Four Wings Better Than Two?

[mikehotwheelz]

Can anyone tell why there could not be a successful bi-plane design for a C130 or A400 sized transport aircraft? Wouldn't there be some advantages to this configuration? The extra wing would provide more lift meaning more load and a better rate of climb. Wingspan could be reduced for a more compact design. I realize there would be a speed penalty but is this such an important factor in a transport aircraft?

 

[Twickiwi]

Can anyone tell why there could not be a successful bi-plane design for a C130 or A400 sized transport aircraft? Wouldn't there be some advantages to this configuration? The extra wing would provide more lift meaning more load and a better rate of climb. Wingspan could be reduced for a more compact design. I realize there would be a speed penalty but is this such an important factor in a transport aircraft?

Increase in wings = increase in drag = decrease in fuel efficiency = decrease in endurance

Under and over wings gives structural compromising problems for fuselage space (hence the over wing design of most cargo planes).

Wing clearance is an issue for rough landing strip usage (another reason for overwing design),

However, I've seen designs for an enlarge tilt rotor aircraft with a 4x4 over wing design.

 

[mikehotwheelz]

Thanks, Twickiwi. Yes I can see how ground clearance could be a problem. I hadn't realized there would be such an increase in drag though.

 

[qw56q]

Can I also point out that a monoplane with 100 foot wingspan provides more lift then a 50 foot biplane, this is mainly because the the air passing over each of the wings interferes with the airflow of the other. This effect is so dramatic that the addition of the second wing only adds about 20% lift.