58

That's called the step. Without it, you'd have to fight against the buoyancy of the rear end of the hull when you rotate for takeoff. However, a seaplane float or hull must be designed to permit the seaplane to be rotated or pitched up to increase the wing's angle of attack and gain the most lift for takeoffs and landings. Thus, the underside of the float ...


56

Note that the windows are a safety feature: You need to see outside in case of emergency, e.g. to know which side of the plane is surrounded by flames, or how deep in the water you are. This is actually the reason why the inner lighting matches the outside conditions for take-off and landing and the window shades have to be open. Even worse, the potential ...


46

These are rain gutters. They are designed to catch rain that runs off the upper surface of the aircraft fuselage and channel it away from the open aircraft door so that the water does not enter the cabin. This is a close up of the rain gutter over the main cabin door of a Beechcraft King Air B200, showing the channel that would catch and redirect water ...


37

Problem #1: What gets displayed on the screen? While I'm aware of Emirates' recent 'virtual windows,' there is a big problem with this idea in general: what should actually be displayed there depends on the location of the viewer relative to the window! This is not an easy problem to solve - and it's effectively impossible to solve for multiple viewers ...


35

how could it be trusted? Like all aircraft, type certification requires that these be tested. I think the wings are tested to 1.5 x their load limit. A380: STRUCTURAL STATIC TESTS The A380’s structural static tests on began in November 2004, in preparation for the first flight clearance. The tests included: Flight Test Installation (FTI) ...


34

If you pressurize any hollow structure, it will try to assume a round shape. If you want to create a lightweight pressure vessel, again a sphere will be the most efficient result, because there the stresses in the skin will be equal at every point. Blow up a party balloon if you are in doubt. A sphere is not the most efficient shape for aerodynamics, so ...


34

Emirates Airlines have recently launched their new First Class with a similar concept. It is only available in First Class and I doubt it has much to do with the structural implications as of now, but that could change if the idea catches on. The virtual windows are a feature on the otherwise windowless cabin suites along the middle aisle, and project a ...


33

As you mentioned, drag is one of the reasons why retractable landing gears are used in the first place. But in order to use it, there are way more considerations than just drag. Scale: Size of the aircraft plays a big role here. Big aircraft have more room to keep the retracted landing gear. This is an issue as planes get smaller. Weight: Retractable ...


32

That's called a 'fuselage boundary layer diverter channel', or splitter plate. The air near the fuselage or wings is slowed down (thereby losing energy). Those plates ensure the jet engines get free stream air, which improves the engine performance. This free stream air will be undisturbed, allowing a more uniform intake of air. You can also find it on the ...


31

What part aft of the bulkhead would leak pressure? That's a partial misunderstanding of what a bulkhead is there for. You could build the aft cone section to keep the pressure, but it would be a much heavier solution. The shape of the final aft section is not well suited to resist pressurization stresses: the best shape is a sphere; the cylinder (with ...


30

The ugly truth is: Cracks do occur, and have occurred on the A380 wing root, but that is normal. Read on for more. The static load is only one aspect. Normally, what is driving the design is the fatigue load, which is the constant jerking of aerodynamic and inertial forces on all parts of an airplane. Today, aircraft are designed such that cracks will not ...


29

The fuselages are circular (or nearly circular) in shape for two main reasons: The main reason is that for a circular cross section, the pressure loads are resisted by tension, rather than by bending loads in non-circular sections. Also, the non-circular sections have stress concentrations when pressurized, which may lead to failure. In case of a circular ...


29

(Source) Ju 88 model. Not just the 87, some Ju 88 models also had it, with no access to it in-flight. As mentioned, it's an antenna. The antenna is part of the EZ6 direction-finding unit. The glass is not for viewing. It's the construction method to keep the installation as thin as possible. The sense antenna is painted on the glass. The PRE/6 ferrite ...


28

It's called a hull step. Below is with and without: It reduces water drag. As the plane gains speed and the aft body is lifted, only the forward hull will be in contact with the water. Source: Laté 631 Replica - Chapter 3 - Hydrodynamics


28

The Auxiliary Power Unit (APU) exhaust This is answered by the following image (taken from this question, color markings are unrelated to this answer): The item 72 is what you are looking for and it is labelled "APU exhaust". The black residue is soot from incompletely burned fuel. The Eurofighter Typhoon can use its APU to start the main engine or to ...


27

The doors are painted like this because it is a federal law that all cabin doors on commercial airplanes should be outlined in a color which contrasts with the fuselage color. It is done so that in case of an emergency on ground, rescue crew can find the doors easily and open them quickly. It happened in past years that passengers survived some crash ...


24

① Main outflow valve door (Source) A valve used for controlling the pressure in the cabin. Air is pushed into the cabin by the air conditioning packs, and exits by this hole. The flow can be adjusted using a valve which is located behind this door. (Source) The valve opening is controlled by the pressure controller when the automatic mode is selected, ...


22

No, they are just the boundaries between skin panels. See below for a picture of the 747-8 fuselage during assembly. [ Boeing 747-8 front from side (picture source) And this is how the panels for the cylindrical section look like before they are joined: Boeing 747-8 fuselage panels. The original picture (source) is named "wing panel skins", but these are ...


20

The details of the strength required are likely to be complicated and proprietary. However, we can do a very rough estimate. Using the equation for estimating root bending moment here, and the following numbers: Fuselage weight: 230,000 kg MTOW: 577,000 kg Engines: 25,000 kg Fuel: 260,000 kg Wings: 60,000 kg Wingspan: 79.75 m Wing taper ratio: 0.17 The ...


19

Why don't [airliners] have square shaped fuselage? Shorts Skyvan photo from Wings over Europe Shorts Skyvan diagram from A Tall Guy Most airliners are pressurized. If you inflate a rubber balloon you'll notice that the most economical and strongest shape for a pressurized container is one with a circular cross-section. You'll also notice, when you ...


19

Let's take a Boeing 737 as a generic example, and spitball some numbers. I'll make the post community wiki so someone can come along and plug in more accurate numbers. Aluminum has a density of 2.7 g/cm3 (For our purposes let's assume the skin alloy is "close enough to pure aluminum" because I'm too lazy to look up the proper alloy density). Plexiglass (...


19

Boeing had already a fuselage for the 757 that fit the bill. It came originally from the 707 via the 727. To accommodate more baggage, the rear fuselage was deeper, as on the 737. During development Boeing engineers were afraid that directional stability might be insufficient with a deeper forward fuselage, so the lower half of the fuselage was kept from the ...


18

The additional mass due to windows can best be estimated by statistical methods. By comparing the structural mass of windowed and window-less fuselages of otherwise identical aircraft and formulating a numerical equation which fits all cases with the least error, you get formulas like $$n_{Windows}\cdot 4.641\cdot S_{Window}^{0.976}\cdot(1.0 + \Delta p)^{4....


17

I assume the hole has been properly deburred, otherwise you could suffer cuts on the sharp edges of the hole. What happens else depends on altitude and flight speed. At low level, the outside temperature should be tolerable and the pressure difference between inside and outside should be small, so your hand will be fine. At higher altitude, outside air ...


16

Strictly speaking, a 'pure' aerobatic aircraft doesn't need a retractable landing gear. For such an aircraft maneuverability is much more important than speed. In fact, the aircraft can't fly too fast or the spectators are going to miss the show. In case of air races, the weight penalty of having a retractable landing gear is huge- in addition to the ...


16

It's not a stress concentrator; it's just the opposite. What you're missing is that the floor itself at the pinched part forms a tension bridge that allows a more or less 'ovalized' circle while still maintaining tension loading on the skins and frames as if it was a pure circle. If I had a rubber balloon filled with air and was able to run a string ...


15

They are Conformal Fuel Tanks. See http://israeli-weapons.com/weapons/aircraft/f-16i/F-16I.html: Conformal Fuel Tanks (CFT) - These tanks are manufactured by the "Israel Aircraft Industries" and increase the aircraft's amount of internal fuel by 50%. Their purpose is to significantly prolong the aircraft's flight range and ability to remain in the air. ...


15

You can think of an airliner (or any other pressurized airplane, or a submarine) as a pressurized container with control surfaces and a nosecone stuck to it. Rather like a submarine, an airliner has a floor with seats, a nose to make it aerodynamic, wings for lift, and a tail section for control (yes, I know I am way oversimplifying it, and that's the whole ...


14

It's for the passengers on a rainy day. If this strip would not be diverting the rainwater flowing from the upper fuselage, a curtain of water would soak the passengers upon entering or leaving the aircraft, and the cabin floor.


14

That's cabin insulation - probably fiberglass. It's not always in green bags (blankets), and not always fiberglass, but some kind of insulation is necessary to help control temperature and reduce cabin noise (air moving over the fuselage is REALLY loud). Here are some other photos of different types of insulation: Basic fiberglass with a plastic backing, ...


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