28

The "extension" at the front is called "dorsal fin". Its main purpose is to improve directional stability in high side-slip situations (asymmetric flight due to engine failure, crosswind landings, etc). The double-sweep of the leading edge of the vertical stabilizer helps the vertical stabilizer to be effective at a larger range of side-slip angles (high ...


23

From whats written here f100 skin is 1.0 - 1.4mm b747 skin is 1.8 - 2.2mm a320 skin is about 1.1mm According this article on the 757 ...Although Boeing specified that the skin in that area of the fuselage must be 0.039in (0.99mm) thick... Some interesting info here as well.


22

Geodesic (sometimes also spelled geodetic) designs were used in aviation as early as 1909, in the Schütte-Lanz SL1 airship. It had a wooden structure with fabric covering, and Professor Johann Schütte, the scientific head of this design, used the most efficient method conceivable. However, planning the shape of all structural members was an enormous amount ...


19

The vertical tail stabilizes the aircraft in the yaw axis. The fuselage is unstable, so a stabilizing fin must be added. Since the vertical has a much higher aspect ratio than the fuselage, it will stall first. Beyond the stall angle of sideslip, the vertical will not be able to overcome the still increasing instability of the fuselage. To remedy this, a ...


19

Just a couple of mm thick, about 2-3 is enough. The fuselage barrel gets its strength from the large diameter: bending moments of the fuselage (and wing) get translated into tension and compression loads in the skin. The aircraft skin is the main load bearing structure. It's the same principle as that for I-beams:they are that shape because the top and ...


14

Depending on how you classify the control surfaces, the B-2 Spirit does not have a horizontal stab, since it is a "flying wing" design. As you have changed the question, the other part of the answer is that the flying wings have been able to get by without vertical stabilizers as well, at least in the case of the B-2. It uses both spoilers ("split brake ...


14

Short answer These holes are vents used to discharge air from the primary (core/hot) flow into the secondary (bypass/cold) flow. They are normally closed by valves (variable bleed valves, VBV). The valves open to maintain the compressor pressure/flow within a safe area. VBV in operation: Youtube VBV on a CFM56-5 (also visible the VSV). Source VBV are a ...


14

If a plane of the L-1011's range makes two flights per day for a century without any maintenance breaks, that would be 73,000 flights. The answer is yes, more or less, literally, if you look at wing loads, or pressurization, respectively. If you account for AOG (aircraft on ground) time, then most certainly yes for both: A total of 1,696,000 load cycles, ...


13

Depends on how you define it but there have been a variety over the years: The P-38 Lighting has 3 bodies there was also a later experimental version the XP-49 that only saw a single airframe. The F-82 was a a twin fuselage version of the P-51 The boomerang which was also designed by Burt Rutan (the designer of the stratolaunch) A one off twin fuselage ...


11

Magnesium has initially been held back by technical difficulties in the removal of chloride inclusions. These had been solved only after a lot of progress had been made in aluminum alloys. Also, magnesium parts should only be used in a dry environment - when the metal is exposed to water, rapid corrosion must be expected. The first application of magnesium ...


11

An interesting thought. Control the aeroplane through its propeller(s), like a helicopter does. Propeller torque differential would control roll Propeller cyclic would control both pitch and yaw Propeller collective would control engine thrust, like already done in constant speed propellers. The thing that immediately comes to mind is moment arm for pitch ...


10

The switch from internal frames to structural skin airframes -- called monocoque construction -- is fairly well covered in Wikipedia: Early aircraft were constructed using internal frames, typically of wood or steel tubing, which were then covered (or skinned) with fabric3 such as irish linen or cotton. The skin added nothing to the structural ...


10

Helicopters are also subject to metal fatigue and there have been accidents attributed to it but the primary determination is component life times. All of the engine, transmission and rotor parts are lifed and most of the control mechanisms. Depending on the helicopter, there will be many more lifed components. Some helicopters also have fixed intervals ...


10

They appear to be related to changing the oil. The Tornado's flight manual is available online. Page 448 shows what seem to be the features you're talking about: The features are the ones marked as "12." The previous page has a legend describing them simply as "engine oil." This probably also explains why they're not placed symmetrically. It seems the ...


9

Flaps have different actuation mechanisms from primary flight controls. Flaps deflection brings a shift of pitching moment with it, and it is done slowly to give the pilot time to adjust the aerodynamic trim. Usually with electrical screwjacks, with a fine pitch that stops the forces on the flaps from feeding back into the motors. Yes flipping the switch ...


9

On a light aircraft, the answer is somewhat similar to the mechanism you might be used to in a RC aircraft. The image below shows the important parts - a hinged flap and a "control rod" which is attached to an electric actuator. This is controlled internally by a simple switch (Both images source: http://www.weekendcfii.com/frame_c172_preflt.html?...


8

Yes, short range airliners are designed for up to 90.000 cycles whereas long range airliners can be designed for 40.000 cycles or less. And it is not only the pressurized cabin that needs to be designed for more load cycles, also the landing gear has a lot more work to do. This should become clear when you calculate how many miles/kilometers an airplane will ...


7

Based on the wording of your question, the Flying Wing design would qualify. These aircraft do not have proper "tail" stabiliser sets and they still fly.


7

Among the earliest aircraft to fly were the models of Alphonse Pénaud, and they flew without a vertical tail. The rubberband-powered pusher propeller was sufficient for stabilization. Admittedly, they did not need to maneuver. Pénaud's Planophore (picture source). The spinning propeller replaced the vertical tail. After Friedrich Ahlborn published a study ...


7

To give an answer, I first need to get answers to a few more questions: First question: Which titanium alloy would you consider? The choice of alloy will impact the answer much more than the base metal of the selected alloy. Since strength at elevated temperature is the figure of merit here, consider the spread of values: Strength of various Ti alloys over ...


7

It's partly pragmatic (you start from +1.0 G, so why not optimize for that???) and partly because (most) aircraft are designed to carry human beings. Humans as well as a lot of other things are FAR more tolerant of positive G-forces than they are negative G-forces. There's very little technical reason that you couldn't design an aircraft wing and other ...


7

This will work as long as the propellers produce enough thrust and blade pitch can be adjusted fast enough to outrun all eigenmodes. As soon as you need to throttle back (and eventually you must, to come down again), the control effectivity of the propellers will be greatly reduced. Granted, you can float down in autorotation like an autogyro, but the ...


7

Yes they do, and here is why. Airplanes are made mostly of aluminum rather than steel. It is possible to design a steel part in such a way that it will never succumb to fatigue failure (crack propagation at a stress significantly below the yield stress) but this is not true of aluminum and its alloys. For this reason it is necessary to periodically tear ...


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 aircraft ...


7

Yes, the plain wing area is also used for wing loading. How the value is calculaed depends on the method used. In all cases the center section and ailerons are included but the horizontal tail is excluded. Common is also the use of the projected area of the clean wing in the x-y-plane, because that is the area relevant for lift. For airliners, the two most ...


6

I am a Aerospace Systems Engineer and former Royal Air Force. Although my qualifications and experience are within the avionics arena I feel I can answer this question: There are basically 3 types of Helicopter and for that fact any aircraft: Military Civil – Private Civil – Commercial The military aircraft have the shorter life in terms of flying hours, ...


6

Before answering the questions, let's try to see how simple is the notion of a geodesic. In planar construction, we use latices to rigidify a structure, e.g. a truss: The structure is made of straight segments that don't deform when axial forces are applied. If we switch from the plane to an arbitrary curved surface, something similar can be done, but ...


6

There are a few ways to sense ice on an airframe. The DOT has a document here that outlines the various types of sensors. First and foremost planes have ice lights that project onto the wings so they can be visually inspected. There are completely optical sensors that use a variety of methods to detect ice. There are also some electro mechanical ...


6

As far as i know, the helicopter airframes are not reinforced asymmetrically due to this reason. Note that the helicopter has to yaw in both ways- so there is no point in reinforcing only one side. The helicopter airframes are not weak- they are designed to withstand the full envelope of expected loads. Also, it is easier to design and manufacture a ...


6

It does not reduce drag, but creates more of it. This concept is called a "box wing" and is one variety of closed wings. Another is called a "joined wing" and was popularized by Julian Wolkovitch. However, only people who don't understand how a wing produces lift can be enticed by this concept - it has too many drawbacks for the modest reduction in induced ...


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