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UAS Airframe Design
Published in R. Kurt Barnhart, Douglas M. Marshall, Eric J. Shappee, Introduction to Unmanned Aircraft Systems, 2021
Michael T. Most, Michael Stroup
The preceding highlights several of the ways sUAS designs are similar to those of manned aircraft. However, due to scale effects among other factors, certain differences also exist. On average, the size (mass) of both unmanned fixed- and rotary-wing aircraft are orders of magnitude less than their manned counterparts (Austin 2010). As we “scale down” aircraft to smaller sizes, all attributes are not affected in the same way. For example, wing surface area, being two dimensional, will vary inversely as the square of the scaling factor, whereas volume, a cubic, will vary inversely as the cube of the scaling factor. Thus, all other factors held constant, wing loading—that is, weight (mass in the gravitational field of the earth) divided by wing area—tends to increase with a decrease in UA size. Higher wing loading affects aircraft performance, decreasing the rate of climb and increasing stall speed. Decreasing the rate of climb may negatively affect endurance, and consequently, range. Increased stall speed increases stress on all recovery structures (main and nose landing gear system primarily). Higher wing loading may compel the designer to use a catapult launch system in lieu of the less equipment intensive hand launch. Higher wing loading also reduces maneuverability. Conversely, any reduction in mass affects the ability of the UAS to resist the disturbing or upset force of wind gusts, an important consideration in many data gathering missions. Neither are rotorcraft immune to the effects of reduced scale. Narrower blade chords and smaller rotor disks produce low Reynolds numbers, which reduce the efficiency and lift of the rotor system (Seddon 1990) that, in turn, decreases range, endurance, and payload. Thus, in UAS design, size is important, affecting several operational characteristics that may, in turn, affect the ability of the platform to meet mission requirements.
UAS Airframe and Powerplant Design
Published in Douglas M. Marshall, R. Kurt Barnhart, Eric Shappee, Michael Most, Introduction to Unmanned Aircraft Systems, 2016
The preceding highlights several of the ways UAS designs are similar to those of manned aircraft. However, due to scale effects among other factors, certain differences exist, as well. On average, the size (mass) of both unmanned fixed- and rotary-wing aircraft are orders of magnitude less than their manned counterparts (Austin 2010). As we “scale-down” aircraft to smaller sizes, all attributes are not affected in the same way. For example, wing surface area, being two-dimensional, will vary inversely as the square of the scaling factor, whereas volume, a cubic, will vary inversely as the cube of the scaling factor. Thus, all other factors held constant, wing loading—that is, weight (mass in the gravitational field of the earth) divided by wing area—tends to increase with a decrease in UA size. Higher wing loading affects aircraft performance, decreasing the rate of climb and increasing that of descent. Decreasing the rate of climb may negatively affect endurance and, consequently, range. Increasing the rate of descent may result in excessively hard landings, necessitating the installation of a parachute recovery system. Higher wing loading may compel the designer to use a catapult launch system in lieu of the less equipment intensive hand-launch. Higher wing loading also reduces maneuverability. Conversely, any reduction in mass affects the ability of the UAS to resist the disturbing or upset force of wind gusts, an important consideration in many data gathering missions. Neither are rotorcraft immune to the effects of reduced scale. Narrower blade chords and smaller rotor disks produce low Reynolds numbers, which reduce the efficiency and lift of the rotor system (Seddon 1990) which, in turn, decreases range, endurance, and payload. Thus, in UAS design, size matters, affecting several operational characteristics which, may, in turn, affect the ability of the platform to meet mission requirements.
What factors may influence decision-making in the operation of Maritime autonomous surface ships? A systematic review
Published in Theoretical Issues in Ergonomics Science, 2022
Kirsty M. Lynch, Victoria A. Banks, Aaron P. J. Roberts, Stewart Radcliffe, Katherine L. Plant
In this case, the GCS crew had Air Vehicle Display Computers (AVDC) for each of the pilots and client displays showing the live video feed from the camera mounted at the back of the UAV. The camera on the UAV is designed for reconnaissance missions but is stowed away and turned round to face rearwards during the final stage of landing to protect it. The UAV’s flight modes had been displayed throughout the incident on the AVDC, these modes were being monitored and read out by Pilot 1 during the landing sequence. Pilot 2 was monitoring the Warnings Cautions Advisories for the landing and the video feed from the camera now facing rearwards. After the UAV failed to register ground contact when it landed long of its touch down point, it auto aborted the landing attempt giving an auto-abort alert. The Automatic Take-Off and Landing System’s (ATOLS) auto-abort caption on the AVDC was illuminated red. However, there was no audio alert associated with the caption and the caption had minimal visible indication on the AVDC display. Although, several other visual indications on the AVDC showed that the UAV was attempting to land again such as, flight mode, artificial horizon indicator, altitude readout and rate of climb value. However, in the high workload and stress environment, the illuminated auto-abort caption and other visual indicators on the AVDC were not spotted by the GCS crew.
A hybrid-electric propulsion system for an unmanned aerial vehicle based on proton exchange membrane fuel cell, battery, and electric motor
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2022
Amir Hamzeh Farajollahi, Mohsen Rostami, Mohammad Marefati
The optimal value obtained for wing loading is equal to the selected lower limit. Because the choice of the lower limit for wing load was done due to the achievement of a practical structural layout and its value is about close to the wing load for a Pointer UAV. For the wing cross section, any type of ordinary design can be used (with a maximum lifting coefficient of 1.25). The optimal values obtained for theoretical and actual endurance speeds as well as stall speed are used for the optimal design of the electric motor. Figure 4 shows the electrical power required curve as a function of the velocity for different mission segment. The maximum and minimum power required is related to the maximum speed and theoretical endurance segments, respectively. It was also found that the theoretical endurance speed was lower than the drone’s stall speed. In addition, the required power at the theoretical endurance speed is about 42.13% lower than that at the actual endurance speed. Note that the required power in the climb mode is calculated to provide the required rate of climb (ROC).
Which aircraft has a better fuel efficiency? – a case study in china
Published in Transportmetrica B: Transport Dynamics, 2022
Yun-Qi Gao, Tie-Qiao Tang, Jian Zhang, Feng You
In the figure, is the lift; is the gravity; is the engine trust and is the resistance; V is the true air speed(TAS); α is the angle of attack; γ is the angle of climb and θ is the angle of pitch. Here, α,γ and θ satisfy the following equation: According to the bearing, the dynamic equation during the climb can be formulated as follows: During the climb the angle of attack α is small, so it can be considered that equals 1 and equals 0. So Equation (6) can be rewritten as follows: The rate of climb is: And the time required, distance and fuel consumption when climb from height to can be formulated as follows: where , and are the correction factors for the influence of external factors such as wind and temperature; is the fuel flow of the engine during climb.