Unmanned Aircraft Design. Mohammad Sadraey H.

      Another basis for UAVs classifications in military is echelon: Class 1 supports platoon echelon, (e.g., Raven), micro air vehicle (MAV), and small UAV; Class 2 supports company echelon, (e.g., Interim Class 1 and 2 UAV); Class 3 supports battalion echelon, (e.g., Shadow 200 Tactical UAV); and Class 4 supports unit of action (brigade), (e.g., Hunter), Extended Range/Multipurpose (ER/MP) UAV.

      Some current U.S. UAVs [46] are listed here: (1) Army UAV Systems: RQ-1L I-GNAT Organization; RQ-5/MQ-5 Hunter Aerial Reconnaissance Company; RQ-7 Shadow Aerial Reconnaissance Platoon; RQ-11 Raven Team. (2) Air Force UAV Systems: RQ-4 Global Hawk; RQ/MQ-1 Predator; MQ-9 Predator B; Force Protection Aerial Surveillance System, Desert Hawk (Figure 8.3). (3) Navy UAV Systems: RQ-2 Pioneer; RQ-8B Fire Scout. (4) Marine Corps UAV Systems: FQM-151 Pointer; Dragon Eye; Silver Fox; Scan Eagle. (5) Coast Guard UAV Systems: Eagle Eye. (6) Special Operations Command UAV Systems: CQ-10 SnowGoose; FQM-151 Pointer; RQ-11 Raven; Dragon Eye.

      It will be very helpful to know the features of some old and current UAVs. Hunter (RQ-5): Range: 125 km; Max speed: 110 knots; Dimensions: length: 22.6 ft; span: 29.2 ft; Endurance: 10 hr; Weights: Max Takeoff: 1600 lb; Ceiling: 16,000 ft. Hunter, was cancelled in January 1996 after some 20 air vehicle crashes. Pioneer RQ-2A: First flight: 1985; Dimensions: length: 14 ft span: 16.9 ft; Max. TO Weight: 450 lb; Speeds: cruise: 65 knots; dash: 110 knots; it was used extensively in Falujeh, Iraq, 2006. During Operations Desert Shield, the U.S. deployed 43 Pioneers that flew 330 sorties, completing over 1,000 flight hours. In 10 years, Pioneer system has flown nearly 14,000 flight hours. Since 1994, it has flown over Bosnia, Haiti, and Somalia.

      Outrider: First flight: 2,000; Range: 200 km; Wing span: 11.1 ft; MTOW: 385 lb; Ceiling: 15,000 ft; Max speed: 110 knot; Endurance: 7.2 hr. Predator RQ-1A (Figure 5.4): First flight: 1994; Endurance: 25 hr; Ceiling: 26,000; Payload: 450 lb; Cruise Speed: 90 knots; MTOW: 2100 lb; Wing span: 48.4 ft. Extensively employed in Iraq, Afghanistan, Pakistan, … Predator RQ-1B (Figure 4.10): Honeywell TPE-331-10T, flat-rated to 750 shp; 4,500 kg take-off gross weight; Max speed/altitude: 210 knot/50Kft; - 20 m wingspan; Triplex systems; 1,360 kg fuel; 340 kg internal payload; 1360 kg external payload; 6 store stations/14 Hellfire missiles.

      Figure 1.1: Northrop Grumman RQ-4 Global Hawk.

      • Global Hawk RQ-4 (Figure 1.1): First flight was in 1998; Endurance: 41 hr; Ceiling: 65,000; Payload: 2,000 lb; Ranges: 14,000 nm; Cruise Speed: 345 knots; MTOW: 25,500 lb; Wing span: 116 ft. The Defense Advanced Research Projects Agency (DARPA) developed Global Hawk to provide military field commanders with a high-altitude, long-endurance system that can obtain high-resolution, near-real-time imagery of large geographic areas. Flew for the first time at Edwards Air Force Base, California, on Saturday, February 28, 1998. The entire mission, including the take-off and landing, was performed autonomously by the UAV based on its mission plan. The launch and recovery element of the system’s ground segment continuously monitored the status of the flight.

1.3 DESIGN PROJECT PLANNING

      In order for a design project schedule to be effective, it is necessary to have some procedures for monitoring progress; and in a broader sense for encouraging personnel to progress. An effective general form of project management control device is the Gantt chart is. It presents a project overview which is almost immediately understandable to non-systems personnel; hence it has great value as a means of informing management of project status. A Gantt chart has three main features.

      1. It informs the manager and chief designer of what tasks are assigned and who has been assigned to them.

      2. It indicated the estimated dates on which tasks are assumed to start and end, and it represents graphically the estimated ration of the task.

      3. It indicates the actual dates on which tasks were started and completed and pictures this information.

      Like many other planning/management tools, Gantt charts provide the manager/chief designer with an early warning if some jobs will not be completed on schedule and/or if others are ahead of schedule. Gantt charts are also helpful in that they present graphically immediate feedback regarding estimates of personnel skill and job complexity. A Gantt chart provides the chief designer with a scheduling method and enables him/her to rapidly track and assess the design activities on a weekly/monthly basis. An aircraft project such as Global Hawk (Figure 1.1) will not be successful without a design project planning.

1.4 DECISION MAKING

      Not every design parameters is the outcome of a mathematical/technical calculations. There are UAV parameters which are determined through a selection process. In such cases, the designer should be aware of the decision making procedures. The main challenge in decision making is that there are usually multiple criteria along with a risk associated with each one. Any engineering selection must be supported by logical and scientific reasoning and analysis. The main challenge in decision making is that there are usually multiple criteria along with a risk associated with each one. There are no straightforward governing equations to be solved mathematically.

      A designer must recognize the importance of making the best decision and the adverse of consequence of making the poorest decision. In majority of the design cases, the best decision is the right decision, and the poorest decision is the wrong one. The right decision implies the design success, and the wrong decision results in a fail in the design. As the level of design problem complexity and sophistication increases in a particular situation, a more sophisticated approach is needed.

1.5 DESIGN CRITERIA, OBJECTIVES, AND PRIORITIES

      One of the preliminary tasks in UAV configuration design is identifying system design considerations. The definition of a need at the system level is the starting point for determining customer requirements and developing design criteria. The requirements for the system as an entity are established by describing the functions that must be performed. Design criteria constitute a set of “design-to” requirements, which can be expressed in both qualitative and quantitative terms. Design criteria are customer specified or negotiated target values for technical performance measures. These requirements represent the bounds within which the designer must “operate” when engaged in the iterative process of synthesis, analysis, and evaluation. Both operational functions (i.e., those required to accomplish a specific mission scenario, or series of missions) and maintenance and support functions (i.e., those required to ensure that the UAV is operational when required) must be described at the top level.

      Various UAV designer have different priorities in their design processes. These priorities are based on different objectives, requirements, and mission. There are primarily three groups of UAV designers, namely: (1) military UAV designers, (2) civil UAV designers, and (3) homebuilt UAV designers. These three groups of designers have different interests, priorities, and design criteria. There are ten main figures of merit for every UAV configuration designer. They are: (1) production cost, (2) UAV performance, (3) flying qualities, (4) design period, (5) beauty (for civil UAV) or scariness (for military UAV), (6) maintainability, (7) producibility, (8) UAV weight, (9) disposability, and (10) stealth requirement. Table 1.2 demonstrates objectives and priorities