Originally Posted by
Paul Cantrell
My question is what's the deal with mounting it to the mast? Seems like it would have made more sense to mount it to the cabin structure so that if the mast/rotor decided to leave and go away that the parachute would stay with the aircraft?
Where else would you put it, where it wouldn't be snagged by the main or tail rotors? It does depend on the mast and rotor head surviving, but complete departure is fairly rare. This is designed for the most likely scenarios, not every possible scenario.
Aside from clearing the rotor, that location guarantees an upright (or nearly upright) landing, where the undercarriage might absorb some of the shock, and some seats are designed to collapse vertically if it's a rough parachute touchdown. The occupants also have the best chance of exiting safely if the helicopter is upright, especially if ditching in water. It's why Cirrus locates their ballistic parachute at, or near the C.G. as well. I still think it's not a great idea, and it sure isn't going to help the aerodynamics. But the location seems sound to me.
What I've always wondered is why we can do the giant airbag thing like the Mars Exploration Rover and Mars Pathfinder used? Just how big an airbag would a S92 require?
Well for a start, Mars has 38% of Earth's gravity, so the dyamics are a wee bit different! Those landers are also designed to survive high G-loads.
On Earth, an air bag wouldn't do anything a successful autorotation wouldn't accomplish. In a situation where an auto isn't possible -- like that awful Leicester City crash -- I don't think any airbag of reasonable size and weight would have cushioned the landing enough for survival. Not from that height. A ballistic parachute
might have worked, but it would have to be huge, and fired immediately. I think that accident happened around the minimum altitude for this smaller system to be effective.