Basic Considerations for Selecting UAS

Basic Considerations for Selecting UAS

In this section, you will understand the requirements for selecting a UAS. Selecting a UAS depends on many factors that are closely related to the intended use of the UAS. Such use requirements will determine the size and weight of the UAS, and its endurance and range of flight, among other factors. In the following sections, we will briefly discuss each of these factors.

Size and weight

Size and weight a play great role in determining payload size and weight and in limiting its range and endurance. Large UASs have the capability of carrying a larger and heavier payload, including the power source. The larger the UAS, the more fuel or battery power it can carry on board. The more power the UAS can carry on board, the better range and endurance of the UAS.

Range and Endurance

The range of a UAS is an important performance characteristic. It is dependent on a number of basic aircraft parameters and weight of the payload. Maximum UAS range and endurance can be achieved with high propeller efficiency, low fuel consumption, and large onboard fuel (or battery power) capacity. A project that requires long hours in the air will need a larger UAS. However, most UASs that are employed for geospatial mapping purposes now days have an endurance of 90 minutes and a maximum range of around 50 miles.

Stability

In physical mechanics, stability refers to the tendency of an object to stay in its present state of rest or motion despite small disturbances. An aircraft must be stable in order to remain in flight. The forces acting on the aircraft, such as thrust, weight, and aerodynamic forces, have to be in certain directions in order to restore the aircraft to its original equilibrium position after it has been disturbed by a wind or other forces. An aircraft has angular degrees of freedom. Those are rotation around the X-axis or roll, the rotation around the Y-axis, or pitch, and the rotation around the vertical to the ground, or yaw. The aircraft has to remain stable around each of these axes. The most critical rotation is the pitch, and stability about it is called longitudinal stability. Some instability can be tolerated around the roll and the yaw.

Stability is essential for aerial data such as imagery acquisition in order to achieve gap-free imaging results. The use of a gyro-stabilized mount for the camera or the imaging sensor is preferred for mapping missions, as it results in uniform coverage free of gaps.

Cost

UAS costs play a great role in the decision for acquiring one. The price of a large UAS sometime exceeds the price of a typical manned aircraft, such as various models of Cessnas, used for aerial imaging. However, the cost of a UAS is justified by the type of jobs that are expected for the use of the UAS. Smaller UAS-based aerial imaging jobs are only justified through the use of a small UAS that costs under $100,000. It is worth mentioning here that due to strict regulations by the FAA on flying UAS, there are no large jobs for the UAS at the current time within the geospatial mapping community. No one can commercially utilize UASs for money-making projects, therefore only smaller UASs are utilized by the mapping community. Once the FAA eases the regulation, we should expect larger demand for medium or large UAS.

Payload Capacity

The maximum weight that a UAS can carry on board also plays an important role in the decision of UAS selection. Different applications require different sensors and therefore different payload capacities. Current UAS used by the mapping community can carry a payload varying in weight between a few to 100 lbs. The payload capacity directly affects the cost of the UAS, as it limits the range and endurance for the UAS. UAS with longer range and endurance cost more than those that fly a maximum distance of 35 miles and for a period of 60 minutes.