64-20-03 VICKERS: Amdt. 796 Part 507 Federal Register August 20, 1964. Applies to Viscount Model 810 Series Aircraft.
Compliance required as indicated.
Fatigue cracking has occurred in the rib structure of the inboard rib at Station 96 of the inboard nacelles, illustrated in Figure 1 of Preliminary Technical Leaflet No. 113 (800/810 Series). To preclude further failures, accomplish the following in accordance with the PTL referenced herein or FAA approved equivalent:
(a) Within 275 landings after the effective date of this AD unless already accomplished within the last 225 landings, conduct dye penetrant or an FAA approved equivalent inspection for cracks in the rib reinforcing plate and rib web plate in accordance with PTL 113.
(b) If no cracks are found, reinspect at intervals not exceeding every 500 landings from the last inspection until Modification FG.1960 Part "B" is accomplished, after which no further inspection for this defect will be required.
(c)If cracks are found during the initial inspection described in paragraph (a), accomplish paragraphs (e), (f), or (g), as appropriate, within 275 landings after the effective date of this AD.
(d) If cracks are found during a reinspection, accomplish paragraphs (e), (f), or (g), as appropriate, within 275 landings from the time the cracks are found.
(e) If a crack is found in the rib reinforcing plate only, incorporate the repair scheme Figures 2 and 3 of PTL 113 or an FAA approved equivalent and reinspect within every 1,500 landings to ensure that there is no progression of damage in the reinforcing plate and no initiation of damage in the web plate. These repetitive inspections may be discontinued after incorporation of Modification FG. 1960 Part "C".
(f) If a crack is found in the rib web plate only, incorporate Mod. FG.1960 Part "B" and reinspect the rib web plate within every 3,000 landings to ensure that cracking has not been initiated in the reinforcing plate. Theserepetitive inspections are no longer necessary after the incorporation of Mod. FG.1960 Part "C".
(g) If cracks are found in both the reinforcing plate and the rib web plate, incorporate Mod. FG.1960 Part "C".
(Vickers-Armstrongs Preliminary Technical Leaflet No. 113 Issue 2 (800/810 Series) and Modification FG.1960 cover this subject.)
This directive effective September 21, 1964.