Commonwealth legislation

AD/BELL 47/90 - Hydraulic Servo Cylinders

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This airworthiness directive requires Bell 47 helicopters fitted with hydraulic servo cylinders (PNs 103650-3, 103650-5, 47-691-273-1) to have the servos checked for corrosion and binding, to free or remove/overhaul any units that stick, and for most units to be modified per a service bulletin within a set flight-hours window. Owners/operators pay for inspections and repairs; pilots may perform and certify the daily check or a licensed engineer may certify. The rule changes routine maintenance actions and timing for the specified parts.

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AD/BELL 47/90 - Hydraulic Servo Cylinders

COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY

SCHEDULE OF AIRWORTHINESS DIRECTIVES

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Bell Helicopter Textron 47 (All Variants) Series Helicopters

AD/BELL 47/90 Hydraulic Servo Cylinders 1/84

Applicability: All Bell 47 models equipped with hydraulic servo cylinders part number 103650-3, 103650-5 and 47-691-273-1.

Requirement: Part 1: (a) Gain access to hydraulic servo cylinders.

(b) Inspect for corrosion and verify freedom of input lever pivot bolts by rotating each by hand. If stiffness or binding is felt, spray bolts with WD- 40 or equivalent.

(c) If condition persists, remove servo from service and return to overhaul facility for repair, upgrade and/or overhaul as required.

Part 2: Inspect and if necessary modify, each servo in accordance with Flight Accessory Services, Service Bulletin 004 Part A.

Note 1: Part 2 does not apply to servo part number 47-691-273-1.

Note 2: Bell Alert SB 47-83-9 and Flight Accessory Services SB 004 refer.

Compliance: Part 1: At the next daily inspection after 28 November 1983 and each daily inspection thereafter. For aircraft maintained in accordance with ANO 100.5.1 this Directive shall be entered on the Maintenance Release as maintenance required. The inspection Part 1 Para (a) and (b) may be performed by the pilot in command, in which case certification is not required. In all other cases certification may be made on the Maintenance Release. This inspection may also be performed and certified by any Licensed Aircraft Maintenance Engineer.

Part 2: Within the next 100 hours time in service after 28 November 1983 but no later than 31 March 1984.

Background: The manufacturer advises a recent failure of the servo valve input rod assembly, due to corrosion and binding within the assembly linkage and has recommended the above inspection to eliminate this condition.

Source text

Sourced from the Federal Register of Legislation (legislation.gov.au), CC BY 4.0.

1 AD/BELL 47/90 - Hydraulic Servo Cylinders