Flight Data Analysis and Simulation of Wind Effects During Aerial Refueling

Lewis, Timothy A.

doi:10.2514/1.36797

Cited by 76 publications

(30 citation statements)

References 31 publications

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“…The magnitude of the wind at a point is dependent on the strength of each vortex filament and is computed using Biot-Savart law and the NASA-Burnham horseshoe vortex model. 9 The vortices induce a non-uniform wind distribution on the follower with wind gradients depending on its location relative to the leader. The dynamic effect of this non-uniform wind is modeled using the NonUniform Wind Effect Modeling Technique (NUWEMT).…”

Section: B Non-uniform Wind Effect Modelingmentioning

confidence: 99%

“…The turbulence is represented either as a random velocity disturbance or natural turbulence recorded in wind tunnels or in the atmosphere. 8,9 The prevailing wind, which can be modeled by any appropriate function was, obtained from previous test flight data of the leader. 8,9 In addition to these two sources of wind, the follower is also subjected to the wind field in the wake of the lead aircraft.…”

Section: B Non-uniform Wind Effect Modelingmentioning

confidence: 99%

“…8,9 The prevailing wind, which can be modeled by any appropriate function was, obtained from previous test flight data of the leader. 8,9 In addition to these two sources of wind, the follower is also subjected to the wind field in the wake of the lead aircraft. This wind field is modeled using the lifting line theory.…”

Section: B Non-uniform Wind Effect Modelingmentioning

confidence: 99%

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Aircraft Lateral Trim Using Internal Fuel Transfer & Differential Thrust In Formation Flight

Okolo

Dogan²,

Blake

2011

AIAA Atmospheric Flight Mechanics Conference

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This paper investigates alternative moment generation mechanisms for aircraft as fuelsaving techniques in formation flight. Aircraft flight generates wake vortices that induce a nonuniform wind distribution in the wake of the aircraft. A follower aircraft, flying in the wake of the leader aircraft, can experience induced wind components and gradients with various magnitudes and directions, depending on the location within the induced nonuniform wind field. It has been demonstrated that there is a "sweet spot" within the wake of the leader aircraft where the follower aircraft experiences upwash, which leads to drag reduction. When an aircraft flying in formation flight is at the "sweet spot", the aircraft experiences lower drag but at the same time experiences induced aerodynamic moments. The deflections of control effectors required for trimming the aircraft under the effect of these moments induce additional drag, which reduce the benefits of fuel efficiency. This report investigates two different mechanisms of moment generation for alleviating the drag induced by the deflection of the control effectors: (1) internal fuel transfer among fuel tanks and (2) differential thrust. It was seen that an elimination of the control effector deflections led to a reduction in the thrust required and thus savings in fuel. Internal fuel transfer, in the configuration studied, was seen to reduce the aileron deflection of the follower by generating a rolling moment, and differential thrusting reduced the rudder deflection by the generation of a yawing moment. Furthermore, the combination of the two techniques provided the highest fuel savings of 11 percent by reducing the need for the aileron and rudder deflections. The results of this analysis will allow for further studies ultimately leading to the development of a fuel-saving method of flight with various applications.

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Section: B Non-uniform Wind Effect Modelingmentioning

confidence: 99%

Section: B Non-uniform Wind Effect Modelingmentioning

confidence: 99%

Section: B Non-uniform Wind Effect Modelingmentioning

confidence: 99%

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Aircraft Lateral Trim Using Internal Fuel Transfer & Differential Thrust In Formation Flight

Okolo

Dogan²,

Blake

2011

AIAA Atmospheric Flight Mechanics Conference

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“…The local air velocity u K is due to the wake of the tanker, steady wind, and atmospheric turbulence. The air velocity due to the tanker wake can be modeled using a Helmholtz horseshoe-vortex model [14,15]. The model contains velocity components in all three spatial directions.…”

Section: Forces On Lumped Massmentioning

confidence: 99%

Modeling and Simulation of Hose-Paradrogue Aerial Refueling Systems

Kamman

2010

Journal of Guidance, Control, and Dynamics

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A dynamic modeling and simulation analysis of hose-paradrogue aerial refueling systems is presented. A set of governing equations of motion is derived using a finite-segment approach that describes the dynamics of the hoseparadrogue assembly under a prescribed motion of the tanker. The hose is modeled by a series of ball-and-socketconnected rigid links subject to gravitational and aerodynamic loads that account for the effects of tanker wake, steady wind, and atmospheric turbulence. Numerical simulations show a good correlation of the model's steady-state characteristics with previously reported flight-test data. Also investigated are the dynamic characteristics of the paradrogue assembly resulting from atmospheric turbulence and a typical pitch doublet maneuver of the tanker. Finally, the dynamic motion resulting from an in-flight adjustment of the paradrogue drag associated with strutangle changes is studied. Nomenclature a K = acceleration of lumped mass K, ft=s 2 a 0 = acceleration of the system tow point (hose exit point from a pod), ft=s 2 B = vehicle mass center C drogue = drag coefficient of paradrogue C X N Z N = vertical plane in which the aircraft moves c n;K , c t;K = normal and tangential drag coefficient of the link K D K = aerodynamic force acting on link K, lb d K , d drogue = diameters of link K and paradrogue F K = frame fixed in link K with axes x K ; y K ; z K F N = inertial frame with axes X N ; Y N ; Z N F W = aircraft (tanker) mean air trajectory frame with axes X W ; Y W ; Z W c GS = normalized paradrogue gore spacing; ranges from ( 1-1) for gore spacing from 5-8:5 deg g = gravitational acceleration vector, ft=s 2 L H = straight-line distance from hose exit point to paradrogue coupling, ft ' K = length of link K, ft m drogue = mass of paradrogue, slug m K = mass of lumped mass K (one-half of the total mass of adjoining links), slug N = number of links n K1 , n K2 , n K3 = mutually perpendicular unit vectors fixed in link K n K1 = unit vector pointing from lumped mass K to lumped mass J (along link K O N = origin of the inertial frame p K = position vector of lumped mass K relative to J; components in F W , ft p K; Ki = @p K =@ Ki , ft Q K = external force vector acting on lumped mass K (one-half of the total force acting on the adjoining links), lb r K = position vector of lumped mass K relative to an inertial frame, ft c SA = normalized paradrogue canopy characteristic length, ranges from ( 1-1) for lengths from 3-5:5 in: (7:62-13:97 cm) S Ki , C Ki = sine and cosine of Ki t K = tension in link K, lb u K = local air velocity due to steady wind, tanker wake, and turbulence at lumped mass K, ft=s V D = altitude difference from hose exit point to paradrogue coupling, ft V 1 = tanker speed, ft=s B t = inertial velocity of the vehicle mass center, ft=s K = velocity of lumped mass K, ft=s K=air = velocity of lumped mass K relative to the local air velocity ( K u K ), ft=s K;n , K;t = vector components of K normal and tangent to link K, ft=s w 1 , w 2 , w 3 = mutually perpendicular unit vector...

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“…In this system these effects are the modelling errors of the nonlinear aircraft dynamics and the external disturbances. This is shown in (13). Here, B d is the disturbance matrix and d x are the disturbances on the states.…”

Section: B Disturbance Observer Definitionmentioning

confidence: 99%