Figure E-4

APPENDIX F

ROLL

Loss of power on one engine reduces prop wash over the wing. Yaw also affects the lift distribution over

the wing causing a roll toward the "dead" engine. (See Figure E-4.) These roll forces may be balanced by

banking into the operating engine.

Figure E-4

CRITICAL ENGINE

The critical engine is that whose failure would most adversely affect the performance or handling qualities

of the airplane. The critical engine on most U.S. light twins is the left engine, as its failure requires the

most rudder force to overcome yaw. At cruise, the thrust line of each engine is through the propeller hub.

But, at low airspeeds and at high angles of attack, the effective thrust centerline shifts to the right on each

engine (see figure E-5) because the descending propeller blades produce more thrust than the ascending

blades (P-factor). Thus, the right engine produces the greatest mechanical yawing moment and requires the

most rudder to counterbalance yaw.

Figure E-5

F-3