Advantages/disadvantages of biplanes over monoplanes?

[sid_galt]

So, does anyone know what are the advantages/disadvantages of biplanes over monoplanes?

 

[Astronuc]

The advantages way back when (1900-1930's) was the having twice the surface area and a stiff structure. Remember they had wooden frames, and the first models were held together with wire. The structural alloys introduced during the early years of WW II were not available in years prior. Although Louis Bleriot introduced the first monoplane in 1906, there was limited production, and the Spad (biplane) was considered far superior.

The early monoplanes were fine in straight flight, but severe stresses (high speed turns and banking) during dogfighting would be too much for the wing.

The major disadvantage is the greater drag associated with two wings, and any wires and struts.

See - http://www.centennialofflight.gov/essay/Aerospace/Bleriot/Aero47.htm

 

[wolram]

But the string bags had more character.

 

[sid_galt]

The advantages way back when (1900-1930's) was the having twice the surface area and a stiff structure. Remember they had wooden frames, and the first models were held together with wire. The structural alloys introduced during the early years of WW II were not available in years prior. Although Louis Bleriot introduced the first monoplane in 1906, there was limited production, and the Spad (biplane) was considered far superior.

The early monoplanes were fine in straight flight, but severe stresses (high speed turns and banking) during dogfighting would be too much for the wing.

The major disadvantage is the greater drag associated with two wings, and any wires and struts.

See - http://www.centennialofflight.gov/essay/Aerospace/Bleriot/Aero47.htm

Thank you for the reply.

Wouldn't the two wings interfere with each other and reduce lift? What are equations aerodynamicists use to determine optimum placement for the two wings?

 

[Astronuc]

Wouldn't the two wings interfere with each other and reduce lift? What are equations aerodynamicists use to determine optimum placement for the two wings?

If you look at early models, the wings were about 6 feet apart or so. A man could stand up between them. I believe that separation was reduced. The airflow is only affected within a few inches of the wing surface. I imagine it was trial and error back then, more experiment than theory. I haven't delved into the detail of aircraft design back then.

Try this - http://naca.larc.nasa.gov/reports/1929/naca-tn-310/

Specifications on a Curtiss "Jenny" - http://www.airminded.net/jenny/jn4_spec.html

 

[FredGarvin]

Like Astronuc, I have not spent any real time studying biplanes. However there are a few things I have learned. With two wings:

- You get more induced drag.
- You have more parasitic drag due to struts and wires.
- You do not have good visibility in either the upward or downward directions.

A slight improvement in the idea was to stagger the wings (when looking from the side) so as to try to induce more flow over the bottom wing. I really don't know if that works or not.

Danger could add more to this as well.

 

[sid_galt]

Thank you for the replies.

I was wondering, if the top wing was made at a slightly higher angle of attack than the bottom one and the bottom wing had its leading edge someplace after the top wing's leading edge, wouldn't the airflow have been faster over the bottom wing due to the venturi effect?
Would this have increased performance?

 

[Astronuc]

I was wondering, if the top wing was made at a slightly higher angle of attack than the bottom one and the bottom wing had its leading edge someplace after the top wing's leading edge, wouldn't the airflow have been faster over the bottom wing due to the venturi effect?
Would this have increased performance?

The wings aren't close enough to establish a venturi effect. A higher angle of attack would increase the drag. The lift on the wings is by the same principle as a single wing.

 

[NateTG]

BTW, there are some modern 'biplanes' like the SAAB 37 Viggen, but that's probably not what you had in mind.

 

[FredGarvin]

There are plenty of new biplanes today. Probably one of the most popular is the Pitts Special. You see them at airshows quite a bit.

Many aircraft had a slight dihedral in the top wing to increase stability, but I have not heard of varying the AoA between the two.

 

[sid_galt]

Thank you for the help.