A team of researchers at the Technical University of Munich (TUM) and project partners have successfully landed a modified Diamond DA-42 automatically and for the most part without human intervention using a vision-assisted navigation system to align the airplane with the runway centerline.
Unlike autoland systems in air transport aircraft, which have been in use for decades, the TUM “C2Land” automatic landing system combines navigation inputs with vision-assisted navigation to fly the airplane to the airport then position the airplane precisely on the runway. An advantage of vision-assisted navigation is that it can work on any runway that the airplane is capable of using; there is no need for ground-based navigation facilities such as the instrument landing system that is needed for air transport autoland, which in any case is available only at a limited number of runways.
Automatic landing is necessary, according to Martin Kügler, research associate at the TUM Chair of Flight System Dynamics, because of the incipient development of automated cargo and urban air mobility eVTOL aircraft. Fly-by-wire (FBW) flight controls are becoming more widespread in airliners and business jets, and, he said, “Thus, in our opinion, it’s only a question of time until ‘advanced autopilots’ or even full FBW systems become attractive for general aviation aircraft. With our research platform, we want to showcase how that could work and what the benefits are.”
C2Land could help recover the airplane in case of an incapacitated pilot. Other possible applications include helping a pilot land if for some reason a manual landing isn’t preferred or when weather conditions are below instrument approach minimums.
For the C2Land project, TUM added a FBW flight control system to the DA42, connected via clutch-equipped electromechanical actuators to the airplane’s mechanical controls. The FBW system is connected to ailerons, elevator, rudder, and nosewheel steering, and it also incorporates an autothrottle. A full set of conventional controls for the safety pilot in the left seat is still available.
TUM has been working on the autoland program since 2013, focusing on the development of the FBW flight controls and autoland capability.
Technical University of Braunschweig is a partner on the program and developed the navigation system, which includes the vision-assisted navigation. This system employs a visible-light camera and an infrared camera connected to “image-processing software that lets the system determine where the aircraft is relative to the runway based on the camera data it receives.”
The DA42 made its first autolanding on November 30, 2016, but without the vision-assisted navigation, using GPS-based augmentation (GBAS). Later, satellite-based augmentation (SBAS) was added.
The concept of vision-assisted navigation was to enable future certification of C2Land, Kügler explained, as TUM believes that an autoland system based on GBAS/SBAS isn’t certifiable for IFR approaches to the typical 200-foot decision height.
On May 21, 2019, the first autoland with vision-assisted navigation was accomplished. During the automatic landing in Wiener-Neustadt, Germany, test pilot Thomas Wimmer acted as safety pilot. The FBW system does not yet automatically lower the landing gear and flaps, although it does output a signal to indicate when the test pilot should do so. TUM would prefer that the landing gear and flaps switch positions correspond to the condition of the landing gear and flaps, instead of allowing the FBW to lower these devices without the switches also moving to the correct position. “However, we have plans already for how we want to do this,” said Kügler.
After the flight, Wimmer said, “The cameras already recognize the runway at a great distance from the airport. The system then guides the aircraft through the landing approach on a completely automatic basis and lands it precisely on the runway's centerline.”
The autoland system does not automatically apply brakes, although it does keep the DA42 aligned with the runway centerline. TUM is planning to add autobrakes, but currently the safety pilot must apply brakes.