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Aircraft
Published in Milica Kalić, Slavica Dožić, Danica Babić, Introduction to the Air Transport System, 2022
Milica Kalić, Slavica Dožić, Danica Babić
The four forces acting on an aircraft in straight-and-level flight are thrust, drag, lift, and weight (Figure 2.1). Thrust is the force that moves an aircraft in the flight direction, provided by a piston, turboprop, or jet engine. Thrust itself is a force than that can best be described by Newton’s second law. This forward force opposes the force of drag. Drag is the aerodynamic force component parallel to the direction of relative motion. This is a retarding force caused by the disturbance of airflow by the aircraft and its parts. In other words, drag tends to slow the motion of aircraft, and acts opposite to the direction of motion. Lift is a force that is produced by the dynamic effect of the air flow acting on the aerofoil. This force opposes the downward force of weight. Lift represents a component of the aerodynamic force, perpendicular to the direction of aircraft movement through the air, which is equal to or exceeds the weight. Weight is the force that pulls the aircraft downward owing to gravity. When the four forces of flight are balanced, a plane flies in a level direction. The plane climbs if the forces of lift and thrust are greater than gravity and drag. To descend, thrust must be reduced below the level of drag and lift below the level of weight.
Longitudinal Feedback Control
Published in Nandan K. Sinha, N. Ananthkrishnan, Advanced Flight Dynamics with Elements of Flight Control, 2017
Nandan K. Sinha, N. Ananthkrishnan
The output of the flight path block—the desired flight path profile—is passed on to the next block in the sequence, the attitude block. The attitude block computes the variation of AOA/normal acceleration and thrust required to meet the V, γ profile demanded by the flight path block. To take the same example cases as previously: Accelerate in level flight: V profile, γ = 0—thrust required to accelerate; change in AOA to compensate for the increase in V so that lift is unchanged and level flight is heldSteady climb: fixed V, fixed γ—thrust required to hold steady climb angle; AOA for lift to balance out weight component at fixed VAccelerate and climb: such as, pull-up with fixed V, varying γ—normal acceleration for the pull-up; thrust required to hold velocity fixedSteady, level flight: fixed V, γ = 0—AOA for lift to balance weight at fixed V; thrust to balance drag
Straight-level flight
Published in Mohammad H. Sadraey, Aircraft Performance, 2017
In a steady-level flight, the lift is assumed to be equal to weight, and thrust is equal to drag (Equations 6.5 and 6.6). When Equation 6.7 is inserted into Equation 6.103, T (i.e., thrust) is replaced with a D (i.e., drag). Furthermore, both numerator and denominator are multiplied with an L (i.e., lift), and then L in denominator is replaced with a W (i.e., weight): () dt=−dWCP=−ηPdWCTV=−ηPdWCTVLL=−ηPdWCDVLW
A comparison of optimized deliveries by drone and truck
Published in Transportation Planning and Technology, 2021
Youngmin Choi, Paul M. Schonfeld
D'Andrea (2014) formulates drone energy consumption considering various factors, such as air resistance, battery cost, and cost of electricity usage. Figliozzi (2017) refines the formula to derive energy E for level flight at a constant speed as follows: where p is power required for level flight in watts, t is flight duration in seconds, d is flight range in meters, mp is payload in kg, is drone weight including battery in kg, r is lift-to-drag ratio set as 3, is power transfer efficiency for motor and propeller set as 0.5, and g is the gravity acceleration constant (9.81 meters/second2).
Topology optimization of the internal structure of an aircraft wing subjected to self-weight load
Published in Engineering Optimization, 2020
Luís Félix, Alexandra A. Gomes, Afzal Suleman
The material model proposed in this work is first applied to design a two-dimensional cantilever beam that is subjected to self-weight and to a vertical, upward point force at the beam tip. This loading condition is similar to a wing in level flight, since the structure weight may be seen as a secondary load that counteracts the aerodynamic lift. The objective is to find a design with less than 40% of the volume of the initial domain that minimizes the beam compliance. The dimensions of Ω are 2 m by 1 m, modelled with a regular mesh of four-node elements with two degrees of freedom per node. The mechanical properties of the base material to be distributed in the domain are Pa and , whereas the specific mass is 1.25 kg/m3 and the point load is 1 N. The initial design is a uniform distribution of material that satisfies the volume restriction.
Mathematical optimization in enhancing the sustainability of aircraft trajectory: A review
Published in International Journal of Sustainable Transportation, 2020
Ahmed W.A. Hammad, David Rey, Amani Bu-Qammaz, Hanna Grzybowska, Ali Akbarnezhad
The flight path undertaken by aircraft is governed by predefined trajectories in the vertical and horizontal profiles. As an example, thrust cut back departures have been developed to reduce noise at specific locations (Thomas et al., 2017). The continuous descent approach (CDA), also referred to in the literature as the optimized profile descent (OPD) (Clarke et al., 2013), comprises a vertical profile which permits aircraft to descent from a higher altitude at idle or near idle thrust. The procedure eliminates the level flight segments and their associated thrust transients at low altitude. Due to the low thrust setting required where the flight is near idle descent trajectories, this leads to lower fuel consumption and less noise and gas emissions (Cao et al., 2014; White et al., 2017). It should be noted that noise abatement procedures are classified according to whether flight is in descent or departure mode.