ren0312
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How well would a swept forward wing airliner work theoretically?

Wed Mar 27, 2019 1:33 am

Has anybody carried out a working concept on paper of a swept forward wing airliner, say how well would the 777 work if you put swept forward wings on it? It has been shown to work well on smaller aircraft like fighter jets, and would theoretically work on a 777 with the help of fly by wire technology.
 
LU9092
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Re: How well would a swept forward wing airliner work theoretically?

Wed Mar 27, 2019 2:12 am

IIRC, aircraft with swept forward wings are inherently unstable. That's fine, maybe even great, for a FBW fighter. It would be disastrous for an airliner. I imagine a swept forward wing is also bad in a stall. I may be wrong, but intuitively it seems like a stall, no matter which part of the wing stalls first, would induce a pitch up, making the stall worse.
 
osiris30
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Re: How well would a swept forward wing airliner work theoretically?

Wed Mar 27, 2019 2:24 am

Structurally with the right materials forward swept wings are no worse in a stall while being lighter. The problem is yaw control not pitch control.

With modern systems it could probably done but I am unsure if the yaw counteraction requires enough drag to be induced by control surfaces to offset the efficiency gains.

I am sure if they were viable someone would do it. At the end of the day the next stop for aviation efficiency may be very long span trussed composite wings or bwb. Both have inherent problems and benefits much like the forward swept wing.

Historically the biggest challenge on forward swept wings was materials related to combat aeroelasticity induced torsion. With modern composites that may be more easily overcome leaving yaw as the largest issue and where I am unsure of data for or against.
I don't care what you think of my opinion. It's my opinion, so have a nice day :)
 
LU9092
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Re: How well would a swept forward wing airliner work theoretically?

Wed Mar 27, 2019 2:32 am

osiris30 wrote:
Structurally with the right materials forward swept wings are no worse in a stall while being lighter. The problem is yaw control not pitch control.

With modern systems it could probably done but I am unsure if the yaw counteraction requires enough drag to be induced by control surfaces to offset the efficiency gains.

I am sure if they were viable someone would do it. At the end of the day the next stop for aviation efficiency may be very long span trussed composite wings or bwb. Both have inherent problems and benefits much like the forward swept wing.

Historically the biggest challenge on forward swept wings was materials related to combat aeroelasticity induced torsion. With modern composites that may be more easily overcome leaving yaw as the largest issue and where I am unsure of data for or against.


Very interesting, thanks!
 
strfyr51
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Re: How well would a swept forward wing airliner work theoretically?

Wed Mar 27, 2019 3:57 am

I worked on the HFB-320 Hansa Jet, Up to then? It was the only Fwd swept wing Airplane I had ever seen and I haven't yet seen another, N130MW, N132MW and N136MW. All 3 are scrapped by now as was 35 years ago that I last saw them. I have only seen e. experimental airplanes since then with Fwd swept wings at NASA.
I can say the airplane was damn Stable in flying on it but with CJ610-5 engines on it? That sucker was LOUD!!
 
dcajet
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Re: How well would a swept forward wing airliner work theoretically?

Wed Mar 27, 2019 4:00 am

Well, there was one: the Hamburger Flugzeugbau HFB 320 Hansa Jet.

Image

By RuthAS - Own work, CC BY 3.0, https://commons.wikimedia.org/w/index.p ... d=30747309
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Utah744
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Re: How well would a swept forward wing airliner work theoretically?

Wed Mar 27, 2019 4:01 am

All it would need is a MCAS.
You are never too old to learn something stupid
 
strfyr51
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Re: How well would a swept forward wing airliner work theoretically?

Wed Mar 27, 2019 4:09 am

Utah744 wrote:
All it would need is a MCAS.

Didn't have it and didn't need it. What it Did need? was smaller power Relays, more reliable windshield heating system and a slat heating system that wasn't so prone to chipping and Failure (It was a crude ceramic, Not at all flexible enough to survive a bird strike) And? It was damn hard to replace.)
 
strfyr51
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Re: How well would a swept forward wing airliner work theoretically?

Wed Mar 27, 2019 4:12 am

the HFB-320's main service center was Walker's Cay Aviation in Florida. Another damn interesting Airplane.
 
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PatrickZ80
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Re: How well would a swept forward wing airliner work theoretically?

Wed Mar 27, 2019 6:11 pm

Early age aircraft all had their wings swept forward, but this caused instability.

Watch this video:

https://www.youtube.com/watch?v=wexLhuDLZGw

At 13:45 it is being explained how they came up with a new revolutionary wing design that swept the wings backwards instead of forwards. This was done during the testing of the DC-1, a scale model for what would later become the DC-2. It's one of the reasons the DC-2 became as successful as it did, and the DC-3 even more so.
 
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DrPaul
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Re: How well would a swept forward wing airliner work theoretically?

Wed Mar 27, 2019 6:38 pm

Is there any advantage in having swept-forward wings on an aeroplane?

I used to see the occasional Hansajet flying into Heathrow at the end of the 1960s; its unusual design would attract attention from people who would normally take little notice of planes.
 
Waterbomber2
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Re: How well would a swept forward wing airliner work theoretically?

Wed Mar 27, 2019 7:46 pm

DrPaul wrote:
Is there any advantage in having swept-forward wings on an aeroplane?

I used to see the occasional Hansajet flying into Heathrow at the end of the 1960s; its unusual design would attract attention from people who would normally take little notice of planes.


In theory, you could reduce wake turbulence and induced drag as the fuselage acts as a fence.
In reality, it creates issues at the wing root where you would see a spike of drag and turbulent air especially at high mach number subsonic flight. Not impossible to deal with, but not simple either and could be noisy in the cabin as mini shockwaves occur.
Basically, the typical induced drag would be replaced by another form of induced drag which would be imo more significant.

Stability is not much of an issue in this day and age.
Eagles and many other birds also have slightly forward sweep at the root.

So basically, not many merits nor disadvantages, but aft sweep is the norm so no need to rethink it at this point.

Better look at how best you can eliminate the tailplane, which is a major source of non-productive and even counter-productive drag.
 
GalaxyFlyer
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Re: How well would a swept forward wing airliner work theoretically?

Wed Mar 27, 2019 7:57 pm

strfyr51 wrote:
Utah744 wrote:
All it would need is a MCAS.

Didn't have it and didn't need it. What it Did need? was smaller power Relays, more reliable windshield heating system and a slat heating system that wasn't so prone to chipping and Failure (It was a crude ceramic, Not at all flexible enough to survive a bird strike) And? It was damn hard to replace.)


Did you fly it? It was underpowered as I understand.
 
OldAeroGuy
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Re: How well would a swept forward wing airliner work theoretically?

Thu Mar 28, 2019 2:12 am

Waterbomber2 wrote:
Eagles and many other birds also have slightly forward sweep at the root.


But very few eagles cruise at M0.80.

Waterbomber2 wrote:
Better look at how best you can eliminate the tailplane, which is a major source of non-productive and even counter-productive drag.


But tailplanes allow you to use high lift devices on the wings with a significant wing area reduction which reduces drag even more than eliminating the h.tail.

Plus h.tails are ever so useful in providing a useful CG range for better loadability.
Airplane design is easy, the difficulty is getting them to fly - Barnes Wallis
 
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Pudelhund
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Re: How well would a swept forward wing airliner work theoretically?

Thu Mar 28, 2019 7:13 am

What about forward swept wing until the engine mount and then swept back again? Then it would resemble a bird wing.
 
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CARST
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Re: How well would a swept forward wing airliner work theoretically?

Thu Mar 28, 2019 7:41 am

Pudelhund wrote:
What about forward swept wing until the engine mount and then swept back again? Then it would resemble a bird wing.


It was more of down-, than forward-swept wing, but what you describe kind of resembles the Vought Corsair...

Image

https://de.wikipedia.org/wiki/Chance_Vought_F4U
 
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keesje
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Re: How well would a swept forward wing airliner work theoretically?

Thu Mar 28, 2019 11:34 am

Image

I remember seeing this one fly over in 1978. I wasn't interested in aircraft & never came in that area but was struck by the wing angle. That's the only reason I remember anyhow. :smile:
"Never mistake motion for action." Ernest Hemingway
 
mjoelnir
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Re: How well would a swept forward wing airliner work theoretically?

Thu Mar 28, 2019 12:01 pm

I we look at this as a technical discussion, than yes forward swept wing should work on an airliner theoretically, it even works practically. I think that is really the wrong question. The question should be do forward swept wings bring more or less of a disadvantage than backward swept wings, or would forward swept wings bring an advantage over backward swept wings.
The point is, you can not lock at the forward or backward swept wings by themselves, but the whole aeroplane is an aerodynamic system that you would have to look at as a whole.
And even if forward swept wings would pose an advantage in level flight, would it pose an disadvantage at landing and takeoff? In stall and so on.
 
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SEPilot
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Re: How well would a swept forward wing airliner work theoretically?

Thu Mar 28, 2019 1:37 pm

Seeing as how when the idea of swept wings was developed by the Germans they looked at both forward and rearward sweeps, and since then nearly every plane (and all airliners) that have been built with swept wings have had rearward sweeps, I would venture to say that rearward sweeps must offer more advantages, else someone would have built an airliner with forward sweep. I can offer a couple of theories as to why. When Boeing was testing the 367-80, they discovered that as speed increased, the center of lift moved forward. But this was compensated by the fuselage bending more, increasing the angle of attack of the horizontal stabilizer exactly enough to compensate for the nose up tendency that would cause. I am not sure that it would work the same with forward sweeps. But more important, I think that forward sweep would have very different and less desirable airflow characteristics at the rear end of the sweep coming up on the fuselage as opposed to going off into the air, or encountering a winglet. I am sure Boeing, Douglas, Lockheed, and all other airframe manufacturers have thoroughly explored this, and the fact that they have universally stuck with rearward sweeps speaks volumes. Not even Burt Rutan has advocated for forward sweeps.
The problem with making things foolproof is that fools are so doggone ingenious...Dan Keebler
 
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northstardc4m
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Re: How well would a swept forward wing airliner work theoretically?

Thu Mar 28, 2019 1:46 pm

The X-29 demonstrator found that while there were small improvements in efficiency, the tradeoff was massive control issues, for example the inboard wing would stall at relatively low AOA and pilots reported many "washing machines" aka uncommanded rolls, some quite sudden.

Now granted the F-5/T-38/F-20 it was based on are not known to be super stable designs but still...

Image
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