11 Endurance

Question 1

What is the equation for the Endurance of a Jet AC?

Answer 1

Endurance is proportional to 1 / Fuel Flow = 1 / (SFC x Drag)

Question 2

What is the speed for a Jet to fly for maximum Endurance?

Answer 2

• For Endurance to be greatest the Drag must be minimum

- Speed for greatest Endurance is Vmd

Question 3

What is the optimum altitude for a Jet to fly for greatest Endurance?

Answer 3

• Endurance will be greatest when SFC is lowest (i.e. when temperature is low and RPM is optimal)
• High altitude (higher than for maximum range)

Question 4

What is the equation for the Endurance of a Prop AC?

Answer 4

Endurance is proportional to 1 / fuel flow = 1 / (SFC x Pr)

Question 5

What speed must a Prop AC fly at to achieve maximum Endurance?

Answer 5

Vmp (0.76 x Vmd)

Question 6

At what altitude will a Prop AC achieve the best Endurance?

Answer 6

• Low altitude where the power required is smallest

- Since Endurance = 1 / (SPC x Pr)

Question 7

What is the effect of Mass on Endurance?

Answer 7

• A greater Mass will decrease the Endurance
• More Mass = More Lift = More Drag = More Thrust = More Fuel Flow
• Endurance is proportional to 1 / Fuel Flow

Question 8

What is the effect of Wind on Endurance?

Answer 8

• Endurance is not affected by Wind

- The horizontal position of the AC is not relevant for endurance, only the amount of time in the air

Question 9

For any given AC, what does it’s Endurance depend on?

Answer 9

• Altitude
• Speed
• Mass
• Fuel on board