Design Study to Reduce the Single Engine Minimum Control Speed of the SJ30-2 Twin-Engine Business Jet 1999-01-1601
A 500 pound (2.2 kN) increase in takeoff thrust per engine was predicted to increase the SJ30-2’s single engine minimum control speed (VMCA) to 109 knots (201.9 km/hr). To meet runway performance goals, VMCA had to be pushed below 97 knots (179.6 km/hr). Six types of vertical tail and rudder modifications were investigated analytically. Two vertical tail modifications and three ventral rudder configurations were tested in the wind tunnel. The tunnel showed 30° of ventral rudder deflection would reduce VMCA over 16 knots. Flight tests showed the deflected ventral rudder reduced measured VMCA speeds from 7.2 knots (13.9 km/hr) to 11.6 knots (21.5 km/hr). Other flight test techniques showed ventral rudder effectiveness to exceed that measured in the tunnel. In light of these results, a ventral rudder bias system has been incorporated into the production SJ30-2 design to assist the pilot during single engine events.