2.3 - Blog: Unmanned Aerial Systems

Dear All,

            Safety is paramount in aviation. Unmanned Aerial Systems (UASs) are part of the regulatory frameworks. Pilot or controller must conform to the rules and regulations of local aviation authorities. In order to fly safely, pilot must be aware of the airspace he/ she occupies. In the U.S, there are two categories of airspace: regulatory and non-regulatory. Within these two categories there are four types: controlled, uncontrolled, special use, and other airspace (FAA, 2016). More importantly, UAS pilot must seek approval with Air Traffic Control (ATC) when flying at controlled airspace. Controlled airspace consists of:

• Class A: Airspace from 18,000 feet mean sea level (MSL) up to and including flight level (FL) 600.

• Class B: Airspace from the surface to 10,000 feet MSL surrounding the nation’s busiest airports in terms of airport operations or passenger enplanements.

• Class C: Airspace from the surface to 4,000 feet above the airport elevation (charted in MSL) surrounding those airports that have an operational control tower, are serviced by a radar approach control, and have a certain number of IFR operations or passenger enplanements.

• Class D: Class D airspace is generally airspace from the surface to 2,500 feet above the airport elevation (charted in MSL) surrounding those airports that have an operational control tower.

• Class E: If the airspace is not Class A, B, C, or D, and is controlled airspace, then it is Class E airspace.

            For general public, majority of the pilots fly theirs drones at Class G airspace, which is uncontrolled. Class G airspace extends from the surface to the base of the overlying Class E airspace. Although ATC has no authority or responsibility to control air traffic, pilots should remember there are visual flight rules (VFR) minimums which apply to Class G airspace.

            The applications of UAS increased significantly in view of the improved technologies and lower operating cost. More pilots are flying the drones within the same airspace with others UAVs or manned aircraft. Collision between two flying objects is a concern to FAA and a safety threat to the public. In order to minimize or prevent collision, the installation of sense and avoid system on UAS has become necessary.

            Angelov, P. (2012) emphasizes the sense functionalities of UAS must include detection of all hazards in the environment. It includes bad weather, wake turbulence and terrain proximity. Basic sense parameters to be considered in the design phase are:

·       The detection range of hazardous objects and avoidance maneuvering to be executed within sufficient time.

·       The field of regard, to be perceived or monitored by a sensor (camera).

·       Measurement accuracy, reliability and update rate.

·       Detection distance also depends on UAS cruise speed, turn rate, climb/ descent rates.

            After a collision threat is sensed, the UAV must perform avoidance maneuvering within structural and aerodynamic limits. These avoidance or resolution maneuvers include changes in flight trajectory, airspeed, altitude or heading. If the avoidance leads to deviation of flight path from an ATC clearance, it must be notified as soon as possible. After the conflict is solved, subsequent maneuvers must return UAV to original flight plan or to newly assigned flight path.

            Stepan. K et al. (2012) from Czech Technical University further elaborate the principle of conflict detection and resolution (CDR). The function of the collision detection and resolution system is to detect the collision and provide the resolution in the form of an evasion maneuver which is executed by UAV’s autopilot. The CDR system has five basic functions: sensing, trajectory prediction, conflict detection, conflict resolution and evasion maneuver generation.

Reference:

Angelov, P. (2012). Sense and Avoid in UAS. UK: Wiley.

FAA. (2016, April 1). Chapter 14- Airspace. US.

Stepan. K et al. (2012). Sense and Avoid Concepts: Vehicle Based SAA System. UK: Wiley.