AD/ENST 28/9 Amdt 4 - Main Rotor Mast

Administered by Department of Infrastructure, Transport, Regional Development, Communications, Sport and the Arts

Legislation au F2006B09599 In force Legislative Instrument

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AIRWORTHINESS DIRECTIVE

For the reasons set out in the background section, the CASA delegate whose signature appears below revokes Airworthiness Directive (AD) AD/ENST 28/9 Amdt 3 and issues the following AD under subregulation 39.1 (1) of CAR 1998. The AD requires that the action set out in the requirement section (being action that the delegate considers necessary to correct the unsafe condition) be taken in relation to the aircraft or aeronautical product mentioned in the applicability section: (a) in the circumstances mentioned in the requirement section; and (b) in accordance with the instructions set out in the requirement section; and (c) at the time mentioned in the compliance section.

 

Enstrom F-28 Series Helicopters

 

AD/ENST 28/9

Amdt 4


Main Rotor Mast 10/2002 DM

 

Applicability: Model F-28, F-28A, F-28C, F-28F, 280, 280C, 280F, and 280FX helicopters.

 

Requirement: 1. Determine the part number of the main rotor transmission, and the radius of the upper fillet of the shaft as specified in Figure 1 of Enstrom Helicopter Corporation Service Directive Bulletin (SDB) No. 0094 Revision 2, dated 15 February 2002.

2.        For Model F-28C, F-28F, 280C, 280F, and 280FX helicopters, replace any transmission having a small radius shaft fillet with a serviceable transmission having large radius fillet as specified in Table 1 of SDB No. 0094 Revision 2.

 

3.        For Model F-28, F-28A, and 280 helicopters:

 

(a)      If the transmission has a shaft with a small radius fillet and the transmission part number is not listed in Table 1 of SDB No. 0094 Revision 2, replace the transmission with a serviceable transmission specified in Table 1 of SDB No. 0094 Revision 2.

 

(b)     If the installed transmission is part number 28-13101-1 or -1-R, or part number 28-13101-3 or -3-R, and has a small radius shaft, visually inspect each transmission for a crack in the shaft upper fillet using a 10X or higher magnifying glass.

(i)       If a crack is suspected, before further flight, dye-penetrant inspect the shaft.

(ii)    If the shaft is cracked, before further flight, replace the transmission with a serviceable transmission having a large radius shaft fillet.

 

Enstrom F-28 Series Helicopters

 

AD/ENST 28/9 Amdt 4 (continued)

 

(c)      If the transmission is part number 28-13101-1 or -1-R, or part number 28- 13101-3 or -3-R:

(i)       Dye-penetrant inspect the shaft upper fillet for a crack, a nick, or a scratch.

 

(ii)    Polish out nicks or scratches less than 0.005- inch deep.

 

(iii)  If the shaft is cracked or has a nick or scratch 0.005- inch or more deep, replace the transmission with a serviceable transmission having a large radius shaft fillet before further flight.

(d)     Replace transmission, part number 28-13101-1 or -1-R, or 28-13101-3 or -3- R with a serviceable transmission having a large radius shaft fillet.

Note 1: Installing a serviceable transmission with a shaft, part number 28-13104-1 or -1-R, Revision K, L, M, N, P, R, or S, or part number 28-13140-1 or -1-R, is terminating action for the requirements of this Directive.

Note 2: FAA AD 2002-08-03 Amdt 39-12710 refers.

 

Compliance: 1. Before further flight after 28 August 2002, unless already accomplished.

 

2.        Before further flight after 28 August 2002, unless already accomplished.

 

3.        a. Before further flight after 28 August 2002, unless already accomplished.

 

b.    Unless the initial inspection is already accomplished, before further flight after 28 August 2002. Thereafter at intervals not to exceed 25 hours time in

service.

 

c.    Unless the initial inspection is already accomplished, within 5 hours time in service after 28 August 2002. Thereafter at intervals not to exceed 100 hours time in service.

d.    Unless already accomplished, within 300 hours time in service after 28 August 2002 or at the next overhaul, whichever occurs first.

This Amendment becomes effective on 28 August 2002.

 

Enstrom F-28 Series Helicopters

 

AD/ENST 28/9 Amdt 4 (continued)

 

Background: Emergency FAA AD 76-17-08 required repetitive inspections of the shoulder radius of the main rotor shaft.

Amendment 1 reduced the dye-penetrant inspection periods following further investigation by the manufacturer.

 

Amendment 2 removed from service main rotor shafts not modified in accordance with SDB No. 0036.

 

Amendment 3 was prompted by the failure of a shaft on a Model F-28A helicopter due to a fatigue crack. This Directive added models previously unaffected, which have a “small radius fillet” main rotor shaft installed.

 

Amendment 4 is issued in response a new FAA AD which adds additional main rotor gearbox part numbers to the AD requirement.

 

Amendment 3 of this Airworthiness Directive became effective on 28 November 2001.


 

David Alan Villiers

Delegate of the Civil Aviation Safety Authority 22 August 2002

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 


The above AD is notified in the Commonwealth of Australia Gazette on 28 August 2002.

Overview

The Civil Aviation Safety Authority (CASA) introduced Amendment 4 of the Airworthiness Directive (AD) AD/ENST 28/9, effective 28 August 2002, to address identified safety issues concerning the main rotor mast of the Enstrom F-28 Series Helicopters, including models F-28, F-28A, F-28C, F-28F, 280, 280C, 280F, and 280FX. This legislative instrument revokes the previous AD AD/ENST 28/9 Amdt 3 and establishes new requirements to mitigate risks associated with the small radius shaft fillet of the main rotor transmission, as identified by Enstrom Helicopter Corporation Service Directive Bulletin (SDB) No. 0094 Revision 2. The policy objective is to ensure the continued airworthiness and safety of these helicopters by mandating specific inspections and replacements of the main rotor transmission components, thereby preventing potential catastrophic failures.

Scope and Application

This Airworthiness Directive (AD) applies specifically to Enstrom F-28 Series Helicopters, including models F-28, F-28A, F-28C, F-28F, 280, 280C, 280F, and 280FX. The AD mandates corrective actions to address safety concerns associated with the main rotor mast. The directive applies to these aircraft regardless of their registration status within Australia, effectively imposing compliance requirements on all operators of the specified models. It mandates that certain actions be taken to ensure the airworthiness of these helicopters, such as determining the part number of the main rotor transmission, inspecting and replacing transmissions with small radius shafts, and conducting dye-penetrant inspections where necessary. Compliance with the AD is mandatory for all affected aircraft, and failure to adhere to the specified requirements can result in the aircraft being deemed unairworthy. This AD extends its regulatory reach through subordinate instruments and notifications, ensuring that all stakeholders are aware of and comply with the stipulated safety measures.

Key Provisions

This Airworthiness Directive (AD) addresses the maintenance requirements for the main rotor mast of Enstrom F-28 Series Helicopters. Specifically, it mandates actions to be taken to address potential unsafe conditions with the main rotor transmission. The AD applies to various models of the Enstrom F-28 Series Helicopters (section 1). The directive requires the determination of the main rotor transmission part number and the measurement of the upper fillet radius of the shaft, as specified in Figure 1 of Enstrom Helicopter Corporation Service Directive Bulletin (SDB) No. 0094 Revision 2. For certain models (F-28C, F-28F, 280C, 280F, and 280FX), any transmission with a small radius shaft fillet must be replaced with one having a large radius fillet as specified in Table 1 of SDB No. 0094 Revision 2 (section 2). For other models (F-28, F-28A, and 280), specific inspections and replacements are required based on the transmission part number and condition of the shaft (section 3). The directive outlines a compliance timeline, requiring certain actions to be completed before further flight after 28 August 2002 unless already accomplished (section 4). The AD imposes several obligations on the operators and maintenance personnel of the affected helicopters. They must determine the part number of the main rotor transmission and measure the shaft fillet radius. Depending on the model and part number, they may need to replace the transmission or conduct visual inspections and dye-penetrant tests for cracks, nicks, or scratches. Operators must ensure these actions are taken before further flight and adhere to the specified inspection intervals (section 2 and 3). Failure to comply with this AD may result in the aircraft being deemed unairworthy. This could lead to enforcement actions by the Civil Aviation Safety Authority (CASA), including fines and potential grounding of the aircraft until the required actions are completed. The specific penalties for non-compliance are not detailed in the AD but are governed by the Civil Aviation Act 1988 and the Civil Aviation Regulations 1988, which may include substantial fines and other enforcement measures (section 5).

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Enstrom F-28 Series Helicopters

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Sourced from the Federal Register of Legislation at 26 August 2026. For the latest information on Australian Government law please go to https://www.legislation.gov.au.