68-04-01 HAWKER SIDDELEY: Amdt. 39-742. Applies to Model Series DH.125-1A, -1A/R-522, -1A/522, -3A, -3A/R.
Compliance required as indicated, unless already accomplished.
To detect fuel leakage past the fuel filter de-icing system non-return valves, P/N A.W.E. 124-25, -26, -27, and fuel or methanol leakage from the fuel filter and windshield de-icing systems, accomplish the following:
(a) Immediately prior to each flight after the effective date of this AD, check for signs of fuel leakage past the non-return valves, P/N A.W.E. 124-25, -26, or -27, and inspect for fuel or methanol leakage from the fuel filter and windshield de-icing systems in accordance with Hawker Siddeley Aviation Ltd., Service Bulletin No. 28-A23, Revision 2, dated July 4, 1968, or later ARB-approved revision, or FAA-approved equivalent.
(b) Within the next 7 days after the effective date of this AD and thereafter at intervals not to exceed 7 days from the last serviceability test, accomplish a serviceability test of the fuel filter and windshield de-icing systems, in accordance with Hawker Siddeley Aviation Ltd., Service Bulletin No. 28-A23, Revision 2 dated July 4, 1968, or later ARB-approved revision, or FAA-approved equivalent. However, whenever an airplane has not been operated for a period in excess of 7 days, the serviceability test required during that period may be postponed until immediately prior to the first flight after such period.
(c) If unserviceable non-return valves or leaks in the de-icing systems are found during the checks, inspections, or tests required by paragraphs (a) and (b) of this AD, before further flight, replace defective parts with serviceable parts of the same or approved equivalent part numbers, and continue the checks, inspections and tests required by paragraphs (a) and (b) of this AD.
(d) The pre-flight checks and serviceability tests required by paragraphs (a) and (b), respectively, of this AD may be discontinued after either
(1) The fuel filter and windshield fluid de-icing systems have been inspected as specified in paragraph (e) and have revealed no evidence of corrosion for a period of at least six months, and the non-return valves P/N AWE 124-25, AWE 124-26 and AWE 124-27 have been replaced by P/N AWE 124-25A, AWE 124-36 and AWE 124-37, respectively, as specified in paragraph (e); or
(2) The aluminum alloy lines and components have been replaced with corrosion resistant lines and components, and non-return valves P/N AWE 124-25, AWE 124-26 and AWE 124-27 have been replaced by P/N AWE 124-25A, AWE 124-36 and AWE 124-37, respectively, as specified in paragraph (e).
(e) The inspection for corrosion, the replacement of the non-return valves, and the replacement of the aluminum alloy lines and components covered in paragraph (a), must be accomplished in accordance with Hawker Siddeley Aviation Limited, Service Bulletin No. 28- A23, Revision 2, dated July 4, 1968, or later ARB approved revision or anFAA approved equivalent.
Effective February 13, 1968.
Revised March 27, 1969.