Wings of a SPAD VII/XIII

[Kuro Nezumi]

Good afternoon.

The SPADs VII and XIII had superb speed both level in a dive but had poor manoeuvrability. Did the wing design the cause of the lack of manoeuvrability? If so, would replacing the wings with those of a Nieuport make any difference?

Any other comments and information would also be appreciated.

Thank you.

[wyverns4]

Well, my 2 ...

The SPAD were capable of a more stable faster dive because the wing structure, like the fuselage, was more robustly built than that of the lighter Neiuport sesquiplane.

The SPAD wing, (both upper and lower), were built around two spars, to which the interplane structs were attached. The Neiuport upper wing, only, had two spars whereas the lower wing had one. Hence the distinctive V-shaped interplane strut. The problem that the Neiuport had was that the interplane strut was attached to the lower spar by a circular, (two halves bolted together), coupling, which under stress, i.e. a dive), allowed the lower spar and wing to start to flutter, then rotate and eventually fail.

Thus the Neiuport was a much lighter and therefore more nimble airframe than the heavier SPAD.

Incidentally, the Germans copied the wing plan of the Neiuport from a captured example and this was used in the design of the Albatros D III, IV V and Va airframes, with similar flutter induced problems.

HTH!

Christian, exiled to the dark place

Edited November 23, 2015 by wyverns4

[Beardie]

I suspect that a big difference between the handling of the Spads and the Nieuports was the inline v-type engine versus the rotary engine. The torque of the rotary gives aircraft fitted with it a significant advantage banking in the direction of the engine's rotation where the inline types would have more stability and less quirks.

Comparing power, speed, ceiling I I think I would opt for the trade off of less manoeuverability against all the other advantages.

[Old Man]

To add to what Wyverns4 has said, Sir.

The original Nieuport sesquiplane design, the two-seat N-10, was intended to have adjustable incidence for its lower wing. Variable incidence was not uncommon in early French designs, with Paul Schmitt going so far as to make incidence variable in flight. Most, though, Nieuport included, were only adjustable on the ground. Increased incidence increased lift, letting more of a load be carried, but also increased drag, slowing speed. Decreased incidence reduced lift and drag, increasing speed. Once in production, the adjustable feature went by the board in the Nieuport, but the fittings for it remained as the attachments. I am not sure when this was finally revised, it may have persisted into the production of the N-17.

One of the advantages of the extreme sesquiplane configuration displayed by the Nieuport was increased efficiency of the lifting surfaces. Wings work by developing less air pressure above and more air pressure below (quick and dirty explanation). It can be readily seen that where wings are stacked one above the other, as in a biplane, things can work at cross-purposes in the space between the wings. In a biplane without stagger, neither wing produces as much effective loft as it would were it the wing of a monoplane, and the lower wing is more greatly hampered than the upper. The sesquiplane design contrived by Nieuport allowed the upper wing to develop more lift than it would have in a standard biplane, because the lower wing was so much smaller, an the lower wing, being set so far back from the leading edge of the upper wing, was also rendered more efficient, being in effect staggered back (stagger being one other means of reducing this inefficiency in 'stacked' wings).

Another benefit of sesquiplane design, carried to the extremity of the Nieuport scouts, is that it gives the pilot a much better view. Part of the reputation of the Nieuport for nimbleness in combat likely owes to the pilot being able to react quicker, because he could see better.

The S.P.A.D. wing was thin and almost flat, producing minimal drag. This contributed greatly to the type's high speed, which, along with its robust construction, was a great asset, and what made it a leading fighter.

[Kuro Nezumi]

Thank you for this information, most appreciated.

I was planning on building a fictitious aircraft based on SPAD XIII fuselage with Nieuport 23 to give it some manoeuvrability.

But, by the sound of what you are saying, the SPAD's fuselage and engine give it it's stability rather than the wings which were designed to maximize speed and rate of climb. So changing the wings would not make much of a difference.

So would there be no way of improving manoeuvrability at all?

[Beardie]

Hmmm very difficult one to do and actually make a successful new variant as there would be so many factors involved. The Spad is a very solid and pretty heavy design in comparison to the Nieuports.

Perhaps a better 'what if' for the spad would be conversion to a monoplane?

The design would lend itself to a nice sleek single wing design

[Old Man]

Thank you for this information, most appreciated.

I was planning on building a fictitious aircraft based on SPAD XIII fuselage with Nieuport 23 to give it some manoeuvrability.

But, by the sound of what you are saying, the SPAD's fuselage and engine give it it's stability rather than the wings which were designed to maximize speed and rate of climb. So changing the wings would not make much of a difference.

So would there be no way of improving manoeuvrability at all?

What you are suggesting, Sir, is pretty close to what the Germans did with the Albatros. The improvement in maneuverability came at a great cost in structural strength.

The S.P.A.D. 13 actually was a pretty lively machine, not much less nimble than the Nieuport sesquiplanes by many accounts. This owed to its much more powerful motor.

The Nieuport 17 was indeed very light, but its power loading was about 5kg per horsepower. The S.P.A.D. 7 with a 150hp motor had a similar power loading. Between these two, wing design made a great difference in nimbleness. The S.P.A.D. 13 with a 220 hp motor, though much heavier overall, had a power loading much lighter than either of those earlier design, about 3.7 kg per horsepower. This not only gave it more speed but more lift (a wing moving faster generates more lift), which increased nimbleness and, in any case, got the S.P.A.D. 13 through any maneuver undertaken more quickly. It was justly considered far superior to the last generation of Nieuport sesquiplanes (the 'round-body' 24bis, 24, and 27), which themselves did not maneuver quite so well as the earlier Nieuports, though this owed mostly to problems with how the ailerons were attached, which reduced the quickness of response to the pilot's movement of the controls --- another factor in maneuverability, and one very difficult to account for without reference to pilot's accounts of actually flying a machine. The last round of Nieuport sesquiplanes only went into production because of delays in producing the S.P.A.D. 13, delays caused by problems with mounting and cooling the motor.

Edited November 24, 2015 by Old Man

[Beardie]

Actually if you have a look at one of the last Nieuports, the 29, you can see that Nieuport-Delage themselves had decided that the Spad type design was a better option.

In-line Hispano Suiza engine and equal span, twin bay wings. The only real differences being the wings are slightly staggered and have ailerons on both upper and lower wings.

[melvyn hiscock]

The SPAD is not a two bay biplane, it is a single bay with additional struts

[Beardie]

My apologies, I see I am, indeed, incorrect and that the middle pair of struts of the design are not actually structural to the wing design but serve to tension the rigging. Thanks for that, I wasn't aware of this and was merely going on the visual appearance of the wings.

You learn something new every day

[stevehed]

As you're researching a possible whif might I suggest you stick with the Nieuport wings but change the stationary engine for a rotary and cowling. A lighter engine, no radiator and lighter wing structure has to help manoeuvrability.

Regards, Steve