Why Single Engine?
An obvious question is "why single engine versus twin engine?" The primary reasons are increased safety (see below), lower costs (acquisition and operating) and simplicity for the operator. As a result of the proven reliability of modern turbine engines, single engine aircraft are widely accepted today.
General aviation accident statistics are consistent in showing flying to be safer in single engine than in twin engine aircraft. Further, the statistics show that occupants are more likely to survive an engine failure (which situation is twice as likely in a twin) if it is the only engine. Convinced by these safety statistics, the FAA, has allowed single engine commercial IFR flights since 1995. The evidence accumulated since then shows that single engine turbines are the safest of all general aviation aircraft types.
The cost savings of designing around one rather than two engines are long established. In fighter aircraft it is acknowledged that a single engine aircraft like the F16 or Gripen provides almost the functionality of a twin engine aircraft such as the F15 or Eurofighter Typhoon at around half the cost.
The compelling economics of single engine aircraft is illuminated by comparison with a "Twin engine Stratos". If such an aircraft were designed to match the Stratos 714´s capabilities, it would have a 5% greater gross weight, and require two engines of combined static thrust 5% greater than the single engine of the Stratos 714.
These engines would likely have a 14% greater combined weight and have specific fuel consumption (lbs of thrust per lb/hour of fuel) 4% worse than the Stratos 714´s single engine. On typical missions, the twin engine aircraft would burn around 10% more fuel than the Stratos 714.
A twin engine version of the Stratos would be significantly more costly than for the equivalent single engine version. This is from the added cost of two smaller engines and the associated systems. Furthermore, maintenance costs on two smaller engines versus one larger engine would be significantly greater.
The Stratos 714 was designed with the owner-operator in mind. As such, the design evolved around designing an aircraft that can be safely operated by the typical owner operator of today´s high performance aircraft. Given the reliability of the modern turbofan engine, the choice for single engine was obvious.