Flightglobal:

The US Federal Aviation Administration and Sikorsky "are working to identify all the modes of failure that might lead to Sikorsky S-92A main gearbox oil......

Author: John Croft

Date: 26 June 2009

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I'm just wondering why the Sikorsky S-92A has not been grounded altogether? In this latest article we can see that in addition to the gearbox leak and the failure of the flotation devices to inflate, that very important safety device (unfortunately postmortem) - the black box - also mysteriously failed minutes before the crash. With so many safety issues in question for this aircraft, and an emergency airworthiness directive just issued by the FAA to replace the titanium studs in the gearbox with steel ones, there are many more questions than answers to continue using this aircraft for such important emergency services like search and rescue and emergency medical transport. A growing body of evidence gathering on sites like: http://s92facts.wordpress.com/ seems to indicate that Sikorsky may have known about some of these problems, but failed to inform their customer's and the regulatory authorities. These birds should be grounded until a full investigation can be completed.

 

I take issue with the comment in the story:

"...Without the anti-torque control produced by the tail rotor, a helicopter is uncontrollable in its yaw axis when the engines are producing torque..."

Most helicopters have a cambered vertical tail, which provides a sideforce sufficient (without tail rotor thrust) to compensate for the main rotor torque above a minimum airspeed (think of a wing on its side).  The minimum airspeed is usually around 50-60 knots.  So as long as the pilots maintained an airspeed above this minimum they would still have some yaw stability.

 Once the engines are taken off line and the main rotor autorotates, the need for anti-torque compenstaion vanishes.

 The active word here is control.  The tailfin provides some lateral stability, but nowhere near enough to counter main rotor torque and there is no ability to control the machine in yaw if the tailrotor is lost.   (The tailfin does not provide the pilot with any ability to change direction)