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High Wing Airliner  
User currently offlineBigJimFX From United States of America, joined Jun 2005, 321 posts, RR: 0
Posted (8 years 5 months 3 weeks 4 days 16 hours ago) and read 3075 times:

Ok I did a search and couldn't find anyone discussing it so here it goes...

How come there are no new airliners with a high wing design. The only one I can think of off the top of my head is the BAE 146 (avro) and the Dash 8. Is there a particular reason why, or is just because nobody really thinks about it anymore?


I'd like to thank me for flying Me Airways...
14 replies: All unread, jump to last
 
User currently offlineZkpilot From New Zealand, joined Mar 2006, 4836 posts, RR: 9
Reply 1, posted (8 years 5 months 3 weeks 4 days 15 hours ago) and read 3022 times:

For Turboprops they are a good design, for larger aircraft not so much, exceptions being Cargo military types (Antonovs, Galaxies, Hercs etc). Anhedrels vs dihedrels... designers have debated this in the past.
One downside of the high wing design in larger aircraft is crosswind landings. This is because the wingtip is lower than on a low wing design thus higher chance of striking the ground if not flown properly, for smaller aircraft its not so much of an issue because the wings don't extend out so far.



56 types. 38 countries. 24 airlines.
User currently offlineBigJimFX From United States of America, joined Jun 2005, 321 posts, RR: 0
Reply 2, posted (8 years 5 months 3 weeks 4 days 15 hours ago) and read 3000 times:

Quoting Zkpilot (Reply 1):
One downside of the high wing design in larger aircraft is crosswind landings. This is because the wingtip is lower than on a low wing design thus higher chance of striking the ground if not flown properly

I'm not quite sure I understand. I recal it being an issue for X-wind landings due to the fact that air can get between the wing and fuselage and push up... That could be a problem in a cessna (IS a problem in a cessna) But if the weight is increased, would it still be an issue? ( to a certain extent of course)



I'd like to thank me for flying Me Airways...
User currently offlinePelican22 From Ireland, joined Mar 2006, 65 posts, RR: 0
Reply 3, posted (8 years 5 months 3 weeks 4 days 1 hour ago) and read 2748 times:

What about the AN-72 and the new AN-148,this is in flight test at the moment,it seats about 90-110 passengers,it is a high wing design,powered by PS-90 turbofan engines and d'ont forget the Donier 328 jet,high wing and two jet engines.

User currently offlineOldAeroGuy From United States of America, joined Dec 2004, 3527 posts, RR: 67
Reply 4, posted (8 years 5 months 3 weeks 4 days 1 hour ago) and read 2734 times:

Three quick reasons I can think of:

Interference of the wing spar in the passenger cabin plus wing center section fuel over the passenger cabin.

Difficulty with integration of the landing gear. It pretty much has to go in external pods.

Airplane flotation in the event of a ditching. Although this event is very remote, it's still a design consideration.



Airplane design is easy, the difficulty is getting them to fly - Barnes Wallis
User currently offlineBigJimFX From United States of America, joined Jun 2005, 321 posts, RR: 0
Reply 5, posted (8 years 5 months 3 weeks 4 days ago) and read 2689 times:

Quoting Pelican22 (Reply 3):
d'ont forget the Donier 328 jet,high wing and two jet engines

I did forget... I apologize. It didn't come to me cause the only donier that popped into my head at the time was the turbo prop that looks just like it.

Quoting OldAeroGuy (Reply 4):
Three quick reasons I can think of:

Interference of the wing spar in the passenger cabin plus wing center section fuel over the passenger cabin.

Difficulty with integration of the landing gear. It pretty much has to go in external pods.

Airplane flotation in the event of a ditching. Although this event is very remote, it's still a design consideration

Ok that makes sense. I didnt think about any of those considerations. Thanks!



I'd like to thank me for flying Me Airways...
User currently offlineFlyDreamliner From United States of America, joined Jan 2006, 2759 posts, RR: 15
Reply 6, posted (8 years 5 months 3 weeks 3 days 23 hours ago) and read 2641 times:

Quoting Pelican22 (Reply 3):
What about the AN-72 and the new AN-148,this is in flight test at the moment,it seats about 90-110 passengers,it is a high wing design,powered by PS-90 turbofan engines and d'ont forget the Donier 328 jet,high wing and two jet engines.

The Do 328 sold very few examples, and the line was closed. AN-72 and An-148 aren't the best sellers either......



"Let the world change you, and you can change the world"
User currently offlineArrow From Canada, joined Jun 2002, 2676 posts, RR: 2
Reply 7, posted (8 years 5 months 3 weeks 3 days 23 hours ago) and read 2623 times:
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Quoting Zkpilot (Reply 1):
One downside of the high wing design in larger aircraft is crosswind landings.

I'm no engineer, but I think you've got this backwards. It's the low-wing that has the limitations because the vertical distance between the main gear and the wing tip is less than it is for a high wing, meaning its ability to lower the wing in a slideslip is reduced as the ground gets closer. I don't think there's enough dihedral on the main wing to overcome the high-wing advantage on that score. Correct me if I'm wrong. Any engineers out there?



Never let the facts get in the way of a good story.
User currently offlineBigJimFX From United States of America, joined Jun 2005, 321 posts, RR: 0
Reply 8, posted (8 years 5 months 3 weeks 3 days 8 hours ago) and read 2444 times:

Quoting Arrow (Reply 7):
I'm no engineer, but I think you've got this backwards. It's the low-wing that has the limitations because the vertical distance between the main gear and the wing tip is less than it is for a high wing, meaning its ability to lower the wing in a slideslip is reduced as the ground gets closer. I don't think there's enough dihedral on the main wing to overcome the high-wing advantage on that score. Correct me if I'm wrong. Any engineers out there?

I was thinking the same thing, but I didn't want to point it out because I wasn't sure

Another thing...

Quoting OldAeroGuy (Reply 4):
Difficulty with integration of the landing gear. It pretty much has to go in external pods

Wouldn't this almost be cheaper, I mean adding all the gear stuff into the wing has to be some kind of an issue. Not to mention, now you dont have to make tall gears for normal engines(airbus) or make De De Der looking engines (737).

Quoting OldAeroGuy (Reply 4):
Interference of the wing spar in the passenger cabin plus wing center section fuel over the passenger cabin

Can't you just put the center tank in the belly and just us a pump system. Plus without the gear in the wing, theres more space for fuel.



I'd like to thank me for flying Me Airways...
User currently offlineOldAeroGuy From United States of America, joined Dec 2004, 3527 posts, RR: 67
Reply 9, posted (8 years 5 months 3 weeks 3 days 6 hours ago) and read 2365 times:

Quoting BigJimFX (Reply 8):
Wouldn't this almost be cheaper, I mean adding all the gear stuff into the wing has to be some kind of an issue. Not to mention, now you dont have to make tall gears for normal engines(airbus) or make De De Der looking engines (737).

What track do you want to have on the gear and how do you stow it?

A wide track is desireable for both ground handling and pavement loading. For a high wing airplane (assuming you don't want to make the gear wing mounted so it's long and spindley), the gear will be mounted in the lower body. To get a wide track, the gear must be either housed in external fairings (ala military transport) or have a complex retraction mechanism (ala military fighters).

The external fairings create extra drag that puts the high wing airplane at a disadvantage. The complex retraction mechanism adds an additional reliability risk and a maintenance burden. Either of these solutions create economic costs that a low wing airplane doesn't have.

Quoting BigJimFX (Reply 8):
Can't you just put the center tank in the belly and just us a pump system. Plus without the gear in the wing, theres more space for fuel.

Where do you route the fuel lines? Either they need to run external to the body (a drag penalty and potentially subject to damage) or they need to run through the passenger cabin, inside the pressure vessel. Flammable fluids in the pressure vessel are never a good idea. The APU fuel line is an exception, but it needs to be inside a double walled fuel line. This is acceptable because the line is rather small and it stays below the cargo floor. Your lower lobe-to-wing fuel lines need to be large and run through the passenger cabin if they're not external. The certifying authorities will probably take a dim view of this arrangement.

By the way, putting the gear in the wing of a low wing airplane does not impact the fuel volume. The fuel is carried between the forward and aft spars. For structural reasons, the gear does not penetrate the spars. Instead, it is housed in the inboard portion of the wing aft of the rear spar.

Now as a counterpoint, what do you think the advantages of a high wing airliner would be?



Airplane design is easy, the difficulty is getting them to fly - Barnes Wallis
User currently offlineHiFi From Brazil, joined Apr 2005, 192 posts, RR: 0
Reply 10, posted (8 years 5 months 3 weeks 3 days ago) and read 2231 times:

Both high-wing and low-wing designs have lots of advantages and lots of disadvantages.. The conclusion you get after spending hours and hours thinking about it is: it just doesn't matter (unless you have a very specific mission or constraint).

Manufacturers that usually go with high-wing will probably continue designing high-wing... the same goes for low-wing... simple as that, because you already know what to do to compensate for the disadvantages. It's not lack of imagination or creativity, it's just that for the majority of design cases there's no real gain in preferring one option over the other.



no commercial potential
User currently offline787engineer From United States of America, joined Dec 2005, 572 posts, RR: 15
Reply 11, posted (8 years 5 months 3 weeks 2 days 23 hours ago) and read 2182 times:

There's also a structural advantage with a low-wing airplane. By podding the lading gear against the fuselage (a la military transports) the gear mechanism is simpler (less weight), but the fuselage must now be strengthened. The fuselage must support the landing gear loads whereas earlier it is integrated into the wingbox structure. With a high wing not only must the fuselage be strengthened up top so the fuselage will "hang on to" the wing, but the fuselage walls have to be strengthened to support the wing and plane especially on landing. Also note the "flattened bottom" of most military transports, this is to achieve the desired cargo-floor height but really isn't as optimal as a circular fuselage, and is generally heavier. In the end gear stowage is probably the primary advantage of low-wing planes.

Most military transports use the high-wing design mostly because of its advantages in landing/takeoff: 1) engines higher up to avoid FOD when landing on rough unpaved runways, 2) the high wing position allows for larger flaps which improves STOL performance 3) A high wing tends to prevent a "floating" effect (ground boundary layer), which makes it easier for pilots to nail their landings right where they want to.


User currently offlineBigJimFX From United States of America, joined Jun 2005, 321 posts, RR: 0
Reply 12, posted (8 years 5 months 3 weeks 2 days 21 hours ago) and read 2131 times:

Quoting OldAeroGuy (Reply 9):
Now as a counterpoint, what do you think the advantages of a high wing airliner would be?

Your gonna hate me..... I think it looks cool hyper , and people who sit on the wing seats have a good view.

Quoting OldAeroGuy (Reply 9):
Where do you route the fuel lines? Either they need to run external to the body (a drag penalty and potentially subject to damage) or they need to run through the passenger cabin, inside the pressure vessel. Flammable fluids in the pressure vessel are never a good idea

Where are the fuel lines routed in a rear engined aircraft? Through the cabin, outside the pressure vessel I guess. I'm not an engineer (obviously) I just think with modern technology, it seems like we have hit a wall with aircraft design. After composites and super-efficient engines... where do we go? Maybe thats the way some felt just before jets. I just think we could use technology to do something different.

Quoting OldAeroGuy (Reply 9):
What track do you want to have on the gear and how do you stow it?


Any way we can put them into miniature lifting surfaces? Kinda like a helicopter?



I'd like to thank me for flying Me Airways...
User currently offlineM404 From United States of America, joined Nov 2003, 2226 posts, RR: 5
Reply 13, posted (8 years 5 months 3 weeks 2 days 20 hours ago) and read 2099 times:
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BIGJIM I understand your preference. I loved the 146 and F-27.

I'm thinking that possibly engine accesibility on a large hi-wing would be more difficult.



Less sarcasm and more thought equal better understanding
User currently offlineOldAeroGuy From United States of America, joined Dec 2004, 3527 posts, RR: 67
Reply 14, posted (8 years 5 months 3 weeks 2 days 18 hours ago) and read 2040 times:

Quoting HiFi (Reply 10):
Both high-wing and low-wing designs have lots of advantages and lots of disadvantages.. The conclusion you get after spending hours and hours thinking about it is: it just doesn't matter (unless you have a very specific mission or constraint).

Manufacturers that usually go with high-wing will probably continue designing high-wing... the same goes for low-wing... simple as that, because you already know what to do to compensate for the disadvantages. It's not lack of imagination or creativity, it's just that for the majority of design cases there's no real gain in preferring one option over the other.

Compare the number of A320/737 or larger airliners that are low wing vs high wing. Low wing airplanes far out number the high wings. This says that there are more low wing airplanes says that for airliners, low wings have fewer design compromises and/or are more efficient. If it were a toss up, there would be a more even distribution. There are real advantages for a low wing airliner and the market is skewed accordingly.

Quoting BigJimFX (Reply 12):
Where are the fuel lines routed in a rear engined aircraft? Through the cabin, outside the pressure vessel I guess.

Nope, they're just like APU fuel lines. Inside the pressure vessel but below the passenger and/or cargo floor. Not through the passenger cabin. And while rear mounted engine airliners are more numerous than high wing airliners, they are still very much in the minority. The market is skewed by efficiency here as well.

Quoting BigJimFX (Reply 12):
Any way we can put them into miniature lifting surfaces? Kinda like a helicopter?

Is there any mechanical flying object with more drag than a helicopter?



Airplane design is easy, the difficulty is getting them to fly - Barnes Wallis
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