What is DAA, and how does this system help drones?

Dangerous cases of drones approaching with PVA or other drones can occur at high speeds, outside the line of sight and rely on visual controls or is extremely unreliable or simply impossible, it was to resolve such dangerous situations that the DAA system was created - Detect-And-Avoid- System

DAA functions can be divided into three large groups

  1. Detection and tracking of surrounding aircraft for potential hazardous activities.
  2. Identification of hazardous activities.
  3. Prevention of dangerous and conflict situations, building a safe route-evasion and the implementation of maneuver-evasion.

DAA includes a number of subsystems

Each subsystem solves separate tasks:

  1. Airborne radar for determining non-equipped transponders.
  2. TCAS collision avoidance system compatible with civil aviation technology.
  3. Satellite automatic dependent surveillance-broadcasting (AZN-V In / Out) for broadcasting flight information and receiving similar data from other air traffic participants.
  4. System for forecasting and displaying information (Conflict Prediction and Display System).


About a year ago, in the USA, NASA performed flights and system testing on the Ikhana UAV. On June 12, 2018, the UAV first flew in the U.S. national airspace without escorting a special aircraft. Typically, such flights always require that the drone be followed by a PVA to ensure safety. But in this case, an escort aircraft was not used, and the drone used its own DAA (Detect-and-Avoid System) collision avoidance system. The FAA’s special permission allowed remote pilots of the Ikhana UAV to rely completely on the work of a special airborne complex.

Credits: NASA / Ken Ulbrich

During the test flight, a dangerous approach of the manned aircraft to the Ikhana UAV was intentionally performed, and the DAA system successfully informed the pilots and allowed for safe maneuver-evasion.

Currently, the weight of the DAA kit is about 50–70 kg. And, as you might guess, such a system is the prerogative of large UAVs, like Ikhana or SkyGuardian. However, it is worth noting that NASA also carried out work with a system adapted for mid-size UAVs. These were tests on the SIERRA-B drone.

NASA SIERRA-B (Sensor Integrated Environmental Remote Research Aircraft)

The main problem of the test team with SIERRA-B was the smaller size of the UAV, SIERRA-B has a wingspan of 20 feet and weighs about 500 pounds, compared to 66 feet and 8,000 pounds in Ikhana. However, the SIERRA-B flight tests were successful and allowed us to evaluate how the DAA standards developed for larger and faster UAVs would need to be adapted for mid-sized and slower drones in order to open them access to commercial flights in the national airspace.

For smaller drones, options without using an on-board locator are considered, in this case, automatic dependent monitoring-broadcasting, which is also part of the complex, is used as a key technology. Today, several large companies offer special mobile transponders for drones. Sagetech Corporation, as part of the DAA test, NASA provided its mobile transponder for the SIERRA-B drone. There are others, including Russian ones.

Learn more about the composition of DAA

Let's take a closer look at the components of DAA.

1. Onboard radar developed by GA-ASI.

It consists of a two-panel active antenna with electronic scanning, which gives the pilot the opportunity to detect and track aircraft in the same field of view as a person. The onboard radar allows you to track several targets at once, as well as continue the background search for new ones. It is a key component of DAA avionics.

Due Regard Radar assembly



DAA should detect and avoid collisions with aircraft that are not equipped with defendants. Detection and tracking of aircraft with defendants is carried out using ADS-B, a collision avoidance system (TCAS).

2. TCAS collision avoidance system.

The system is compatible with civil aviation technologies and allows drones to interact with PVS equipped with a similar collision avoidance system. The second-generation TCAS, which was used on Ikhana, includes a number of elements: among others, the data processor and mode S transponder can be distinguished by significance. The transponder should always be turned on. If it fails, TCAS Performance Monitor will detect this failure and automatically put the system into standby mode.

Introduction to TCAS II / faa.gov

3. Satellite automatic dependent surveillance-broadcasting.

Transmitter and receiver AZN-B Out / In. It allows broadcasting information on speed, altitude, etc. in the broadcast mode in real time to other air traffic participants, as well as ground services. The ADS-B In receiver on board the drone is able to receive similar information broadcast by other PVS or drones.

ADS-B Flight Tests on Ikhana Unmanned Aircraft System

In practice, in the USA there are three possible interaction schemes:

  1. Directly, when the AZN-B Out transmitter on an airplane transmits data, and the AZN-B In receiver on a drone receives it.
  2. Through the ground relay station. It is necessary in cases where the PVS transmits data and uses the 1090ES line (most often these are large commercial liners), while the drone receives AZN-B UAT data at a frequency of 978 MHz.
  3. If the PVA is not equipped at all with any of the existing AZN-V systems, data on such a PVA is issued from secondary radars, and then transmitted to the ground station, where the signal is converted to the AZN-V UAT format with its subsequent transmission. The signal from the ground station is received by the ADS-B In receiver on the drone in the same way as in the second embodiment. This method provides a slower update rate, since the secondary locator is the source of information, however, it allows you to see even non-equipped AZN-V PVS.

4. System for forecasting and displaying conflicts.

The system includes a set of algorithms for calculating trajectories and mechanisms for displaying this information to pilots.


NASA flights conducted by NASA in 2018 were the first to use airborne detection and avoidance equipment. The tested solution was fully consistent with the FAA concept of “see and avoid” (detect and aviod), and the tasks were successfully solved.

“Our goal is to create unmanned aerial systems that can be certified for flying in non-segregated airspace,” said Linden Blue, CEO of GA-ASI, a hardware development company.

“Today’s successful flight demonstrates the efficient work we are doing with the FAA, NASA's Armstrong Flight Research Center, and Honeywell to develop the ultimate standard for high-traffic unmanned aerial vehicles,” added Linden Blue.

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