Vmc Flashcards
What is Vmc?
Minimum control speed with critical engine inoperative.
Marked with a red radial line on most airspeed indicators.
Only about directional control. No requirement the aircraft be capable of climbing at this airspeed.
What must occur if engine fails before Vmc while still on the ground?
Aborted takeoff
Is directional control possible if engine failure occurs below Vmc while airborne?
No it is not.
What is the accelerate stop distance?
Runway length required to accelerate to a specific speed, experience engine failure, and come to a complete stop
What is accelerate go distance?
Horizontal distance required to continue takeoff and climb to 50’ AGL, assuming engine failure occurs at Vr.
What is rate of climb defined?
Altitude gain per unit of time
What is climb gradient?
Actual measure of altitude gained per 100’ of horizontal travel, expressed as a %.
Ex: 15ft altitude gain per 100’ = 1.5% climb gradient
Is climb gradient affected by wind?
Yes, it is. Unlike the rate of climb
What are the type of twins called that have props that rotate in the same direction?
Conventional twins
What are the motions that occur when an engine fails?
Yaw and Roll
What is the critical engine?
The engine, that if it were to fail, would most adversely affect the performance or handling characteristics of the plane
What factors determine a critical engine?
P-Factor
Accelerated Slipstream
Spiraling slipstream
Torque
What does P-Factor have to do with making the left engine critical?
The arm of the descending blade on the right engine is further away than the arm of the left descending blade, making it where the aircraft will yaw to the left more than if the right engine failed.
How does accelerated slipstream make the left engine critical?
If the left engine fails, the arm of the right engine is further away making the rolling action stronger than if the right engine failed.
How does Torque make the left engine critical?
Newton’s 3rd Law.
The props are spinning to the right, providing a force to the left from Newton’s law. If the left engine fails, the torque from the engine and from Newton’s law will make the aircraft yaw more than if the right engine failed since the left engine would have torque yawing the engine to the left along with Newton’s law pushing to the left to oppose the force of yawing to the right.
What does Vmc deal with?
Directional control and not performance.
What are the 4 warning signs that Vmc is occurring?
Loss of directional control
Stall warning horn
Buffeting before the stall
Rapid decay of control effectiveness
What 2 actions must occur to recover from Vmc?
Reduce power on operating engine
Pitch the nose down
What are the factors that affect Vmc?
Standard atmosphere Max power on operating engine Aft CG Critical engine windmilling Flaps up/gear up Up to 5 degrees of bank Most unfavorable weight
What are 2 causes that will allow Vmc to decrease?
Anything moving the CG forward, making rudder more effective
Anything allowing less rudder to be used, making more rudder available
How does using power effect Vmc?
Increases, more rudder needed to stop resulting yaw
How does increase in Density Altitude effect Vmc?
Decreases Vmc, output of engine thrust will decrease, making less rudder needed to oppose yaw
How does CG location affect Vmc?
The CG changes the length of the arm to the rudder. The longer the arm, the more effective. The shorter the arm, the less effective.
As CG moves forward, Vmc decreases
As CG moves aft, Vmc increases
What are effects of forward CG?
Stall speed - higher Cruise - slower Spin/Stall recovery - good Flare - more difficult Endurance - unchanged Range - worse
