What it does
This Airworthiness Directive (AD/PHZL/68 Amdt 4), effective 3 May 2006 (amendment signed 1 May 2006 by James Coyne, Delegate of the Civil Aviation Safety Authority), mandates removal and replacement of specific Hartzell variable-pitch steel hub propellers by serial number, and requires inspections of blades and blade clamps when the propeller is disassembled for hub replacement. The Directive (the text reproduced above) applies to a defined list of Hartzell hub models and serial number series shown in Table 1, and sets calendar-month deadlines (columns headed MAR 97, SEP 97, through SEP 2005 in the table) by which hubs in each serial-number range must be replaced (see the Requirement and Compliance rows in the reproduced Directive). The Directive also requires fluorescent penetrant inspection of blades for cracks in accordance with Hartzell Aluminium Blade Manual 133C and magnetic particle inspection of blade clamps in accordance with Hartzell Service Manual 202A; both inspections are tied to propeller disassembly for hub replacement (see Requirements 2 and 3, Compliance items 2 and 3).
Mechanically, the Directive changes operator obligations in three discrete ways:
- It prescribes mandatory replacement of hubs whose serial numbers are listed in Table 1, with replacement hubs that are not listed in Table 1 (Requirement 1).
- It requires a fluorescent penetrant inspection of blades per Hartzell Aluminium Blade Manual 133C when the propeller is disassembled for hub replacement (Requirement 2).
- It requires magnetic particle inspection of blade clamps per Hartzell Service Manual 202A when the propeller is disassembled for hub replacement (Requirement 3).
The Directive attaches operational detail that affects compliance decision-making: the two-letter serial-number prefixes may be followed by an 'A' suffix in some hubs but the presence or absence of that suffix has no significance for determining compliance. The Directive also states that where a hub may be used in various propeller models, the hub serial number takes precedence over the model number shown in the table for identifying affected units (Requirement 1, paragraph explaining S/N/model precedence). The Directive cites an FAA AD (FAA AD 96-18-14 Amdt 39-9738) as a reference (Note 1). The document records a background justification: reported hub, blade, and shank failures overseas on Mitsubishi MU-2 aircraft including one fatal accident and states the FAA has mandated replacement of certain Hartzell turbine propeller hubs over a ten-year time period (Background paragraph).