Chapter 0: Service reuirements

Question 1

What are/discuss the 5 design factors/considerations for aircraft?

Answer 1

1. Types of services
2. Speed
3. Altitude
4. Range
5. Operation hours

Question 2

What is the meaning range in design factor?

Answer 2

It is the point to point distance travelled

Question 3

Discuss speed in Design factors

Answer 3

The higher the speed, the higher the skin temperature

Question 4

Discuss altitude in Design Factor

Answer 4

Decreasing air density, temperature and pressure with altitude

Question 5

Discuss Operation hours in design factors

Answer 5

Number of flights per day, total hours per flight and maximum time between maintenance

Question 6

Discuss Types of services in Design factors

Answer 6

Civilian, military and reconnaissance

Question 7

What are types of mechanical properties for property requirements

Answer 7

Strength, fatigue, toughness and stiffness

Question 8

What are the types of physical properties in property requirements

Answer 8

Reflectivity, conductivity, density and melting point

Question 9

Metallic materials are made up of grains. List 2 methods how the grain size can change/vary

Answer 9

1. Cold working

2. Heat treatment

Question 10

What is microstructure insensitive properties and give all example.

Answer 10

Microstructure insensitive properties are properties that are not affected by the change in grain structure. Density, Melting point, Conductivity and Reflectivity

Question 11

What is microstructure sensitive properties and give all examples.

Answer 11

Microstructure sensitive properties are properties that change and is dependent on the grain structure.

Question 12

The composition of the material can be studied by the use of

Answer 12

Scanning Electron Microscopy –

Energy Dispersive X-Ray Spectroscopy or SEM-EDX

Question 13

State two main criteria used for ranking suitable materials for aircraft construction

Answer 13

1. Specific strength: Strength/Density

2. Specific Stiffness: Young’s modulus/Density

Question 14

In the mode of operations, What are the properties of a Civil flying object?

Answer 14

1. Lower stresses compared to military
2. Good fatigue behaviour requirement
3. Must be cost-effective

Question 15

In the mode of operations, What are the properties of a Military flying object?

Answer 15

1. Able to handle high loads
2. Functional material
3. Cost less of an issue
4. Weight less of an issue

Question 16

Contrast the material requirements for the wings

Answer 16

Expectation - Highest and complex stress

• Cantilever maximum bending moment at the root
• Hang down due to self weight, fuel and engine

Requirements - Resistant to compression

• High static tensile strength
• Resistance to fatigue

Question 17

Contrast the material requirements for the landing gears

Answer 17

Expectations
-High stresses on taking off a full load of fuel
-Greatest during landing; whole aircraft weight on
touchdown
-Retract during flight

Requirements

• Highest possible static strength
• Low cycle fatigue strength
• High fracture toughness
• Minimum volume

Question 18

Contrast the material requirements for the control surfaces

Answer 18

Expectations
Lightly loaded

Requirements
Adequate stiffness High cycle fatigue

Question 19

The ASTM standard to calculate the ASTM grain size number is based on the magnification of

Answer 19

100 X

Question 20

Can you use the formula 2^n-1 if the magnification is 200 X

Answer 20

No. That formula only applies for 100 X

Question 21

The temperature at 35000 ft is?

Answer 21

-55 degree Celius

Question 22

The formula for temp increase (in Kelvin)

Answer 22

V^2/87^2

V = airspeed in knots

Question 23

If V = 500 kts and the Skin temperature = -55 + 33 = -22

what is it?

Answer 23

Not critical for commercial airlines

Question 24

If V = 1400 kts or more and the Skin temperature = -55 + 259 = 204
what is it?

Answer 24

Critical skin temperature for military jets