Certified Flyers II
Duchess Multi-Engine Study Guide
5
2.
Stall warning horn-
a single engine stall may be just as dangerous as running out of
rudder authority and could even result in a spin
3.
Buffeting before the stall-
same reason as the stall warning horn
4.
A rapid decay of control effectiveness-
any loss of control effectiveness could result in a
loss of control of the aircraft
To recover from Vmc, these two actions
must occur simultaneously
:
1.
Reduce power on the operating engine-
this will reduce the asymmetrical thrust
causing the Vmc in the first place (remember, reducing power all the way to idle may
help stop the Vmc, but the loss of airspeed and power can lead to a stall)
2.
Pitch down-
lowering the nose of the airplane will increase the forward airspeed making
the rudder more effective in regaining and maintaining directional control
AND IT’S RELATIONSHIP TO STALL SPEED
As density altitude increases, Vmc
speed will decrease because as
density altitude increases engine
power will decrease (less engine
power at higher density altitude
less asymmetric thrus
less yaw
towards dead engine= lower
).
Stall speed is an indicated airspeed
which will remain constant as
altitude increases or decreases.
FACTORS AFFECTING Vmc AND SINGLE ENGINE PERFORMANCE
Vmc is defined using a very specific set of conditions, thus published Vmc and actual Vmc can
be two very different numbers. Remember, Vmc only addresses directional control and is not
related to aircraft performance. While controllability is important, the degradation of
performance in a single engine situation also has serious consequences. A variety of factors
affect both controllability and performance with one engine inoperative, such as aircraft
configuration, flight conditions, and pilot action. In some cases, an element which provides an
increase in controllability (translating into a decrease in Vmc) may actually hinder performance.
Refer to the chart on the next page to review how certain factors affect both Vmc and
performance.
