61 votes
Accepted

What is the offset in a seaplane's hull?

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 ...
  • 10.2k
56 votes

Can cameras and LCD screens replace cabin windows?

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 ...
  • 1,144
49 votes
Accepted

What is this line found above the door on many aircraft?

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 ...
  • 16.4k
44 votes
Accepted

Why was the SR-71 made of titanium?

Because the specific strength of titanium at higher temperatures is better than that of steel (both are much better than that of aluminium). Specific strength vs. temperature is shown on the above ...
  • 60.4k
41 votes

Why is the fuselage on an airliner circular-shaped?

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 ...
37 votes

Can cameras and LCD screens replace cabin windows?

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 ...
  • 19.1k
35 votes
Accepted

Why is the fuselage on an airliner circular-shaped?

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 ...
  • 99.2k
35 votes

Why is the A380's fuselage designed with a flat bottom?

There are 2 main reasons: The wing spars run through that area. If you wanted to keep the wing spar within the oval cross-section, you'd have to install the wing much higher on the fuselage which ...
  • 10.2k
34 votes
Accepted

Can cameras and LCD screens replace cabin windows?

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, ...
33 votes

Why use an airplane with non-retractable landing gear for aerobatics?

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 ...
31 votes
Accepted

Why do airliners have "pressure bulkheads"?

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 ...
  • 32k
27 votes
Accepted

Why are cabin doors outlined with a different color than the fuselage?

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 ...
  • 29.2k
24 votes
Accepted

What are these elements on the back of a Boeing 737?

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 ...
  • 68.4k
23 votes
Accepted

What are these lines on the fuselage of a 747?

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 ...
23 votes

Why don't airliner vertical tails extend to the very aft of the fuselage?

Spin resistance and area ruling Locating the vertical a bit ahead of the horizontal tail brings it out of the probable wake of the horizontal at high angle of attack, so it still is effective in ...
22 votes

What are these "winglets" on the roof of the 737?

In general, those are called blade antennas. They consist of a monopole antenna (a single rod sticking out of the fuselage) with an aerodynamic fairing around it.
  • 10.2k
21 votes

What is the weight saving of windowless fuselage for cargo aircraft?

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 ...
21 votes
Accepted

Why did water come into USAirways Flight 1549 if an airplane is sealed and pressurized?

Two reasons: Airplanes are not completely, perfectly hermetically sealed. They are pressurized using positive air pressure from the engine bleed air and packs. If there is a failure in the system, ...
  • 16.4k
20 votes

Why is the fuselage on an airliner circular-shaped?

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 ...
20 votes

Why was the SR-71 made of titanium?

There is a great article here that breaks it down in depth but its combination of factors made it the best choice, not a single factor (i.e. heat resistance). But, in reality, the strongest titanium ...
  • 97.6k
19 votes
Accepted

Why didn't the Boeing 757 share the 767 fuselage?

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 ...
18 votes
Accepted

What is the weight saving of windowless fuselage for cargo aircraft?

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/...
18 votes

What are these "winglets" on the roof of the 737?

It looks like a VHF and ELT antenna. References: Boeing 737NG Radio Equipment Communications
18 votes
Accepted

What are the random, differently-coloured rectangular patches on the top of this Boeing 737's fuselage?

They aren't "repair patches" themselves, they are repainted areas where some sort inspection and/or repair was done to the underlying structure, that required removal of the paint in the ...
  • 114k
17 votes

What is this line found above the door on many aircraft?

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 ...

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