X45

Why is the nose of a subsonic aircraft shaped like a paraboloid?

I understand the reasoning for having a sharp point for supersonic aircraft, but what's the reason for the shape of the nose of subsonic aircraft? Why isn't it a point, like the Concorde, for example.

Public Comments

1. Good question, Just wondering what the heck your talking about.
2. Because its aerodynamic and reduces drag.. If they had a square nose it would create drag and slow it down. Oh i see your question -- A neetle point nose is only necessary when it's practical. In supersonic travle, it is practical, but not in subsonic. So, supersonic aircraft kinda need it, but if you are not going to be flying supersonic, then it is not necessary. The fuselage and nosecone of the aircraft need to produce 2 shock waves in supersonic travel. An over-pressure, and under-pressure. Nose cones help in this. if you are not traveling at supersonic speeds, then there is no point. The fuscelodge of a large aircraft, like a boeing 777 is much larger than a supersonic aircraft. Having a neetle nose cone on a large commercial aircraft can cause problems when they travel at low speeds. On a concorde, they needed to lower the nose cone, but that would be harder to do with a larger aircraft. Plus, concorde's wing design worked better with the neetle nose. A neetle nose would not be compatable with a boeing 777's wing design. Plus, the neetle nose of the aircraft produce an extreme amount of sound when traveling; a normal nose cone on aircraft do not produce as much noise. The size of the nosecone would also need to be proportional to the aircraft's length and width. Concorde was not very large, so the nose cone didn't need to be too big. but, on a boeing 747, it would need to be Much bigger, and extend much longer, which is not good either because its never good to have a large nose cone in front of an aircraft when landing. They need to be made out of very light material, usually a carbon fiber. This is why in most aircraft crashes, the nosecone is always destroyed. A nosecone that large would need to be strenghtened with heavier materials, which is not good either.
3. In order to have an effective needle nose on a lage, sub-sonic aircraft, it would have to be quite long (like the Concorde's). This creates design and logistical headaches for pilots, as well as leaving one more moving part to maintain and/or risk failure on the aircraft. Why does a supersonic jet need the needle? Because of huge increases in drag as you try to break and travel at the sound barrier. A rounded nose would seriously hamper the ability of an aircraft to travel through the sound barrier. Why doesn't a sub-sonic jet need a needle nose? Actually, because it doesn't need a needle nose. The aerodynamic gains do not even come close to off-setting the complications and difficulties of a long, pointy nose.
4. they felt like it
5. The blunt shape is more aerodynamic. That is why sub-sonic bullets (like the .22) are blunt nosed as well. There is an optimum shape for each speed. At slow speeds it starts very blunt and gradually gets more pointed as the speed increases. A sharp point would actually create more drag than a blunt shape at subsonic speeds. Compare the 757 and the 727 noses and you will see the 727 nose is more pointed because it was designed to cruise 100MPH faster than the 757. The 737 cruises slower but in its case it was easier to use the off-the-shelf 727 nose for it than to design an aerodynamically perfect nose for the aircraft. Accommodating a radar antenna is the least of the concerns when designing the shape of a nose. If you've ever seen an aircraft with the radome up, you see that the radar is tiny. The only thing that matters to the radar is the transparency of the radome.
6. Let us not forget that the radome has to accomodate the weather RADAR dish while it is rotating inside the radome. That would be hard to accomplish with a pointy nose, unless it was quite long.
7. As Bitburger mentioned, the nose of a subsonic aircraft is also the radome, the "dome" that the weather radar is scanning behind. For practical purposes, all US Transport aircraft are required to have weather radar, and the nose is one of the most logical places to put it. A larger radar antenna has better performance, but then it would need a larger and less aerodynamic radome to be placed in front of it. But regardless of how big the radar antenna is, there must also be a size of scale relationship between the size of the radome, the size of the cockpit, and the size of the main cabin. So the nose of a narrow-body B737 will always seem more "sharp" than the "flatter" nose of a wide-body B777 because of the larger fuselage behind the cockpit. You're correct in that a sharp pointy nose is best for most airplanes, from an aerodynamic point of view. But to put a large pointy nose on the front of a wide-body A330 would simply be too difficult to deal with on the ground at airports. And after the airplane designers decide where to put the engines and the weather radar, a parabolic radome on a subsonic aircraft is what you end up with!
8. The point on the supper sonic aircraft is to piece the sound barrier where as the the noise on Subsonic aircraft must reduce the drag thus rounded.