UAV updates: Overcoming a navigation challenge, autonomous UAS rolls out

The Boeing B-777 or “Triple-7” is a big airplane — at over 200 feet long, with a wingspan of more than 200 feet, it carries more than 300 people. But getting it from one airport to its destination, which could be up to 8,500 nautical miles away, presents a significant navigation challenge. Combined Air Data and Inertial Reference Unit(s) (ADIRU) and three GPS L1 receivers form the certified primary navigation sensor cluster for the B-777-200.

Boeing has been undertaking its ecoDemonstraor program using various models of its aircraft, and in 2019 a B-777-200 was available for a number of technology demonstrations.

Along with the basic objective of testing out new fuel efficient technologies, Collins Aerospace collaborated with Boeing to demo and test their new generation navigation system using dual frequency, multi-constellation GNSS receivers.

Boeing B-777-200 ecoDemonstrator (Photo: Boeing)

The aircraft is normally equipped with buyer selected, certified GPS receivers which also track world-wide Satellite Based Augmentation System (SBAS) signals — not only improving accuracy but also improving (or reducing) the size of integrity bounds of the position solution. Currently, GPS/SBAS L1 is the only signal permitted under current FAA approved MOPS (Minimum Operational Performance Standards) for aircraft use in the US, but new MOPS standards are under development for the use of DFMC. Hence, this demonstration program would significantly aid towards validation of the new MOPS standards.

For the demo program, the Collins Aerospace GLU-2100 Dual-Frequency Multi-Constellation (DFMC) enabled multi-mode receiver (MMR) was used as the primary position source. The three GLU-2100 MMRs fitted were loaded with modified software that enabled the tracking and use of GPS L1/L5 and Galileo E1/E5a for the navigation solution using multi-frequency GNSS antennas.

The navigation mode and position integrity algorithms were also revised so the DFMC navigation outputs could be used as the primary navigation outputs for the Flight Management System and the transponder. The Collins GLU-2100 certified L1 position solution was computed in parallel and used to bound the integrity of the Collins DFMC position solution.

The demo gathered stacks of data on this first use of a DFMC receiver as the primary position source on a civil air transport aircraft. The lessons learned will undoubtable support the effort towards the introduction of dual frequency multi constellation GNSS for regular use in civil aviation.

Meanwhile, in the world of unmanned aircraft, several thing of note were recently reported, including:

• Aveum Inc. rolled out its Ravn-X autonomous UAS, which is claimed to be a large, fully autonomous unmanned vehicle which can deliver satellites to low earth orbit.
• General Atomics demonstrated its Avenger UAV with autonomous CODE (Collaborative Operations in Denied Environment) capability and completed static load testing of the MQ-9B SkyGuardian wing, part of the regular qualification program for civilian aircraft certification.
• Airbus Zephyr High Altitude Platform Station (HAPS) UAV completed another phase of high-altitude flight testing in Arizona.

The Ravn-X is a large UAV which apparently uses regular jet fuel, yet claims to be able to get to low-orbital altitudes. With a 60-foot wingspan, 80-f00t length and up to 55,000-pound take-off weight, this is certainly a large vehicle.

There looks to be a long tubular belly protrusion which could be a rocket motor, or fuel tank, or even a payload bay — absent any explanation of how regular air-breathing engines could reach space, we’ll have to speculate — maybe a new type of engine? Nevertheless, burning jet fuel alone, gaining space access might be difficult. Apparently the US Space Force is a sponsor and future customer, so there should be credibility to these claims.

Ravn-X new-gen space UAV (Photo: Aveum)

X-37B U.S. Spaceplane (Photo: U.S. Air Force)

The object is to provide rapid access to space for small payloads with a reusable, autonomous, unmanned vehicle. The current vehicle is apparently 60% re-usable, soon to become up to 95%. And minimizing turn-round time is also a major target, with a claim of 3 hours being possible — quite an achievement. Of course, the U.S. already has the X-37B Orbital Test Vehicle spaceplane in operation, with a record 780 day stay in space already under its belt.

During the recent two-hour test flight of the General Atomics Aeronautical Systems Inc. (GA-ASI) Avenger UAV, equipped with tactical radio/data links and targeting capability, independence between control and mission systems was demonstrated.

The flight also tested a degree of autonomy related to the U.S. Air Force Skyborg (aircraft-UAV teaming) program. The USAF Collaborative Operations in Denied Environment (CODE) software controlled the flight for over two hours without regular ground operator inputs, and coordinated air-to-air search operations with one actual and 5 simulated aircraft.

GA-ASI Avenger UAS (Photo: GA-ASI)

The Airbus Zephyr High Altitude Platform Station (HAPS) successfully completed another series of flight tests in Arizona in the first weeks of November. The UAV has undergone weight reductions and was equipped with revised control software which improved system robustness. The UAV is powered solely by sunlight, operates in the stratosphere and provides persistent services currently provided by satellite.

Zephyr is prepared for flight-test (Photo: Airbus)

Operational flexibility and aircraft maneuverability were demonstrated, particularly during lower altitude flying and during transition into the stratosphere. A new flight planning tool suite was put through its paces and a number of different operational concepts were tested by conducting many flights in quick succession.

These tests again demonstrated Zephyr’s capability for take-off, climb, cruise, the performance of the upgraded flight control system, descent and successful landing. Day and night on-station performance of almost 26 days was previously demonstrated during July 2018 flight tests.

It’s good to see demonstrated progress towards dual frequency GPS/Galileo civil aircraft operations through the Boeing ecoDemonstrator program, along with UAV initiatives in potential space-launch capability, autonomous aircraft-UAV teaming, and advances in the HAPS concept. All this, even with the work managed despite these interminable COVID-19 restrictions.