The amazing thing about suction fuel systems is how easy it is to make them - just demand from the engine manufacturer that the engine pump be powerful enough to lift the fuel without a boost pump. Every Sikorsky model from the 1970's on has had suction fuel, and with great success. The S-70's, S76's, and S92 are all the same that way, and the effect on post crash safety is quite terrific. I do not know why no other manufacturer has chosen to make suction fuel systems standard!