AD 70-13-02

70-13-02 GENERAL DYNAMICS: Amdt. 39-1016. Applies to all Model 340 and 440 Series airplanes including those modified in accordance with STC SA4-1100 or STC SA1096WE.

Compliance required as indicated.

To detect cracks in the main windshield lower longeron splice channel, and prevent possible failure of the windshield support structure and loss of pressurization, accomplish the following:

(a) Within the next 150 hours' time in service after the effective date of this AD or before the accumulation of 10,000 hours' time in service, whichever occurs later, unless already accomplished within the last 1850 hours' time in service, inspect the longeron splice channel P/N 340-3110113-15 for cracks in accordance with General Dynamics 640(340D) Service Bulletin No. 53-3, dated April 24, 1970, or later FAA approved revision, or an equivalent inspection procedure approved by the Chief, Aircraft Engineering Division, FAA Western Region.

(b) If no cracks are found, repeat the inspection of paragraph (a) above at intervals not to exceed 2000 hours' time in service.

(c) If cracks are found, either:

(1) Replace the longeron splice channel P/N 340-3110113-15 before further flight, and perform the inspection per (d) below, or

(2) (i) Install on the instrument panel in full view of both the pilot and copilot, a placard limiting operation to a maximum of 18,000 feet above sea level.

(ii) Change the cabin pressure relief valve nominal setting to 3 psi.

(iii) Visually inspect the adjacent areas per S.B. 53-3 at intervals not to exceed 150 hours' time in service, until the channel can be replaced. A cracked channel must be replaced with a new channel within 1000 hours' time in service from the initial discovery of the crack. Channel P/N 340-3110113-15 must be replaced before further flight if any cracking of the adjacent structure is found during these 150 hour interval inspections.

(iv) The cabin pressure relief valve setting may be returned to normal and the placard removed from the instrument panel when the cracked channel is replaced. Compliance with the inspection intervals of (d) below is required after replacing the channel.

(d) Normal inspection intervals may be resumed for a period of 10,000 hours' time in service when a cracked channel P/N 340-3110113-15 is replaced with a new channel. Before the accumulation of 10,000 hours' time in service after replacement of the channel and thereafter at intervals not to exceed 2000 hours' time in service, inspect the channel for cracks in accordance with General Dynamics 640(340D) Service Bulletin No. 53-3, dated April 24, 1970, or later FAA approved revision, or an equivalent inspection procedure approved by the Chief, Aircraft Engineering Division, FAA Western Region. If cracks are found, comply with Paragraph (c) above.

(e) Upon request of the operator, an FAA maintenance inspector, subject to prior approval of the Regional Director, FAA Western Region, may adjust the repetitive inspection intervals specified in this AD to permit compliance at an established inspection period of the operator if the request contains substantiating data to justify the increase for that operator.

This amendment becomes effective July 28, 1970.