PIQUA, Ohio — April 21, 1998 — Hartzell Propeller Inc. has announced the availability of a new parts upgrade that eliminates Airworthiness Directive (AD) 97-18-02 affecting various Beech, Cessna, Navion, Piper, Twin Commander and other aircraft from the 1950s and 1960s. The new upgraded propeller model will be designated H(A or C)-(A or D)(2 or 3)MV()-() (see illustration comparing to previous V shank model.) While this propeller model will not be listed on most Aircraft Type Certificate Data Sheets (TCDS), the upgrades will be made eligible for these aircraft via amendment to the existing Propeller TCDSs.
Safety And Continued Airworthiness A Major Concern.
In the three years leading up to the issuance of Service Bulletin 217 by Hartzell and AD 97-18-02 by the FAA there were a growing number of cracked blades, clamps, and hubs being found, as summarized below:
37 cracked blades, including two blade separations one which resulted in a fatal accident
4 cracked blade clamps, including one separation
5 blade separations from hub fatigue cracks, all on HC-8 series hubs
Since the bulletin was issued through the end of January, 1998, a significant number of additional cracked components have been discovered:
40 cracked blades
3 cracked clamps
3 cracked hubs, including one blade separation
While most of these additional reports were found during the AD inspection process, one of the cracked hubs was discovered due to blade separation resulting in an aborted take-off. These results certainly validate the FAA’s decision to mandate the inspections called out in Service Bulletin 217 and should provide added impetus for owners and operators to promptly comply with this AD. Failure of the hub, clamp, or blade could result in death or serious injury.
Service Bulletin 232 “Introduction of MV Shank Propellers,” issued March 20, 1998, provides general information about the improved propeller design, including application, propeller model and pricing data. Service Bulletin 233 “Conversion of V Shank Propellers to MV Shank,” issued April 17, 1998, provides the requirements for upgrades of existing propellers in the field. As previously announced, the upgrade converts the double shoulder design of the X and V shank blades to a single shoulder design, similar in configuration to Hartzell’s proven steel hub turbine propellers. This is to be accomplished by either reworking existing blades according to the requirements of Service Letter 182 or replacing the blades with those manufactured in the MV configuration as new.
Service Letter 182, also issued April 17, 1998, was developed specifically to create a method to modify existing blades in the field, however, the process or re-contouring the outboard shoulder is difficult and will be limited to selected propeller repair stations utilizing highly skilled machinists. Hartzell will begin working with these shops to develop this capability. On modified blades, the inboard shoulder, where most of the cracks have been discovered, will no longer be load bearing.
In order to accommodate the single shoulder MV blade, new blade retention clamps are required. The wall and outboard flange thickness of the new clamps has been increased to retain the single shoulder blade. In addition, this upgrade will only be applicable to HC-A or -D style hubs. Operators with HC-1 or -8 style hubs will need to purchase the A or D style hub and associated parts.
Due to the design improvements provided by this upgrade, not only are the requirements of the AD eliminated, but also the recommended time between overhaul (TBO) has been increased to 2,000 hours or 5 years. Operators are urged to adhere to these recommendations to maintain the benefits of this new design.
“V” Style Blade Retention System
New “MV” Design Blade Retention System
New Components Are Covered Under Hartzell’s 1/2 Pricing Program.
Major components of the upgrade (blades, hubs, clamps) and complete MV propellers will be included under Hartzell’s special 1/2 list pricing program through the end of September, 1999, which coincides with the initial compliance period of the AD. Newly introduced components (new design clamps and new MV blades and props) will be priced identically to the components they replace. Cost of the upgrade will vary dramatically by configuration, number of blades, and condition of the propeller. A 2-bladed propeller in good condition may be upgraded for approximately $4,000, however, the upgrade of a 3-bladed propeller with a 1 or 8 style hub and unserviceable blades could cost over $10,000. Under the 1/2 price program, new MV configured 2-bladed propellers will generally run in the $6,500 – $9,000 range and 3-bladed props will sell for approximately $10,000 – $14,000.
In many cases operators may also have the option to replace their propellers with alternate designs, such as a Hartzell Top Prop™ or McCauley STC. Since the issuance of the AD, Hartzell has received new STCs from the FAA for Piper Apaches and all Cessna 310s affected by the AD. In addition, Johnston Aircraft working with Hartzell and separately McCauley have received STCs for the Piper Comanche 250. Hartzell has also launched a program with Twin Commander Aircraft that utilizes a Type Certified replacement for Aero Commander 500 B, S and U models. See attached chart of alternate propellers.
Operators Encouraged Not To Wait Until The End Of The Compliance Period.
New parts have begun shipping into Hartzell’s distribution system. Operators are encouraged to comply with the AD, upgrade, or replace their propellers at their earliest opportunity due to concerns with continued flight safety outlined earlier, as well as concern for production capabilities. If a significant percentage of operators prolong compliance until September, 1999 this will likely result in shortages of parts and long delays may be possible at that time. Although replacement or upgrade is highly recommended, Hartzell will continue to produce most parts for the earlier designs (except 1 and 8 style hubs and X shank blades) through September, 1999. After this date, Hartzell will discontinue parts support for V shank blades and C-3 model blade clamps.