Evolution. From “wired wings” to cyclorotor

 

  After formulating the “flying elevator” conception I tried to implement it on straightforward manner: as some system of wired wings connected to common fuselage with winding abilities of those wires. I reference it as "wired wings" configurations. Four variants of this kind were considered. They are represented on the chart below.

"Wired wings" diagram

  Simplest variant A. has only one wing connected by a wire to a fuselage. The fuselage has a powered winding system, which is placed inside, near CG of the fuselage. The system also has locking abilities, when it motionless. Also the fuselage has a stabilizer, which permits tuning its attitude upon flight. The wing is designed with elements providing longitudinal and transverse stability, like wing of hang glider and has a central node, where the wire connects, with ability moving the connection point in longitudinal and transverse direction under a remote control, handling commands from pilot.

 

  Variant B. has two wings equal to the wing described for variant A., connected by wires to a common fuselage, which is differed from the fuselage of variant A. by having set of two winding systems instead of the one. Here, wings are referenced as Wing 1 and Wing 2 with winding speeds WS1 and WS2 respectively. In the configuration exists a problem of transition one wing near of vicinity of wire of other. This avoidance is too tricky for handling. So it practically disables use of this aircraft. Nevertheless, the configuration is useable for a flight simulation analysis.

 

  Variant C. resolves the neighbor wire avoidance problem of the variant B. by placing one wing over other permanently, and the Wire 2 from the upper Wing 2 is going trough a pulley of enhanced central node of the lower Wing 1.

 

  Variant D. is like as the variant A., but the fuselage has its own Wing 1 pivotally connected to it, and the upper wing is referenced as Wing 2. So fuselage here becomes a glider. Also stabilizer here is moved up on the tail from proximity of the main wing. The main wing here is pictured as kind of symmetric airfoil for decreasing its steering moment, although I used for simulation a non-symmetric airfoil. Also here can be used standard glider scheme with fixed main wing and stabilizer with elevator surface.

 

  A variant of implementation of the enhanced central node from the variant C. is represented on the chart below.

Enhanced central node

 

  The main element of the node is a caret, which can move in X-direction on rods mounted on the Wing 1, by using the X-screw, which is rotating by respective servo. For Y-direction a gimbal can move on respective rods of the caret, by using the Y-screw, which is rotating by respective servo. By this way the connection point for wires will be displaced, providing desired steering of the Wing 1. The Wire 1 is connected to a pulley assembly, which is used for conducting movement of the Wire 2. The pulley assembly is mounted in the gimbal. The implementation provides zero-moment footprint on entire Wing 1 from wires.

 

  All four variants of these "wired wings" configurations were tested on a flight dynamics simulation program. I used angles of attack (AoA) of wings and the winding speed as input handling parameters. Also I approximated the simulation to reality as much as possible, by including strain dynamics of wires themselves and also aerodynamic drag of wires and fuselage. The self-explaining diagram below represents the "wired wings" simulation constraints grouped by their modalities. I tried to find optimal handling parameters for each variant of aircraft.

Constraints for "wired wings" simulation

  I prepared result of those simulations in form of composed charts, where upper side is flight profile of each component of aircraft, including wires, which keeps connectivity of the data. Also there is labeling of numbers of resulted samples, one per five. The bottom part is plot composed from handling AoA of related wings and components of acceleration of fuselage, which is normalized on gravity acceleration. The horizontal axis of the plot is simple number of sample, correspondent to same number on flight profiles. I placed labels of the sampling in appropriate places instead of the axis itself. Also keep in mind, the zero lifting AoA for the used airfoil is about -4°. Results of entire simulation are represented below with respective analysis.

Variant A.

  The chart above represents result for the one wired wing connected to fuselage. This configuration has some similarity with bird’s flight. There exists only one possibility for recovering altitude of wing, because the wing is only one. It is partially weightlessness on short time. But bird has an advantage in that operation, because its wings aren't wired. For keeping the aircraft in horizontal flight only, I need using high magnitude of the winding speed. So vertical acceleration is changed from 3g, when fuselage is going up with increased AoA, to -1g, when fuselage is going down with decreased AoA. Horizontal acceleration is changing from 0.3g to -1.4g. Let look on the sample 18, where a positive powering phase begins, when fuselage has significant sink after particular fall. The wing is placed significantly more forward than fuselage, so accelerating force is inclined, inducing an inertial force. Horizontal component of the inertial force inclines normal of a gravitic vertical, so it becomes an inertial vertical. Fuselage begins accelerating in both directions. Also the slow flying wing promptly reaches speed of fuselage upon gravitic acceleration and they continue moving together, keeping the inclination up to sample 35. Now fuselage has significant positive vertical speed and increased horizontal speed. At the sample 39 the phase finished, the wing and fuselage are in almost vertical relation, but I don't switch to the negative powering phase. I locked the wire and wait when the vertical speed of fuselage will be maximal. Upon the intermediated phase the wing is accelerating and undergoing pendulum oscillations with short period, which is reflected in those oscillations of the acceleration. A recovery phase begins on the sample 53. In the time the speed of fuselage was decreased. Previous recovery phase begins on the sample 7. AoA is decreased to -1° and to -3° on the next sample. Before that, the wing was in strong acceleration due to high inclined flight path and reached high speed. The high speed induces high aerodynamic force, reflected in the mentioned vertical acceleration of 3g, which was possible since the wire was locked. Remember, there is the slipping constraint in 1.4g without the locking. In the recovery phase the wing continues moving forward und up, winding out the wire. Its flight path angle was switched to positive direction and the gravity force begins to decelerate it. The speed of wing was significantly dropped, and so the aerodynamic force. The fuselage enters in almost weightlessness and begins increasing its sink until of end of this phase. So it isn't a comfortable flight. Also it is too dangerous.

Variant B.

  The chart above represents result for two equal wings connected to the fuselage. It permits less level of oscillations of the acceleration, below 2g for the vertical component and 0.5g for the horizontal with both signs. Positive phase of one wing is overlapped by recovery phase of other. But this overlapping induces mutual dependence in phases. This dependence leads to higher resonance of long-periodic pendulum oscillations of the fuselage and wings. So amplitude of speed-oscillation for wings is very high, because mass of wings is low. It leads to periodical occurrences of very low speeds of wings, when wing almost cannot support its own weight. It is very dangerous, since the wire begins forceless in end of the recovery phase.

Variant C.

  The chart above represents result for the aircraft with two wired wings on separated levels. The aircraft performs a bit better than need for a cruise flight. The Wing 1 through the pulley of central node applies additional constraints on horizontal position of the upper wing and vice versa. So the amplitude of horizontal oscillations of wings reduced significantly. There I succeeded in simple handling of the aircraft. Each wing has AoA of 5° while the fuselage going up toward it. And in this time opposite wing has AoA -1.5°, when it flaring up, winding its wire out. Nevertheless, this regular pattern of handling isn't symmetrical. The phase with upper wing providing sustain is longer then phase with its recovering. The vertical acceleration was reduced there to a range between -0.3g and 0.65g, and the horizontal acceleration to a range between -0.3g and 0.15g. Also these accelerations have pattern of decremented oscillations replenished after each transition between handling phases. I use here low winding speed, so phases are long, permitting observing details of these oscillations. Nevertheless, the system has a drawback: the winding speed I use is maximal. Additional increasing of the winding speed leads to switching to a mode of highly increased and irregular fluctuations with significant loss of altitude and increasing of rotational energy of entire system, i.e. high entropy behavior. So gaining cruise altitude for this variant is still problematic.

Variant D.

  The chart above represents result for the glider with additional wired wing. The aircraft performs a just enough for a cruise flight. The pattern of handling is also regular like for the variant C., but there exists a prolonged intermediate state for both main and recovery AoAs of the wired wing only. The system has a prolonged recovery phase, when the glider is mainly sustained by its own wing with AoA of 6°, and the wired wing is flaring up with AoA from -2.5° to -2°. After it, there is shorted lifting phase, when the wing of glider is idle with AoA of -2.5°, and the wired wing sustains the glider with AoA from 3° to 6°. The vertical acceleration lays here in a range between -0.28g and 0.18g, and the horizontal acceleration in a range between -0.17g and 0.15g. Although the winding speed used there is higher then for previous variant, the short powering phase doesn't permit to gain cruise altitude at all.

 

  Finally, the "wired wings" configurations permit having only an aircraft with ability of performing cruise flight, low ability of gaining cruise altitude and zero ability of performing runway operations for takeoff. These limitations follow from the constraint of self-sustaining abilities of wired wings and from the lack of control their angular kinetic energy relative of center of gravity of entire aircraft. So for implementation the "flying elevator" conception there needs an aircraft with wings of full controlled movement and steering. Ideally, wings of such aircraft should be in some conveyer movement with some winding speed over their pivots, which path has a segment where the lift powering performs and other segment, where simple return back performs to upper position with low level of the aerodynamic force. So I designed a variant of such "conveyered" configuration, which is represented on the chart below.

"Conveyered" configuration

  The aircraft is pictured in a cruise flight and has a standard fuselage with an upper tail stabilator, which is used for compensating variations of moment of both sides of "conveyered" actuators under broad range of flight operations. The pathway of wings on the actuator is a rectangle with rounded corners, which inclined back on a Skew angle from its vertical position. This inclining is used for distributing the load of lifting wings along of fuselage direction, decreasing overall height of the aircraft and driving force of entire actuator along its pathway. The pathway of the actuator has a segment "I", where the lift powering is performed, a segment "II", where recovering altitude of wings is performed, segment "III", where transition from the recovering to the powering is performed and segment "IV", where transition from the powering to the recovering is performed. Also, due to duality of representation of the power, the lifting segment "I" can be considered as be in propulsion powering. And also same possibility exists for segment "II", when its wings have negative load. Such negative load wasn't being possible in the "wired wings" configuration, but it is possible now for the aircraft. I suppose the number of wings per actuator pictured there is near to optimal, since having lower number can lead to high level of vibration and having higher number leads to too weak wings. Also I suppose the wing separation pictured there is near to optimal too, for having enough compact actuator with enough low level of wings interference.

 

  Although from operational point of view this aircraft looks perfect, it has a significant drawback. It is almost impossible to implement. The main challenge for it is resolving a problem of having the pictured motion of wings with their simultaneous rigidness with unsupported opposite ends under their big length for desired high aspect ratio. Indeed, the aircraft should have high aspect ratio of wings (AR) to be enough efficient. But its wings should be enough rigid for withstand the high load on the segment "I" and the high level of centrifugal forces on segments "III" and "IV". Best method to obtain the enough rigidness is: bring wings in a neighborhood support on their free ends. Doing that for a circular path can be simple resolved by a ring. But it doesn't work there. So one way to resolve it is using wings between two fuselages, which has a great number of disadvantages, such as having additional transverse elements for frame rigidness. I don't exclude one day the problem will be resolved, but currently I don't have a multi-tiered correct solution for it.

 

  So remained way for the correct implementation of the "flying elevator" conception in an aircraft is using of circular actuator. Exemplary variant of such kind of aircraft is represented on the chart below.

Cyclorotor configuration

  The aircraft has same fuselage as for the aircraft before, and now the stabilator is used for compensating variations of moment implied by the circular actuator of the aircraft, which I reference as rotor. The rotor has same number of wings as for previous aircraft and same wings separation. Now the specific segments of wings pathway have an overlapped placement, since lifting ability of wing has some variance over forward side of the pathway, and so related equivalent of propulsion abilities of the negative loaded wings on rear side of the pathway. Also the mentioned ring, which provides the rigidness to the rotor isn't shown there, for having wings non-obscured on the view.

 

  Aircrafts with circular actuators are known as cyclorotor aircrafts. I discuss matter of them in a separated topic "Cyclorotor aircrafts”.

 

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