# Tag Info

25

Fuel tanks take most of the space in aircraft wings, but not all. There are other things on wings too. They are ailerons, flaps, slats, air brakes. On most airliners, the engines are attached to the wings too, so their assembly takes up space. On the two aircraft of your interest, here are the pictures: A380 (its nickname is not jumbo, but superjumbo) ...

25

Typically, a little gain is obtained. Larger airplanes use anti-skid technology. Anti-skid works by modulating brake pressure to ensure the tires never skid. It's important to understand the relation between a tire's load, brake pressure, and actual retarding force. First, look at this image : It shows how as you increase pressure and the wheel starts ...

24

First, let's figure out how much power a 747 needs to takeoff: Assume: Engine thrust = 284 kN Takeoff speed = 170 knots Takeoff power = 90% max power Using $P=Fv$, converting the variables to SI units, we get $$Power=88,948,800 W$$ Or, in other words, around $90MW$. EDIT: This calculation is only correct if the engine efficiency is 100%, because it is ...

16

Those are Outlet Guide Vanes / Fan Exit Guide Vanes. They prevent the flow (bypass flow in this case) from rotating. The these vanes do not rotate, they are fixed to the housing. They also provide structural support. Because there is no energy lost on the rotation of the flow the efficiency is increased.

15

Increasing the number of wheels with brakes will decrease the braking distance as there's more sources of friction to convert the kinetic energy. Doubling the number of wheels per brake (I think what you're asking in the second part of the question) wouldn't automatically decrease braking distance as the brakes are limited to absorb a certain amount of ...

12

Yes of course. And even with nose wheel brakes the main braking force would still be generated by the main wheels, so a substantial pitching moment is generated. Now for a crude first-order approximation. We have an answer about the braking forces here, and using those 235 kN per wheel (the 747 has 16 main wheels) means that the center of gravity, which I ...

11

The 747-8 has three packs, and it is feasible to complete the flight with one of them inoperative (in case of aircraft with two packs, cabin altitude can be maintained win any one). The following is taken from the Minimum Equipment list of 747-8: Screengrab from 747-8 MEL As can be seen, flight is possible with some limitations. In case of a failure in-...

11

The airfoil profile you've shown is called a supercritical airfoil. Typical airfoil sections are curved on the top and the bottom. The airflow over the top of the airfoil is accelerated i.e. the airspeed over the top of the airfoil is more compared to the free stream velocity. The associated reduced pressure helping to create lift. Source: www.symscape.com ...

11

What's behind those windows is the crew seating and rest area. There are no passenger seats on those planes, the seats are specifically for the pilots and the people handling the cargo.

10

Here’s something on Physics.SE that you may find interesting. It’s all about the force and mass, not the contact area. More wheels, same brakes = no change Adding more wheels but keeping the same number of brakes would have negligible affect on stopping distance, as the total force going through the wheels and brakes would be the same and the mass change ...

10

I can't quickly find the necessary numbers for 747-8, so I'm going to go with the numbers for Rolls-Royce RB.211-524G-T, one of options on 747-400, taken from here. The engine can produce static thrust $$T_s = 58,000\ \mathrm{lb}_\mathrm{f} = 258\ \mathrm{kN}$$ using mass flow rate of $$\dot m = 1,604\ \mathrm{lb/s} = 727.5\ \mathrm{kg/s}$$ Now due ...

8

The pilot crew rest areas are not as large as flight attendant rest areas as they only provide space for 2 occupants. A380 and B747-800 pilot rest areas will have 2 sleeping berths, and most airlines will also have 2 comfortable seats equipped with the same in-flight entertainment as the passengers. This gives the resting pilot the choice to sleep in a bed, ...

8

The answer is quite simply, no, at least, not if it is or was intended to compete as an airliner of roughly the same size. That's because your question is based on a false premise, that the struggles of the A380 in the current market are due to its fuel economy. The A380 is indeed uneconomic to operate except on few routes, but that is because of its size ...

7

Well, the GEnx-2B67 engines with which the 747-8 is fitted each produce a maximum of $284 \mathrm{kN}$ thrust (according to its Wikipedia page). This translates to a total of $1136\mathrm{kN}$, since it has 4 engines. Power, which has the units Watt, is the product of force (thrust) and velocity. The 747 has a takeoff speed of about $290 \mathrm{km/h}$, ...

7

Photo source: own work. In-flight with the Right Pack inoperative—the button with the sticker. It is legal; the flight was limited to FL250, and the air conditioning was switched off for the take-off. If the flight is a long haul, the limited cruise altitude will limit the range. Grounding the plane would make sense then, fuel wise. The airline and the ...

6

The first 747-8 built was not a protype, but a production unit. The first delivered aircraft in both the versions (747-8i Intercontinenal and 747-8F Freighter) are in service, the Passenger version with Lufthansa and the cargo version with Cargolux. The first 747-8 customer was Cargolux for the 747-8F version. The first 747 ever built, 747 RA001 'City of ...

6

Yes. Automatic operation exists as well (may not be installed/chosen by the operator). Nitpicking: this bleed air is for anti-ice, not de-ice (but even manufactures get it wrong in the manuals sometimes, see below). Saving this bleed air when not needed saves fuel and engine wear, and allows higher more efficient cruise altitudes. Speaking of the A380, ...

6

From federalregister.gov: The FAA also assumed that the average safety door system adds 100 pounds to a large airplane. This additional weight would have minimal impacts on weight and distance limitations. For a large airplane, like say the 747, it seems the weight addition is around 100 lb (including the other safety features such as the surveillance). ...

6

You can find some footage of the A380 crew cabin here. There appears to be about a dozen or so sleeping berths as well as a bathroom. You can find some pictures here and according to the article. The aviators also have their own entertainment screen when they’re away from the cockpit, and unlike the tight-squeeze crew bunks, there’s extra headspace ...

6

Sure, the 747 is a Type Certified and airworthy aircraft, the FAA does not really care who owns it so long as they play by the rules. Boeing even sells them directly to the private market via their BBJ line. There are even a few used ones listed for sale right now. Some people even buy them for other purposes than flying them... for how long will ...

5

Would installing 6 engines on an Airbus A380 and or Boeing 747-800 achieve a shorter take off distance? Yes in theory, more thrust is faster acceleration. No, because engine/wing interaction is not simple: For the 747: the flaps will need an additional thrust gate, which will reduce the flaps capability. For the A380: since it doesn't have a thrust gate,...

5

Well, just because it is stronger than steel does not mean that it is a useful structural material. For example, the tensile strength of spider silk is higher than steel, but no one is building gearboxes out of spider silk. For a graphene gearbox, the big challenge as I see it: graphene by definition is one atom thick. You aren't going to build a gearbox ...

4

Some things to keep in mind when comparing two very different planes: The 737NG is the latest version of the 737, and it was designed in the 90's. The design changes included a new wing. The 737 is designed for short flights, with a top range of about 3,000 nmi. The 737 has a design cruise speed of about M0.78. The 747-8 is the latest version of the 747, ...

4

The main purpose of the Chevrons is the reduction of engine noise. During research into this, NASA tested a number of configurations under simulated flying conditions and measured the nozzle thrust coefficient given by, $C_{T_{r}} = \frac{F^{d}_{g}}{F^{i}_{g}}$ where, $F^{d}_{g}$ is the measure gross thrust and $F^{i}_{g}$ is the ideal gross thrust We ...

4

An initial thought is that at 10X the RPM, it is likely that the blades would be well into Mach numbers, which would have a negative effect on power requirements (that is substantially more torque in particular) to spin the fan, and more importantly the fan would not be effective at those speeds. There would likely be blade damage as well from the loading. ...

4

There's more weight on the main gear when the aircraft pushes back from the ramp and is taxiing than on the takeoff roll, due to the lift generated from the wings. When the aircraft rotates the higher angle of attack generates enough lift to 'offset' the aircrafts weight and it takes off. The most weight a main gear set will take will be on a firm landing at ...

4

Cabin crew and pilot's rest area. Here's a pretty good article that also has videos on the upper deck as well as general cargo plane life Life on the Upper Deck

4

The Boeing 747-8 (unlike the 777) is not a full fly-by-wire aircraft, but some fly-by-wire controls have been added to the original 747 design. The inboard ailerons are mechanically connected to the flight controls, while the outboard ailerons are not. This allows them to droop without hydraulic power. From the Boeing 747-8 FCOM (9.20.6 Flight Controls - ...

3

Turbofans don't need to spin faster, they need to spin slower to limit fan tip speed: Compressibility drag is not a good item to spend fuel on. Blade tension is a quadratic function of rotational speed. At 10x spinning speed, blade tension is 100 times higher. The blade root would have to be 100 times thicker at current technoloy. Magnetic gears are made ...

3

How much fuel is used for preheating the outer engines of a four-engine airliner that were not used for taxiing? It's not a lot. The engines are only run at idle, and only for a few minutes (3-5). Given that fuel burn at idle is only 5-10% of full power operation, and that a 4 engine planes are typically performing long haul missions (8+ hours), the ...

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