Yesterday the FAA issued an Emergency Airworthiness Directive (2012-02-51) that mandates the immediate replacement of main rotor blades on 697 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, effectively grounding hundreds of helicopters.

Not all Bell 206L models are covered under this EAD, which resulted from the discovery of undetectable cracks in main rotor blades manufactured by a Bell supplier. 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 requires 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.”