Aero II Flashcards
DEFINE boundary layer
layer of airflow over a surface that demonstrates local airflow retardation due to viscosity
DESCRIBE different boundary layer flows
laminar flow: air moves smoothly along in streamlines, little friction, easily separated
turbulent flow: streamlines break up and flow is disorganized and irregular, higher friction drag, adheres to surface better, delays BLS
DESCRIBE BL separation
when airflow separates from the surface due to lack of KE, and airflow beyond is a turbulent wake of low pressure (sucks wing back = form drag)
DEFINE CL MAX AOA
- stalling or critical angle of attack
- maximum CL achieved
- beyond this AOA, CL drops rapidly and plane stalls
DEFINE stall
condition of flight in which an increase in AOA decreases CL
EXPLAIN how stall occurs
airflow begins to separate from the sfc with the sep. point moving forward and thereore decreasing lift
IDENTIFY aerodynamic parameters causing a stall
- excessive AOA (above CL MAX AOA)
- BLS = less lift
- Low pressure wake = more drag
COMPARE power-on and power-off stalls
p-on stall speed wil be less since at high pitch, part of W is supported by T and propellor forces air over wings
DESCRIBE order of losing control effectiveness approaching stall in T-6B
A=>E=>R
ailerons to elevator to rudder
EXPLAIN diff. btwn true and indicated stall speed
- true AS is affected by altitude so true stall speed will increase
- indicated AS uses SL density so it will remain constant
EXPLAIN effects of gross weight, altitude, LF, and maneuvering on stall speed
- Weight decreases, stall speed decreases since L decreases
- altitude increases, stall speed stays same (sea level density used for indicated)
- LF icnreases, stall speed increases
- maneuvering increases stall speed
STATE purpose of using high lift devices
reduce T/O and landing speeds by reducing stall speed
DESCRIBE how different HL devices affect values of CL, CL MAX, and CL MAX AOA
CL for given AOA remains the same, CL Max, and CL MAX AOA increase
- Slots: HP air from below increases KE on top and delays separation
- either fixed or slats (automatic slots)
DESCRIBE devices used to control BLS
- Fixed slots are gaps at LE of wing that suck in HP air from bottom and push to top
- Slats are moveable LE sections used to form slots and are deployed aerodynamically, mechanically, hydraulically, or electrically
- Vortex generators: small vanes that disturb laminar airflow into turbulent
DESCRIBE devices used to change camber of an airfoil
Flaps
TE: plain (simple hinged portion), split (plate deflected from lower surface), slotted (moves away from wing to open a narrow slot btwn flap and wing for BLC), and fowler (moves down and aft for more camber and surface area plus slot for BLC)
LE: plain and slotted (same as TE versions)
DESCRIBE methods of stall warning used in T-6B
buffet, stick shaker, AOA display on PFD/HUD, AOA indexers (in each cockpit)
DESCRIBE stall tendencay of general types of wing planforms
Swept Wing: strong tip stall tend., easily stalled High Taper: strong tip stall tend. Rectanguler: strong root stall tend. Elliptical: even stall Moderate Taper (T-6B): even stall
DESCRIBE various methods of wing tailoring, including geom. twist, aero twist, stall strips, and stall fences
geom twist (T-6B): decrease in AOI from root to tip (root stalls first) aero twist (T-6B): gradual change in airfoil shape that increases CL MAX AOA at tip stall strips: sharply angled piece of metal on LE of root designed to induce stall on root first stall fences: redirect airflow along the chord and delay tip stall
DEFINE T/O and landing airspeed in terms of stall speed
- T/O: 20% above power off stall speed
- landing: 30% above
STATE various forces acting on a plane during T/O and landing transition
- T/O and landing: rolling friction (F_R), T (lots), W, L, and D
- net accelerating force: T-D-F_R
- net decelerating force: D+F_R-T
STATE the factors that determine the coefficient of rolling friction
rwy surface, rwy condition, tire type, and degree of brake application (little to none on T/O)
DESCRIBE the effects on takeoff and landing performance, given variations in weight, altitude, temperature, humidity, wind, and braking
Effect on T/O distance:
-^weight: direct squared relationship
-^altitude/temp/humidity: increase (T/O AS stays same)
-HW: decreases
-braking: increases (why the hell would you do this?)
Effect onlanding distance:
-^weight: direct squared relationship
-^altitude/temp/humidity: increase
-HW: decreases
-braking: decreases (why the hell would you not do this?)
DESCRIBE the effects of outside air temperature (OAT) on airplane performance
4H Club: High, Hot, Heavy, Humid
When 3 or more present, expect degraded perf.
DEFINE maximum angle of climb and maximum rate of climb profiles
max angle: occurs at velocity and AOA of T_E max (@ L/D max for TJ and up/left for TP)
max rate: occurs at veloicty and AOA of P_E max (up and right for TJ and @ for TP)