Deutscher Luft- und Raumfahrt-Kongress (DLRK 2024): Dynamic adaption and test bench evaluation of Engine-off emergency landing routes

Speech summary : 
Today, we want to address a critical challenge in aviation: what happens when a complete engine failure occurs. This situation places pilots under enormous pressure, both in terms of time and mental strain. They must solve two critical problems almost immediately.

First, they need to identify a suitable landing site. If no official airport is within range, the pilot must choose an appropriate emergency landing area. Second, and equally important, is the precise calculation of the glide trajectory to reach that site—something that differs significantly from a standard, engine-assisted landing.

Under normal conditions, when the engines are functioning, energy can be added whenever needed. But during a glide, only the aircraft’s existing potential and kinetic energy are available—and they are constantly decreasing. This makes it essential to model the energy balance of the aircraft accurately. The trajectory must be designed to end at the exact runway threshold, with the correct altitude and heading. Excess energy can be dissipated through flight maneuvers like turning or deploying the landing flaps. However, any misjudgments—whether it’s wind or thermals—cannot be corrected by simply increasing power.

The problem is that most commercial landing assistance systems available today, such as Garmin, Foreflight, or SkyDemon, offer limited support. Some systems, like Garmin Autoland, still require engine power, while others only indicate the range you can reach in a glide, such as Garmin SmartGlide or SkyDemon. Unfortunately, none of these systems calculate the exact glide trajectory, making them unsuitable for fully autonomous applications. Additionally, no system currently provides data on emergency landing fields outside of registered airports—this is a crucial factor when altitude is too low for a long glide.

This is where Safe2Land, the system we developed, comes into play. It solves both of these issues. Using advanced pattern recognition techniques, based on artificial neural networks, Safe2Land identifies suitable emergency landing sites from geodata, such as digital orthophotos, digital surface models, and OpenStreetMap. To give you an example, in the state of North Rhine-Westphalia alone, we identified over 103,000 potential emergency landing sites, all stored in a specialized database.

But identifying the landing site is just part of the solution. Using our concept of kinematoide chains, Safe2Land also calculates glide trajectories that model environmental changes along the flight path, such as air density or wind vectors at different altitudes. The system generates precise control instructions—like target heading and bank angle—which are displayed to the pilot through a flight director. What’s more, Safe2Land enables fully autonomous landings by converting these instructions into commands for an autopilot. This capability has been successfully tested in a flight simulator.

During our presentation today, we will demonstrate the Safe2Land system using a workbench that is integrated with a flight simulator. This allows us to quickly evaluate the effectiveness of our trajectory algorithms. It’s important to note that while we use parameters such as optimal glide speed, glide ratio, and wind conditions at various altitudes to model the glide characteristics, these can only be estimated and may change during the flight. There are also interactions to consider. For example, an overestimated glide ratio can affect the glide path in much the same way as an unexpected updraft would. Using our workbench, we can analyze how such disturbances can be compensated for by dynamically adjusting the trajectory. In some cases, deploying the flaps earlier during the final approach can reduce the impact of an updraft.

However, if these disturbances become too strong, recalculating the trajectory might be necessary. We monitor this by comparing the predicted touchdown point to the threshold of the (emergency) runway. If the touchdown point is predicted to be too far beyond the threshold, Safe2Land will deploy the flaps earlier. Conversely, if the predicted touchdown point no longer falls on the runway, flap deployment is delayed or even skipped.

In conclusion, the Safe2Land system offers pilots a reliable tool for managing engine failure scenarios. Not only does it provide critical guidance, but it is also capable of performing the emergency landing entirely autonomously through the autopilot.

Autonomous Emergency Landing of a Bristell B23 in a small mountainvalley 

In this video you see how our Smart Emergency Assistance (SEA, App Safe2Land) controls an Auto pilot after a total engine failure. Safe2Land calculates an optimised route to glide to an emergency landing site that was identified by our AI-based methods. Without  the database of emergency landing locations the pilot would be lost in space and it would be unlikely that she could find that site by looking out. In this way only Safe2Land can safe the life of the pilot and passenger. Even if a pilot incapacitation occurs at the same time, the passengers can be rescued by the help of Safe2Land.

Autonomous Emergency Landing of a Bristell B23 on Runway 22 in Dresden 

In this video you see how our Smart Emergency Assistance (SEA, App Safe2Land) controls an Autopilot atfer a total engine failure. Safe2Land calculates an optimised route to glide to the threshold of a nearby airport, here runway 22 in Dresden. 
Note that not only the path is precisely followed by the autopilot but the flaps are automatically set during the final approach.

Engine-out emergency landing during heavy thunderstorm 

In this video you can see how our Smart Emergency Assistance (SEA) assists pilots in the event of total engine failure. SEA calculates an optimised route to glide to the threshold of a nearby airport.
If there is no registered airport within reach, a database of AI-recognised airfields for the specific aircraft will help the pilot find a safe place to land. The guidance shown is provided by our Smart Flight Director (SFD), which consists primarily of two red lines. The intersection can be thought of as the tail of an aircraft flying ahead. The pilot must follow it and move the intersection to the origin of the base axes. 
In addition, his plane flies at best glide speed towards "magic" waypoints calculated by SEA. After following these waypoints and setting the flaps as required for the final approach, the aircraft will arrive over the threshold at a suitable altitude for flaring out.

Remark: the video is partially accelerated in order to shorten the total length.

A320-Simulation of Azore glider emergency

In 2001, an  Air Transat Airbus 330 had a complete engine failure due to a leak in the fuel line. At that time, the plane was about 120 km away from an island in the Azores and fortunately had such a high cruising altitude that it could glide to a military airfield without thrust. However, the problem was the heights
division during the final approach, because the pilots have flown too high and too fast. We flown this emergency in an A320 flight simulator from the Aachen University of Applied Sciences and were able to show that Safe2Land would have given the pilots the best possible support both during the approach and the subsequent landing.

Remark: the video is partially accelerated in order to shorten the total length

Safe2Land TestFlights  in Nordholz-Spieka

Here you see a time-lapse video about the three emergency test flights described in the report section in more detail. The test flights were conducted with a Bristell NG5 (D-MMBX) that uses a Garmin G5 for measurement of flight data like IAS, pressure altitude, pitch, roll and GPS location data. These data were transmitted via Wifi to an Android tablet PC and than used by our Safe2Land app to calculate a three dimensional Dubin path from the emergency position to the threshold of Spieka airfield.

Remark: the video is partially accelerated in order to shorten the total length

Safe2Land App in action

Safe2Land was implemented for Android and in the video above you can see how it works in case of an engine failure emergency. My means of the Smart Flight Director (SFD) even less experienced pilots will manage to safely glide with the airplane to an airfield that is within reach by the excess altitude over ground. 
The SFD is very easy to use. By moving the stick or yoke the objective is to chase the disc and keep it centered within the "hole" of the primary flight. In this case, the airspeed corresponds to the best glide speed of the aircraft and the route's track error is zero. Thus the aircraft glides along the route optimized by Safe2Land and it will arrive in approx. 20ft over the threshold of the selected runway. 

Safe2Land controls a Garmin1000-Autopilot in X-Plane 11

Safe2Land can directly control an Autopilot to fly an emergency route in case of engine-out. This is demonstrated in an X-Plane 11 setup. We program the required heading and and sink rate by means of commands via UDP to the G1000 within a C172 airplane in the flight simulator. In the video the simulated engine-off emergency is south of EDLA and the Safe2Land App selected a route to the threshold of runway 23. In the Video you can see that this route can be easily flew by means of the autopilot connected to the G1000. Of course, we could also control an autopilot in a real airplane and in the near future we will demonstrate this by means of a research aircraft. Stay tuned!

Real Emergency Landing Exercise with the brand-new Safe2Land with SFD 

Another real emergency landing exercise with the Katana DV20. Again, this video shows a simulated emergency landing at Arnsberg-Menden Airport (EDLA or FAM). The pilot approached the airfield inbound to southeast and set the engine to idle at about 1600 ft above the center of the runway. Then he flew at the speed of best gliding (65-70 kn) guided by the integrated Smart Flight Director (SFD) of the Safe2Land App. Note that by means of SFD the pilot doesn't need to know the best gliding speed. Even laywoman oder -men are able to fly the airplane in case of an engine-out or pilot's incapacitation  emergency. Although there was significant crosswind from the south, an unexperienced copilot easily managed control the airplay to the threshold of runway 23 at the perfect height for a landing flare. There is also a wind estimator and the Safe2Land's App glide path was permanently adapted to the  updated wind situation. Besides the SFD there is also a flight path trend line over a moving satellite image. Note, that in case of an emergency, the pilot can select between a published runway of the EDLA airport and various emergency landing fields that are stored in a precomputed database. In an upcoming video we show that Safe2Land can also advise an Autopilot to fly  the emergency route to the threshold.

Engine-out in IMC with lack of ILS or during night flights

Emergency landing in blind flight. In this video you can see an emergency landing approach at Instrument Flying Conditions (IMC). Due to the high speed of the glide path calculation by our moving target method, it is possible to make an emergency landing even with complete loss of visibility and lack of any conventional instrument based approaches (FPV, ILS). This is demonstrated here on the flight simulator X-Plane 11 for an emergency landing on the airfield Santa Cilia De Jaca.

Real Emergency Landing Exercise with an older ELA-Version

Real emergency landing exercise with a Katana DV20. This video shows a simulated emergency landing at Arnsberg-Menden Airport (EDLA or FAM). The pilot approached the airfield inbound to southeast and set the engine to idle at about 1600 ft above the center of the runway. Then he flew at the speed of best gliding (65-70 kn) along the route prescribed by ELA and reached the runway threshold at the right height for landing. The ELA glide path was calculated for the current wind situation (from 190 to 7kn) and is displayed in the navigation software AirNavigationPro.

Fixed wing drone autopilot landing

In the video you see our latest achievements regarding autonomous engine-out emergency landing. The drone has an autopilot that is controlled by our moving target algorithm to safely guide the drone to an emergency landing field. In contrast to trochoid based approaches it is one million times faster and can run on an embedded microprocessor. The integration of the moving target algorithm into an autopilot-controlled fixed wing model airplane was realized as part of a master thesis by Nikolai Voget. We work towards to integrate it into a real airplane as well.

Flare Assistant

The Flare Assistant (FA) helps pilots to make a smooth touchdown. Pilots are guided by a so called smart flight director SFD that indicates how they have to move the elevator. If the red disc is within the circle no action is required because the aircraft is on track for a perfect landing. Also audio signals announce the flare altitude and loud beeps require pulling the elevator. If there are no audio hints the aircraft is on track.

Thermals Assistant

The Thermals Assistant (TA) visualizes the thermal situation around the sailplane. It leaves a trace of red or blue dots along the flight path. The red dots indicate upwind and should be circled it order to gain height. The small line in heading direction helps the pilots to accomplish this task.

Circling Autopilot

On the following video you can see our "Circling Autopilot" in action. We developed that Autopilot in connection with a graphical tool called "Variomap" that illustrates the thermal situation around a sailplane and helps the pilot to get more lift out of the thermals. By means of the Circling Autopilot the human pilot has just to guide the airplane close to the thermal and then the Autopilot takes care for centering the thermal.