Certified Flyers II
Duchess Multi-Engine Study Guide
4
Single-engine absolute ceiling-
the altitude where climb is no longer possible with one engine
operating at full power and one engine’s propeller is feathered
Vmc- MINIMUM CONTROL SPEED
Rudder is applied to counteract yaw and roll from an inoperative engine in a multi-engine
aircraft. As airspeed decreases the rudder becomes less effective, eventually an airspeed will be
reached where full rudder deflection is required to maintain directional control. At this point, any
further airspeed reduction will result in a loss of directional control. This airspeed is Vmc, the
airspeed at which it is still possible to maintain directional control with an engine inoperative.
§23.149 Minimum Control Speed
Vmc
is the calibrated airspeed, at which, when the critical engine is suddenly made inoperative
it is possible to:
1.
Maintain control of the airplane with the engine still inoperative
2.
Maintain straight flight at the same speed with an angle of bank not more than 5
degrees.
The method used to simulate critical engine failure must represent the most critical mode of
powerplant failure expected in service with respect to controllability.
Vmc must not exceed 1.2 Vs1 at maximum takeoff weight.
Vmc must be determined with:
1.
Most unfavorable weight (not necessarily gross weight)
2.
Most unfavorable center of gravity position
3.
The airplane airborne and the ground effect negligible
4.
Maximum available takeoff power initially on each engine
5.
The airplane trimmed for takeoff
6.
Flaps in the takeoff position
7.
Landing gear retracted
8.
All propeller controls in the recommended takeoff position
When recovering from Vmc:
1.
The rudder pedal force required to maintain control must not exceed 150 pounds
2.
It must not be necessary to reduce power of the operative engine(s)
3.
The airplane must not assume any dangerous attitude
4.
It must be possible to prevent a heading change of more than 20 degrees
RECOGNIZING AND RECOVERING FROM Vmc
There are four warning signs that Vmc is occurring or about to occur:
1.
Loss of directional control
- the rudder pedal is depressed to its fullest travel and the
airplane is still turning towards the inoperative engine