80-13-10 DEHAVILLAND: Amendment 39-3812. Applies to DeHavilland Model DHC- 6 airplanes fitted with main landing gear legs which have not been inspected in accordance with DeHavilland Modification No. 6/1660.
To prevent possible failure of the main landing gear legs at the Y-joint weld, accomplish the following:
(a) Within the next 10 hours in service, unless accomplished within the last 590 hours in service, inspect the weld juncture at the Y-joint of the main landing gear legs for cracks using dye penetrant or X-Ray inspection methods. If dye penetrant inspection is used, all paint must be removed from the Y-joint weld junction area, and the area must be reprotected after completion of the inspection. If X-Ray inspection is used, paint removal is not required. An acceptable X-Ray method calls for a Phillips 300 KVA constant potential unit or equivalent with exposure of 250 KV and 10 milliamps (MA) for 2.5 minutes. The film to focal spot distance is to be 48 inches with a focal spot size of 4 mm square. Use Kodak Type AA film or equivalent sandwiched between .010 inch thick lead screens in flexible cassettes. The leg material is HY-TUF to AMS 6418B specifications.
(b) If no cracks are found, repeat the inspection in Paragraph (a) at intervals not to exceed 600 hours in service or six months, whichever occurs first, until the "D" inspection or equivalent, per DeHavilland Maintenance Manual PSM 1-6-2, is accomplished by 6000 hours in service.
(c) Within the next 50 hours in service, unless accomplished within the last 2350 hours in service, inspect the inside of the leg assembly around the crevice location at the Y-joint in accordance with the method noted in Paragraph (e)(1) of this directive for the presence of corrosion and integrity of the internal finish coat. If no corrosion or failure of the inner coat is found, repeat the inspection at intervals not to exceed 2400 hours in service or one year, whichever occurs first, until the "D"inspection, or equivalent, of the leg is accomplished.
(d) When complying with Paragraphs (a), (b), or (c) of this directive,
(1) If cracks are found, repair in accordance with a method approved by the Chief, Engineering and Manufacturing Branch, FAA, Eastern Region or replace before next flight with a part satisfactorily inspected in accordance with Paragraphs (a) and (c) of this directive.
(2) If irregularities are found in the internal finish coat integrity, or if internal corrosion is detected, repair in accordance with DeHavilland Overhaul Manual PSM 1-6- 6, Chapter 32-10-11, revised December 15, 1978, or equivalent, before next flight.
(e) For inspection and repair of the main landing gear leg:
(1) For an internal inspection, a borescope requiring removal of the leg assembly may be used. X-Ray inspection, or equivalent, which does not require removal of the leg assembly, also may be used. X-Ray inspection is to be accomplished in accordance with Paragraph (a) of this directive.
(2) Remove and install the main landing gear leg in accordance with procedures specified in DeHavilland Maintenance Manual PSM 1-6-2 Part 2 or PSM 1-63-2 Chapter 32-00-00, or an equivalent.
(3) For local removal of the leg finish and details of a "D" inspection of the leg, comply with Maintenance Manual PSM 1-6-2 Temporary Revision No. 85 or PSM 1-63-2 Chapter 32-10-11, Temporary Revision No. 32-8 dated December 15, 1978, or an equivalent.
(4) Disassemble the leg, clean and remove internal and external protective treatment in accordance with Overhaul Manual PSM 1-6-6 Chapter 32-10-11, revised December 15, 1978, or an equivalent.
(f) After accomplishment of the "D" inspection, or equivalent, no further action is required for compliance with this AD.
(g) Upon submission of substantiating data by an owner or operator through an FAA Maintenance Inspector, the Chief, Engineering and Manufacturing Branch, FAA, Eastern Region, may adjust the compliance times specified in this AD.
(h) Equivalent inspection procedures and repairs may be approved by the Chief, Engineering and Manufacturing Branch, FAA Eastern Region.
(i) The aircraft may be flown in accordance with FAR 21.197 to a base where the inspection or repairs can be performed.
This amendment is effective July 1, 1980.