In the first chapter, I began the introduction to the world of Un Manned Aircraft systems (UAS) by clarifying terminology and reviewing the central characteristics of “A system”. The chapter ended by describing the fundamental process for designating mission characteristics, explaining the first two elements of mission objective and mission tempo.
In chapter two, I completed the initial overview by clarifying the mission’s third element of work area characteristics, and elaborated on the issues of crew structure, selection and characteristics. At the second half, I expended your UAS knowledge base by reviewing and explaining common UAS elements, components and characteristics, such as platform types, power source and engines, payloads, weight, flight Altitude.
In this third and final chapter, I will go on to expend your knowledge base by reviewing and explaining on additional critical UAS elements which are commonly misused and misunderstood, such as range, endurance, airspeed and groundspeed, take-off and landing methods, ground control systems, communication (UPL/DNL), external lights, training, maintenance, emergency, redundancy/Backup and safety.
I hope you enjoyed these chapters and feel free to contact me qith any questions.
Range supposedly represents the system's distance-coverage capabilities, with everybody seeking to expand it, despite the fact that when it comes to range, longer is not always better. A system's range must coincide with the mission parameters, be relevant to the data require, and adhere to external forces, such as response teams. But what is "real range" and what are the factors affecting it?
In airborne systems, range simply refers to the distance an aircraft can fly in standard conditions, typically limited by the platform’s innate aerodynamical characteristics, average speed and the amount of fuel.
It goes without saying, that range is affected greatly by flight modes and environmental conditions such as winds and temperature.
In UAS, this range is additionally limited by the required communication range, be it Uplink alone or also Downlink.
Please remember that as a general rule – longer range is not always better as it has to be balanced with mission needs and other supporting characteristics.
Recommended manufacturer range typically refers to the maximum flight distance the system can achieve via the system's communication. Some manufacturers refer to the maximum uplink capability, while others are more accurate and refer to the relevant downlink distance.
Real or effective range refers to the range that still enables mission performance while allowing relevant data to be collected, if needed, via a downlink. If the mission is meant to follow suspected criminal activity, then the range must enable us to view the image from the aircraft (DNL) in order to enable the teams to respond accordingly. If the mission is a simple mapping mission, then the uplink becomes the relevant operational criterion. It is critical to note that in many cases manufacturers display uplink range, while the relevant issue is actually the effective DNL range.
Range is affected by four main issues:
Communication: One of the cornerstones of a UAS is communication, and the development of features that enable increasing amounts of information to be transmitted in real-time to the operators on the ground. Most civilian systems rely on line-of-sight communications, which are sufficient for their market's missions. The uplink commonly contains small batches of data and commands to the platform and payload, which decreases its sensitivity and increases the ease of transmission over greater distances, thus enabling longer range; while the downlink usually includes large batches of data, which require a wider bandwidth and stronger power-consuming transmitters. In non-real time systems, the UPL becomes the proverbial weaker link.
Flight time (endurance): Flight time refers to the time between takeoff and landing, but it also includes the necessary flight time between the base and the target, making the operational time over the target a critical factor. If a system can endure a long range flight because of its communications but can hover over the target for only one minute, then it is completely useless. Users must therefore understand their area of operation, possible sites and the operational time actually required over targets.
Wind and airspeed: Airborne systems are greatly affected by both winds and their speed capabilities. An area where winds are routinely strong may shorten mission ranges and endurance dramatically.
Supporting factors: In various UAS missions, especially ISR missions, the range must be supported by secondary factors, such as ground teams that can support/respond according to the mission's findings and more.
Below is a basic division of operational ranges, meant to enable prospective users to identify their needs:
Immediate proximity (Urban or ~<500m) – Refers usually to immediate response missions in urban areas or in areas that are in immediate proximity to the operator. These missions require smaller platforms that can provide a quick birds-eye view of the area or an insider view of a building. These systems are characterized by micro size (~500 g), very short flight time, very short communication range and, fixed angle cameras.
Proximate (<3km) – Refers to activities that require a rapid-response system, for open air areas, or units that need to routinely cover a relatively small region. These missions are typically more for monitoring, response purposes and less as a preventative or early detection ISR tool. These systems are characterized by small size (~1kg), short flight time, short communication range and usually fixed angle cameras
This range refers to activities that are required to cover small to medium size areas, under their direct management, allowing for constant monitoring and preventative or early detection activity in the form of ISR. The variability in this category is extensive, as areas may differ in their operational requirements. These systems are typically characterized by small-medium size (~2-15kg), short/medium flight time, and short /medium communication range that may include gimbaled or fixed angle cameras.
This refers to activities that are required to cover medium-to-large areas, sometimes beyond their direct management, allowing for constant monitoring and preventative or early detection activity in the form of ISR. These systems are characterized by medium weight/size, medium flight time, medium/long communication range and usually high quality gimbaled cameras with possible other sensors. The variability in this category is also extensive as areas may differ in their operational requirements.
This range refers to activities that are usually required to cover varying areas at a state-level, beyond their direct control but in coordination with local ground activity. These units usually enable long-term, long endurance monitoring and preventative/detection activity in the form of ISR.
Ultra long range:
This refers to activities that are required to cover varying areas at a federal/international level, beyond their direct control, usually via satellites, but in coordination with local ground activity. These enable long term, long endurance monitoring and preventative/detection activity in the form of ISR, but due to their cost they are usually deployed for very specific missions.
Endurance usually represents a system's overall flight-time capability. A system's endurance must therefore coincide with the mission, be relevant to the data required and the distance between base and target, and consider various external forces, such as response teams and the time necessary to complete the mission.
Most systems experience slow erosion in endurance over time and over environmental conditions such as wind.
The recommended manufacturer endurance typically refers to the maximum flight time the system can achieve.
Real or effective endurance refers to the flight time that still enables mission performance by allowing sufficient time to fly to the target, execute the mission and return safely.
A system used for mapping areas or ISR requires an endurance range that will enable the most efficient coverage of the entire area, or enable the platform to fly to the mission area and collect the data while still leaving it sufficient operational time to return to its base. In contrast, a fast-response system may be required to work at short intervals only, enabling it to recharge every time it lands.
In most cases, the manufacturer-supplied endurance details refer to flight under optimal or standardized conditions. It is important to note that at times, this means flight time either without a payload or with a basic payload only.
Endurance is affected by four factors:
System weight and power source quantity: Power is one of the UAS cornerstones, with developments in this field striving to enable extended flight time. A system's size usually alludes to its required power source (fuel, batteries, etc.), theoretically facilitating increased endurance.
Platform aerodynamics and subsystems' power consumption: A system's aerodynamic design and the selection of subsystems will have a direct impact on its endurance. Unmanned aerial systems classified in the same category may appear to be externally similar, but they may eventually have very different endurance due to their design, engine selection and internal components' consumption levels.
Payload: In most UAS, the main power consumption is expended in favor of creating thrust, but the secondary highest power consumption is by the payload and communication. The selection and use of these components will have a direct impact on endurance.
Environmental conditions: Environmental conditions have a direct effect on endurance. Calm weather conditions allow the system to operate efficiently, increasing endurance, while rough weather conditions, such as strong winds. May diminish endurance dramatically, as they may require more thrust, depending on the systems design and mission.
Airspeed and groundspeed
Airspeed refers directly to the system's velocity in relation to the air. It is usually designated as Indicated Air speed (IAS) and it is measured by the Pitot tube and is measured in knots. Groundspeed refers to actual progress in relation to the system's last position via horizontal movement only, and it is usually calculated and displayed in km/h.
To clarify: Airspeed:
Airspeed is measured in the air. In propelled systems it is typically derived from engine activity.
All systems have minimal airspeed under which the aircraft will stall and lose lift.
All systems have a designated maximum speed which the system cannot exceed without potential damage to external systems.
Most systems have optimal speeds in which they have optimal power/fuel consumption.
Some systems allow complete flexibility, while others may only provide preset airspeeds.
Higher velocity systems can reach the mission area faster, but are much harder to operate and may complicate the payload's operation. Lower velocity systems usually afford higher efficiency and better payload operation.
Several other versions or airspeed can be used, such as true airspeed(TAS), equivalent airspeed (EAS), calibrated airspeed (CAS) etc.
Groundspeed is calculated as if the aircraft was moving on the ground.
Groundspeed takes into account the actual horizontal movement of the platform.
If a platform is flying 70 knots, in 70 knots head/nose wind towards the aircraft, the ground speed will be “zero.”
Groundspeed is critical to operational understand, as it defines the system's ability to reach a target area and return safely.
The takeoff or launch stage is critical for any aircraft, as it is when the platform becomes airborne. In such, every system design affects and is affected differently by many factors.
In VTOL and transitional flight systems typically have a straightforward takeoff stage via vertical lift, while fixed-wing platforms the lighter the system is, the greater the variety available. Large platforms usually require appropriate logistical preparation, such as a runway with sufficient safety margins and arrest mechanisms; while smaller platforms try to find takeoff solutions that will diminish their logistical footprint while emphasizing efficiency and safety.
Other manners of takeoff may include hand launching, bungee, catapult, cord-assistance, air-pressure, rockets and more.
Since takeoff is such a sensitive, critical stage the process requires special end-user attention, emphasizing its suitability to field conditions such as altitude, terrain, weather conditions, mission structure, safety protocols, personnel capabilities, maintenance procedures and more.
Landing or recovery is a critical stage, where the platform comes back down to the ground in an organized manner. Every system has its own design that affects and is affected by many factors.
In VTOL and transitional flight systems the landing stage is straightforward, and is performed via vertical descent; while in fixed-wing platforms, as in takeoff, the lighter the system is, the greater the variety of options available. Large platforms usually require appropriate logistical preparation, such as a runway, while smaller platforms can find landing solutions that diminish their logistical footprint, while emphasizing simplicity and safety.
Other manners of landing may include the use of a net, cable catch, belly landing, parachute, air-bag, deep stall and more.
As landing is a sensitive, critical stage the process requires special end-user attention emphasizing its suitability to field conditions such as altitude, terrain, weather conditions, mission structure, safety protocols, personnel capabilities, maintenance procedures and more.
Ground control station (GCS)
The GCS is one of the four main components of any UAS. As such, it includes all the necessary equipment that directly enable the ground-based control process of the airborne platform and payload used for the mission, including the operator's display, operator software and controls (screen, joystick, button, etc.), station computer, power source and communication kit (transmitter, receiver, antennas, etc.).
The quality of the GCS' subsystems, combined with the quality of the platform and flight software, will determine the interface's ease of use, safety and mission efficiency. The complexity of the GCS usually coincides with the platform's size and complexity, as it affects range, mission complexity etc. Some short range systems, compensate for their communication range by enabling the use of a mobile GCS, which requires a light system with directional antennas that constantly update their angles in respect to the platform's location.
It is crucial to assess the quality of the GCS thoroughly including, user interface, operator's display levels, ease of control/change, warnings, emergency protocols, safety protocols, limitations, etc.
Communication (UPL, DNL)
UAS are based on well-planned communication systems that relay commands and data to the aircraft via uplinks (UPL), and enables the collection and display of the platform and payload data in the GCS via downlinks (DNL).
There are various types of integrated communication methods in UAS, each selected because of specific characteristics in favor of balancing the mission's needs (range), power consumption (endurance), interferences, available components, decryption needs and available frequencies. Most commonly, the communications used by line-of-sight-based systems will use UHF as their uplink band, and S or C band for downlink. Ultra long-range systems will use satellite-based communication, which is much more complex and includes additional safety issues.
It is important to note that the availability and licensing of frequencies around the world has been recognized as a fundamental threat to UAS, as available communication bands are becoming overloaded.
An unmanned aerial system is only as good as its operators and maintainers -- not as individuals but as a team. It makes little difference if a system can fly for 24 hours and across 1,000km range if the operators do not know how to properly control the system and yield its best output for the mission. Training is usually divided to two groups of operators and maintenance teams, who at times will initially begin their training together, to facilitate the foundations for team work. Unfortunately most companies, in their attempt to cut costs, try to focus training on the basic flight characteristics and leave the mission adaptation up to the end-user. Training must begin with the selection of the most appropriate personnel and include an overview of the flight industry, an introduction to the airspace in which they will operate, an in-depth review of the aircraft, subsystems and payloads and flying and mission operation. It is highly recommended to enable a period of on the Job training, with an instructor who can help the end-user to refine its skills and create a preliminary mission routine.
Maintenance will determine the lifespan of the system and the actual output derived by the operating team. As in every flying platform the maintenance protocols must be clear, respected and adhered to, in order to enable the system to fly safely and efficiently perform its mission without causing safety events in the process.
Quality maintenance is especially important in unmanned systems, as they completely rely on internal systems and instructions from an external command post. All UAS maintenance refers to the system as a whole (platform, payload, GCS, GSE) and is usually divided into three levels: the operational level (O), which includes field teams who are proficient at preparing the system for the mission, including daily inspections, performing pre and post-flight checks, and addressing any technical difficulty in the field. The intermediate level (I) , which includes personnel who are trained to address higher maintenance issues, perform long term maintenance procedures, solve more serious malfunctions, access and maintain deeper systems and sign off on any O level procedures. The Depot level (D), which is a costly one, is usually reserved for factory-level maintenance, or is used by units that maintain a large number of systems, and enables all system components to undergo maintenance as needed.
Beyond the personnel and their training, maintenance refers to protocols that enable the team to reduce the system's operational risk using a planned, long-term maintenance protocol, complete with the necessary spare parts, meant to maintain the system's smooth operation over time.
The system's lifespan is analyzed by the manufacturer, and is affected by many internal and external factors, such as the technical lifespan of components (e.g. batteries), on-site environmental conditions, operator level, mission tempo, and more. The main facilitator of a system's correct lifespan and operability is based on the proper execution of maintenance protocols.
The relevant systems should be selected with the understanding that each system has an expected, realistic and limited lifespan, depending on the quality of its maintenance and the availability of its spare parts.
Most UAS (not RCA’s) require external lights that enable them to be seen during night-time missions for safety purposes, although such lights can be turned off for covert operations. The most basic external illumination includes:
Navigation (NAV)/Right of Way lights – Mark the right and left side of the aircraft in a standard manner (i.e., red-left, green-right). This feature enables the operator, or any other individual, to identify a system's flight pattern at night and discern whether it is flying towards or away from him.
Strobe light – Strong blinking lights, which are usually red or white, enable other aircraft/operators to see the aircraft in poor visibility conditions.
Front/Flood lights – Such light are more commonly used in manned aircraft but are also used in UAS, to lighting ahead of the aircraft. They also commonly assist RC landings performed by an external operator.
Frame lights – Some UAS have additional, “lower” lights that are usually yellow. These lights signal the edges of the aircraft's frame and enable an external operator to safely guide the UAS when necessary.
Unmanned aircraft systems differ from manned systems by the simple fact that no pilot is present on board to assist their operations as a last resort, in addition to the existing technical backup systems meant to counter severe malfunctions to critical subsystems, such as the landing gear, engine, etc.
Striving for higher safety standards in unmanned aerial systems, led to designs that include onboard backup systems for key subsystems and sensors, such as for the wing servo, pitot tube, Gyro etc., depending on the platform and manufacturer.
Under normal flight conditions all backups remain redundant, but they may come into play automatically, or engaged by the operator when there is a suspected malfunction.
Backups are more common in large-scale systems that can facilitate them without have them dramatically affect their weight.
All airborne platforms are complex technical systems and as such, even the highest quality systems may suffer a severe malfunction while airborne.
Airborne malfunctions can be termed as emergencies if they pose a risk to the platforms ability to remain controlled and airborne.
Every system relies primarily on its manufacturer-specified design and its end-user operator to recognize when it is experiencing malfunctions, either by negative sensor data, by irregular display or behavior, or by their own built-in warning systems.
The responsibility of the manufacturer lies primarily in the creation of a reliable system, with appropriate display systems that enable easy malfunction recognition, a reliable warning system and the appropriate emergency protocols.
A qualified operator must be trained to primarily recognize normal system behavior, so he can recognize irregularities as early as possible; and to respond to these irregularities, investigate negative readings and when necessary, react to emergency situations according to protocols and training.
Safety and Home protocols
Safety is one of the cornerstones of all aircraft activities, especially in unmanned aircraft systems.
As UAS edge closer to the civilian/commercial market, this issue has become even more crucial, as the public expects these system to operate safely and harmoniously with existing aircraft activity, ensuring continuous high-quality safety standards.
Safety in UAS stems from national regulations, as well as from standards each specific manufacturer seeks to achieve, affecting almost every system component:
Platform – Manufacturers balance their desire to expand system capabilities with the required safety regulations, by ensuring engine reliability, installing backup systems and sensors, automatic emergency protocols, inherent limitations, etc.
Payloads – Ensuring the payloads are appropriately and safely connected to the platform and enabling automatic responses when needed.
GCS – Manufacturers seek to provide end-users with an operating station that is easy to use while still displaying all the necessary flight and operational data, including early warning systems and rapid response commands. In addition, most systems have inherently designed limitation for the operator meant to minimize, as much as possible, any pilot error.
GSE – Safety also addresses all of the system's aspects while on the ground, from takeoff and landing protocols and equipment, clear and organized checklists, safe maintenance equipment and more.
Crew – Quality training for operators and maintenance crews is essential, while also ensuring long-term and periodic reviews to enhance the crew’s professional level.