Module 4 Concepts Flashcards
What is the relationship between AoA and velocity in level flight?
Inversely proportional according to:
CL=2piAoA
As V increases, AoA must be decreased to maintain level flight - remember that increasing one does not necessarily lead to the other, but to maintain level they must both be manipulated.
How doe parasite drag and induced drag change with increasing airspeed?
Parasite drag increases at V^2
Induced drag decreases and becomes flatter
Where does the minimum drag speed occur on a graph of parasite and induced drag?
- When parasite drag and induced drag are equal
- At the bottom of the total drag curve
On a Pr curve, where is the minimum drag speed?
- It is higher than the minimum power speed
- It is at the point where line drawn from the origin is tangental to the Pr curve.
What is the difference between brake horsepower, thrust horsepower and shaft horsepower?
BHP: power created at the crankshaft
SHP: power created at the propeller hub
THP: the power that is actually use to create thrust
What is the propeller efficiency?
THP/SHP
How does power available change with altitude for a normally aspirated engine compared to a turbocharged engine?
- Pa decreases to about 50% of sea level at 19,000ft for a normally aspirated engine
- Pa can be maintained at 1005 of sea level up to 19,000ft for turbocharged engine
How can level flight airspeed limits be determined for an aircraft? Lower and upper?
Lower: Pa & Pr intercept or Stall speed
Upper: Pa & Pr intercept
What happens to Pr and Pa at altitude of a piston aircraft?
- Pr increases and moves to the right
- Pa moves straight down
What two things can be used to achieve a high thrust?
- large mass flow rate
- Large change in velocity
How does thrust available change with velocity for a jet aircraft?
It is assumed to be constant for a given RPM
Do you need a high efficiency for high thrust?
No
How does thrust available change for a jet at altitude?
decreases
How does power available change for a jet aircraft with increased velocity?
Increases
Pa = Ta*v
Where on the Pa vs. Pr curve does the max rate of climb occur?
Point of greatest excess power
When does the maximum angle of climb occur?
When there is the greatest excess thrust
How does increasing altitude affect the rate and angle of climb?
Decreases both
How does increasing velocity change the angle of climb?
Decreases it
What is the difference between absolute and service ceiling? Jet vs. piston?
Absolute ceiling: rate of climb = 0
Service ceiling: rate of climb less than 0.5m/s (piston)
rate of climb less than 2.5*m/s (jet)
or other specified rate
What happens to lift in a level banked turn?
Total lift must increaser to provide the centripetal fore to make the aircraft turn.
How can CL in a bank be determined?
Multiply level CL by load factor
When can the maximum angle of bank be obtained?
- When the CL(stall) and V(stall) and LF(max) are maintained.
- Produces maximum lift
