Threat Analysis: Denver International Airport and the Drone Threat

Unmanned Aerial Vehicles (UAV’s), also known as drones, have become very popular within the military as well as the commercial and private sectors. They allow us to obtain a birds eye view without the need for expensive and dangerous aircraft. And best of all, anyone can purchase a drone off the internet and fly it within hours; the technology has come so far just in the past decade.

The military has also proven that Unmanned Aerial Vehicles and drones are an important piece in conducting tactical and strategic operations in overseas conflicts. This ever-advancing technology allows US and coalition forces to observe from the sky over long periods of time and vast distances in enemy terrain without the risk to human life or expensive equipment. Even more so, they are provided with the capability to use precision force against hostile targets. The size, weight, range, and payload are advancing each year and provides a great advantage over enemy combatants.

However, what is being neglected in research and study is the use of UAVs in a domestic setting and how small, commercially or privately owned drones can be a great threat to US infrastructure, energy, government, and transportation. We have seen ISIS and other terrorist groups use UAVs to target coalition forces in Syria and Iraq. And US intelligence has proven that although their techniques are not sophisticated, they prove highly effective in creating damage and casualties. This is apparent even in state sponsored terrorism like Iran who provide Houthi rebels in Yemen with UAVs to conduct attacks against the government.

This is important for us to study because it is only a matter of time before domestic terrorists and criminals understand the effectiveness of UAVs and the vulnerabilities within our airports. This is most true with extremist efforts from ISIS and al Qaeda who seek to find people to radicalize and conduct “lone wolf” attacks. Airports are also seen as major targets to terrorist organizations because “they recognize the economic damage that may result from even unsuccessful attempts to down aircraft or against airline terminals, as well as the high loss of life and the attention media devotes to these attacks”.

The purpose of this paper is to examine the threat of unmanned aerial vehicles against Denver International Airport and how technology and public awareness can mitigate and prevent these threats to allow the airport to safely function at maximum efficiency. This paper will use several case studies of both Denver International Airport as well as other research that will support how drones and UAV’s pose a realistic threat to airports and air travel. Finally, I will a conclusion and recommendations for what DIA should do to mitigate the risk of drone and UAV encounters.

Why are drones so dangerous?

Civilian and commercial drones are becoming more and more popular as they are becoming increasingly available and significantly cheaper to purchase. Not only are they recreational for the common person but have become more integrated in commercial and private sectors for use in surveying, search and rescue, and photography. The biggest threat thus far however, is the possibility of drones interfering or colliding with aircraft, both commercial and private, and the possible danger that it creates to passengers and pilot, as well as people on the ground. Preliminary studies have been conducted which will be grouped and analyzed in the following section.

Generally, we always try to find both the pros and cons of studies and what they are trying to prove. However, in the case of drones, it is widely accepted that drones and aircraft do not mix, and encounters will be more numerous without some sort of regulatory policy or hard deterrence to keep the two apart. When it comes to drone and aircraft encounters, we have two players in any incident; the pilots of the plane and the pilots of the drone. We understand that to become an airline or aircraft pilot, one must have extensive training, experience, and in-depth knowledge of the aircraft and its critical safety features to ensure the safety of its passengers and those one the ground. One such article explains that people are likely to make mistakes when flying drones and could potentially cause inadvertent harm to an aircraft. “It is found that RPAS [remotely piloted aircraft systems] operations are more likely to experience (1) loss of control in-flight, (2) events during takeoff and in cruise, and (3) equipment problems”. This merely proves that despite the relative ease of flying a drone, there are plenty of mishaps and mistakes that can be made by the pilot of the drone because of inexperience. Moreover, we must also understand that evasive action in an airliner or even a medium sized aircraft will find it difficult to evade small drones.

An article in Wired describes how “the risks that come with mixing drones and planes aren't as well studied as those of bird strikes, but there's a good chance a medium-sized UAS could take out an engine running at high power, or do serious damage to a windscreen”. There was a great experimentation and study performed by the University of Dayton Research Institute in Ohio, where their impact physics students tested how a drone could damage and aircraft wing. Using a DJI Phantom II drone, a popular rotary winged drone used by hobbyist, researchers used compress air in a wind tunnel to shoot the drone at approximately 238 mph into the wing of a small jet aircraft. The drone was able to penetrate the skin of the aircraft wing and severely damage fasteners, electrical cables, and structural tubing. Although the study confirms that the damaged airplane would have most likely been able to land, change in velocity, size of the aircraft, size of the drone, and point of impact could be very substantial. A simple YouTube search will bring you to the actual video of the impact and the severity of the damage. Further down on said YouTube page, there are plenty of example of people posting footage of their flights around aircraft and you can see just how close they really are. This is of course anecdotal, but interesting nonetheless.

Though we are discussing the physical damage of what a UAV can do to an aircraft and the potential harm both in the air and on the ground, just the sight a drone can cause great havoc. Recently, Heathrow and Gatwick international airports in the United Kingdom have both had to shut down their airports due to drones flying in and around their airspace. On 19-21 December 2018, Gatwick Airport had to shut down all flight operations completely due to multiple sightings of a drone. The ensuing chaos saw the cancellation of over 1000 flights and stranded approximately 140,000 people in the run up of the Christmas holidays. It is estimated that the closure cost the airlines and airport up to 20 million pounds for a 36 hour closure.

Finally, an article by Loffi, J. M., Wallace, R. J., Jacob, J. D., & Dunlap, J. C. evaluates the ability to spot drones while flying an aircraft. Drones possess a true threat “until such benchmarks are established for electronic Detect, Sense & Avoid Systems, pilots must rely on visual means to ensure positive separation from UAS platforms” and evaluates a pilots ability to even visually see the drone they are flying near. This study is significant because it concludes that drones were only sighted 40% of the time by pilots or air traffic controllers, which means that most of the drone data that has been recorded and published, mostly by the FAA, is most likely incomplete. We don’t really know how many encounters or near misses happen unless it is visually seen by the pilot, air traffic control, or other airport officials. This study is also important because their methodology used test pilots in real aircraft or control towers, which makes the data much more reliable.

To add some personal anecdotal observations to this paper, I have personally experienced just how dangerous drones are in the battlefield. During my deployment to Iraq in 2016-2017, the US military experienced multiple attacks from drones piloted by the Islamic state that was able to do substantial damage to coalition forces. Besides being very difficult to detect, the drones were especially difficult to defeat once they were sighted. Although payload was limited to the size of the drone, their effectiveness was very effective. Both fixed wing and rotary wing drones were utilized. The fixed wing drones were often used like kamikazes and efforts were made by the enemy to fly these UAV’s, combined with armor penetrating munitions, directly into fighting positions or vehicles. Rotary winged UAV’s could hover above coalition forces and drop small munitions with relative accuracy. Finally, enemy drones were used to gather information about patterns of life and troop movements, gaining vital knowledge of how and when to attack.

Thankfully, we haven’t seen this sort of technique used at airports within the United States or Europe. Most cases of drone encounters or near misses were a result of foolish people flying their drones too close to an airport or runway. However, I believe this will change and terrorist groups and extreme individuals will understand how effective this tactic is.

Laws pertaining to flying drones

The federal government is doing their best to regulate and enforce laws concerning UAVs within the United States. Title 14, Ch 1, SubCh F, Part 107 of the Code of Federal Regulations outlines the regulations of flying UAV’s and what an operator is required to do when owning a drone. For the purpose of this paper, the most important regulation is §107.4, Operation in the vicinity of airports. The regulation states that “No person may operate a small unmanned aircraft in a manner that interferes with operations and traffic patterns at any airport, heliport, or seaplane base”. There are two problems with this regulation. First, it is very vague language in determining what the operational distance is of an airport. One could argue that 1 mile distance is enough, however depending on flight patterns that could be in the direct approach of take off or landing. Second, the biggest issue is that it is very difficult to actually find the operator if there is a violation of airspace. Depending on the type of drone, operators could be a good distance away from the drone, and by the time law enforcement can respond, the drone with its operator could be long gone and never found.

Denver International Airport Background

When talking about threats and security postures of any particular site or area, detailed background information is important in understanding risks, mitigations, and recommendations. No two airports are exactly alike and this must be taken into account when analyzing security posture. For example, size, square mileage, terrain, population density, and weather will make each and every airport unique and thus recommendations and security plans will differ.

Denver International Airport officially opened on February 28th, 1995, with the price tag of $5 billion and sits on 53 square miles of facility, making it the 5th largest airport within the United States. Currently there are 23 airlines who operate out of DIA that provides approximately 1600 flights a day. DIA sits about 30 miles to the Northeast of downtown Denver, where the population is significantly less in numbers and in density. Looking at a satellite image, one can easily see how the airport is far removed from the metropolis of downtown Denver and its sprawling suburbs. Although the construction project was delayed and over-budget, DIA was not only built with bigger runways that were able to accommodate more flights, but it also had more room to grow than the previous airport at Stapleton, which was in service for 65 years and closer to Denver.

Denver is also one of the worst airports in the nation for turbulence. Because of the airport’s proximity to the mountains, aircraft often experience excessive shaking and rumbling due to mountain wave turbulence. Mountain wave turbulence occurs on the lee ward side of a mountain or mountain range where air is forced up and then gets trapped within the upper atmosphere where it will create a circular wave like pattern. This weather phenomenon makes DIA especially difficult to land and take-off as well as perform evasive maneuvers if there is a foreign object within its flight pattern.

Security Posture of Denver International Airport

First, lets look at the security advantages of DIA. As stated before in the background section, DIA is far removed from the heavily populated area of Colorado’s largest city and capital, Denver, which actually serves the airport in a positive manner because there are simply less people in the area. For example, populated airports like LaGuardia in New York City or McCarran Airport in Las Vegas are situated in densely populated areas where people physically live next to runways or under flight patterns. Someone who is not familiar with aviation law or does not understand the operational capabilities of a drone could possibly fly their small aircraft right into an approaching aircraft.

However, the vulnerabilities to DIA are quite real and apparent. Because DIA is so massive with multiple runways and terminals, this makes monitoring and defending the area very difficult. As stated before, DIA has 53 square miles to monitor. This alone is a massive undertaking and manning the perimeter with personnel and technology would be a funding nightmare.

DIA does have an array of radar systems that tracks and maintains its 1600 daily flights in and out of the airport. However, these radars are large and designed for tracking medium to large sized aircraft at 25 miles away. They are not designed to pick up smaller unmanned aircraft at lower altitudes. There has to be some discrepancy with the frequencies and what radars pick up. Although they can be programmed to detect smaller objects, the data would be too broad and too massive to conclude what you are seeing. Cars, trucks, and even people would be detected on radar screens and the data would be very difficult to decipher. Furthermore, they would also pickup flocks of birds that routinely fly in and around airports. This could potentially block out entire screens and confuse an operator on what they are seeing. Ultimately, priority the priority is deconflicting aircraft patterns to keep people in the plane and on the ground safe, not intensely monitoring the perimeter fencing. Therefore, precedence is taken on using these high-powered radars to maintain control of inbound and outbound aircraft.

DIA resorts on visual sightings of drones by pilots in the aircraft, air traffic controllers, or by other airport personnel who were able to see the threat. As previously mentioned by Loffi, J. M., Wallace, R. J., Jacob, J. D., & Dunlap, J. C., these drones are very difficult to see in the air, even if you are looking for them, and often times we do not see them until they are too close.

DIA does have a robust security force available to respond to various threats, but I have not been able to find viable sources on how they deal with drones directly. I have been in contact with several officials about drone threats and I have not been able to get real answers. Funding seems to be a large roadblock in obtaining real technology to thwart drone threats, but because incidents have not been numerous, little emphasis has been made at mitigating the risk. After the panel presentation on 23 January with the Homeland Security and Emergency Management of Colorado, I do not feel confident that risk assessments towards drones have been taken seriously within the state of Colorado or the airport.

Defense systems

Currently, there are multiple private companies and government initiatives that are taking the drone threat very seriously and creating techniques and procedures that can defeat a drone in several manners. There are several strategies we will evaluate to understand the pros and cons of these techniques and available technologies.

We can first look and an obvious technique of defeating a drone and that is simply shooting at it with a gun. This is highly ineffective for two reasons: one, even someone who is a very good shot will most likely miss several times before effectively hitting the small aircraft. Bottom line, it is very hard to do. Two, consideration must be made to where the drone is flying and what is behind it. Someone trying to shoot at a drone with a rifle or shotgun could be potentially firing bullets into a populated area, or highway, or strait into a terminal. This technique, most often referred to as a hard defeat, would not be suitable at DIA or many other airports throughout the United States.

There are several companies within the industry that seek to use net guns and net capture techniques to hard kill UAVs. This technique seeks to capture drones without firing projectiles that could possibly harm people or property in the surrounding area. Some of these systems seek to use existing platforms such as 40mm grenade launchers or shotgun shells, and others have created their own firing platforms to shoot projectiles. There have also been efforts to create drone on drone platforms that will deter unwanted UAVs from an area. Called “Skynet”, this drone flies around with a giant net attached to it to envelope the enemy drone. What are good about these techniques is not only the defeat of the drone but the important biometrics that can be pulled from the drone. Data such as finger prints can help find the operator, and GPS data can determine where takeoff and landing was. However, the problem with these systems are that they are slow to respond and react to a drone threat. Often times, when a threat is identified and determined, the response team is often too slow to shoot it down and the drone, with its operator, can vanish before law enforcement can make an arrest.

Early warning systems are also a possible technique to defeating drones. As stated before, most airports have larger radar systems that are designed to track aircraft many miles away. But a smaller radar that can be programmed to detect drone movement is a viable solution to detecting incoming drones. If early detection can be established, it could give airport security enough time to respond to the drone to either defeat it by a hard kill, or by locating the operator of the drone. These radars systems could also be more economical as they could be placed sparingly throughout the airport perimeter. This can help solve the problem that was stated earlier to defending and surveilling a large area without increasing personnel. The problem with this however, is that it merely detects incoming drones, not defeats them. Therefore, some other system of defeat should be utilized with radar tracking systems.

Another technique that can be utilized is RF inhibitors. Because there has to be a connection made between the operator of the drone, either through radio frequency or by GPS, severing this link can be an easy way to defeat incoming drones. By combing inhibitors with radars or some other tracking system, this could be the quickest response to defeating drones before it enters critical airspace. The major problem with using this technique is that RF inhibiting can affect other forms of frequencies that are ever present around us. Inhibitors that are not directional or wavelength specific can jam radios, cell phones, and other forms of communications that are integral to airport operations. And because of the possible communications interference inhibitors create, RF inhibiting is federally illegal. The FAA’s Spectrum Management Regulations and Procedures Manual greatly restrict the use of RF inhibitors because of its many uses in American infrastructure. However, testing of such systems are allowed under the strictest supervision at military installations that have the space available to inhibit without damaging critical communications.

Finally, there are several university research initiatives that believe using falcons and other birds of prey will be the most effective at defeating drones. Scientists believe that Peregrine Falcons have the ability to navigate and adjust flight patterns to intercept and defeat drones while in flight. The argument is that these falcons already have the instinctual data processing needed to attack drones, whereas programming and expensive high-tech systems are much more complex and require a greater need for engineering and computer processing. As fascinating as this is, there are plenty of unknown variables by using falcons as a means to defeat drones. Training, number of birds needed, time of day, weather, are just a few consideration when using trained birds as a defense system. Not mentioned in the research paper was how a rotary drone would affect the birds during an interception. This could be highly detrimental to the bird and prove not affective.

Recommendations

In my opinion, Denver International Airport does not have a viable solution There are several defensive actions I would recommend to Denver International Airport in order to mitigate any risk of drone threats to its airspace and perimeter.

1. Education of security personnel. Personnel tasked with airport security should understand the capabilities, types, and techniques of drones and how they threaten air travel. Furthermore, education on different types of drone will also help determine what defense techniques will be needed to defeat the drone or redirect aircraft. A fixed wing drone will have much different capabilities than rotary winged quad copter.

2. Integrated Radar systems. Defense systems such as radar should be utilized around the perimeter of the airport. Depending on the radar system, its range and configuration, even a small number of radars at strategically positioned locations can offer a great deal of information in identifying a possible threat. Integrations with cameras will also help identify what the threat is and if it posses a real threat to aircraft. Much like the previous recommendation, education on types of drones that are identified by radar can offer a better response to the threat.

3. Drone response team. Man and train a team to respond to any drone threat. Have teams available both inside and outside perimeter in order to apprehend the operator.

4. Aircraft deviation plane. Have a plan in place to divert aircraft away from the airport in the case of drone infiltration of critical airspace.

5. Defeat technology. I would recommend a directional inhibitor that worked on multilevel bands to defeat the link between drone and operator. This would require training and funding on the airport’s end, as well as federal deregulation of inhibiting in multispectral bands.

What scares me the most?

Unfortunately, we are more reactionary than proactive. Despite great leaps in technology in within the defense and private sector, I believe it will take an unfortunate event for airports and the federal government to actually do something about the very real threat of drones. As stated before, even several hours of airport closures due to drones can cost billions of dollars and disrupt the complex system of air travel. And my greatest fear is that UAVs will be used by terrorist organizations in a multi-facetted attack to hurt the American people. I believe it is only a matter of time before this threat will cause great harm to airports and air travelers.

Conclusion

The research goal is to arrive at a conclusion of whether Denver International Airport can effectively defend and defeat unmanned aerial vehicles that pose safety threats to the airport grounds and its aircraft. After analysis, I have concluded that Denver International Airport, as well as emergency management services, are not prepared for a drone or UAV encounter in critical airspace. They are lacking in critical detection and defeat systems that could render a drone inoperable and ensure the safety of travelers. Furthermore, I believe that any sort of disruption of airport operations will have critical financial consequences to the airport and airlines that would render proper drone defense viable to funding. Finally, I can only hope that DIA will not be reactionary to the drone threat; I hope that it does not take a catastrophe and loss of life to understand the real threat of drones.

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