Vengeance Drone - Design Features
From a technical perspective, distinguishing features of the Vengeance Drone design include the forward canard, with the main wing to the rear, and no horizontal tail. The main wing has a high aspect ratio [the tip-to-tip span of a wing, or wing shaped structure, divided by its root chord]. And with the propeller at the ear of the vehicle, it has a pusher propeller - rather than the tractor [pulling] propeller seen on most aircraft.
Vengeance Drone - Aspect Ratio
Aspect ratio is a measure of how long and slender a wing is from tip to tip. The Aspect Ratio of a wing is defined to be the square of the span divided by the wing area and is given the symbol AR. For a rectangular wing, this reduces to the ratio of the span to the chord length. The front of the wing (at the bottom) is called the leading edge; the back of the wing (at the top) is called the trailing edge. The distance from the leading to trailing edges is called the chord, denoted by the symbol c. The ends of the wing are called the wing tips, and the distance from one wing tip to the other is called the span, given the symbol s.
The shape of the wing, when viewed from above looking down onto the wing, is called a planform. In this figure, the planform is a rectangle. For a rectangular wing, the chord length at every location along the span is the same. For most other planforms, the chord length varies along the span. The wing area, A, is the projected area of the planform and is bounded by the leading and trailing edges and the wing tips. The wing area is NOT the total surface area of the wing. The total surface area includes both upper and lower surfaces. The wing area is a projected area and is almost half of the total surface area.
High aspect ratio wings have long spans (like high performance gliders), while low aspect ratio wings have either short spans or thick chords (like the Space Shuttle). There is a component of the drag of an aircraft called induced drag which depends inversely on the aspect ratio. A higher aspect ratio wing has a lower drag and a slightly higher lift than a lower aspect ratio wing. Because the glide angle of a glider depends on the ratio of the lift to the drag, a glider is usually designed with a very high aspect ratio. The Space Shuttle has a low aspect ratio because of high speed effects, and therefore is a very poor glider. The F-14 and F-111 have the best of both worlds. They can change the aspect ratio in flight by pivoting the wings--large span for low speed, small span for high speed.
Vengeance Drone - Pusher Propeller
Aircraft have had two types of propeller configurations: pusher propellers and tractor propellers. Tractor aircraft have the engine and propeller at the front of the aircraft where the thrust draws or pulls the airplane. Modern aircraft use this type of configuration. Aircraft with pusher propellers place the propeller assembly behind the engine. The thrust produced by the propeller pushes the airplane forward. Most of the Wrights' planes used this type of configuration. during World War II They appeared to offer better visibility, less drag, and the opportunity to carry more guns in the nose.
With a pusher less of the airframe will be in the high speed prop wash so there will be less airframe drag. The tractor configurationr contaminates the fuselage with a noisy, vortex-laden propwash that changes widely with the throttle position. By contrast, in the pusher configuration the propeller is in the fuselage's slipstream, so the air velocity at the leading edge is slightly less uniform than in the tractor configuration due to drag effects from the fuselage. This makes the propeller slightly more effective because it receives relatively slower air and the propwash is unimpeded.
A suprising finding for almost all popular pusher aircraft was that they are 5-6dB noisier than "equivalent" tractor aircraft. This is claimed to be due to the turbulent flow into the prop disk. All apparently have a characteristically "raspy and beating" prop signature.
Vengeance Drone - Canard
Canard airplanes are inherently more efficient and safer than airplanes with a horizontal tail. The canard lifts where the horizontal tail pushes down. Hence there is less lift induced drag in a canard airplane. A properly loaded canard airplane cannot stall or spin. Hence it is safer. Still, canard airplanes have never been very popular. Existing designs have compromises that limit their usefulness. The major compromises include a severely limited range of position for the center of gravity (CG) and high takeoff and landing speeds.
In the last couple decades, experimental aircraft builders have made significant improvements in the performance of small planes. The major proponent of canard aircraft is Burt Rutan. His best known planes are the VARI-EZE (which spawned a whole family of canard aircraft) and the Voyager (which flew around the world without refueling). A good quality VARI-EZE typically reaches a top speed of 90 m/s with a 75 kW engine. In the mid 1970's, Rutan's new homebuilt airplane design, the VariEze, made a significant impact on the general aviation community because of its canard design and other advanced features.
The main difficulty in designing a single engine canard airplane is that the engine must be at the front or rear of the airplane, not on the wing, as is possible in a twin engine airplane. Placing the engine above the airplane is theoretically possible, but that introduces a whole set of undesirable mechanical and aerodynamic problems. In existing airplanes with the engine in front, as in the Quickie family, the canard has to carry the majority of the weight of the airplane. This forces the canard to be large, and it almost becomes the wing.
Stability can be obtained for any planform configuration by locating the center of gravity ahead of the aerodynamic center. If the engine is in the rear, as in the EZ family, and in the original incarnation of the race airplane named Pushy Galore, the wing carries most of the weight, but the pusher configuration introduces a new set of limitations, including the impossibility of making a taildragger configuration (with a small tail wheel as opposed to a nose wheel) and less efficient engine cooling.
The first human-powered flight was achieved by a canard-configured air-craft (Wright Brothers). Although other canard concepts were flown withvarying degrees of success over the years, the tail-aft configuration hasdominated the aircraft market for both military and civil use. early canard concepts suffered adversely in flight behavior because of alack of understanding of the sensitivities of these concepts to basic stabil-ity and control principles. Modern canard designs have been made competitivewith tail-aft configurations by using appropriate handling qualities design.
Recent articles in the popular press have extolled the virtues of canards, pointing out that because canards provide positive lift, the aircraft can be smaller with less drag, and safety is improved because of natural aerodynamic angle of attack (AOA) limiting. There may be several reasons for a change in popularity of this aerodynamic concept, including (1) the potential for increased performance in terms of an expanded high/low speed operating range or increased maneuverability (tied in with mission requirements); (2) newly available structural materials that favor a specific design layout (use of aeroelastically tailored composites); and (3) potential improvements in handling qualities for safer operating characteristics (better stall behavior).
Vengeance Drone - A Comparison
While there do not appear to be well known drones with a canard, high aspect ratio wing and a pusher propeller, there is at least one piloted aircraft design with these features. The e-Go is a single-seat light sport aircraft (LSA) designed and developed by e-Go Aeroplanes, a UK-based aircraft manufacturer. The aircraft, also called e-Plane, is developed under the Single Seat Deregulated (SSDR) category in the UK. The first flight of the aircraft was completed in October 2013. The first SSDR e-Go aircraft prototype was produced and delivered in June 2016.
The e-Go stems from Giotto’s desire to design a canard aeroplane with efficient aerodynamics, The e-Go is made almost entirely of carbon composite materials. This results in a very stiff, strong construction but at very low weight. The nose down pitching moment increases with speed, the aircraft rests increasingly on the canard wing of higher aspect ratio and the mainwing is unloaded. Thus at speed, the aircraft flies on the higher aspect ratio front wing while load on the main wing is kept to a minimum and the efficiency is improved. In the cruise at 90kn the canard is providing around 70% while close to the stall the front wing is relatively unloaded with around 30% of the lift.
The e-Go range is 610 Km (330 nm, 380 sm) – at 90 kts + half hour reserves. The aircraft has an empty weight of 139kg and can carry a maximum all-up mass of 270kg. The exterior dimensions of the aircraft include a length of 3.79m, height of 1.8m, wingspan of 7.99m, and wing area of 11.5m².
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