AD 57-12-05

57-12-05 CONVAIR: Applies to All Model 340 Aircraft.

Compliance as indicated below.

Several reports have been received of cracks occurring in the spar of the left-hand elevator in the area of the cutouts for the tab controls. The cracks originated in the area of the bolts that attach the support bracket for the tab control idler to the spar and in some cases, the cracks extend to a corner of one of the spar cutouts. Reports also indicate that the two angles P/N 340-2210114-10 and -111 above and below the spar openings have been cracked.

1. Compliance required as soon as possible but not later than the next 100 hours of operation unless already accomplished and at each 250 hours of operation thereafter. Inspect the left-hand elevator spar for cracking as described above. If cracks are found, they shall be repaired before the next flight.

(Convair "Service Airgram" No. 212, dated March 15, 1957, sections 1 through 7 illustrate a satisfactory means of repairing cracks in the elevator main spar.)

2. The special inspection period specified in item 1 may be discontinued and the regular inspection periods resumed after the following is accomplished:

(a) Repair of all cracks found during the inspection of the left-hand elevator spar as indicated in item 1.

(b) Reinforce the elevator spar in the vicinity of the tab control idler attachment. A satisfactory means of reinforcing the elevator spar is described in sections 8 and 9 of Convair "Service Airgram" No. 212. Reinforcement to be accomplished regardless of whether or not cracks are found.