Multiengine Aerodynamics Flashcards
S.M.A.C.F.U.M.
S - Standard Day
M - Most Unfavorable Weight (light)
A - Aft CG
C - Critical Engine Windmilling
F - Flaps Up, Gear Up, Trim T/O
U - Up to 5° of Bank
M - Max Power
S - Standard Day
- Increased Performance
- Decreased Control
- Increased Vmc
M - Most Unfavorable Weight (Light)
- Increased Performance
- Decreased Control
- Increased Vmc
A - Aft CG
- Increased Performance
- Decreased Control
- Increased Vmc
C - Critical Engine Windmilling
A windmilling propeller creates more drag and, therefore, stronger yaw moment
- Decreased Performance
- Decreased Control
- Increased Vmc
F - Flaps Up, Gear Up, Trim T/O
Flaps increase drag near the fuselage which stabilizes the a/c
Landing gear increases keel effect which stabilizes the a/c
With both retracted, the a/c is less stable and better performing
- Increased Performance
- Decreased Control
- Increased Vmc
U - Up to 5° of Bank
This is actually a benefit
With wings level and ball centered, the a/c is in mild side-slip - decreased performance, increased drag
With 5° of Bank and ball centered, the a/c is in zero side-slip - increased performance, decreased drag
Even though performance increases, control also increases
- Increased Performance
- Increased Control
- Decreased Vmc
M - Max Power
- Increased Performance
- Decreased Control
- Increased Vmc
Vmc Certification Requirements
- No less than 1.2xVs1
- Most unfavorable Weight (light)
- Up to 5° of Bank
- <= 150 lbs rudder force
- <= 20° change in heading
- T/O config (flaps up, gear up, trim t/o, prop t/o)
- Critical engine inoperative
For A/C <6,000 lbs., add landing config (flaps ldg, gear down)
Critical Engine
The engine that, when inoperative, has the most drastic effect on airplane control
In conventional twins, always left engine
Determining Critical Engine
P.A.S.T
P - P-Factor (thrust-line to mid-line of a/c)
A - Accelerated Slip-Stream (more lift closer to fuselage)
S - Spiraling Slip-Stream
T - Torque Effect
How is climb rate affected when operating on 1 engine?
A/C loses about 80% of climb rate
varies with specific models, but always >50%
What is Vmc?
The airspeed at which the a/c will lose directional control - “run out of rudder”
What is Critical Density Altitude (CDA)?
The altitude at which Vmc = Vs
Above CDA, a/c will stall first
Below CDA, a/c will yaw first
How is Vmc indicated?
By a red radial line on the airspeed indicator
Be aware, Vmc is a calibrated airspeed!
