WHITE PAPER - Amtech-usa.org

see-and-avoid requirement in the FARs. Hence, a system that detects non-participating
traffic is required.
Search Volume
One critically important factor for any SAA system is the search volume defined by
azimuth and elevation. The Convention on International Civil Aviation, Rules of the Air,
establishes the regulatory criterion that differentiates between a converging or
overtaking 9 situation. The critical factor for a SAA system is that it provide surveillance
of all of the airspace that lies within the converging angle: ±110° with respect to the
longitudinal axis of the ROA, although a lesser field of regard may achieve the desired
level of safety. No regulatory guidance for search elevation exists. NASA and DoD
studies have shown that, in head-on scenarios, a search elevation of ±15° with respect to
the flight path provides adequate coverage to detect converging aircraft that are using
climb and descent angles as high as 20° (rare for civilian aircraft and also for military
aircraft operating outside special use airspace). Overtaking scenarios, which are highly
unlikely at controlled airports, may require greater vertical coverage from the onboard
sensors. Further analysis and a review of the ROA’s concept of operations may be
required in order to determine the appropriate sensor coverage required to provide an
ELOS.
Detection Range
The sense-and-avoid system must detect the traffic in time to process the sensor
information, determine if a conflict exists, and execute a maneuver according to the
right-of-way rules. If pilot interaction with the system is required, transmission and
decision time must also be included in the total time between initial detection and the
point of minimum separation. (see Annex 1)
5. Sense-and-Avoid Requirement
a. General. The probability of a ROA colliding with another aircraft must be
comparable to that for manned aircraft (i.e., equivalent level of safety). The measure of
overall system performance shall take into account onboard sensors, beacons,
transponders, air traffic control, concept of operations, and reliability. The SAA system
shall possess the capability to detect both participating and non-participating aircraft day
and night (weather permitting), notify the ROA pilot/operator of the contact, and
determine if a potential collision hazard exists (Threshold). Should the contact
represent a hazard to safe operations, the system shall either provide a suggested conflict
resolution for pilot action or maneuver autonomously to avoid the other aircraft
(Threshold). The SAA system must consider warnings/directions from other avoidance
systems such as traffic collision alert system (TCAS) (Objective). The system shall
provide information to the pilot/operator on the progress of the resolution/avoidance
maneuver, time and conditions permitting (Objective). After conflict resolution, the
system will provide a recommended return-to-course action (Objective).
9 Convention on International Civil Aviation, Annex 2, Rules of the Air, Section 3.2.2.4
8