AD 72-19-05 ACTIVE

72-19-05 PITTS AVIATION ENTERPRISES, INC: Amdt. 39-1520. Applies to Pitts Model S-2A series Airplanes, S/N 2001 through 2030.

Compliance required as indicated.

(a) Within the next 10 hours time in service after the effective date of this AD, unless already accomplished, to prevent failure of the horizontal stabilizer leading edge support tube, accomplish the following:

(1) Remove the left and right horizontal stabilizers as follows:

NOTE: Keep track of all hardware and replace the same parts in their original locations, unless other options are indicated.

(i) Disconnect the elevator trim tab push rods from the horns beneath the stabilizers (leave the rods connected to the tab horns).

NOTE: Some airplanes may have AN310-1032 nuts and AN380 cotter pins installed on the AN3 bolts, instead of AN365-1032 nuts. If so, you may either reinstall the AN310-1032 nuts with new AN380 cotter pins, or use AN365-1032 self-locking nuts and undrilled AN3 bolts.(ii) Remove the two AN4 bolts through the flying wire lugs and elevator hinges, left and right.
NOTE: It is not necessary to loosen the flying wires.

(iii) Remove the 4 AN3 bolts through the stabilizer leading edge and trailing edge tubes, left and right.

NOTE: It is not necessary to remove the stabilizer root fairings.

(iv) Remove the access plates adjacent to the stabilizer trailing edge, reach inside the aft fuselage and remove the two AN3 bolts through the elevator trim control shaft.

NOTE: It is not necessary to disconnect the elevator horn.

(v) Remove the left and right horizontal stabilizers by pulling them straight outboard.

(2) Thoroughly clean with solvent the exposed portions of the 2-2123 stabilizer leading edge support tube which protrudes from the fuselage. Dye-check this tube in the vicinity of the AN3 bolt holes, and visually inspect for cracks.

(i) If cracks are found, order a replacement P/N 2-2123 assembly fromthe manufacturer.

(ii) If cracks are not found, accomplish the following.

(3) Cut off the outer ends of the stabilizer leading edge support tube, P/N 2- 2123, so that the dimension from the center of the AN3 bolt hole to the outer end of the tube is 1/2 inch, left and right sides. Remove all burrs and rough edges.

(4) Redrill the AN3 bolt holes in the stabilizer leading edge support tube, P/N 2-2123, and through the mating holes in the stabilizer leading edge tubes with a number 10 drill (.193 to .199 diameter), left and right.

(5) Apply zinc chromate to bare metal surfaces.

(6) Reassemble in the reverse order of Step 1.

(7) Stencil on upper surfaces of both the left and right horizontal stabilizers, near the leading edge, the words "No lift", in letters one-half inch high or higher, and in a color which contrasts sharply with the paint finish on the stabilizer.

Pitts Service Bulletin Number 6 pertains to this same subject.

This amendmentbecomes effective September 20, 1972.