Swept Wings

[bitememesa]

In fact the transonic range can be as low as roughly .80 mach. What we don't realize is that due to the curvature of the wing, swept or straight, we accelerate the air over the wing to create lift. Actually we accelerate the air so fast it goes critical (supersonic) briefly and then creates a shockwave as it decelerates back to normal flow. Depending on the wing's capability in handling this determines our critical mach #. Straight wing, poor ability, swept wing, high ability. This shockwave disrupts the airflow over the aft control surfaces and creates amazing amounts of drag. This is also what gives us some nasty high speed characteristics such as control flutter and mach tuch etc. I'm not sure if the Citation straight wings are mach limited, but the CRJ is at .85. But we have a highly critical wing that's relatively horrible departing on short fields.

It's all a trade off.

And I wouldn't believe it until you held a gun to my head that a swept wing was any structurally stronger than a straight wing. The way wings are designed now anyway, they're put into the airplane in one big piece so design really doesn't matter. Strength is really determined by aspect ratio (ie ~30 on a glider, ~4-5 on an F-16) Try pulling 8gs in your Schweizer someday...

 

[CapnVegetto]

Speaking for the Ultra/Encore, cruise speed is noticably greater than 0.64 M. In fact, Mmo on the Ultra is 0.755 M and we do cruise in the 0.72-74 M range pretty routinely.

As for high-speed vs. low-speed performance, remember that's what slats and flaps are designed to help with. Ask someone from the Air Force about the C-17.

We've got 1 Encore, and I haven't been to school on it yet. I know it's got bigger engines and a more aerodynamic wing, but I have no knowledge beyond that. I'm just talking about the straight 1's and 2's. I can't wait to get checked out in that Encore though.....I hear it's a dream to fly!

 

[CapnVegetto]

In fact the transonic range can be as low as roughly .80 mach. What we don't realize is that due to the curvature of the wing, swept or straight, we accelerate the air over the wing to create lift. Actually we accelerate the air so fast it goes critical (supersonic) briefly and then creates a shockwave as it decelerates back to normal flow. Depending on the wing's capability in handling this determines our critical mach #. Straight wing, poor ability, swept wing, high ability. This shockwave disrupts the airflow over the aft control surfaces and creates amazing amounts of drag. This is also what gives us some nasty high speed characteristics such as control flutter and mach tuch etc. I'm not sure if the Citation straight wings are mach limited, but the CRJ is at .85. But we have a highly critical wing that's relatively horrible departing on short fields.

It's all a trade off.

And I wouldn't believe it until you held a gun to my head that a swept wing was any structurally stronger than a straight wing. The way wings are designed now anyway, they're put into the airplane in one big piece so design really doesn't matter. Strength is really determined by aspect ratio (ie ~30 on a glider, ~4-5 on an F-16) Try pulling 8gs in your Schweizer someday...

I'm fairly certain that the wings ARE mach limited, as our MMO in the old ones is .705. The only way you can get close to that anyway is going downhill from high up. However, the VMO (262) comes from the windshields certification for bird strikes, and not the structural integrity of the wing. The wing is fine way up above 300 knots, as is the airframe. The Air Force bought a bunch of Citations back in the day, and stuck 400 knot windshields in them, and they can run them up around 320 knots or so.

How're things over at Mesa? I'm a former slave there.

 

[Bjammin]

With a supersonic fighter such as an F-18 you have a very thin wing due to the fact you don't want to have a wide speed range when the wing is critical mach. By having a swept leading edge and a not so swept trailing edge you have more attach points with the body making for a stronger route. An extreme example is a delta wing.

 

[Flechas]

Bjammin, did you learn all this studying for the interview? Very informative.

Btw, when do you have the next one?

 

[Bjammin]

I'm in ground school for Cathay now, very fun, lots of good people.
I have a B.S. in aeronautics, really helped with the Cathay interview. Besides that, it's good for round table discussions and thats about it.

 

[Flechas]

Congrats on the job, hope you enjoy it a lot!!

 

[Bjammin]

Thanks. It's great so far.

 

[Flechas]

Where did you get based, and are you getting a window seat or get to seat sideways?

 

[BonesF15]

?

Quote:
Originally Posted by Bjammin

Swept wings are also stronger thus fighters can pull more "g" forces.

QUOTE=AdlerDriver] I don't quite get this. Could you elaborate? Thanks[/QUOTE]

I don't quite get it either.

Any takers?

 

[Daveman]

Actually "Roll due to Yaw"

Nice point.

The T-38 wing is about thin as an IHOP pancake. Unbelievable.
Other than the F-4 or PBY-Catalina, that's one military aircraft I'd like to fly.

 

[FastCargo]

Wings...

Bjammin

Swept wings are also stronger thus fighters can pull more "g" forces.

AdlerDriver

I don't quite get this. Could you elaborate? Thanks

BonesF15

I don't quite get it either.

I think this is the answer you are looking for:

Bjammin

By having a swept leading edge and a not so swept trailing edge you have more attach points with the body making for a stronger route. An extreme example is a delta wing.

You know, I've never thought about that until this point, but most (almost all) modern fighter type aircraft have wings like he described. I think it's the 'aspect ratio' (chord to length)??? My aero terms knowledge is very rusty.

Only a few modern aircraft come to mind that are not designed this way, and both are swing-wingers. Tornado and F-14. I'm not sure what their G-limits are/were compared to their breathren. I know our (B-1B) G limits varied depending on the sweep of the wing.

Daveman

The T-38 wing is about thin as an IHOP pancake.

Not quite, but pretty darn close. It's amazing at airshows how many people look at the wing and wonder how the heck a T-38 can fly. Funnier when we tell them that we can't use mechanical pencils directly on the skin because of the danger of poking through it in some areas.

You think our wing proportions are small, look at an F-104. There is an aircraft I would have wanted to fly...the ol' 'Missile with a man in it'. My father used to work on 'em when he was enlisted in the USAF. They had to put wing gloves on the leading and trailing edges to keep people from cutting themselves (yes, they kept them SHARP)!

Fly Safe
FastCargo

 

[Bjammin]

I'm not sure what the Tomcat's "G" limit is either, but I know It has to be around 6g's after seeing them fight. With the wing swept back the "moment" of force is quite a bit less from the wingtip on in, so I bet with them out the limit is less. However, it wouldn't matter because when the wings are out the jet is slow and would stall long before it got high G anyway.

Flechas, I got right seat on the 747-400 out of LAX.