New answers tagged

1

We used CATIA extensively in the design of the F-22. It helped all the supporting "ilities" also in their tasks. Great tool.


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Yes you can, the tail volume needs to be such that the neutral point shifts aft of the CoG. This answer has some details - positive lift from the tailplane, but it must never stall! More details about tailplane design in the answers to this question. The absolute safest config at a wide range of CoG is the CoG in front of the Centre of Pressure of the main ...


4

It is a wire deflector. It is common for power lines to be strung at the same height that the cropduster wants to operate at, and often multiple cables at exactly the same level, so that the aircraft could be dealing with a bundle of cables as it goes forward. Power lines, especially "last runs" to individual farms or villages can be extremely hard to see ...


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I assume here that the velocity is held constant. For this, both thrust and drag must have forces of equal magnitude and opposite direction. In short, they just balance each other out.


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Speed is the reigning factor here, and aerodynamics as well of course. Speed. Propeller driven aeroplanes operate at lower speeds than jet engines - propellers are more efficient until compressibility effects start to appear, and it is these same compressibility effects that influence the wing shape as well. Compressibility as in: give air enough time to ...


2

Yes it does. The reasons are many, and complicated, but I will try to briefly summarize them here in simple terms. A jet-powered fighter has to pop through the sound barrier with minimum ill effect and be aerodynamically predictable at supersonic speeds. It also has to withstand the great stresses associated with these actions and those imposed by high-G ...


7

The wire shown is a cable deflector which is part of a Wire-Strike Protection System common on most agricultural aircraft. Wire-strike protection systems As a last resort, when pilot situational awareness and on-board systems fail to detect a wire in sufficient time to avoid contact, a passive wirestrike protection system (WSPS) may protect the ...


2

As this film shows with brilliant simpliciy, the drag of a round wire is almost 10 times the drag of the same thickness streamlined shape. Biplanes use streamline rod for flying and landing wires because of this. There is enough flying/landing wire on a biplane for it to make a huge difference. On a long antenna wire however, there really isn't a ...


4

The B777 is a high subsonic aeroplane, and at high airspeeds the ailerons remain stationary because wing twist may cause aileron reversal. By using inboard spoilers as mechanical backup roll control surfaces, there is roll control available at high airspeeds as well. Roll authority would be limited at approach speeds due to the smaller moment arm than the ...


0

Another example of an aircraft with wingtip tanks is the T2-C Buckeye. They hold approximately 102 gallons each, and so add to the total fuel capacity of the aircraft. There are a number of reasons that the wingtip tanks might be part of the design of an aircraft. Decreasing flutter is one reason that you might add wing tips, and this hasn't been ...


6

On a Boeing 777, a tire pressure sensor/fill valve is installed on each of the 12 main gear wheels and two nose gear wheels. There is an in-axle transformer in each of the axles. The tire pressure sensor/fill valve is made of an air fill valve and three independent pressure sensing channels which provide accurate tire pressure. The tire pressure sensor/...


1

On a CFM56, the transient bleed valve (TBV) system controls the quantity of the high pressure compressor (HPC) 9th stage bleed air that goes into the stage 1 low pressure turbine (LPT) nozzles. The TBV system increases the HPC stall margin during engine start and during engine acceleration. The variable bleed valve (VBV) system lets a part of the low ...


5

It's a "simulated ice shape" to simulate a heavy coating of rime ice. This aircraft was likely used in testing to explore the stall behaviour of the outboard wing forward of the aileron in icing conditions. That surface texture would, believe me, NOT improve the stall behaviour. It will not generate vortices or favourable turbulence. It will drop the ...


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The leading edges are roughened to improve the stall characteristics. Typically vortex generators are used for this purpose nowadays. The 5 and the 5a were used by the RAF for pilot training and the nose strakes were fitted to improve the spinning characteristics - the leading edges of the wings had a roughened paint finish to improve the stall ...


2

Highly unlikely. The most efficient way to increase an aircraft's efficiency at converting thrust to lift is by increasing the amount of air that it is able to use. That's increasing the wingspan. It's less efficient to try to get more lift out of air that we are already using -- that's high-lift devices and stacked wings. The increase in materials ...


3

The lift equation: $L = C_L \cdot ½ \rho V^2 \cdot S$, with S the wing area. Wing loading is defined as L/S, equalling: $$\frac{L}{S} = C_L \cdot ½ \rho V^2$$. With a given $C_{Lmax}$, a higher wing loading implies a higher speed. The first option is the correct one.


1

It would save weight and complexity if one combined control surface ran the length of the trailing edge, instead of being split in half. If the trailing edge real estate is there, it makes sense to split control surfaces along their functionality. The issue is maximum deflection: at full flaps, a flaperon cannot command any additional aileron down input. ...


1

From this answer, an accessory gearbox for the Rolls Royce Trent. The accessories connected to the engine spool(s) are: The Engine Driven hydraulic Pump Fuel pump Oil pump Pneumatic starter, requiring the highest loads and therefore dimensioning the gear strength. The IDG: Integrated Drive Generator which provides the AC power. Only the pneumatic starter ...


2

From lowest to highest wing loading: Climb: if a fixed wing plane and the nose is pointing up, some of the vertical force must be generated by the thrust. Cruise: the lift must only compensate for the weight. Inducing a turn: the rolling velocity has very little effect on wing loading. Take-off: a slight positive g-loading during the nose-up motion. ...


1

Adverse yaw is the yawing moment that occurs due to aileron deflection. Yawing moment from aileron deflection: upon a left turn the right aileron deflects downwards and the left one upwards. The downwards deflecting aileron creates more drag friction, pulling the nose of the aeroplane to the right. Yawing moment from roll velocity. The wing rolling up has a ...


0

The general equation during level unaccelerated flight is $L=\frac{1}{2}\cdot\rho\cdot V^2\cdot S\cdot C_{L}$: For a variety of speeds V between the stall speed and the Never Exceed speed. For a variety of altitudes, between under sea level and the stratosphere. For a variety of Angle of Attack of the aeroplane, equating to a range of $C_L$ Resulting in a ...


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Picture source It may seem so when on ground, but in flight the wings flex up. Judging from the photo, the wings seem to have the tiniest bit of dihedral. They also have wing sweep, which provides sideslip-to-roll stability as well.


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From this site, contains links to the profiles which can be used for Xfoil.


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What are the criteria that govern the choice between titanium, composites, and more common materials, like aluminum? Three main criteria: cost, strength-to-weight ratio, and fatigue resistance. Cost. Of the three, aluminium used to be the clear winner, with composites having made large advances due to improved manufacturing processes. Titanium is the most ...


1

Dihedral is included in many wing designs because it is very useful in making the plane fly in a stable, comfortable manner. As Koyovis explained, lift loss is minimal, and if more lift is needed, simply make the wings larger (or reduce weight!). This is called wing loading. Is far as external "ribs", these are called wing fences, and are not usually ...


0

Pitching moment is usually defined relative to the centre of gravity. The main wing does provide a pitching moment, since it has both a force and a moment arm relative to CG. The reason to define pitch relative to CoG is that in a free response in vacuum, the CoG is the centre of pitch rotation. But moments can be defined relative to any point, also to the ...


0

Aeroplane landing gear is dimensioned for maximum weights, the weight data in OP is for empty weights. MTOW of a Citation II is specified as 15,100 lbs in Wikipedia, the F16-C as 42,300 lbs. From Torenbeek, Synthesis of Subsonic Airplane Design, category Light Aircraft. There are two business jets listed with similar MTOW to the Citation II: the 1121 Jet ...


6

Product liability destroyed this industry. In the 1970s GA aircraft were much less expensive. A midrange model cost about twice the annual salary of the average US worker. Annual production was about 14k per year. Then attorneys found out that juries could be persuaded to award ten times as much for a death in a small airplane as for the equivalent death ...


3

From the table in this answer: the tail group of the 747-100 and 747-200 is 11,850 lbs. In order to find the weight of horizontal and vertical stabiliser, we can divide up the weight according to tailplane surface. Table 9-2 in Torenbeek gives the ratio of horizontal tail surface/wing surface as 0.267 in table 9-2, for both the 100 and the 200. Wikipedia ...


3

Weight-to-power ratio of the actuators, but things are changing rapidly. The main advantage of hydraulic vs. electrical actuation of flight controls is the easy way of distributing power of hydraulics. One large pump can be mounted onto a motor or engine, and generate power for multiple small, light hydraulic actuators. Hydraulics do have a disadvantage ...


2

None. What you've come up here is a just holes in the wing, which will allow high pressure air from the lower surface to escape upwards. This will both slow the plane down due to extra drag and reduce its overall lift. An autogyro's rotor is a wing in itself, deriving spin from forward motion, and then converting spin to lift. You don't get extra lift by ...


2

An autogiro derives its lifting force from its rotor, which is not powered by an engine but by the airstream flowing in at a positive Angle of Attack: from a relative flow that is directed upward through the rotor disk. So to an extent, the autorotating rotor provides the same function as the wing surface that was cut for mounting the rotors. How best to ...


2

The amount of lift lost to dihedral is because of a trigonometrical condition, and cannot be fixed by ribs. Lift is always perpendicular to the local surface, and each wing half develops lift at the dihedral angle. Only the vertical bit is useful for suspending the aeroplane weight. In order to quantify: Cos 5° = 0.9962, so less than 0.4% of lift is not ...


0

It should climb, you don't say what rate of climb you're expecting but with a 125cc engine and 250 kg gross weight you should at least get airborne.


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Image source The Sikorsky X2 is (was) a compound helicopter, with an engine driven rotor and a pusher type propeller to offload the main rotor. Image source The Fairey Rotodyne was a compound autogyro: an engine driven rotor, a pusher propeller, and a fixed wing to generate most of the lift at speed. The fixed wing is efficient at generating lift, reduces ...


1

Roll stability, as in an opposing aerodynamic moment caused by a roll attitude of an aeroplane: no there is not. These stabilising roll torques are a result of indirect state variables: Sideslip angle, excluded for this question. Differential air velocities over the inner and outer wing in a turn. Damping forces due to roll velocity.


0

The trimmed position of the flight controls has different meanings for different control systems: For manually controlled flight control surfaces, the flight controls trimmed position is the stick equivalent position that the control surface returns to when it is released, no hand or feet on the controls. The surface position where aerodynamic hinge moments ...


1

As stated in this answer, the Wright Flyer could take off with 12 hp at 274 kg, so you do seem to be in the ballpark. But note that the Wrights had a long wing span, two wings, and two large & slow turning propellers. For successful take-off Lift = Weight and of course Thrust = Drag. The L/D ratio of the whole aeroplane thus becomes equivalent to the W/...


0

The concept drawing shows a safety advantage of the multiple rotor design: You can see the beams that support the multiple rotors. The beams are beneath the rotors. This makes it less likely that passengers will accidentally put themselves in the way of the rotor(s). From the point of view of the concept artist, it is much easier to make the beams that ...


0

Perhaps not the main reason, but an important one in addition to the other answers, is IP. The established players in helicopter design & manufacturing are just that, established; they are all firms that have been refining their technology for decades, often with substantial defence funding, so that all of the performance & efficiency gains in their ...


1

The real reason is that the current concept for aerial taxis came from people who don't understand or don't care about aerodynamics. This is one of ten business ideas that Uber is/was pushing for their IPO, and they have had success with the money they put into its marketing. It originated from extrapolation of camera drone technology to human passenger size,...


1

It’s a good question. Single rotor helicopters exist already, and would make a much more boring investment proposition for private equity than a new sort of vehicle which sports claims of revolution, modernity and cleanliness. Above clip (also posted in this thread of five years ago(!)) has a person controlling an electric ...


4

There are a few main reasons most electric air taxi concepts have multiple rotors. 1) Mechanical simplicity. Helicopters are controlled by varying the angle of attack of the blades as the rotate, and the mechanical mechanisms to do this (swashplates) are complex and expensive to build and maintain. The thinking is that with electric motors, you can ...


1

Probably safer in the belly than anywhere else due to stress, bending, and weight balance issues. The wings would be closest to pitch CG, but loading them with fuel would affect the roll rate as well as a possibility of creating a sickening uneven "sloshing" motion that could affect passenger comfort. The solution is called "inerting" or eliminating one ...


1

Yes the fuel from the centre tank can be moved to another place in the aircraft. It's a lot of fuel though. Some ideas I thought of: Store fuel in anti-shock bodies on the wings (or they could be just small sears-haack bodies on the wings). Technically possible, but there will be a large amount of pods. Store fuel in the empannage. This is already done ...


0

I don't have any data on the Tumanski engine, only on comparable western fighter jets of the same generation. General Electric J79 mounted in the F-104 Starfighter: mass flow = 77 kg/s. Snecma ATAR9K50 mounted in the Mirage III: mass flow = 73.5 kg/s. These are the max. mass flow rates, at maximum thrust. They don't scale much with the thrust at operating ...


0

There are a couple of examples on this site now (here and here for instance) for static propeller thrust calculation, based on existing considerations for helicopter hover. The theory can be found in books like Principles of Helicopter Aerodynamics by J. Gordon Leishman; Helicopter Performance, Stability, and Control by Raymond Prouty. The books start their ...


0

The horizontal tailplane can be longer, in order to keep the tail area constant, the chord would be reduced accordingly. The higher tail aspect ratio would result in a higher root bending moment, therefore a heavier construction. A higher aspect ratio reduces induced drag, very desirable in the main wing but of secondary importance in the tailplane. Induced ...


0

Yes that is possible, but impractical. Such a design would use asymmetrical drag to compensate for moments about the centre of gravity. Conventional tailplanes use asymmetrical lift, which has a much lower drag-to-force ratio. The horizontal tailplane provides an additional spot for lift, so that there is a practical range of CoG locations. The bottom or ...


1

The craft won't be able to fly without addressing some serious balancing issues. Both have their rotors far away from the centre of gravity, and this can only be compensated by the rotors if they exert a high torque, by a fixed rotor head. Which will then create serious controllability issues, since there is no way to input cyclic and collective control.


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