The Stratos Configuration advantage

A single engine jet has many advantages over a twin engine jet. However it poses the question of the optimum location for engine placement.

The general aircraft layout including engine placement is referred to as "configuration". Early in the program, considerable time was spent studying various configurations prior to settling on bifurcated inlets with the engine mounted centrally in the fuselage. This was primarily the result of three considerations:

1. Thrust Line vs. Center of Gravity

A decision was made early in the program to have the thrust acting close to the center of gravity to minimize pitch changes with power and the consequential effects on adverse handling qualities and certification requirements. This engine location design element avoids the requirement to develop an automatic trim system to deal with the issues of power-pitch coupling. While such systems have been proposed for other aircraft, none has yet been certified on this category of aircraft.

2. Tail Arm

Tail Arm
A second requirement established was to design a long tail arm. A tail arm in simple terms is the distance between the aircraft center of gravity (cg) and the horizontal tail (see graphic left). Locating the engine centrally and forward gives a longer tail arm than aircraft with aft mounted engines. A long tail arm reduces the required tail size and provides good short period damping. The negative tail lift coefficient at the stall is also lower than aircraft with shorter tail arms, reducing the trim decrement between the wing maximum lift coefficient and the aircraft maximum lift coefficient. The longitudinal position of the engine also puts the aircraft cg close to the payload and fuel locations, thereby minimizing the required cg range.