If a large plane (i.e. 747) has to "water land" and it has no body damage, would it sink or float?

Question

This is a questioned raised in class. The arguments were that the plane had compressed air hence pressure dropping would cause the oxygen mask to drop. Some argued that the weight of fuel and girth of plane would cause it to sink, other argued that with no body damage the air inside would keep it a float.

Answer 1

The buoyancy force of any object is equal to the weight of the water displaced. The 747-8 has a maximum take off weight of 970,000 lbs. The basic interior dimension are 20 feet dia by 250 long giving the plane approx 78000 cu ft interior space not counting the wings and tail. Assuming this plane was air tight the buoyancy force upward is 78000cu ft.x64 lbs/ cu. ft. = approx 5 million pounds of buoyant force or 5 times more than the maximum take off weight. The fuel is also a none issue as jet fuels density is less than water making it also buoyant.

The plane would easy float.

Answer 2

I don't know the answer for sure, but I can tell you that the argument of the weight of fuel sinking the plane is not valid. Jet fuel is less dense than water, and would thus make the plane *more likely* to float. The girth of the plane is also irrelevant.

To solve this problem, you would have to calculate the overall density of the plane, including the metal, the air inside, the fuel, etc. If this density is less than that of water (1 g/cm^3), the plane would float.

Regardless, it is very unlikely that a 747 would land on water and not sustain body damage.

Answer 3

it will float for a while but not forever. It will float for enough time to get the life rafts out and get the people in. When planes are aloft, they are pressurized to keep the cabin pressure high enough so we can breathe. If the cabins were not pressurized, the cabin pressure would equal the outside air pressure.

While on the water, the cabin pressure will equal atmospheric pressure. But the pressure of the seawater along the underside of the fuselage and wings will eventually find ways into the body of the aircraft. Eventually the buoyancy afforded initially will disapper and the plane will sink.

Answer 4

I say it will float, it is air tight. So how does water get in,if air can not. Talking about, fuel and girth, look at a aircraft carrier,fuel,girth and weight it floats. I don't know I'm not a rocket scientist, but I still say it will float

Answer 5

Torn apart into many pieces by the water resistance of 4 jet engines. if engine removes, yes it will float by gliding like space shutter or run out of fuel jet. sigh another paperboys again. lol.

The one and only Boeing 737 Indonesia national carrier had successfully made a water landing at the river. Garuda airlines check it out. No casualities and minor body damages only.

Answer 6

Why not have the class ask Boeing.