Hartzell Propeller has issued a service bulletin requiring repetitive inspection of propellers fitted to "hundreds" of Beech, Cessna, Navion, Piper and Twin Commander aircraft manufactured in the 1950s and 1960s. The bulletin affects two- and three-bladed steel-hub units.

Hartzell says that service bulletin 217 is a result of several blade separations within the past two years - a problem which has recurred over the past 30 years despite the issue of airworthiness directives.

"We are very much aware of the negative impact of the added costs, but have concluded that the safety implications simply require this action," says Hartzell chairman Jim Brown. Separations have been caused by fatigue failures of some blade-retention components. The bulletin requires initial inspections within 200h or 24 months, and Repetitive inspections are required every 500h or 60 months.

For older style "1-"and "8-" style hubs, initial inspections must be within 100h and they then have to be made at every 250h. The bulletin specifies eddy-current inspection of blade shanks.

Hartzell is putting replacement parts for these propellers back into production and will offer hubs, clamps and blades at half price during the initial inspection period. Operators are being encouraged to upgrade to new propellers.

Source: Flight International