Why do jets have swept wings?

[hillmanr2]

	Quote: Originally Posted by GremlinX
	Wow, this thread has gone crazy...

If you want crazy, ask "why do airplanes fly"

[tommy321]

	Quote: Originally Posted by Roll'nCircles
	The straight forward answer over a dinner table conversation is that the wings are swept so that they do not come in contact the shockwave coming off the nose as an aircraft as it approaches and passes through the speed of sound.

A good mental model... if you understand where it breaks down. It works when you're super sonic, but doesn't quite explain why swept wings also help in transonic and high subsonic flight. The bow shockwaves off the nose only happen when you're above Mach 1. Avoiding the bow shock was the only reason, then you'd only see swept wings on super sonic aircraft.

The first place to experience supersonic flow on the aircraft is actually the top of the wing. (Where Bernoulli accelerates the flow. You get a shockwave here at high sub-sonic speeds which is where your increase in drag comes from as you approach the sound barrier. Sweeping the wing presents the air with a longer, thinner, less cambered airfoil, and delays these initial shockwaves on the top side of the wing.

I'll agree that aerodynamics is certainly not always intuitive. If there's one thing I've learned is that (especially in our applications) it's easy to get bogged down in the details when the TLAR method will get you to the same end result.

Tom

[Dan767]

Wow.

[krashmaster81]

	Quote: Originally Posted by hillmanr2
	If you want crazy, ask "why do airplanes fly"

This question is easy.... Coming from a certified flight instructor, the main ingredient that makes airplanes fly is MONEY!! END OF STORY!

-Matt

[OverTemp]

	Quote: Originally Posted by Dan767
	Wow.

No kidding. Kinda sorry I said anything now.

What do you notice when your 767 goes supersonic? How about your Extra 300? I'm hoping with the new DA-170 I'll be able to hit about 1.2.

[OverTemp]

Duplicate

[Dan767]

It's all good. I'm hoping to get 1.1, downhill with the 157 !

[wizard]

	Quote: Originally Posted by hillmanr2
	If you want crazy, ask "why do airplanes fly"

Why they fly is an easy answer! When speed overcomes drag and lift overcomes gravity you have flight.

You want to have fun get an aeronautical engineer and a pilot drunk and start a discussion on Bernoulli's Principle vs. angle of attack and downward deflection of air.

[Dan767]

Bigger flies better and faster. Most of the heavy airplanes, (747, MD11 etc.) cruise above .80 mach, while the smaller jets (MD80 series, some 737's ) are closer to to the mid .70's mach numbers. If you're in a hurry, go big.

[Craven]

	Quote: Originally Posted by jwilliams
	You are all wrong, they have swept wings so they can fit more of them in the hangar. Jeff W.

How many can UPS fit in a hangar?

[Dan767]

I don't get to Louisville very much, but I can't remember seeing any more than three or four.

[Craven]

	Quote: Originally Posted by Dan767
	I don't get to Louisville very much, but I can't remember seeing any more than three or four.

LOL.....I was actually just messing with Jeff