Development of highly configurable rescue systems for UAVs/drones, manufactured according to high EU standards in our own production facility. We offer comprehensive support and enable our customers to participate in the development process in close collaboration with our development team.
THE STAGES OF THE DEVELOPMENT PROCESS
a) Requirements analysis.
b) Definition of the requirements profile and system configuration.
c) Analysis of the key technical data and construction volume of the UAV / drone.
d) Concept designs / construction plans.
e) Production of prototypes.
f) Tests / drop tests.
g) Support with certification (if desired).
h) Series production
What information do we need to develop a customized rescue system for you? Here, we have listed the most important factors and explanations that are crucial for us in the design of the system. The terms UAV and DRONES are used interchangeably and always mean the same thing. If you want to start a specific inquiry, please use our Questionnaire.
PASA distinguishes between two variants:
A) The system is designed so that the impact on the ground does not cause significant damage and does not endanger people. The drone may be damaged in the process, or
B) The impact must be softened by the rescue system so that the drone also does not suffer significant damage. In the end, it almost always comes down to a cost question of whether, and if so, what can be damaged on the drone and what cannot.
Landing systems are rescue systems that are used when the landing of the drone always involves deploying the parachute, and no other type of landing is possible because, for example, there is no landing gear. Landing systems are therefore used and packed much more frequently than rescue parachutes, and this must also be taken into account during development. The demands on landing systems are therefore significantly higher than those on emergency rescue systems. In many cases, the constant use of one or more landing dampers (such as one or two airbags) will also be required.
In general, the horizontal and vertical flight speeds have a very significant impact on the opening time and opening shock of the rescue or landing system. The mentioned UAV types differ greatly in terms of flight speed ranges. At high horizontal speeds, such as those of eVTOLs with tilt-wings/propellers (tilt-wing eVTOL) or fixed-wing UAVs, it may be necessary to equip the main parachute canopy with a “slider” to prolong the opening time and reduce the G-forces during the opening shock.
Sliders are small polygonal sails that keep the suspension lines tighter and longer at the start of the main canopy deployment. The initially high air resistance allows the slider to slowly glide towards the UAV, slowing down the filling behavior of the main canopy. The opening speed can thus be reduced from, for example, 300 km/h to approximately 80 km/h. It is important to note that the anchorage of the main line in the drone must withstand the resulting G-forces and distribute the load across the drone. This strong speed reduction is particularly important for fixed-wing UAVs to prevent wing breakage during the opening shock. Additionally, camera manufacturers guarantee the functionality of their products only up to certain G-forces. The operational limits of these cameras should be inquired with the manufacturer in advance.
In mini-helicopters, the rescue parachutes are installed in the lower part of the drone and are ejected sideways by air pressure, a spring, or pyrotechnics. Once the parachute deploys, the main line swings upward and positions itself between the rotor blades of the helicopter, which have automatically switched to idle mode. Experience has shown that this process, despite the powerful rotor, does not cause any problems as long as the motor is disengaged.
For horizontally oriented propellers (fixed wings or tilt rotors, such as tilt-eVTOLs), the parachutes are primarily housed in the rear part of the drone and are ejected backward using pyrotechnics, air pressure, or springs. In most cases, however, the airflow is utilized to deploy the pilot chute. A pilot chute is a small canopy that inflates quickly, pulls out the main canopy, and tensions the suspension lines.
The total takeoff weight naturally has a very significant impact on the size of the canopy. With high takeoff weight and greater inertia due to flight speed, not only do the requirements for anchoring the main line in the drone increase, but also the reinforcements on the canopy to withstand the opening shock.
Built-in cameras or camera mounts, or similar equipment, should also be able to safely withstand the opening shock.
When developing the rescue or landing system, it is essential to consider the entire speed range of the drone. The larger the speed range, the more components the rescue system will require, and the more design volume must be accounted for during development.
For a large flight speed range (e.g., 0-300 km/h), the design of the system needs to be carefully considered. The higher the average flight altitude above ground, the more time can be allotted for the system to deploy.
At low flight speeds, such as with multicopters and mini-helicopters, sliders are not required, which reduces opening times. For these types of UAVs, it is crucial to ensure that the rescue system does not get entangled in the propellers/rotors and that the deployment occurs as far away from the UAV as possible. These UAV types often face the most unfavorable scenario: a combination of low altitude (below 70m) and low flight speed. As long as this situation persists, the drone should remain in a secured flight area (e.g., an airfield). Upon exiting the safety zone, the drone should have the necessary minimum altitude and forward speed to successfully deploy the system(s) in an emergency.
The standard operating temperature range of our systems is between -30°C and +50°C. If extremely low operating temperatures are common, this should be considered in the design and material selection. At very low temperatures, parachutes may open slightly slower because the fabrics become stiffer.
The systems should always be stored as dry as possible (under 75% humidity), not exposed to direct UV rays, and never packed while wet. After water landings, it is very important to thoroughly dry all materials in the shade to prevent mold or the fabric sticking together later.
It is important because, at 4,500 meters above sea level (ASL), air pressure is almost halved. The lower the air pressure, the higher the flight and descent speeds of the drones, and this also applies to the rescue and landing systems. If operations predominantly occur at higher altitudes, the size and design of the system must be adjusted accordingly.
All the previous answers determine the size and scope of the rescue or landing system. If you, as a UAV manufacturer, want to avoid an additional build-up, you should plan for enough space for the system in the right location and provide a solid anchorage from the beginning. The packing volume of the most common parachute sizes can be found in product tables on the PASA website.
If the anchorage of the main line is not near the center of gravity of the drone, it may rotate during the fall. However, it might be desirable for the manufacturer or user for the drone to land upside down when the parachute is deployed. This is advantageous if, for example, there are expensive cameras or other equipment on the underside.
For a drone, the anchorage point of the rescue or landing system should be able to withstand at least 10g over a period of 50 milliseconds.
For reusable landing systems, we recommend that during impact with the ground, a peak value of 6g should not be exceeded to avoid damaging the drone. By installing airbags, this value can be reduced to 4g. For drones that can be partially damaged, the manufacturer or user decides what potential damage they are willing to accept.
Regulations and guidelines often focus on ensuring that the total kinetic energy of the drone, including the system, does not exceed a certain value during impact, in order to avoid endangering people or causing significant property damage on the ground. More details can be found in point 12).
Our tests and experience have shown that at zero forward speed, rescue systems tend not to fully deploy below 70 meters above ground. At higher flight speeds, this altitude can drop to 50 meters. However, below 50 meters, even in this case, is often too low for full deployment.
There are no specific regulations regarding this, but PASA recommends that the descent rate at impact should not exceed 7 m/s (23 ft/s). However, there may be regulations concerning the total kinetic energy with which the drone is allowed to impact. The kinetic energy is calculated as:
E-kin = ½ * m (mass) * v² (speed).
A damping system is a part of the landing system and, in most cases, consists of airbags that can be filled in various ways (more details in Answer 1). Their necessity is often related to the value of the drone and its equipment. If the drone always lands with a parachute, a landing system is usually required. In such cases, the construction and packing volume for the airbag system beneath the drone must also be considered. Airbags can be inflated during the fall using blowers to speed up the process. This is particularly recommended for large and heavy drones.
The determining factors are the payload and the desired descent rate. If you have enough space in the fuselage, we recommend a descent rate of 4.5 m/s.
These serve to distribute the load during canopy deployment. The connection points on the UAV should be designed to withstand 10 times the Maximum Takeoff Weight (MTOW). Theoretically, one attachment point could suffice, but using three or four points can significantly better define the position of the drone during impact. This is particularly important if there is expensive equipment on board that must not be damaged during ground impact. Additionally, multiple points help distribute the tensile load across the entire drone during deployment.
The parachute is designed to withstand 10g of the specified Maximum Takeoff Weight (MTOW).
A separation system is needed if you intend to use the parachute in strong wind conditions. It cuts the main line, allowing the parachute to separate from the drone so that the drone is not dragged across the ground. An optional safety line can be attached to the lower edge of the parachute and connected to the drone to prevent the parachute from flying away.
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