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Oshkosh, WI – July 31, 1997 … Hartzell Propeller made a presentation to the aviation press and public today at the EAA Convention to discuss its recently released Service Bulletin 217. This bulletin affects 2- and 3-bladed Hartzell steel hub propellers with double shoulder blades, identified as HC-( )(2,3)(X,V)( )-( ) or HA-A2V20-1B models, also referred to as ìXî and ìVî shank propellers. These propellers are fitted to hundreds of aircraft produced in the 1950ís and 1960ís, including many Beech, Cessna, Navion, Piper, and Twin Commander models.
There have been several events of blade separation on ìXî and ìVî type propellers within the last two years. Propeller failures involving blade separations can be catastrophic, potentially life threatening events. Blade separations may induce enough vibration to shake engines off mounts, resulting in loss of control of the aircraft. Separated blades may also pass through the airframe, with one such event resulting in a fatality. Due to the seriousness of this issue Hartzell took action in the form of SB217. Hartzellís overall objective with this bulletin is to ensure flight safety by improving the reliability of the propellerís blade retention system.
There have been several Airworthiness Directives (ADís) applied to some of these propellers over the past 30 years for similar reasons. According to Richard Edinger, Vice President of Engineering at Hartzell, however, ìThe existing ADís do not cover all of the ìXî and ìVî type props and the inspection procedures and service intervals called for have not maintained flight safety. Cracks and failures that have been discovered are not limited to the installations covered by these ADís, nor are they restricted to the highest loaded or highest time installations.î
The failures are a result of a reduction in the fatigue life of the blade retention components, namely blades, clamps, and hubs. This is likely due to their extreme age as well as by factors such as: corrosion, inaccurate tachometer readings, previous ground strikes, out-of-tune engines, worn crankshaft dampers, and lack of adequate maintenance.
The failure data was used to develop an appropriate inspection program for these propellers. Service Bulletin 217 calls for inspections of the blades, clamps and certain model hubs. Generally they are:
Initial Inspections …
Must be completed within the next 200 hours or 24 months …
And must be completed within the next 100 hours or 24 months for older ì1î and ì8î style hubs (identified as HC-(1,8)XXX-X).
Repetitive Inspections …
Must be completed every 500 hours or 60 months thereafter …
And must be completed every 250 hours or 60 months for older ì1î and ì8î style hubs.
Previous inspection methods, specifically the dye penetrant inspection of the blade shank has been found to be unreliable in detecting cracks in the inboard retention groove. Service Bulletin 217 specifies a more effective eddy current method of crack detection. In addition, various other inspection techniques will be employed including optical comparitor inspections of the blade shank, dye penetrant inspection of the blade internal bearing bore, and magnetic particle inspection of the clamp and hub.
Hartzell is estimating the cost to comply with these inspections to be between $1,000 and $2,000 per prop. Mike Disbrow, Hartzellís Vice President of Marketing and Customer Support says, ìHartzell is committed to supporting operators of these propellers. In order to provide for replacement of components that do not pass inspection, Hartzell is involved in re-tooling parts that have been out-of-production. Hartzell will also be offering hubs, clamps, blades, and complete propellers at half-off list price for the 2 year period required for initial inspection. In addition, Hartzell will extend warranty coverage for components purchased under this program to 5 years, covering operators through the following inspection.î Other options may include upgrading to a newer design propeller where Type Certified or STCíd. Hartzell has Top Prop STC kits for several affected model aircraft and are working on additional STCís. Other propeller manufacturers may have certified alternatives as well.
Hartzell Chairman, Jim Brown, has said in regard to the companyís decision to issue the bulletin, ìWeíre very much aware of the negative impact of the added costs to many of these operators, but have concluded that the safety implications simply require this action.î In an ongoing effort to communicate to aircraft owners and operators about the new service procedures, Hartzell has had a series of meetings with representatives from ownerís groups of affected aircraft, including the one just concluded today.
Appendix A
Popular Aircraft Affected by Service Bulletin 217
Aero Commander 500 Series, 520, 560, 680
Beech 35 Series Bonanzas
Beech B50, D50 Twin Bonanzas
Beech 95-55 Series Barons
Beech 65 Series Queen Airs w. Excalibur Conversion
Cessna 180 – 180F, 182 – 182G
Cessna 310 – 310H, 320 – 320B
Grumman G44 – G44A Widgeon
Navion and Twin Navion
Piper Comanche 250 and 400
Piper Apache and Aztec
Republic RC3 Seabee
Appendix B
Airworthiness Directives on this Series of Propellers
68-13-2 – Blade Inspection, check for cracks every 400 hours
68-19-4 – Blade Inspection, check for cracks every 1000 hours
75-17-34 – Blade and Clamp Inspection, check for cracks every 1000 hours
77-14-07 – Blade and Clamp Inspection, check clamps every 32 hours, check blades every 400 hours and shot peen every 1200 hours
85-14-10R2 – Clamp Inspection, inspect within 60 days and for certain clamp serial numbers check every 100 hours
Appendix C
Alternative Certified Propeller Designs
Twin Commander 500 B, S, U – Available from Twin Commander (Type Certified).
Beech Bonanza w. IO-470 or -520 – Available from Hartzell (Top Prop STC).
Beech Baron w. IO-470 – Available from Hartzell (Top Prop STC).
Cessna 180 – Available from Hartzell (Top Prop STC).
Cessna 182 – Available from Hartzell (Top Prop STC).
Piper Comanche 250 – Available from Johnston Aircraft Service (STC).
Pending Certification
Piper Apache – Available from Hartzell (Top Prop STC Pending).
Cessna 310 – Available from Hartzell (Top Prop STC Pending).
Appendix D
Appendix E
