FAA reauthorization bill just passed by the House and the Senate contains dozens of directives from Congress to the FAA. One of them, which forces the FAA to speed up the introduction of Unmanned Aircraft Systems (UAS) into the National Airspace System, may inevitably lead to more mid-air collisions. To date, UASs have been authorized solely along the Mexican border and within restricted airspace. In the near future, pilots may be sharing all airspace with these unmanned aircraft.
Small, low altitude UASs will be here very soon. Within 90 days of signing the bill, the FAA will be required to “enter into agreements with appropriate government agencies to simplify the process for issuing certificates of waiver or authorization with respect to applications seeking authorization to operate public unmanned aircraft systems in the national airspace system.” Under this provision, any government agency can apply to operate an unmanned aircraft weighing 4.4 pounds or less, in daylight conditions, less than 400 feet AGL as long as they remain within Class G airspace and at least 5 statute miles from any airport, heliport, seaplane base, spaceport, or other location with aviation activities.
Rules for larger UASs, weighing up to 55 pounds, must be published within 27 months. As part of that process, within 270 days the FAA needs to “develop a comprehensive plan to safely accelerate the integration of civil unmanned aircraft systems into the national airspace system.” Part of that plan requires that the FAA “ensure that any civil unmanned aircraft system includes a sense and avoid capability” and establish standards for pilots and operators of UASs.
At least one UAS has already had a mid-air collision. In August 2011, over the skies of Afghanistan, a 450-pound UAS hit a C130 cargo plane, damaging the plane and forcing an emergency landing. The drone was destroyed.
Near mid-air collisions are also occurring. In August 2004, a dramatic series of images from a German-built Luna UAS documents its own near miss with an Airbus A300B4 airliner with more than 100 passengers on board. The two aircraft missed each other by less than 50 feet. The UAS crashed after encountering the airliner’s wake turbulence.
The reauthorization bill’s requirement for UASs to have a “sense and avoid capability” will help, but is unlikely to avoid all collisions. Research in the last decade has produced a variety of systems that equip UASs with some combination of video cameras, transponders, radar and even microphones to detect nearby aircraft.
Many current UASs flying over Iraq and Afghanistan meet ASTM standard F2411 – 07, which requires unmanned aircraft to detect other aircraft within plus or minus 115 degrees of its heading and within an elevation of plus or minus 15 degrees. After detecting an aircraft, the standard requires a UAS to avoid a collision by at least 500 feet. For flying in the National Airspace System, the FAA could required UASs to have 360 degree surveillance to detect faster aircraft overtaking from behind, something not required under ASTM F2411 – 07.
Technology will help, but eliminating all accidents and mid-air collisions between aircraft and UASs will be impossible. Already the NTSB database documents at least seven UAS accidents in the United States. In the future, pilots will need to use all of their resources to avoid an increasing number of unmanned aircraft in the skies.