Module 4 Concepts

Question 1

What is the relationship between AoA and velocity in level flight?

Answer 1

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.

Question 2

How doe parasite drag and induced drag change with increasing airspeed?

Answer 2

Parasite drag increases at V^2

Induced drag decreases and becomes flatter

Question 3

Where does the minimum drag speed occur on a graph of parasite and induced drag?

Answer 3

• When parasite drag and induced drag are equal

- At the bottom of the total drag curve

Question 4

On a Pr curve, where is the minimum drag speed?

Answer 4

• 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.

Question 5

What is the difference between brake horsepower, thrust horsepower and shaft horsepower?

Answer 5

BHP: power created at the crankshaft
SHP: power created at the propeller hub
THP: the power that is actually use to create thrust

Question 6

What is the propeller efficiency?

Answer 6

THP/SHP

Question 7

How does power available change with altitude for a normally aspirated engine compared to a turbocharged engine?

Answer 7

• 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

Question 8

How can level flight airspeed limits be determined for an aircraft? Lower and upper?

Answer 8

Lower: Pa & Pr intercept or Stall speed
Upper: Pa & Pr intercept

Question 9

What happens to Pr and Pa at altitude of a piston aircraft?

Answer 9

• Pr increases and moves to the right

- Pa moves straight down

Question 10

What two things can be used to achieve a high thrust?

Answer 10

• large mass flow rate

- Large change in velocity

Question 11

How does thrust available change with velocity for a jet aircraft?

Answer 11

It is assumed to be constant for a given RPM

Question 12

Do you need a high efficiency for high thrust?

Answer 12

No

Question 13

How does thrust available change for a jet at altitude?

Answer 13

decreases

Question 14

How does power available change for a jet aircraft with increased velocity?

Answer 14

Increases

Pa = Ta*v

Question 15

Where on the Pa vs. Pr curve does the max rate of climb occur?

Answer 15

Point of greatest excess power

Question 16

When does the maximum angle of climb occur?

Answer 16

When there is the greatest excess thrust

Question 17

How does increasing altitude affect the rate and angle of climb?

Answer 17

Decreases both

Question 18

How does increasing velocity change the angle of climb?

Answer 18

Decreases it

Question 19

What is the difference between absolute and service ceiling? Jet vs. piston?

Answer 19

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

Question 20

What happens to lift in a level banked turn?

Answer 20

Total lift must increaser to provide the centripetal fore to make the aircraft turn.

Question 21

How can CL in a bank be determined?

Answer 21

Multiply level CL by load factor

Question 22

When can the maximum angle of bank be obtained?

Answer 22

• When the CL(stall) and V(stall) and LF(max) are maintained.
• Produces maximum lift