The expanded comprehensive arrangement will cover additional readiness-critical components, including main and tail rotor blades, main gearbox, main
rotor head, flight control components as well as accessories such as refueling probe and cargo system components.
The two Cobras' blades struck approximately 3 feet from the blade tip, tearing the
rotor head and transmission assemblies from both aircraft.
Using this new testing capability, OmniSeal[R] lip seals were recently qualified for a helicopter
rotor head and transmission retrofit program due to their great flexibility in creating a custom design with a precise fit in existing hardware.
Also the teetering
rotor head that holds the rotorblades to the
rotor head while allowing them to pivot and twist as required.
Investigators found metal fatigue in its gearbox cause a catastrophic failure and the
rotor head detached.
During post-flight inspection, we found nothing wrong with the
rotor head, rotor blades, or transmission assembly.
As a result, the blade-fold test set, aka the cheater box, was used to drive the lock pins against the micro switches to ensure a fully spread
rotor head. To everyone's surprise this did not produce the desired result.
"Currently a minute number of cases have come forward of helicopters of the same model found to have cracks in the
rotor head, if anything is found concerning our helicopter then we will take the appropriate action."
The tower's 6,000-lb
rotor head will enable Sikorsky to spin blades weighing up to 500 pounds each, thereby easily accommodating blades flown by U.S.
The UK Air Accidents Investigation Branch has now issued the following information: "The investigation has determined that a failure within the epicyclic reduction gearbox module of the main rotor gearbox resulted in the rupture of the gearbox case, which allowed the main
rotor head to separate from the helicopter.