Bi-Planes

AustralianAce · 26 January 2002, 12:22 PM

I was wondering as most of you know in WWI most of the planes used were Bi-Planes but then in WWII nearly every single plane was a mono plane. Obviously these one winged planes in WWII were very fast and strong but the mono planes in WWI Niueport,Fokker and Morane were all difficult planes to fly.
Can you helpm me?

Lufbery · 26 January 2002, 05:50 PM

Hi AA,

The quick answer is that, for the most part, designers before and during WWI were using more art than science in their craft. The prevailing attitude was that two (or more) wings provided more lift and a lower stalling speed for a given wing span. This is true, but the penalty for the additional lift is more drag. Some of the additional drag is from the second wing, and more drag is from the interplane struts and wires.

Fokker was ahead of the times because he noticed three things:

(1) A thicker wing makes for better handling with little or no drag penalty compared to the thin wings on other contemporary planes. Look at a Dr.1 or D7 and compare their wing cross sections to that of a Spad 13.

(2) Internal bracing gets rid of the need for interplane struts and wires. This in turn makes the plane less dragy. The Dr.1 prototype apparently had no interplane struts, but pilots were nervous without them, so they were later added.

(3) A monoplane with those features was faster than a bi-plane. The D8 was, by all accounts a great plane, but it arrived too late in the war to see much (any?) action. In my opinion, the rotary engine was less desirable than the in-line engine used in the D7, but what do I know?

The upshot, then, is that even during the war at least one designer realized the advantages of a monoplane configuration. The vast majority, however, looked to a biplane configuration for its structural strength, additional lift, and redundancy (had the N28 not been a biplane, Rickenbacker, for one, would probably have died when his top wing shed its fabric).

In short, monoplanes are more aerodynamically efficient than biplanes.

There's a lot of oversimplification and misinformation when it comes to aerodynamics, and I don't want to add to it. Please take a look at the following web site, hosted by NASA: Quest for Performance: The Evolution of Modern Aircraft (http://www.hq.nasa.gov/office/pao/History/...P-468/cover.htm)

It's got great info, hard numbers, and tons of drawings. Scroll to the bottom of the page that I posted for the table of contents.

Regards,

Lufbery · 28 January 2002, 03:36 AM

Quote:

Obviously these one winged planes in WWII were very fast and strong but the mono planes in WWI Niueport,Fokker and Morane were all difficult planes to fly.
Can you helpm me?

AA,

I just realized that I haven't answered the second part of your question. :-[ The fact that early monoplanes were difficult to control has little to do with the fact that they were monoplanes, and everything to do with the fact that they were wing-warpers. The Morane Bullet and Fokker Eindecker (for example) had now alierons; instead, they whole wing was warped a bit and that was how the plane changed directions. Wing warping worked, but it wasn't as effective or as efficient as having alierons, and was soon abandoned as a way of controlling a plane.

Regards,

FinnN · 28 January 2002, 04:16 AM

There's something I've always wondered about wing warping planes - just how much did the wings warp? A couple of degrees of twist or more?

Have fun
Finn

28 January 2002, 04:28 AM

Quote:

There's something I've always wondered about wing warping planes - just how much did the wings warp? A couple of degrees of twist or more?

Have fun
Finn

I recall a pilot of a modern wing-warping Eindecker replica saying that the movement at the wingtip was less than 3" with full control input.

DJ · 28 January 2002, 05:55 AM

One of the big problems of monoplanes in WW1 was stall speed. The Bristol M1 was considered to fast on approach for WW1 airfields. AA, What made you think that all WW1 monoplanes were ill handling????

PeterL · 28 January 2002, 06:17 AM

A wire braced bi-plane is always going to be stronger than a wire braced monoplane. It's in the nature of the structure. Once you get away from bracing wires the monoplane is no longer at a structural disadvantage and designers can concentrate on it's superior qualities.

I'm with DJ on whether or not they were more difficult to fly or posessed inferior flight characteristics. Some did, but the MIC and the Fokker EV/DVIII were as good as any of their contemporaries and better than some.

28 January 2002, 06:18 AM

HI

The thing about monoplanes and bipes is a structural and aerodynamic problem. Simply this...the wrights flew first. Their aero data was treated as holy writ. Their Windtunnel was about 12 inches(300mm) in diameter and was built with no understanding of boundry layer effects.
The Germans had been doing some work with full sized wings on rail flat cars, but the work was ignored because the WRIGHTs flew.
Now, airmolecules do not scale up or down, so the data they had worked well for a 10" wing, but not a 25' wing. The airfoils used mostly have a real "pitch forward" moment(thus the really short noses) and the knowledge of the time required them to be really thin. For this reason, they all suffered a LOT of flutter at speeds in excess of 85mph or so. As speed increased....the pitch forward movement increases causing weird handling changes with speed. These thin airfoils produce weak wing cells. The easy solution to the weakness is a Biplane. This lets you produce a big triangulated box with wire and struts and is a bunch stronger than you can make a monoplane.
Wing warping has other problems than mentioned, AND putting aelerons on a warper did not solve the problem, often the forces on the aeleron would produce a reversal as the wing flexed due to the forces on the 'control' surface. Remember many early bipes were also wing warpers.
The thick airfoils chosen by the later Junkers and Fokkers produced all sorts of dividends besides making monoplanes practical.
20/20 hindsight is Wonderful

Rocky

Lufbery · 28 January 2002, 06:56 AM

Quote:

One of the big problems of monoplanes in WW1 was stall speed. The Bristol M1 was considered to fast on approach for WW1 airfields. AA, What made you think that all WW1 monoplanes were ill handling????

I thought he was talking about the early monoplanes (i.e. wing-warpers) as being hard to handle.

Regards,

Brad · 28 January 2002, 04:41 PM

Just to throw in my $.02...

The early monoplanes, like the Eindecker, and ever WORSE the Moranes... (going by the pictures) appear to be lacking in tail surface. I suspect they were marginally controllable/stable partially due to that. Also full-flying tail surfaces have some advantages, but stability is NOT one of them.

Brad