In the previous 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 this chapter, I will complete the initial overview by clarifying the mission’s third element of work area characteristics, and elaborate on the issues of crew structure, selection and characteristics. At the second half, I will go on to expend 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 the third and final chapter in the upcoming weeks, 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.
Mission (Purpose of use)
Element 3 -- Mission work area characteristics:
Defining the expected work area is a crucial step before selecting any UAS system. The mission area refers to the geographic location in which the system will be designated to operate in; outlined primarily by operational needs to perform the required mission and not by straightforward land borders.
In addition to the required area coverage or expected size, the topographic and meteorological characteristics will frame the system's requirements to operate and achieve mission goals.
The Mission area characteristics may affect multiple aspects of UAS selection, but most directly influences the required range, required endurance and mission time and lifetime.
Unfortunately, a common error among potential users is to seek a system with the “best” endurance or range without relating and balancing them to actual mission needs and area characteristics.
In airborne systems, range simply refers to the distance an aircraft can fly in standard conditions (Farthest point from takeoff) - typically limited by the platform’s innate aerodynamical characteristics, airspeed and the fuel amount.
See additional information in chapter 3 - under “Range.”
“Required” ranges can be generally divided to the following groups:
As a general rule – longer range is not always better as it has to be balanced with mission needs and other supporting characteristics such as ground troops.
Unfortunately, many manufacturers refer only to the farthest flight distance without referring to operability at that range.
In UAS, this range is additionally limited by the required communication range, be it Uplink alone or also heavier Downlink.
Range is naturally affected greatly by flight modes and environmental conditions such as winds and temperature.
Expected mission endurance:
Endurance typically refers to the longest single flight-time for each system, or how long a platform can remain airborne once in flight
Endurance is naturally affected greatly by flight modes, mission activity and environmental conditions such as winds and temperature.
In UAS, endurance may be additionally limited by the required communication, be it Uplink alone or also heavier energy consuming downlink (More in electrical system).
Unfortunately, many manufacturers refer only to the longest possible flight time without referring to payload carrying or mission related activity.
In reality, endurance should refer to the amount of time the system will be able to remain airborne to perform its mission with an active payload (time over target).
Endurance necessarily affects range, and together define the possible/necessary coverage.
Eventually, the prospective user must discern between the expected time that is required to fulfill the mission, taking into account the area characteristics, safety margins and the necessary flight time in each direction.
See additional information in chapter 3 - under “Endurance.”
2. Expected mission lifetime:
The expected mission lifetime refers to the planned duration of the entire long-term mission and accordingly, affects the required system lifetime. This can range from several hours to years.
Every manufacturer designates a system’s lifetime (In actual flight time or number of flights), which is calculated from expected flight, number of units, operational and maintenance routines. These specifications may change between users.
The prospective user should take into account the system expected lifetime as it pertains to the potential mission's intensity, need of materials, cost and cycle.
Topography is the three-dimensional arrangement of physical attributes of a land surface in a specific place or region. These may include mountains, valleys, plains, bodies of water and vegetation coverage along with human made features such as roads, railroads villages etc.
Understanding the area’s topography is crucial before selecting any system, in issues such as:
Basic ground altitude:The area’s altitude above sea level is a crucial factor as it directly effects the aerodynmical characteristics of the platform, causing changes in capabilities and risk in takeoff, flight and landing.
Mountains/Valleys: A system required to work in a mountainous area may be required to operate in harder conditions and in varying flight modes, with possible loss of communication. In addition, the recommended platform may require more VTOL or fixed wing characteristics depending on the mission itself
Vegetation: Vegetation may influence an airborne system’s ability to perform the mission.In some broad leaf forests for example it may be recommended to avoid airborne systems altogether or direct them to conduct the mission in more appropriate areas with different payloads as necessary.
Meteorology is the interdisciplinary scientific study of the atmosphere and weather events bound by the variables that exist in Earth's atmosphere; temperature, air pressure, water vapor, and the gradients and interactions of each variable, and how they change in time.
Understanding the metrological conditions in each area is crucial before selecting any system as it may deeply affect its operability.
Area Temperature conditions: The high, low and average temperatures in the area of operations are crucial as some systems may be affected, limited and fail in certain heat or cold conditions.
Basic wind routine: Winds are crucial to an airborne system’s operability, not only in critical stages such as takeoff or landing, but also during flight as they may drastically affect a systems ability to remain airborne safely, endurance and range.
Humidity/Rain: Humidity or rain/snowfall conditions in the area may influence the selection process as some systems may be more sensitive to humidity or dry conditions than others. In contrast, one must remember that in reality, heavy weather conditions such as heavy rain or snowfall will hinder any effective aerial surveillance work. (Unless required to work in such conditions).
Extreme conditions:Most systems are designed to work in normal/standard conditions, which are extended as needed. In some locations or missions, systems are required to work under extreme conditions, affecting issues such as lifetime, maintenance and ultimately cost.
An UAS is only as strong as its crew.
Despite the fact that nowadays most UAS are highly autonomous, seemingly simple and straightforward to operate, they are still complex airborne systems that entail high risk and require considerable knowledge and training not simply to achieve efficient flight, but mainly for them to perform their missions effectively, especially in ISR oriented systems.
The prospective user should consider the crew composition prior to selecting an UAS in general and particularly before selecting any specific platform. The main considerations should include:
Every UAS system requires a crew that that includes operators and maintainers at all necessary levels.
Operator/Pilot – Operates the system to perform the mission.In larger systems can be subdivided into:
External pilot – Performs by sight T/O, landing and emergency activities.Nowadays most systems will simply use automatic T/O and landing systems.
Internal pilot – Performs all flight activity and monitoring from the control station.
Payload operator – Operates the payload to perform the mission.
Mission commander – commands the entire activity of the platform (Oversees flight and mission).
Operator – In smaller, more autonomous systems,the operator performs all flight and mission activities from a single command station.
Maintenance – Maintains the systems to perform the mission.In some systems, maintenance activity is divided to:
O level – Technical Activity at the operational field level (routine, pre and post flight).
I level – Technical activity at the intermediate level, usually at a central hub for periodic maintenance.
D level – Technical activity at the Depot level, usually by company experts.
In simpler, smaller systems, crew members may be trained at dual roles as operators and maintainers.
In larger and more complex systems, the number of crew members and command levels rises at the operator, maintenance and logistical positions.
For long term operations, a crew should consist of several teams, with a designated team manager in each one.
It is recommended that all systems, simple to complex, have a designated overall crew manager and a maintenance point of contact (POC).
Basic crew capabilities
After training, a team must be able to operate the systems independently, including all flight, payload, mission and maintenance issues - from preflight to after flight and routine activity.
The team must be able to launch the system, maintain a normal flight pattern, respond to emergencies, execute the mission, land and perform routine pre and post- flight maintenance procedures.
The selection of the crew will determine the success of training and operations.
Appropriate screening is recommended to evaluate and select the most appropriate team members (some basic tests are available online).
Some of the basic recommended prerequisites for these advanced systems include, fluent English, high school education, medium-to-advancedcomputer skills, possible gaming experience,good hand-eye coordination, basic technical skills, attention to details, the ability to multi-task, spatial perception and comprehension, previous experience in aviation, managerial skills/experience and basic knowledge of aerodynamics and meteorology.
Chapter 2 – Specifics:
The platform is the vessel providing lift, carrying all the necessary sub-systems for flight and mission.
Under the UAS family, the most basic division is by platform ("bird") type, which includes four main categories, excluding any non-propelled aircrafts:
Fixed wing (FW) – A fixed wing platform refers to the classically-designed aircraft, where the fuselage of the aircraft and its wing/s are in a fixed and relatively perpendicular position. These platforms require a forward motion to propel a lift and will have an engine/thrust mechanism in the front or back. Any directional movement is achieved by moving external subsystems (not all must be present) – propeller, rudder, ailerons, flaps, elevators, etc.
Vertical Takeoff/Landing (VTOL) – VTOL platforms refer to aircrafts with the ability to take off and land vertically, where the fuselage is usually under a set of moving rotating blades that provide the aircraft its vertical and directional motion. This category is divided into two subgroups:
Single/Double main rotor (SR) – Single main rotor aircraft have the classic design of a helicopter, on which a single main rotor (sometimes two) is the source of lift and movement, together with a secondary smaller perpendicular rotor – regardless of the number of blades.
Multi rotor (MR) – Multi rotor aircrafts are very popular but are relatively new to the UAS market and include platforms that use more than two rotors, usually beginning with four and increasing as needed. These systems are typically characterized by user-friendly flight control and relatively stabilized flight.
Transitional flight (TF) – Transitional flight platforms refers to aircrafts that can modify their flight or lift creating mode, usually including a mechanism that enables them to change the angle of thrust/rotors and/or wings and thus to switch from vertical to horizontal movement. Some systems enable such maneuvers at any stage, while others are used mainly to benefit from a VTOL capability and FW flight efficiently. These are relatively new platforms in both the manned and unmanned markets.
Power source and engine types:
Excluding non-propelled systems, every airborne system needs a power source to fly and operate. Following the platform, it is the most fundamental component to define its endurance, range, reliability for critical safety characteristics. This category continuously evolves and changes, as evident by recent fuel cell and hydrogen technology introduction to UAS. The basic, reliable power sources used today include:
Oil-based Fuel – Oil based fuel is a very wide term including various types of oil based energy sources, from regular gasoline to diesel and jet fuel. The common thread among these engines is the use of ignition/fire to move the thrust creating components and electrical power production, typically creating secondary effects, such as pollution and noise. It is important to realize that every engine type has a multitude of characteristics, such as fuel efficiency, noise, pollution, maintenance protocols, reliability, lifespan and much more.
Electric/Battery– Electrical engine systems use direct electrical power from a battery to create thrust and activate subsystems. Typically, batteries are charged on the ground from the main grid or local power and may include a wide range of options, depending on composition, output and performance required from the engine.These power sources and engines commonly work with no moving parts or ignition, reducing noise or pollution.It is important to realize that here too, every power source and engine type has a multitude of characteristics, such as efficiency, charge-time, weight per endurance, safety, secondary pollution, maintenance protocols, reliability, lifespan, charge cycles and more. They are more frequently used as a power source for smaller platforms.
Solar/Other/Rechargeable – In recent years, additional power sources are being explored for manned and unmanned flights such as solar power, bio- fuels, fuel cell technology, hydrogen and aerial recharging systems, etc.While these advances are important, they are less relevant to users seeking a solution here and now.
System weight has been traditionally used as the most basic characteristic to categorize unmanned aircraft systems. The reason was that weight commonly mirrored the system's overall capability – its size, carrying capacity, complexity and logistical and power source requirements - thus endurance and range. In a simple visualization, a light 5kg system will usually be small, with a smaller and thus simpler payload, which are easier to control, launch and land, can manage short-range, short-period flights of up to 30 minutes and up to 2km. In contrast, a very heavy system will usually mean a very large platform, capable of carrying heavy, high-quality payloads for long endurance and extensive range, requiring comprehensive logistics, crew and training.
It is crucial to understand that weight does not reflect actual capabilities and quality, as each subsystem, as well as the entire system, has to be independently evaluated.
In contrast to RC planes, all UAS are ultimately made and operated in order to carry payloads. Payloads can be used simply to deliver goods but they are more commonly used to gather intelligence and information.
Most commonly used payloads are optically-based, but have evolved dramatically in recent years, offering better sensors, better electro-optical capabilities, range, quality, resolution, IR and hyper spectral. Selecting a payload is a critical stage, as it will determine, along with the platform, the quality of the desired output and mission.
It is important to note that most UAS manufacturers will have a specific set of payloads with which they operate, and will allow only relative flexibility. As in the platform, there are many subcategories to attend to in the selection process: weight, sensor quality, communication, power requirements, communication protocols, reliability, and quality of data, resolution, supporting data (LOS, etc.), supporting software, ITAR restrictions, and much more.
For each system, it is important to evaluate the payload's actual capabilities in field conditions, with the platform operating under normal flight and mission conditions.
Flight altitude may seem like a straightforward term, illustrating the system's normal operating flight altitude. However, this term must be clarified, as it is clouded by several parallel definitions that differ in actual meaning and relevance to the mission, and are at times misused by marketing activities.
To continue next week.
please feel free to send in any questions.