A topic close to my heart if you read the twin heli-which one thread. There are twins out there with a significant increase in safety, but it requires compromises on range and payload not always justified if altitude and temperature comes into play. Do we compromise missions for twins in the hope that the second engine will one day safe our butts or do we take the more controversial route of selecting a B3/B4 or even 407 depending on your preference? We just selected the B4 instead of a light twin due to altitude and temps and will test it at worse case scenarios for a 3 month period. According to the graphs it out performs it's twin mates greatly and it is only the B3 beating it in "safety margin" during power margin available in the take off/landing phase. Given, if the engine fails the power margin will not help, but if we do not require max N1/T4/5 every take off, preventative maintenance can go a long way on a already reliable Arriel 2 with 3 control systems? The B4 bought already operated it's young life as a VIP machine at 6500ft, 32-36 degrees C at one of the bases listed in the twin thread.