Aerodynamics Foot Stomps Flashcards
What is the relationship of the 4 forces in level flight?
T = D and W = L
If you decrease your bank angle from 60 degrees to 30 degrees, what happens to stall speed?
Stall speed decreases
What does the induced drag curve look like?
It slopes downwards (high at low airspeed and low at high airspeeds)
What happens to thrust available as RPM increases?
Thrust available increases
What happens in the region of reverse command?
There is airspeed instability and the aircraft response to airspeed deviations in this region is opposite
-If you are at 200 knots with the power at 91% and a disturbance causes your airspeed to decrease to 190 knots, the airspeed will continue to decelerate further until power is increased
How does drag change for a symmetric wing?
There is more induced drag but less parasite drag (for high speeds)
How does a symmetric wing change the stall AoA?
Symmetric wings stall at a higher AoA
What happens to Mach (the speed of sound) as altitude increases?
Mach decreases
What happens to the T-38’s aerodynamic center at supersonic speeds and what does this mean?
the aerodynamic center moves further aft of the CG which makes the T-38 more stable, but less maneuverable
What is Mach Number?
True airspeed / Speed of Sound
Where is your max angle of climb found at?
L/D Max
What happens to your glide distance with a tailwind?
Glide further
What happens to specific fuel consumption with temperature?
SFC decreases when temperature decreases (good thing)
What is max endurance in the T-38?
230 KCAS plus fuel (which occurs at L/D Max)
If you are in a constant G turn, but decreasing airspeed, what happens to your turn radius and turn rate?
Turn radius decreases
Turn rate increases
How do you know two points have the same potential energy on an energy diagram?
they are at the same altitude
Where do you need to be on an EM diagram to climb or accelerate?
+ Ps (positive specific power)
What characteristics does a low-mounted wing have?
More maneuverable
Less stable
What is the recovery procedures for post-stall gyrations?
Neutralize the controls
What is the recovery procedures for a stall?
Max, Relax, Roll (NOT FLAPS)
When initiating a stabilized, constant airspeed climb from level flight, which of the primary forces is the only force that does NOT change in size or direction?
Weight
In a wings-level, constant airspeed climb, lift is ____ weight
less than
In general, what effect does an increase in AOA have on lift if CAS is kept constant?
Lift increases
What effect does lowering the flaps have on the 1-G level flight stall speed?
Decreases the stall speed
What effect does increasing bank angle have on stall speed?
Increases stall speed
An increase in level flight airspeed causes induced drag to ___
decrease
Which figure depicts the relationship between parasite drag and aircraft velocity?
Figure D (parasite drag increases with velocity)
Which dotted drag curve depicts the increase in bank angle on induced drag?
Curve C (Di must increase to hold level flight and total drag will increase MOST at lower CAS where Di is more prominent)
Which dotted drag curve shows the effect of lowering the gear or speed brake on parasite drag?
Curve D (Parasite drag increases and increases MOST at higher CAS where Dp is more prominent)
Which dotted drag curve shows the effect of an increase in weight on Total Drag in level flight?
Curve B (large effect on induced drag but not on parasite drag)
What pressure altitude and temperature combination would produce the most thrust available?
Decrease pressure altitude
Decrease temperature
You are stabilized at 300 KCAS in level flight with the power set at 91% RPM. Due to a wind shear, your airspeed suddenly drops to 280 KCAS. If you continue to maintain level flight without changing power, what will happen?
The aircraft will accelerate back to 300 KCAS and stabilize in level flight
What is the L/D Max?
Airspeed C
What is the maximum continuous airspeed the aircraft can maintain in level flight with current thrust available?
Airspeed D
Which curve represents a symmetric wing like the T-38?
Curve B
A low aspect ratio wing produces ____ parasite drag at high speeds as compared to a high aspect ratio wing.
Less
Sweeping a wing aft will ___ the CL for a given AOA
decreases
Unlike a conventional straight cambered wing which generally stalls at the ____ first, the T-38s sweptback symmetrical wing begins to stall at the ____
wing root; wingtip
What T-38 design features improves the aircraft’s high speed flight performance?
Area rule, irreversible flight controls, and large horizontal stabilator
What is the key factor that determines the speed of sound in air?
Temperature
Mach Number (M) is used to measure the speed of an aircraft and it is simply the ratio of the aircraft’s ____ divided by ____
True airspeed / speed of sound
What is critical Mach number?
the lowest freestream speed at which some point in the flow around the aircraft reaches the speed of sound (Mach 1)
At supersonic speeds, the aerodynamic center moves further ___ of the CG which makes the T-38 ____
aft; more stable but less maneuverable
During transonic flight in the T-38, the formation of shock waves on the wing above Mcrit results in
a decrease in lift and increase in drag
The maximum rate of climb occurs at
maximum excess power
The maximum angle of climb occurs at
L/D Max (airspeed and AoA)
A decrease in aircraft weight will ____ maximum angle of climb performance
increase
An increase in pressure altitude will ____ maximum rate of climb performance
decrease
A tailwind will ____ the maximum rate of climb to a given altitude
NOT AFFECT
Although wind does affect groundspeed in a climb, it has no effect on the climb rate since rate of change in altitude (vertical velocity) is based on time, not distance traveled
The maximum glide ratio is achieved at ____ airspeed and AoA
L/D Max
Gliding into a headwind ____ the maximum glide distance at L/D max airspeed
decreases
An increase in aircraft weight will ____ maximum glide distance at L/D Max
NOT CHANGE
(b/c you compensate for weight by adding fuel to L/D max)
Changing aircraft configuration by lowering the speed brake will increase drag and ____ the L/D Max airspeed
decrease (goes AWAY from where the extra drag was added)
Which SFC rate below indicates the most efficient engine?
0.5
1.0
2.0
0.5
Which of the following is TRUE?
a. An increase in altitude increases SFC
b. A decrease in RPM decreases SFC
c. A decrease in temperature deceases SFC
d. All of the above
c. A decrease in temperature decreases SFC (which is good…remember you want a low SFC)
Which point depicts the no-wind maximum range airspeed?
4
The greatest range is the best tradeoff between fuel flow and airspeed. 2 and 4 are using the same FF, but 4 has a higher airspeed for that FF and thus better range.
Which figure depicts increasing weight on thrust required and the maximum range airspeed?
Figure 1
Remember weight has a bigger impact on induced drag (and thus the Thurst required to meet that induced drag)
Assume the white line is pressure altitude
What figure depicts the effect of increasing pressure altitude on thrust required?
Figure 3
Max endurance TAS increases with altitude (hence the shift right), but max endurance CAS is exactly the same which is why the curves are the same
A strong headwind ____ the maximum range TAS
increases
Which point depicts the maximum endurance airspeed?
Point 3 (L/D Max)
Maximum endurance usually ____ as pressure altitude increases
increases
A lighter T-38 will have _____ max endurance speed
a lower
Maximum endurance speed ____ when the gear or speed brake is lowered
decreases
Which of the following would result in the largest turn radius?
a. 300 KTAS, 45 deg bank
b. 350 KTAS, 45 deg bank
c. 300 KTAS, 60 deg bank
d. 350 KTAS, 60 deg bank
b. 350 KTAS, 45 deg bank
(fastest and lowest angle = biggest TR)
If a T-38 and a C-17 are both at 10,000 feet in a level turn at 300 KTAS and 30 deg of bank, the heavier C-17 will be maintaining ____ load factor in the turn.
the same
Which number in the Vg diagram points to the aerodynamic limit?
1 (the line that shows the accelerated stall speed of the aircraft relative to the load factor)
What is true about cornering velocity?
-the minimum speed at which an aircraft can reach the maximum load factor
-the speed which the maximum turn rate and minimum turn radius can be attained
The red speed limit line in the EM diagram depicts the _____ limit of the aircraft
aeroelastic
What type of energy is considered stored energy?
Potential energy
Which points have the same potential energy?
B and D
How does a constant airspeed climb from C to A affect PE, KE, and TE?
PE increases
KE remains unchanged
TE increases
What is specific power (Ps)?
the rate of change of the aircraft’s total energy (PA - PR) / W
Which point on the Ps diagram an aircraft stabilized in level flight and cannot climb or accelerate?
Point B (on the Ps = 0 line)
What does the green dot represent?
maximum sustained G
Positive static stability is the initial tendency of the aircraft to ____ when disturbed
return to the original equilibrium position
How do you achieve the greatest pitch stability with AC and Cg?
You want the AC as far aft from the Cg as possible
What does a low mounted wing do for the T-38s roll stability?
Decreases roll stability
What T-38 feature is the primary contributor to yaw stability?
Vertical stabilizer/tail
(T/F) You can accomplish single aileron rolls at any load factor or stick deflection assuming asymmetric G limits are observed.
True
How do you recover from a PIO at altitude?
Let go of the stick
What is the primary anti-spin control in the T-38?
Aileron
What is the correct recovery procedures for an inverted spin in the T-38?
Neutralize flight controls
How does lift and weight change in a stable climb?
Lift is less than weight
If you increase bank from 30 to 60 degrees in a level turn, stall speed
increases
As temperature increases, thrust available?
decreases
Low aspect ratio is ___ sensitive to AoA and has a ____ stall speed
less; higher
What is the key factor that determines speed of sound?
Temperature
What happens to stability and maneuverability of the T-38 in supersonic flight?
more stable and less maneuverable
What is Force Divergent Mach Number?
the speed where a sharp increase in the drag coefficient occurs due to energy loss across the shock wave
Max rate of climb occurs
most excess power
What is the T-38’s glide speed with 2,000 pounds of fuel?
250 KCAS
As temperature increases, SFC?
increases (meaning the engine is less efficient)
Kinetic energy is due to?
Motion
Where does max sustained turn rate occur on an EM diagram?
the highest point on the Ps = 0 curve
What is negative static stability?
Tendency of a small disturbance to get worse
What is the recovery for PIO at low altitude or close to another aircraft?
Apply and rigidly hold back stick pressure
What does sweeping the wings do to lift and drag?
Decreases the CL and decreases parasite drag (the reason B-1s sweep their wings back to go faster)
