Why jet fighter planes have acute pointy noses, while commercial airliners have pointy tails?

Answer 1

Jet fighters usually have to be able to fly at supersonic speeds (faster than sound). Except for the Concorde (which has a pointy nose), all commercial airliners fly slower than the speed of sound.

The big difference is that air is not significantly compressed or heated during subsonic flight. So, as long as you stay comfortably under the speed of sound, the shape of the tail is more important than the shape of the nose when it comes to reducing aerodynamic drag (reducing drag saves fuel).

But at supersonic flight, the aircraft is moving so fast that the air "doesn't have time to get out of the way", and it gets compressed a LOT by the nose of the airplane. So, the shape of the nose becomes very important, and a needle nose is best to avoid compressing (and heating) the air, which is very inefficient and wastes a LOT of fuel.

The same thing applies to the wings as well. The cross section of a subsonic wing has a rounded leading edge and a sharp trailing edge. But look at the wing on any supersonic airplane, and the leading edge is very sharp, as is the trailing edge...a sort of "wedge shaped" wing.

Answer 2

All aircraft that have wing mounted engines generally have a streamlined tail trailing edge to minimize wake momentum losses. For supersonic aircraft with fuselage-mounted engines the exhaust nozzle is aft, and so the aircraft cannot be tapered there. However, for F-14 and F-15 twin engine aircraft for example, the tail is finely tapered inboard and outboard of the engines to minimize wake effects. This should be obvious and not justify a question. Many commercial air carrier aircraft have another engine in the aft section, with an exhaust that exits at the trailing end, so the tail isn't pointed at all. Such engines are known as APUs which stands for Auxillary Power Units.
The noses of supersonic A/C are sharply pointed to reduce/minimize normal shock loss, resulting primarily in oblique shocks which exhibit lower total pressure loss and hence lower drag. One might easily conclude this is all merely techno parlor talk to you, as you failed to mention the leading edges of the wings & empennage, and the leading edges of the airframe air inlets.

You might consider this: When the SR-71 is flying at design cruise and Mach (assume 80K ft/3.0 Mach), which produces most of the thrust -- the nozzle, or the inlet?

Answer 3

Fighter jets are designed (most of them at least) to fly in both sub- and super-sonic speeds. The aerodynamic behavior of airplanes at these speeds is different. Commercial airliners primarily fly at about .8 mach (80% the speed of sound) so they are more rounded and their wings are not swept back as drastically as they are for fighters designed to fly 1-2 mach. The pointy nose helps cut through the air better during supersonic flight.

Answer 4

Jet fighters noses are pointed for aerodynamics. It helps keep the amount of surface space minimal that contacts the air head on. Just like it is easier to move your hand through the water in a "chopping" motion instead of a "slapping" motion. The pointed tail on commercial jets helps the air behind the plane move away from the back of the plane. It keeps the plane from creating a "draft" (like with race cars) behind the plane.

Answer 5

Jet fighters go faster, and the commercial airliners are more interested in fuel efficiency.