64-02-07 VICKERS: Amdt. 671 Part 507 Federal Register January 10, 1964. Applies to All Viscount Models 745D and 810 Series Aircraft.
Compliance required as indicated.
Fatigue cracks in the vertical flanges of the rib spar angles at Station 257.75 have been revealed during routine wing overhauls. Associated stiffeners on the opposite face of the rib were also found to have cracked. All areas affected are defined in Preliminary Technical Leaflet No. 241 Issue 3 and Preliminary Technical Leaflet No. 105 Issue 3.
To preclude further failures accomplish the following:
(a) Within 250 hours' time in service on aircraft which have accumulated 6,500 hours' time in service on the effective date of this AD, or before the accumulation of 6,750 hours' time in service on aircraft which have not accumulated 6,500 hours' time in service on the effective date of this AD, unless already accomplished, conduct initial inspection for cracks in accordance with "The Action" paragraphsof the applicable PTL referenced herein.
(b) Subsequent to the inspection per (a) accomplish the following in accordance with the applicable PTL:
(1) Where the inspection per (a) shows no cracks to be present in the stiffeners or rib spar angles accomplish repetitive inspections at intervals not exceeding 6,500 hours' time in service.
(2) Where the inspection per (a) reveals cracks in the stiffeners which do not exceed the acceptable limits as specified in Figure 1, Detail A Note 1 of the referenced PTL accomplish one of the following before further flight:
(i) Replace with stiffeners of the original design, or repair the stiffeners in accordance with Figure 2 of the referenced PTL. Thereafter accomplish repetitive inspection of the rib spar angles and stiffeners at intervals not exceeding 6,500 hours' time in service.
(ii) Replace stiffeners with modified stiffeners locally manufactured from 18 gauge S521 material or FAA approved equivalent. Thereafter accomplish repetitive inspections of the rib spar angles and stiffeners at intervals not exceeding 6,500 hours time in service.
(iii) Repair all stiffeners (whether cracked or not) per (i) or replace all stiffeners (whether cracked or not) per (ii). Thereafter accomplish repetitive inspection of the rib spar angles and stiffeners at intervals not exceeding 12,000 hours' time in service.
NOTE: Vickers Armstrongs Modification D.3067 (for 745D) and FG.1917 (for 810) reinforce the six vertical stiffeners and are similar to the reinforcing schemes outlined in the referenced PTL's.
(3) Where the inspection per (a) reveals cracks in the stiffeners in excess of the acceptable limits as specified in Figure 1, Detail A of the referenced PTL the stiffeners must be replaced per (b)(2)(i) or (ii) before further flight. Thereafter accomplish repetitive inspections of the rib spar angles and stiffeners at intervals specified in (b)(2)(i) or (ii), as applicable.
(4) Where the inspection per (a) reveals cracks in rib spar angles replace the rib spar angles before further flight. Thereafter accomplish repetitive inspection at intervals not exceeding 6,500 hours' time in service if all stiffeners have not been reinforced per (b)(2)(iii), or at intervals of 12,000 hours' time in service if all stiffeners have been reinforced per (b)(2)(iii).
NOTE: Modifications D.3070 (for 745D) and FG.1925 (for 810) change the material of the spar angles. These modifications are summarized in the PTL referenced herein.
(c) Where the inspection per (a) reveals no cracks in the stiffeners or rib spar angles and operators choose to incorporate the reinforcement scheme per (b)(2)(iii) on all stiffeners the following may be substituted for the time set forth in (b)(1):
(1) Inspect rib spar angles and stiffeners within 12,000 hours' time in service after incorporation of the reinforcement scheme. Accomplish subsequent repetitive inspections at intervals not exceeding 12,000 hours' time in service.
(Vickers-Armstrongs PTL 241 Issue 3, Mods. D.3067 and D.3070 for 700 Series aircraft and PTL 105 Issue 3, Mods. FG.1917 and FG.1925 for 800/810 Series aircraft cover this subject.)
This directive effective February 10, 1964.