Range & Endurance

Question 1

Define the goal of range

Answer 1

The goal of range is to achieve the greatest gain of distance on a given amount of fuel

Question 2

In basic terms, how can we achieve the greatest range for a propeller driven airplane?

Answer 2

If we want to move the aeroplane a maximum distance, we need to pull it with minimum force. Force in this case will be drag, so in order to achieve the greatest amount of range we need to fly at the speed of minimum drag. The drag is least where the lift to drag ratio is greatest. However, this

Question 3

At what height will we achieve greatest range for a propeller driven aeroplane? And why

Answer 3

At the height of full power, otherwise the engine will not perform at peak efficiency.

Question 4

What is the object of flying for endurance?

Answer 4

Flying for endurance is the goal of remaining in the air for the longest possible time for a given amount of fuel

Question 5

At what altitude can we find the best endurance?

Answer 5

To achieve the greatest endurance, a piston-engined aeroplane should be flown at the lowest altitude.

Question 6

Define Total Drag or Thrust Required

Answer 6

Total drag is parasite drag and induced drag added together, also known as thrust required. It’s the amount of thrust required to stay level on a given airspeed

Question 7

Define Power Required

Answer 7

Power is work done per unit of time. So in order to find power required, you can multiply your total drag (force required) by your airspeed (distance over time). Power Required = Thrust Required X Airspeed.

Question 8

To obtain the best possible range, a propeller driven aircraft needs to be flown at what speed?

Answer 8

The best lift/drag ratio airspeed

Question 9

To obtain the best possible endurance, a propeller aircraft need to be flown at what speed?

Answer 9

Vmp. The speed for minimum power, which will be slower than the speed for minimum drag, at a higher value of induced drag.

Question 10

Optimum flap is?

Answer 10

The flap setting that will produce a greater increase in lift than an increase in drag.

Question 11

A turbine powered airplane can achieve maximum range at what speed?

Answer 11

1.32Vmd. Unlike propeller driven airplanes, turbine airplanes do not achieve maximum range at the best/lift drag ratio(Vmd) but at a slightly faster speed than Vmd.

Question 12

At what speed can a turbine aeroplane achieve maximum endurance?

Answer 12

At the speed for minimum drag, where the lift/drag ratio is greatest.

Question 13

Why is flying at Long Range Cruise speed more preferable?

Answer 13

Long range cruise speed gives 99% of the maximum range for only a 4% increase in speed.

Question 14

The best gliding speed is at?

Answer 14

Vmd

Question 15

The point where induced drag and parasite drag is equal, will be?

Answer 15

The point of minimum drag, or the best lift/drag ratio.

Question 16

The best range speed for jet aeroplane, on a thrust available/required graph can be found?

Answer 16

By drawing a line from the origin tangent to the thrust required curve, the point of tangency will be our best range speed. Which will occur at the speed slightly faster than L/D max.

Question 17

The best range speed for a prop aeroplane, on power available/required graph can be found?

Answer 17

By drawing a line from the origin tangent to the power required curve, the point of tangency will be our best range speed. Which will occur at the speed of L/D max, or where induced and parasite drag is equal.