multi engine 3b - mastering engine-out aerodynamics

what causes the **yawing tendency** in engine failure?

* the **asymmetrical thrust condition**

what causes the **rolling tendency** in engine failure?

* the **lift differential between the critical engine and active engine**
* the induced flow from the propeller slipstream is lost on the left wing
* the right wing is ^^still producing additional lift^^
* **drag created by the windmilling propeller** contributes to the roll and yaw
* **aerodynamic coupling** (which occurs when one force affects another)
* yaw causes the air traveling over the outside right wing to speed up, increasing the lift on that wing and consequently adding to the roll

why do you want to maintain a certain amount of airspeed during a critical engine failure?

airspeed gives you sufficient **rudder authority** to counteract the yawing and rolling tendency

what airspeed should be used during critical engine failure?

* V**mc,** or **minimum control airspeed**
* if applying full rudder pressure and the plane is still yawing and rolling, the airspeed is below V**mc**

what is the difference between **published** and **actual** V**mc?**

**published Vmc**

* found in the airplane’s POH and displayed on the airspeed indicator by a red radial line
* determined under specific criteria

**actual Vmc**

* determined by various factors

what are the factors affecting V**mc?**

* **weight**
* **longitudinal centre of gravity**
* **lateral centre of gravity**
* **density altitude**
* **temperature**

how does **weight** affect V**mc?**

* heavier → more maneuverability → lower V**mc**

how does **longitudinal centre of gravity** affect **Vmc?**

* the further the tail → more rudder authority → lower V**mc**

how does **lateral centre of gravity** affect **Vmc?**

* the nearer the inoperative engine → the larger the moment → the more force the rudder has to apply → higher V**mc**

how does **density altitude** affect **Vmc?**

* higher → less thrust generated → lower V**mc**

how does **temperature** affect **Vmc?**

* higher → less dense → less thrust generated → lower V**mc**

how does the sideslip adversely affect performance?

* the rise in drag that reduces performance
* significantly reduces rudder effectiveness
* may require a higher airspeed than published Vmc to generate sufficient airflow to maintain directional control

what is the **zero sideslip**

using a sideslip with 5% bank **towards the good engine** to offset the sideslip

* this allows you to regain the controllability and performance lost when the engine is slipping