream facilities helps adjust traffic volume for radar and center facilities. Without a tower to coordinate IFR clearances, however, flight crews may choose other airspace not normally used to accommodating their operations, simply shifting the burden to other controllers.

Beyond delay considerations, I can imagine the potential for high traffic areas to become overburdened with the addition of new traffic workload. Could this cause a controller to become saturated with traffic that they didn’t traditionally serve and potentially neglect other areas? No one wants to think about such consequences, and they are hard to quantify until they end in disaster, but such a scenario isn’t totally out of the realm of possibility.

A tower cannot prevent all accidents, of that there is no doubt. But neither is there doubt that their involvement in the management at high traffic density airports, and airports that have a diverse mix of aircraft types can reduce accidents and incidents.

Control towers are costly. Evaluating the location and operation of towers must be data based in nature and done in earnest. Annual operations data for the airports, and their projected future operations are important, but the type of aircraft and operations should be considered, too. For many airports, these evaluations and characteristics have probably changed since the original establishment of a tower. To accurately determine the airports that should continue to have a control tower, we should methodically evaluate these factors based on current information.

The document that the FAA published in 1990 provides guidance on how to establish and discontinue control towers, and I am sure some would say that the document is no longer applicable because it is over 20 years old. I cannot disagree that it may need updating. It does not mean, however, that the methodology in it is not sound. Before we close any towers, let’s take the time to evaluate the types and volumes of traffic in our modern aviation system warrant a tower to increase safety of all users, both general aviation and air carrier throughout the entire system. Let’s do that as our first step.

Any tower closure will certainly have some painful effects. We know the loss of jobs, potential time delays, and other unpleasant consequences will accompany a closure. These are difficult decisions to make. In the end, safety must come first.

Considering closures is not easy. It should be done with great attention and consideration, rather than draconian, across the board cuts. I think there are locations on the FAA’s list that, due to the traffic density and types of aircraft, safety will be compromised. Battle Creek, Michigan, an airport I fly at regularly when conducting practical tests is an example. With 35-50 GA aircraft operating during some two hour period for training, 5-10 jets added to the mix, and all of this using parallel runways, this traffic volume would be a good example of where a tower closure may result in safety degradation. Will the FAA or our nation’s policymakers take responsibility for a death if an accident takes place where a control tower was closed? Or will we just chalk it up to “pilot error” for failing to see-and-avoid where flight crews traditionally had services that are no longer available to them?

I cannot advocate we shouldn’t close any control towers. And I know that the sequestration is not the FAA’s idea. Math is math, and maybe the aviation community can spare some services during tough fiscal times. But if we must close towers for budget reasons, we should do this methodically and with safety in mind. Politics should not be a factor in the safety of our nation’s transportation system. Hopefully, if we must close towers, we will take the time after to go back and re-evaluate which ones should stay closed.

* Quotes in this article are from the 1990 FAA document, Establishment and Discontinuance Criteria for Airport Traffic Control Towers, available at: http://www.faa.gov/regulations_policies/policy_guidance/investment_criteria/media/establish_atct.pdf


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