Airwolf TT Straps Solution to Emergency AD 2015-04-51 for Enstrom Piston Helicopters
Airwolf Aerospace announces that it is developing an Alternate Method of Compliance [AMOC] modification kit which eliminates the possibility of Spindle Thread Failure outlined in Emergency AD 2015-04-51. The modification allows operators of all Piston Enstrom Helicopters to install TT straps in place of the existing Lamiflex bearings which eliminates the spindle threads. TT Straps are known to be vastly superior to Lamiflex bearings as they are far smoother in flight and do not degrade and cause the rotor system to go out of balance. In addition, they make track and balancing of the blades far simpler.
Enstrom Operators will send Airwolf Aerospace, Enstrom P/Ns 28-14282-11 or -13 Piston Spindles and 28-14279-1 or -3 Piston Grips, for the modifications that will allow them to use Airwolf TT Straps. These Piston parts will be modified to P/N 28-14385-13 Spindles & 28-14386-1 Grips which will be exactly the same as the ones currently used on the 480 Turbine helicopters. P/N 28-14385-13 Turbine Spindles do not have any threads to fail as they are eliminated. The modified parts will be returned to the operator with the Airwolf TT straps and all the additional components required for the conversion. Pricing for the complete modification kit components is anticipated to be less than $12,000. Due to lower blade loads found on Piston Enstrom Helicopters, Airwolf expects that the TT straps will have a service life of 60 months/ 1,200 hours which is the same as the antiquated Lamiflex bearings.
Airwolf has been working with Enstrom to develop and supply 36 month TT straps for Enstrom 480 helicopters and expects to receive FAA certification for the Enstrom 480 TT straps soon. Airwolf’s Enstrom 480 TT straps will have a 36 month/ 1,200 hour life limit which is 50%longer than the TT straps that are currently available.
Airwolf currently has certification and straps in stock for Bell 206 Jet Ranger, Long RangerOH-58 and for Bell 204, 205, 212, & UH-1 Helicopters.