Enstrom F-28 / 280 / 480

Airworthiness Directives; The Enstrom Helicopter Corporation Helicopters

We are superseding Airworthiness Directive (AD) 2015-08-51 for the Enstrom Helicopter Corporation (Enstrom) Model F-28A, 280, F-28C, F-28C-2, F-28C-2R, 280C, F-28F, F-28F-R, 280F, 280FX, and 480 helicopters. AD 2015-08-51 required an inspection of the main rotor spindle (spindle) and reporting the inspection results to the FAA. This new AD was prompted by additional reports of cracked spindles and requires establishing a life limit and a recurring inspection. The actions of this AD are intended to prevent the unsafe condition on these products.

Airworthiness Directives; The Enstrom Helicopter Corporation Helicopters

We are adopting a new airworthiness directive (AD) for the Enstrom Helicopter Corporation (Enstrom) Model F-28, F-28A, F-28C, F- 28C-2, F-28C-2R, F-28F, F-28F-R, TH-28, 280, 280C, 280F, 280FX, 480, and 480B helicopters. This AD requires inspecting certain rod end bearing assemblies. This AD is prompted by an accident. The actions of this AD are intended to prevent an unsafe condition on these helicopters.

Airworthiness Directives; Enstrom Helicopter Corporation Helicopters

We are superseding an existing airworthiness directive (AD) for Enstrom Helicopter Corporation (Enstrom) Model F-28C, F-28C-2, F- 28F, 280C, 280F, 280FX, TH-28, 480, and 480B helicopters to add another trim relay to the applicability and to revise the modification instructions. This AD is prompted by the discovery that another part- numbered trim relay, inadvertently omitted from the current AD, may contain the same unsafe condition. These actions are intended to prevent failure of the cyclic trim system and subsequent loss of control of the helicopter.

Airworthiness Directives; Enstrom Helicopter Corporation Helicopters

We are adopting a new airworthiness directive (AD) for Enstrom Helicopter Corporation (Enstrom) Model F-28C, F-28C-2, F-28F, 280C, 280F, 280FX TH-28, 480, and 480B helicopters with certain trim relays to require modifying and testing the lateral and longitudinal cyclic trim actuator assemblies. This AD was prompted by four failures in the cyclic trim system on certain Enstrom model helicopters that resulted in reduced controllability of the helicopter. These actions are intended to prevent failure of the cyclic trim system and subsequent loss of control of the helicopter.

Airworthiness Directives; Enstrom Helicopter Corporation Model F-28A, F-28C, F-28F, TH-28, 280, 280C, 280F, 280FX, 480, and 480B Helicopters

This amendment adopts a new airworthiness directive (AD) for Enstrom Helicopter Corporation (Enstrom) Model F-28A, F-28C, F-28F, TH- 28, 280, 280C, 280F, 280FX, 480, and 480B helicopters that requires determining the installation dates for each main rotor push-pull control rod (push-pull rod), inspecting the push-pull rods for corrosion, replacing any push-pull rod which has corrosion that is severe enough to cause pitting, or has visible moisture inside the rod, and repairing each push-pull rod that has corrosion but no pitting. This amendment is prompted by one reported incident in which the helicopter pilot encountered severe in-flight vibration due to the failure of a push-pull rod, requiring an emergency landing. The actions specified by this AD are intended to detect corrosion and prevent failure of a push-pull rod, and subsequent loss of control of the helicopter.

Airworthiness Directives; Enstrom Helicopter Corporation Model F-28, F-28A, F-28C, F-28C-2, F-28C-2R, F-28F, F-28F-R, 280, 280C, 280F, 280FX, TH-28, 480, and 480B Helicopters

This amendment adopts a new airworthiness directive (AD) for Enstrom Helicopter Corporation (Enstrom) Model F-28, F-28A, F-28C, F- 28C-2, F-28C-2R, F-28F, F-28F-R, 280, 280C, 280F, 280FX, TH-28, 480, and 480B helicopters. This action requires a visual check to determine if a certain serial-numbered main rotor blade retention pin (retention pin) is installed, and removing and replacing any affected retention pin with an airworthy retention pin. This amendment is prompted by a report from the manufacturer that some retention pins were not manufactured in accordance with specifications cited on the engineering drawing. The actions specified in this AD are intended to prevent failure of a retention pin, separation of a main rotor blade from the helicopter, and subsequent loss of control of the helicopter.

Airworthiness Directives; Enstrom Helicopter Corporation Model F-28, F-28A, F-28C, F-28F, 280, 280C, 280F, and 280FX Helicopters

This amendment supersedes an existing airworthiness directive (AD) for Enstrom Helicopter Corporation (EHC) Model F-28, F-28A, F-28C, F-28F, 280, 280C, 280F, and 280FX helicopters. That AD currently requires determining the radius of the shaft fillet, performing certain visual and dye-penetrant inspections before further flight, and replacing certain main rotor transmissions. This amendment requires the same actions as the previous AD, adds additional main rotor gear box part numbers, and corrects various errors contained in the current AD. This amendment is prompted by a commenter who noted that two additional main rotor gear box part numbers should have been included in the AD. The actions specified by this AD are intended to prevent shaft failure and subsequent loss of control of the helicopter.

Airworthiness Directives; Enstrom Helicopter Corporation Model TH-28 and 480 Helicopters

This amendment adopts a new airworthiness directive (AD) for Enstrom Helicopter Corporation (EHC) Model TH-28 and 480 helicopters. This AD requires establishing a life limit for certain upper and lower main rotor hub plates of 5000 hours time-in-service (TIS), creating a component history card or equivalent record, and replacing each main rotor hub plate (hub plate) having 5000 or more hours TIS with an airworthy hub plate. This AD is prompted by a recent reliability-based stress analysis that indicates a 5000-hour TIS life limit should be imposed on certain hub plates. The actions specified by this AD are intended to prevent failure of a hub plate, loss of control of the main rotor, and subsequent loss of control of the helicopter.

Airworthiness Directives; Enstrom Helicopter Corporation Model F-28, F-28A, F-28C, F-28F, 280, 280C, 280F and 280FX Helicopters

This amendment supersedes an existing airworthiness directive (AD) for Enstrom Helicopter Corporation (EHC) Model F-28, F-28A, and 280 helicopters. That AD currently requires inspecting the main rotor shaft (shaft) for a crack or other evidence of damage until appropriately modifying or replacing the shaft with an airworthy shaft at specified time intervals. This amendment adds EHC Model F-28C, F- 28F, 280C, 280F, and 280FX helicopters and establishes life limits after which all unmodified shafts must be retired. This amendment requires determining the radius of the shaft fillet, certain visual and dye-penetrant inspections before further flight, and replacing certain main rotor transmissions. This amendment is prompted by the failure of a shaft on an EHC Model F-28A helicopter due to a fatigue crack. The actions specified by this AD are intended to prevent shaft failure and subsequent loss of control of the helicopter.

Airworthiness Directives; Enstrom Helicopter Corporation Model F- 28A, F-28C, 280 and 280C Helicopters

This amendment adopts a new airworthiness directive (AD) that is applicable to Enstrom Helicopter Corporation (Enstrom) Model F-28A, 280 and certain serial-numbered F-28C and 280C helicopters. This action requires an inspection of the voltage control system and an owner/ operator (pilot) cockpit check of the amperage of the electrical system. If certain Prestolite-manufactured components are installed, additional tests and actions are required before further flight and at each pre-flight run-up and annual inspection thereafter. A terminating action is provided by replacing the existing voltage control system with a transistorized system. This amendment is prompted by 14 reports of voltage control system problems, including one incident in which smoke emanated from the radio panel during flight, forcing the pilot to make an emergency landing. The actions specified in this AD are intended to prevent an electrical overload and a failure of the voltage regulator and over-voltage relay, that could result in an inflight fire, and subsequent forced landing of the helicopter.

Airworthiness Directives; The Enstrom Helicopter Corporation Model F-28A, F-28C, F-28C-2, 280, and 280C Helicopters

This amendment supersedes an existing airworthiness directive (AD), applicable to The Enstrom Helicopter Corporation Model (Enstrom) F-28A, F-28C, 280, and 280C helicopters, that currently requires an initial and repetitive visual inspections of the upper swashplate bearings for corrosion, and replacement of defective upper swashplate bearings with airworthy bearings. This amendment requires that the visual inspections apply to both the upper and lower swashplate bearings (bearings); expands the applicability to include the Model F- 28C-2 helicopter; limits the applicability to those affected helicopters manufactured prior to January 1, 1981; establishes a retirement life of 1,200 hours time-in-service for certain bearings; and provides a corrected upper swashplate bearing part number. This amendment is prompted by the necessity to require visual inspections of the lower swashplate bearings; to expand the applicability to include the Model F-28C-2 helicopter; to establish a retirement life for certain bearings; and to correct the upper swashplate bearing part number from the existing AD. The actions specified by this AD are intended to prevent failure of the bearings and subsequent loss of control of the helicopter.

Airworthiness Directives; The Enstrom Helicopter Corporation Model F-28, F-28A, F-28C, F-28C-2, F-28F, 280, 280C, 280F, and 280FX Helicopters

This amendment supersedes an existing airworthiness directive (AD), applicable to The Enstrom Helicopter Corporation (Enstrom) Model F-28, F-28A, F-28C, F-28C-2, F-28F, 280, 280C, 280F, and 280FX helicopters, that currently requires initial and repetitive inspections of a certain main rotor transmission clutch assembly (clutch assembly) for bearing roughness, noise, lock-up, or improper oil level and, if necessary, replacement of the clutch assembly. The existing AD also requires replacement of the clutch assembly at certain time-in-service intervals. This amendment requires the same inspections and replacements as required by the existing AD, but would provide for installation of an additional approved replacement part number and provide a reference to three additional manufacturer service documents. This amendment is prompted by the approval of an additional replacement clutch assembly; the manufacturer's issuance of additional service information, and the need to correct a service information letter's number. The actions specified by this AD are intended to prevent failure of the clutch assembly, loss of control of the main rotor system, and subsequent loss of control of the helicopter.