AD 68-04-01
Applicability
| Type | Manufacturer | Model | Details |
|---|---|---|---|
| aircraft | Textron Aviation Inc. | DH.125 Series 1A | Airworthiness Directives; HAWKER SIDDELEY Model Series DH.125-1A, -1A/R-522, -1A/522, -3A, -3A/R |
| aircraft | Textron Aviation Inc. | DH.125 Series 1A-522 | Airworthiness Directives; HAWKER SIDDELEY Model Series DH.125-1A, -1A/R-522, -1A/522, -3A, -3A/R |
| aircraft | Textron Aviation Inc. | DH.125 Series 1A/R-522 | Airworthiness Directives; HAWKER SIDDELEY Model Series DH.125-1A, -1A/R-522, -1A/522, -3A, -3A/R |
| aircraft | Textron Aviation Inc. | DH.125 Series 3A | Airworthiness Directives; HAWKER SIDDELEY Model Series DH.125-1A, -1A/R-522, -1A/522, -3A, -3A/R |
| aircraft | Textron Aviation Inc. | DH.125 Series 3A/R | Airworthiness Directives; HAWKER SIDDELEY Model Series DH.125-1A, -1A/R-522, -1A/522, -3A, -3A/R |
Unsafe Condition
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 due to corrosion or defective parts.
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Required Actions
Before each flight, check for fuel leakage past non-return valves and inspect for fuel/methanol leakage from de-icing systems per Service Bulletin 28-A23. Within 7 days after February 13, 1968, and every 7 days thereafter, perform a serviceability test of the systems. Replace defective non-return valves or leaking parts with serviceable equivalents if found. Discontinue checks after replacing valves with P/N AWE 124-25A, -36, -37 or replacing aluminum lines with corrosion-resistant materials.
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Compliance Time
Immediately prior to each flight after the effective date, within 7 days after February 13, 1968, and thereafter at intervals not to exceed 7 days. Before further flight if unserviceable parts are found.
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Affected Aircraft
Hawker Siddeley Model Series DH.125-1A, -1A/R-522, -1A/522, -3A, -3A/R
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Source: Official FAA Source ↗
Retrieved: Apr 8, 2026
Rights: U.S. Government Public Domain
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