@gulliBell
Binding in the controls must be before the mixing unit if only one axis is affected, in this case only lateral control problem was reported. There is nothin
I have been able to study Sikorsky’s GEN HEL Simulator data together with the integrated EASY/ADAMS modeling analyzes. This modeling will explain how the S76 series helicopter‘s flight control systems behaves in certain situation and how the aerodynamics behaves on these situations.
Before Mixing Unit there are four different rods which will bring PF’s controls inputs to the Mixing Unit. The PF’s controls inputs are shared with the all other dimensions inside the Mixing Unit (lateral servo bell crank, the aft servo mixer, the collective pitch mixer, and collective roll mixer and the forward (quad) yaw angle). After the Mixing Unit there are three control rods which will transfer control rods inputs to the three Servo Actuators (via three control rod tubes, each one to the each Servo Actuator).
In the past the accident investigators have been able to simulate a blockage of some of the control rods by using this GenHel simulator and ADAMS –EASY5 software modelling. The test findings were that if one of the rods is blocked by a locking pin (which means that the whole specific rod line is blocked). After this simulated blockage the investigators made a simulation by the GenHel / ADAMS-EASY5 simulator – modeling. The simulation was run for 11 seconds, 1100 output steps, completing the full simulation.
This GenHel simulation data has been compared to the FDR’s print outs. The simulation data was fully matching FDR’s data from the 10th August, 2005 S76C+ accident in the BalticSea.
I have good understanding how the S76 flight control behaves and what are the consequences and what is the root cause. Due to this I will still keep on my opinion and understanding how the S76 helicopter behaves and what might be the cause why S76 will come unflyable (if it will come unflyable, and how the helicopter will lose its controllability).
QUICK READ OUT FROM THE FDR’S PRINT OUT
The latest accident data 3rd February, 2016 (the parameters which was recovered from FDR data base) shows that the event has been started by a slight increase of IAS to 130-135 KTS (cruising speed has been a steady 125 KTS) and which after by pitch up (about +250 ft).
During next minute the helicopter ISA has dropped down to 90 KTS and the helicopter has started to descent.The descent rate after one minute after the event has been started was averagely –2100 ft. per minute but the last 40 seconds the descent rate has been almost double (4000 ft. per minute). During these first 20 seconds the IAS has been around 90 KTS but during the high rate of descent about 4000 ft. per minute the IAS has increased up to 148 KTS.
When the helicopter has reach 1000 ft. and immediately after this the helicopter has gain an additional altitude of + 500 ft. During this climb the IAS has drop down to 64 KTS. During these first two minutes the both of AP’s has been switched on and no MASTER WARNING or any CAUTION has exist. After these two minutes MASTER WARNING has illuminated for next 60 seconds without any CAUTIONS. The event has lasted an additional 20 minutes. The FDR data shows that the crew has had difficulties to maintain a constant IAS. The IAS has been fluctuated during the last 20 minutes. During the whole event the both AP’s has been switched on excluing on reset of AP1 and two reset of AP2 (this resets has happen about 10 minutes after the event has started when the IAS has been about 80 KTS and the ALTITUDE 1200 ft.).
It looks that the cruising IAS has been 125 KTS all the time since the helicopter has reach 3000 ft. altitude. Is this 125 KTS Bristow Company’s operating speed for S76C++ helicopter? Or is this an indication that the crew has already prepared to be faced some difficulties? Maybe due to the AP1’sand AP2’s repeated disengagement the crew has decided to use reduced cruising speed???
Whatever is the cause for this ditching this accident together with the other related accident is aserious situation for the S76 series heliopter. The future operation of S76 series helicopters will insist that this and the other accidents and quite many related incidents are carefully investigated.
I’m wondering how and why the FDR, FDAU and cockpit camera systems all data could be lost? Also the information of hydraulic fluid condition could be very valuable information to verify if the Servo Actuator’s do not have any inclusion. The information that the hydraulic fluid is clean or the hydraulic fluid is contaminated will be very important information for the decision making to maintain crew and passenger safety.
I hope that I’m wrong but all the facts and the knowledge are supporting my conclusions. Everyone have a right to have their own opinions and their own assumptions. I’m ready to defend my views if needed. I'm pleased to give more specific information if needed?