In response to SASless question and NOT pertaining to what may or may not have happened in this accident:-
The gross weight limitation of the 350 is the controllability without hydraulics at the first instance.
Of the models in current production the B3 has the WORST useful load internally due to this restriction. The B2 is lighter and the B4 has Dual Hydraulics and subsequently a higher MTOW (2427 kg). Frankly unless you are conducting sling or high altitude work I have never understood why you would want a B3. There is no significant internal performance over a B2, unless of course you are operating as mentioned before, and you have a slightly lower specific range ~ 2.5 - 3%.
Problems you can have................
Hydraulic failure and assymetric or no pressure in the accumulators meaning one servo will run out of pressure before the others. The hydraulics should be turned "OFF" prior to the deletion of the accumulators to be sure.
Misuse/Misunderstanding of the "HYD TEST" and "HYD OFF" switches.
"HYD TEST" simulates a failure of the hydraulic pump and is a method of testing for the assymetric problem. Move the cyclic until the accumulators deplete and make sure the assistance stops symmetrically.
"HYD OFF" is exactly that. Turn the hydraulics "OFF" and thats what you get no assistance from the accumulators, but you WILL still have assistance in the yaw channel via the compensator.
Now heres the catch - when there is no hydraulic pressure and you push the "HYD TEST" button you will purge the accumulator in the yaw channel compensator which is standard procedure after shutdown. In flight with a hydraulic failure if you activate the switch this accumulator will no longer assist you and you are out of the bounds of the certifcation limits. The pedal pressure required will lift you out of the seat and the yaw will more than likely be uncontrollable to the left on reduction in airspeed. Couple this with a heavy cyclic and it's interesting. Its worse in the B3 than the B2, have a look at the difference in the tabs added on to the TR blades which you are in competition with.
Exceeding gross weight:- In a B3, unless you keep an eye on what you are loading into the helicopter, it is easy to exceed the maximum internal gross weight without seeing any obvious indications of exceeding these limits. This helicopter can exceed its internal gross weight limit by 550 kgs (1212 lbs) using TOP at SL ~ 25 deg C - i.e 25% over internal MTOW!!!!
This accident report will probably enlighten you as to how it all works. Unfortunately there have been numerous cases of misunderstanding of the system.
http://www.tsb.gc.ca/en/reports/air/...2/A03O0012.asp