Aircraft Performance Flashcards
Effects of lower pressure
Less power
Less thrust
Less lift
Standard atmosphere at sea level
59F or 15C
29.92 “HG or 1013.2 mb
Decrease of 2C, 3.5F per 1000ft up to 35k, then constant up to 80k
Drop of 1”Hg per 1000ft
Pressure altitude
Height above standard Datum Plane SDP
- Setting barometric scale to 29.92 “HG
- Applying a correction factor
- Using flight computer
Density altitude
Pressure altitude corrected for non standard temp
Increased density, better aircraft Performance, vice versa
Effects of pressure on density
Direct proportional
Double increase double density
Effects of altitude on density pressure
Decrease in temp and pressure conflicting effect
Rapid drop in pressure larger effect
Humidity effect on density
Little effect
High humidity less dense, water vapor lighter than air
Decrease in overall performance
Straight and level flight drag vs speed
Parasite drag predominates at high speed, induced drag at low speed
Double speed, quadruple parasite drag, 8x power to overcome draf
Kinetic energy and potential energy
KE = 1/2 x m x v2 PE = m x g x h
Angle of climb AOC
Max AOC performance at Vx, max altitude with minimum distance traveled, with excess thrust
Rate of Climb ROC
Altitude gained over time
Max ROC performance at Vy
ROC for prop at airspeed and AOA closest to L/Dmax, for jet airspeed greater than L/Dmax and AOA less than L/Dmax
Depends on excess power, climb is work, power is rate of performing work
Weight impact on climb performance
Must use higher AOA to maintain altitude, speed. Increases drag. Requires more thrust, less reserve for climb
Service ceiling vs absolute ceiling
Absolute = no excess power, zero ROC Service = unable to climb at more than 100ft/min
Power vs wing loading
Power = weight (lbs) / horsepower Wing = weight (lbs) / sqft wing
Endurance vs range
Range = distance Endurance = time
Specific endurance
Flight hours / pounds of fuel, or
1 / fuel flow
Specific range
NM / pounds of fuel
Knots / fuel flow
Cruise control
Condition for long range cruise
Fuel decreases, weight decreases, control optimum airspeed, altitude, power
Max range condition
Speed / power is greatest
At maximum lift drag ratio L/Dmax (at particular AOA and lift coefficient, uneffected by weight, altitude)
Region of reversed command
Low speed phase of flight
Below speed for max endurance
Higher power settings with decrease in air speed, high pitch
Eg short field landing
Take off and landing performance factors
Function of stall speed
Rate of ac/deceleration, varies directly with imbalance of force and inversely with mass of object, 75kts 4x energy than 37 it’s, 4x distance to stop
Roll distance function of speed
Minimum hydroplaning speed
Multiplying square root of main gear tire pressure in psi by 9 => knots
Lift off speed
1.05 to 1.25 the stall speed
Higher weight impact on take off
Higher lift off speed
Greater mass to accelerate
Increase drag, friction
Wind effect on take off
10% head wind, 19% reduced takeoff distance
10% tailwind, 21% increasr
Effects of density altitude on takeoff
Greater takeoff speed
Decreased thrust, less acceleration
No issue for supercharged reciprocating engine until critical operating limit
Min landing distance vs ordinary landing roll
Max brakes for max deceleration vs use of drag to minimize wear and tear (deceleration to 60-70% of touchdown speed)
Effect of gross weight on landing distance
21% more weight = 10% more landing speed required, 20% more landing distance
Effect of wind on landing distance
Same as effect of wind on takeoff acceleration
Effect of density altitude on landing distance
Does not impact deceleration
Only impact due to higher TAS
Calculate landing distance increase due to altitude
3.5% for each 1000ft
Eg: at 5000ft 16% greater distance
Impact of landing speed on landing distance
Below specified speed, may stall
Above, increase distance
10% more landing speed, 21% more distance
TAS, IAS, CAS, EAS
True, indicated, calibrated, equivalent
V s0, s1, y, x, LE, LO, FE, A, N0, NE
Power-off min speed in landing config ... in specified config Max increase in altitude per time, ROC Max altitude in horizontal distance, AOC Max speed extended landing gear Max speed to extend/retract gear Max speed with flaps Calibrated design maneuvering speed, max speed limit load can be imposed (gusts or control surface deflection) Max structural cruising speed Max speed
Performance charts
Runway length for takeoff and landing
Fuel used during flight
Time to destination
