7. Stagger.—The stagger should be the same all along the wing as it is for the center section. With the machine in rigging position drop a plumb line from the leading edge of the upper wing in front of each set of struts. The distance from the plumb line to the lower edge should equal the stagger. If there is too much, tighten the diagonal wire running from the lower rear socket to the upper front socket, being sure that the other diagonal wire is loosened somewhat. For too little stagger tighten the latter and loosen the former wire.
Check up the dihedral and alignment of the trailing edges to see if these have been disturbed while setting the stagger. If not, the droop may be put in.
8. Droop.—To correct for the torque of the propeller, one wing of a machine is slightly drooped.
In single-motored tractor types, if the propeller turns to the right, when looking from the rear, the left wing is drooped, and vice versa.
The outer rear landing wire of the wing to be drooped should be loosened until the trailing edge, between the outer and intermediate struts, appears to be about an inch (for machines of not more than 100 hp.) lower than the rest of the trailing edge. The practice with the Curtiss JN-4B is to loosen the inner rear landing wire on the left wing ¼ in. and loosen the outer rear landing wire ½ in. after the angle of incidence and stagger have been adjusted so that corresponding wires on the right and left wings are the same length.
9. Tightening and Safetying All Wires.—(a) After the wing is drooped, all flying wires should be tightened to the same tension, and just taut enough to take out all sag.
(b) Next tighten all drift or cross wires between the front and rear struts to the same tension.
(c) Drift wires from the wings to the fuselage, and from the wings to the landing gear, if any, should be tightened last.
(d) Safety all turnbuckles. A wire too loose will vibrate when the machine is in the air.
The flying and drift wires should be so tightened that when they take the weight of the machine in the air, there will be no sag in the landing wires.