Unit 5 Flashcards
What is the most important factor that affects airplane performance?
Air density
As density altitude increases & air density decreases, does performance improve or worsen?
worsens
As air temp increases, air density?
decreases
As altitude increases, air density?
decreases
As barometric pressure increases, air density?
increases
As humidity increases, air density?
decreases
Density altitude
measurement of air density expressed in terms of altitude
(theoretical value)
What is density altitude used for?
determining plane’s performance capabilities
Humidity
amount of water vapor in the air
(affects engine power)
Relationship between humidity & engine performance?
Increase humidity = decrease performance
(less air enters cylinders)
What is the general rule for takeoff distance in humid environments?
add 10% to takeoff distance
What should you do if density altitude is above 5,000ft or power setting is less than 75%?
lean out engine for max power
Minimum takeoff distance
min safe speed that allows for sufficient safety margin above stall speed, provides control, & initial rate of climb
What is the affect of gross weight on takeoff performance?
increase gross weight = decrease in takeoff performance
(more takeoff speed, mass to accelerate, drag)
requires longer takeoff distance
Takeoff speed
min speed at which plane can become airborne
What would happen if takeoff speed were too low?
plane stalls & very low initial rate of climb
What would happen if takeoff speed were too high?
initial rate of climb better, but require LONGER takeoff distance
What does a plane’s climb performance depend on?
reserve thrust & reserve power
Climb Performance
VX
greatest gain in altitude for distance traveled on the ground (clear obstacles)
(most reserve thrust)
Climb Performance
VY
greatest gain in altitude over a period of time
(most reserve power available)
What variables affect climb performance?
Weight, altitude
How does weight affect climb performance?
increase weight → plane must fly at greater AOA to maintain given altitude/speed
How does altitude affect climb performance?
increase power required for climb & decrease in power available
(greater altitude = higher VX lower VY)
Range
ability of plane to convert fuel energy into flying distance
Power
work per unit time
Cruise is based on what % of power?
65%
What does a quartering crosswind mean?
directly across runway
Does the landing distance change at different altitudes & temperature? If so why?
Yes
b/c change in air density
Does the indicated airspeed for landing change at different altitudes & temperature? If so why?
No
General rule for approximating landing distance based on density altitude?
add 3.5% of landing distance for every 1,000ft of altitude
arm
horizontal distance (in) from reference datum to CG
Basic empty weight
standard empty weight + optional equipment installed
Center of gravity (CG)
point of balance along longitudinal axis
CG limits
extreme (forward & aft) CG locations within which plane must be operated at a given weight
Max ramp weight
max weight approved for ground maneuvers
Moment
force that tries to cause an object to rotate
Moment index
moment divided by a reduction number (100 or 1000)
make # smaller and reduce chance of mathematical errors in computing CG
Payload
total weight of occupants, cargo, luggage
Standard weights for gasoline, oil, and water?
- Gasoline: 6 lb / US gal
- Oil: 7.5 lb / US gal
- Water: 8.35 lb / US gal
Useful load
diff between takeoff weight & basic empty weight
Total weight
basic weight + everything loaded on it
Datum
arbitrary point established by plane designers
What should the pilot do before every flight?
determine weight & balance condition of aircraft
Equation for center of gravity (CG)
total moments / total weight
Equation for calculating moment
weight x arm = moment
As air temperature increases, density altitude will
increase
What effect does high density altitude, as compared to low density altitude, have on propeller efficiency and why?
Efficiency is reduced because the propeller exerts less force at high density altitudes than at low density altitudes.
