Performance & Limitations Flashcards
4 Dynamic Forces
Lift- Upward Acting Force
Gravity (weight)- Downward Acting Force
Thrust- Forward
Drag- Backward
Sum of opposing forces is equal
Steady-state, straight and level unaccelerated flight
Airfoil
Air moving over surface = lift
Wings, horizontal & vertical tail surfaces, propellers
Angle of Incidence
Angle formed by Longitudinal Axis & Chord of wing, fixed and cannot be changed
Relative Wind
Direction of airflow with respect to wing
Wing forward & downward- relative wind backward & upward
Flight path and relative wind always parallel but travel in opposite directions
Angle of attack
Angle wing chord line & direction of relative wind
Bernoullis Principle
Pressure of fluid decreases at points where the speed of fluid increases
High speed flow - low pressure
Low speed - high pressure
Pressure decrease of pressure above wing and increase below produces lift
Factors affecting lift and drag
- Wings (Pilot can change with flaps)
- Airfoil shape (upper curvature of airfoil increased, lift increased- lowering aileron/flap)
- Angle of Attack (increased also increased lift and drag)
- Air Velocity (air passing over wing increased lift and drag)
- Air Density (pressure, temp, and humidity defect density which effects lift & drag- increase, increase, decrease, decrease)
Torque Effect
Newton’s third law of physics- every action there is equal and opposite reaction
Internal engine parts + propeller turn one direction = equal force trying to rotate plane other direction
Torque Effect 4 Factors
- Reaction of Engine & Propeller- propeller to right is making plane roll and bank left
- gyroscopic effect of Propeller- if axis of propeller tilted resulting force exerted 90 degrees ahead in direction of rotation
- Corkscrewing effect of propeller- high speed rotation results in corkscrewing of slip stream moving rearward. Pushes tail to right and yaws plane to left.
- P-factor- high angle of attack downward bite of propeller greater than bite of upward moving blade. Plane yaws left
Centrifugal Force
Equal & Opposite reaction of plane changing direction, acting equal and opposite to horizontal component of lift
Load factor
Actual load supported by wings divided by total weight of plane
Plane can be overloaded and increases stall speed
Maximum load factor
Load factor Max during bank angle after 45-50 degrees
Turbulence could cause increase in angle of attack
Speed- flying below maneuvering plane can stall before load factor excessive, faster can be exceeded by controls or strong turbulence
Maximum Safe (Limit) Load Factors
Normal Airplane
+3.8 to -1.52
Maneuvering Speed
Max speed at which limit load can be imposed without causing structural damage (by gusts or full deflection of control surfaces)
Maneuvering speed increase with increased weight, decreases decreased
LOC-I
Loss of control inflight
Significant deviation of aircraft from intended path
LOC-I accidents occur from uncoordinated flight, equipment malfunctions, pilot complacency, distraction, poor risk management
Stall causation
Increased angle of attack, airflow separated from upper surface of wing
Spin
Descent in helical path which flying aoa greater than critical aoa. Aggravated stall in slip or skid.
Scenarios spin likely
Engine failure on take off (increased back pressure/uncoordinated turn)
Slipping or skidding turn from base to final (uncoordinated turn at low speed)
Engine failure on approach to landing (increased back pressure to stretch glide)
Go around with full nose up trim
Go around with improper flap retraction (retracts flaps rapidly causing rapid sink rate and instinctual back pressure)
Spin Recovery
PARE
Power Idle
Ailerons Neutral
Rudder Opposite
Elevator FWD
Then neutralize rudder & begin applying back pressure to return to level
Adverse Yaw
Turning left-
Down aileron on right producing more lift & drag while left aileron has less lift & drag.
This added drag attempts to pull airplanes nose in direction of raised wing. (Adverse yaw)
Ground effect
Airflow around wing restricted by ground surface reducing wings upwash, downwash, and wingtip vortices
Reduced drag on landing and take off:
Excess speed during landing = significant float
Deficiency of speed during take off = marginal climb performance of inability to fly
Empty Weight
Weight of airframe, engines, all permanently installed aircraft, unusable fuel
Gross Weight
Maximum allowable weight (airplane + contents)
Useful Load
Weight of Pilot, copilot, passengers, baggage, usable fuel, drain able oil
Arm
Horizontal distance in inches from reference datum line to center of gravity of item
Moment
Weight of an item multiplied by its arm, expressed in pounds-inches
Center of gravity
Point at which aircraft would balance if it were possible to suspend it at that point
Inches from datum
Datum
Imaginary vertical plane or line from which measurements of arm are taken, established by manufacturer
Center of Gravity Equations
Weight x Arm = Moment
Moment/Arm = Weight
Total Moment / Total Weight = Arm (CG)
Weight Shift
Shifting weight around aircraft, weight remains same BUT total moment change in relation and proportion to direction and distance the weight moved
Weight forward, moment decreased
Weight aft, moment increases
Weight Shift Equation
Weight Shifted divided by total weight
Equals
Change in CG divided by distance weight is shifted
FWD Center of gravity
Higher Stall Speed -increased wing loading
Slower cruise speed- increased drag, greater aoa to maintain altitude
More stable- farther fwd from center of pressure, increases longitudinal stability
Greater back elevator pressure required- longer take off roll, higher approach speeds & problems with landing flare
Rearward center of gravity
Lower stall speed- less wing loading
Higher cruise speed- reduced drag, smaller aoa required to maintain alt
Less stable- stall & spin recovery more difficult, COG closer to COP
Standard weights
Crew & pax 190 each
Av gas 6 lb/gal
Jet A 6.75 lb/gal
Oil 7.5 lb/gal
Water 8.35 lb/gal
New avionics installed, weight and balance record required?
A& P mechanic or tech’s responsibility to know weight and location of changes and to compute the CG and record new empty weight and empty weight center of gravity EQCG in aircraft weight and balance record
Wind & Aircraft Performance
Takeoff- headwind allows ac to reach lift off speed at lower ground speed, shortening take off distance and increasing aoa
Landing- headwind lowers ground speed and steepens approach angle, reducing landing distance
Cruise- headwind decreases performance by reducing ground speeds, tailwind increases
TO/Landing Performance - Weight
Take off- increased weight:
Higher liftoff speed
Slow acceleration
Increased drag & ground friction
Longer take off distance
Landing:
Increased landing distance
TO/Landing Performance- Density Altitude
Increased:
TO Distance (greater TAS required)
True airspeed on approach and landing
Landing roll distance
Reduced rate of climb
Density Altitude
Pressure altitude corrected for nonstandard temperature
Vertical distance above sea level in the standard atmosphere at which a given density is found
Aircraft performance - Air Density
Density effects-
Lift produced by wings
Power output of engine
Propeller efficiency
Drag forces
Factors affecting air density
Altitude (higher, less dense, density altitude increases)
Temp (warmer, less dense)
Humidity (more humid, less)
Best glide speed vs min sink rate
Best glide is greatest distance for loss of altitude
Best sink maximizes time remains in flight, lowest rate for losing altitude
Pressure Altitude
Altitude indicated when altimeter adjusted to 29.92 altitude above standard datum plane
