HAL was lucky that the investigation into the October 2009 Dhruv crash in Ecuador turned out to be a clear case of pilot error (excessive manoeuver leading to cyclic saturation), but the company has obviously drawn lessons from the mortifying episode. HAL has put out a tender to fit the ALH Dhruv with with a Control Saturation Warning System (CSWS). The system will be added to the Dhruvs operated by Ecuador and could be retrofitted on all Dhruvs so far sold to the armed forces. The system will be standard fit on all Dhruvs manufactured from the time the system is finalised.
HAL is looking for a CSWS primarily to detect control saturation and provide incipient audio and visual warnings to the pilots (the audio and visual warnings should be provided to the pilots well before the Dhruv enters into the envelope of control saturation). Secondly, to command piezoelectric actuators towards reducing airframe vibrations Third, to compute and display mast moment and generate mast moment warning on exceedance of predefined limits. And finally, to generate a warning for rotor blade stall.
According to the RFP, "The control saturation warning system (CSWS) should be a current state-of-artfully digital microprocessor based processing unit capable of interfacing various input and output sensors/systems of the helicopter, implementing linear/nonlinear control laws, built in test (BIT) facility to monitor health of the unit, in-flight monitoring, better reliability and growth capacity." Compatibility with the conventional and glass-cockpit variants of the Dhruv is, of course, mandatory. The CSWS will of course be required to interface with the Dhruv's Flight data recorder (FDR) to record control saturation, mast moment and blade stall warnings(discrete output signals) and the analog output of the mast moment.
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