Whether assembling an early model vintage aircraft that  may have been disassembled for repair and restoration, or  constructing and assembling a new aircraft, the following are  some basic alignment procedures to follow. To start, the fuselage must be level, fore and aft and laterally.  The aircraft usually has specific leveling points designated  by the manufacturer or indicated on the plans. The fuselage  should be blocked up off the landing gear so it is stable. A  center line should be drawn on the floor the length of the  fuselage and another line perpendicular to it at the firewall,  for use as an additional alignment reference.  With the horizontal and vertical tail surfaces installed, the  incident angle for the horizontal stabilizer should be set.  The tail brace wires should be connected and tightened until  the slack is removed. Alignment measurements should be  checked as shown in  Figure 2-96 . Figure 2-94.  Securing hardware with cotter pins.  Figure 2-95.  Minimum prevailing torque values for reused self- locking unts.  Figure 2-96.  Checking aircraft symmetry.  The first biplanes were designed with very thin wing  sections and, consequently, the wing structure needed to  be strengthened by external bracing wires. The biplane  configuration allowed the two wings to be braced against  one another, increasing the structural strength. When the  assembly and rigging of a biplane is accomplished in  accordance with the approved instructions, a stable airworthy  aircraft is the result.   Fine Thread Series Thread Size 7/16 - 20 1/2 - 20 9/16 - 18 5/8 - 18 3/4 - 16 7/8 - 14 1 - 14 1-1/8 - 12 1-1/4 - 12 8 inch-pounds 10 inch-pounds 13 inch-pounds 18 inch-pounds 27 inch-pounds 40 inch-pounds 55 inch-pounds 73 inch-pounds 94 inch-pounds Minimum Prevailing Torque Coarse Thread Series Thread Size 7/16 - 14 1/2 - 13 9/16 - 12 5/8 - 11 3/4 - 10 7/8 - 9 1 - 8 1-1/8 - 8 1-1/4 - 8 8 inch-pounds 10 inch-pounds 14 inch-pounds 20 inch-pounds 27 inch-pounds 40 inch-pounds 51 inch-pounds 68 inch-pounds 68 inch-pounds Minimum Prevailing Torque 90° 90° B 1 C 1 C 2 B 2 D 1 D 2 A 2 A 1 Firewall centerline Select easy-to-identify  points from which to  cross-measure. Reference point Vertical tail post (reference) Note • Make cross- measurements with a 50'  steel tape. • Ideally, distances on  both sides should match.  (A 1 -A 2  / B 1 -B 2 , etc.) Top view Rear view 2-57