A Bell Helicopter spokesman said the company is “working on” solutions to deal with the aftermath of an FAA Emergency Airworthiness Directive (EAD) that could impact 697 of its 206L series helicopters on the FAA registry.

On February 1, the FAA issued an Emergency Airworthiness Directive (2012-02-51) that mandates the immediate replacement of main rotor blades on select Bell 206L, L-1, L-3 and L-4 helicopters after 1,400 hours, as opposed to the current 3,600-hour time-in-service limit, due to concerns about fatigue cracking.

Special flight permits are prohibited under this EAD, potentially grounding a significant number of helicopters, although not all Bell 206L models are covered. The EAD resulted from the discovery of undetectable cracks in main-rotor blades manufactured by a Bell supplier, which Bell declined to identify. Bell blames the cracks on a defect in the manufacturing process that it says has since been corrected.

Bell issued Alert Service Bulletin No. 206L-09-159 Revision A, on Nov. 13, 2009 (ASB 206L-09-159), which describes procedures to identify and mark the affected main rotor blades, requires a “recurring wipe check” and a one-time radiographic inspection with the results to be determined by Bell. The EAD lists the serial numbers of the blades affected.

The FAA estimates the cost of compliance at $45,638 per helicopter. A Bell spokesman told AIN that the company “is working with our customers” to “support the affected aircraft and minimize downtime” but as of Saturday, February 11, could not offer specifics on any likely pro-rated warranty or replacement program.

The EAD comes in the wake of one issued by Transport Canada following the November 2, 2011 fatal crash of a 206L near Kapuskasing, Ontario, that a preliminary investigation attributed to main-rotor blade failure.

Main-rotor blade defects in Bell 206Ls had been under the microscope since the fatal crash of a Bell 206L-1 near Greensburg, Ind., on August 31, 2008. That helicopter was operated by helicopter EMS provider Air Evac, the largest fleet operator of 206L-series aircraft in the U. S. with 105 in service.

The NTSB determined that the Air Evac crash occurred due to “the in-flight separation of the main rotor blade due to a fatigue failure of the blade spar, rendering the helicopter uncontrollable, and the manufacturer’s production of main-rotor blades with latent manufacturing defects, which precipitated the fatigue failure of the blade spar.”

NTSB metallurgical analysis of the failed blade in the Air Evac crash revealed that the origin of the fatigue crack “coincided with a large void between the blade spar and an internal lead weight. Further analysis determined that the presence of residual stresses in the spar from the manufacturing process, in combination with excessive voids between the spar and the lead weight, likely resulted in the fatigue failure of the blade.”

The Canadian crash “brought back a lot of bad memories,” said Dan Sweeza, Air Evac vice president of operations. “We made the decision right then to voluntarily replace all of our (main rotor) blades with the affected serial numbers,” Sweeza said. “At no point in the process did we distrust Bell, but this was just something proactive we decided to do on our own.”

Sweeza said Air Evac completed the new blade installations last month. Other large 206L-series fleet operators did not return calls seeking comment. “I suspect a lot of them are scrambling,” Sweeza said.