Aero Flashcards
What are the four left turning tendencies inherent to clockwise-turning props?
Torque Reaction
Corkscrew Effect
Gyroscopic Action
Asymmetric Loading (P-Factor)
What is torque reaction?
The torque from the clockwise spinning propeller generates a left-rolling moment on the airframe.
Corkscrew Effect
This force creates a left yawing moment and a less prominent right rolling moment.
(Prop Slipstream Corkscrew on T-Tail)
Gyroscopic Action
This force can generate a yawing moment or a pitching moment, depending on where the initiating force is applies (e.g., a pitch translates to a left or right yaw)
Resultant force of gyroscopic action is 90 deg ahead and in the direction of the application.
Asymmetric Loading (P-Factor)
During positive AOA, downward blade, on right, creates more lift than upward blade. This lift imbalance generates a left yawing moment.
T-Tail Design Advantage
Moves elevators upwards into air undisturbed by propwash or wing surfaces, under normal conditions.
What is the most dangerous flight regime for a T-Tail A/C.
High AOA, low speed, aft CG.
Airflow across the T-Tail is less clean at High AOA
Low speeds and aft CG both increase the control deflection required to achieve the same effect.
U-28 pusher system designed to mitigate danger
Purpose of Winglets
Winglets reduce the induced drag effect of wingtip vortices by blocking some of this airflow.
Ventral Strakes and Dorsal Fins
Both surfaces reduce adverse yaw.
Primary advantage of fowler flaps
Significant increase in wing area they create in addition to the typical increases in camber.
Stalls in the U-28
Bad enough that it requires stick-shaker/stick pusher.
Computer bases responses on a ‘defined AOA’
5-10 knots prior to pusher: stick shaker and aural warning
Three factors that effect power-off stall speeds?
Aircraft Weight
Angle of Bank
Flap Setting
How is stall speed impacted by weight and angle of bank increases
Stall speed increases linearly with increased weight
Stall speed increases exponentially with increased AOB
0 to 15 flaps results in a significant decrease in stall speed.
Lowering flaps further results in progressively smaller stall speed decreases
This trend is because fowler flaps significantly increase wing area between 0 and 15 deg.
Why shouldnt you raise flaps during Stall Recovery
Raising Flaps:
Lowers the wing’s lift coefficient and increases its stall speed, thus increasing the potential sink rate
Vs
Stall Speed: Minimum steady-state controllable speed
Vr
Rotation Speed: Vs1 for for single engine aircraft
Vref
Landing reference speed: 1.3 Vs
Vmo
Max operating limit speed (maneuvering): 216 KIAS (0.46 M) U-28 236 KIAS (0.48 M) PC-12
List the 3 types of structural loading
Bending Moment
Shearing Force
Torsion Moment
Bending Moment
The moment created by a transverse deflection of a body through and perpendicular to its longitudinal axis
Shearing Force
A force tending to cause deformation of a material by slippage along a plane or planes parallel to the imposed stress.
Torsion Moment
The twisting of a body by the exertion of forces tending to turn one end about the longitudinal axis while the other is held fast or turning in the opposite direction.
Turn-Radius Relationship
As speed increases more bank is required to maintain a given turn radius.
What are the U-28 general design features?
Single Engine TurboProp T-Tail Winglets Dorsal Fin and Ventral Strakes Fowler Flaps
What are the U-28 g limits?
No asymmetric limits are published
Flaps Up:
PC-12: +3.3 to -1.32
U-28: +2.5 to -1.0
Flaps Extended:
+2.0 to 0.0
Load Factor vs Bank Angle
Load factor is (geometrically) proportional to bank angle.
What category aircraft is the U-28?
Normal category
