Aerodynamics 2 Flashcards
DEFINE takeoff and landing airspeed in terms of stall speed
Takeoff Airspeed: 20% above the power off stall speed.
Landing Airspeed: 30% above stall speed
STATE the various forces acting on an airplane during the takeoff and landing transition
- Rolling Friction (FR): friction between the landing gear and the runway.
- Thrust
- Drag
- Net Accelerating Force: Thrust minus Drag and rolling friction.
- Net Decellerating Force: Drag plus Rolling Friction minus Thrust
STATE the factors that determine the coefficient of rolling friction
- Runway surface
- runway condition
- tire type
- degree of brake application
DESCRIBE the effects on takeoff and landing performance, given variations in weight, altitude, temperature, humidity, wind, and braking
- Weight: Increasing weight increases rolling friction, requires greater lift and a higher takeoff velocity. Doubling weight will increase takeoff distance four times.
- Increasing airfield elevation (altitude), increasing temperature, or increasing humidity will increase Density Altitude (DA). Higher DA requires a higher takeoff velocity and decreases the amount of thrust the engine can provide, thereby increasing takeoff distance.
- Braking: A decrease in braking effectiveness will incresae landing roll.
Mnemonic: “4-H Club”: High, Hot, Heavy and Humid. Whenever three or more of these are present, expect extended takeoff and landing distances.
DESCRIBE the effects of outside air temperature (OAT) on airplane performance characteristics
Increasing outside air temperature increases density altitude resulting in less lift. It also decreases thrust available. It will result in a longer takeoff roll, and a lower rate of climb.
DEFINE maximum angle of climb and maximum rate of climb profiles
Maximum Angle of Climb (AOC) is a comparison of altitude gained to distance traveled. Maximum vertical velocity for a minimum horizontal velocity.
Maximum Rate of Climb (ROC) is a comparison of altitude gained relative to the time needed to reach that altitude. Results in maximum vertical velocity.
EXPLAIN the performance characteristics profiles that yield maximum angle of climb and maximum rate of climb for turboprops.
Maximum AOC performance depends upon thrust excess. Occurs at a velocity less than L/DMAX and an AOA greater than L/DMAX AOA for a turboprop
Maximum ROC performance depends upon power excess. Occurs at L/DMAX AOA and velocity for a turboprop.
Max AOC and max ROC are not used in the T-6B. Best climb speed of 140 KIAS is used instead.
DESCRIBE the effect of changes in weight, altitude, configuration, and wind on maximum angle of climb and maximum rate of climb profiles
An increase in weight, increase in altitude, lowering the landing gear, or lowering flaps will decrease max AOC and max ROC performance.
A headwind will increase AOC performance due to the decrease in groundspeed, while a tailwind will decrease AOC. Wind has no effect on ROC
DESCRIBE the performance characteristics and purpose of the best climb profile for the T-6B,
Best climb speed will meet or exceed any obstacle clearance requirements while providing a greater safety margin than slower airspeeds.
DEFINE absolute ceiling, service ceiling, cruise ceiling, combat ceiling, and maximum operating ceiling
Combat ceiling: Altitude where max power excess allows only 500 fpm ROC.
Cruise ceiling: altitude at which an airplane can maintain only a 300 fpm ROC.
Service ceiling: altitude at which an airplane can maintain only a 100 fpm ROC.
Absolute ceiling: The altitude at which an airplane can no longer perform a steady climb since maximum thrust excess is zero.
Operational ceiling: 31,000 ft for the T-6B
STATE the maximum operating ceiling of the T-6B
31,000 ft
STATE the relationship between fuel flow, power available, power required, and velocity for a turboprop airplane in straight and level flight
- Fuel flow varies directly with the power output of the engine (PA).
- Minimum fuel flow for equilibrium flight will be found on the power required (PR) curve.
- The power required curve will tell us the velocity we must fly to acheive equilibrium flight. The pilot must adjust the throttle to eliminate thrust excess.
DEFINE maximum range and maximum endurance profiles
Maximum endurance is the maximum amount of time that an airplane can remain airborne on a given amount of fuel.
- Found at a velocity less than L/DMAX and an AOA greater than L/DMAX AOA for a turboprop.
- 8.8 units AOA for T-6B
Maximum range is the maximum distance traveled over the ground for a given amount of fuel.
- ]Found at L/DMAX AOA for turboprops.
- 4.4 units AOA for T-6B
maximum range velocisty is faster than maximum endurance.
EXPLAIN the performance characteristics profiles that yield maximum endurance and maximum range for turboprops
Maximum endurance is found at the bottom of the Power required curve for a turboprop. (a velocity less than L/DMAX and an AOA greater than L/DMAX AOA)
Maximum range is found at L/DMAX AOA for turboprops in a no wind condition.
Max range airspeed would be higher than L/D max with a headwind and lower with a tailwind.
DESCRIBE the effect of changes in weight, altitude, configuration, and wind on maximum endurance and maximum range performance and airspeed
-
Weight: An increase in weight will decrease maximum endurance
- maximum range unaffected,
- increase max endurance and max range airspeeds.
- Altitude: max endurance and max range increases. These will also be at a higher TAS.
- Configuration: max endurance and max range will decrease when flaps or landing gear are extended.
- Wind: Headwinds will decrease maximum range while tailwinds will increase max range. Wind has no effect on maximum endurance.
DEFINE Mach number
The ratio of an airplanes speed through a given air mass to sound’s speed through the same air mass.
DEFINE critical Mach
The lowest mach number than an airplane can travel at and create sonic airflow somewhere on the aircraft.
STATE the effects of altitude on Mach number and critical Mach number
As altitude increases, temperature decreases, resulting in a higher mach number for the same TAS. Critical Mach number will remain the same regardless of altitude.
DEFINE maximum glide range and maximum glide endurance profiles
Maximum glide range is the greatest distance we can fly without an operating engine and is achieved with a minimum glide angle. L/DMAX AOA gives us the best range velocity (VBEST). VBEST is 125 KIAS for the T-6B.
Maximum glide endurance is a matter of minimizing rate of descent. It is acheived at the bottom of the PR curve, which is a lower velocity and higher AOA than L/DMAX.
EXPLAIN the performance characteristics profiles that yield maximum glide range and maximum glide endurance
L/DMAX<strong> </strong>AOA and velocity will result in maximum glade range.
Maximum glide endurance velocity is less than L/DMAX and AOA is greater than L/DMAX AOA.
DESCRIBE the effect of changes in weight, altitude, configuration, wind, and propeller feathering on maximum glide range and maximum glide endurance performance and airspeed
- Weight: An increase in weight will result in increased velocities for max glide range and max glide endurance, but the AOA will remain the same. Weight will not change the glide range, but will decrease glide endurance.
- Altitude: An increase in altitude will increase max glide range and max glide endurance of an airplane.
- Wind: A headwind will decrease max range while a tailwind will increase max range. Wind has no effect on glide endurance.
- Configuration: By extending the landing gear or flaps, the sink rate will increase and the glide range will decrease
- Propeller Feathering: Feathering the propeller result in significantly increased glide range and glide endurance over a windmilling propeller.
DESCRIBE the locations of the regions of normal and reverse command on the turboprop power curve
The region of normal command for a turboprop occur at velocities greater than maximum endurance airspeed (the lowest point on the power required curve).
The region of reverse command for a turboprop occurs at velocities less than maximum endurance airspeed.
EXPLAIN the relationship between power required and airspeed in the regions of normal and reverse command
In the region of normal command, more power is required for the airplane to go faster while maintaining altitude.
In the region of reverse command, more power is required for the airplane to fly at slower airspeeds and maintain altitude.
DEFINE nosewheel liftoff/touchdown speed
The lowest speed that a heading and course along the runway can be maintained with full rudder and ailerons deflected when the nosewheel is off the runway; The minimum safe airspeed that the noswheel may leave the runway during takeoff, or the minimum airspeed at which the nosewheel must return to the runway during landing.