Hartzell is urging operators to comply quickly with a US Federal Aviation Administration airworthiness directive (AD) affecting older light aircraft types, by upgrading or replacing the propellers. The appeal follows discovery of more cracked components during inspections of so-called "V shank" propellers affected by the AD.

Hartzell says that more than 40 cracked blades have been discovered since the AD was issued last year. In the three years leading up to the AD, 37 cracked blades were found, including two separations - one of which resulted in a fatal accident. Cracked blade clamps and hubs have also been discovered.

The company has introduced an "MV shank" upgrade for the affected propellers, which are found on various Beech, Cessna, Navion, Piper, Twin Commander and other aircraft built in the 1950s and 1960s.

Under a half-price offer available until the AD compliance date of September 1999, upgrades will cost $4,000-$10,000 and new MV propellers $6,500-$14,000. The company warns that it will discontinue parts support for V-shank propellers after that date.

Source: Flight International