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Tyskland NOTES > Engineering (updated 2024) > Flashcards

Engineering (updated 2024) Flashcards

1
Q

Name four different types of rotary-wing aircraft. To which general aircraft category do all these aircraft belong? What other kinds of aircraft are possible?

A

Helicopter, autogyro, gyrodyne, compound helicopter, convertiplane
Category: Heavier-than-air.
Other types: Lighter-than-air (e.g., balloons, airships).

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2
Q

Which rotorcraft requires torque compensation?

A

Single-rotor aircraft with main rotor shaft driven by engine

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3
Q

How is the torque compensated when a helicopter has more than one main rotor (equal number)?

A

Achieved by counter-rotating rotors (tandem or coaxial).

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4
Q

Name the SI base units.

A

Length: Meter (m).
Mass: Kilogram (Kg).
Time: Second (s).
Electric current: Ampere (A).
Temperature: Kelvin (K).
Luminous intensity: Candela (cd).
Amount of substance: Mole (mol).

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5
Q

Combine the base units to derive the units of force, pressure, work, and power.

A

Force: Newton (N). (mass * acceleration)

Pressure: Pascal (Pa). (Force/Area)

Work: Joule (J). (Force * distance)

Power: Watt (W). (Work/Time)

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6
Q

Convert the given velocity into: knots, ft/min, m/s, km/h.

100kt

5m/s

180ft/min

A

100knots:
- 10.127 ft/min
- 51,44 m/s
- 185,2 km/h

5m/s:
- 9,72 kt
- 984,25 ft/min
- 18 km/h

180 ft/min:
- 1,78 kt
- 0,914 m/s
- 3,29 km/h

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7
Q

Name and describe the three laws of motion developed by Newton. Give an example of each law.

A

First law (Inertia): Object in motion stays in motion (e.g., car braking).

Second law (F = ma): Force = mass × acceleration (e.g., pushing a cart).

Third law (Action-Reaction): Equal and opposite reaction (e.g., rocket launch).

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8
Q

Explain Bernoulli’s law.

A

Ptot = Pdyn + Pstat = constant
Is constant if:
- incompressible fluid
- closed system

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9
Q

Explain the principle of a nozzle and a diffusor.

A

Nozzle: area decreses, velocity increses

Diffusor: area incresas, velocity decreses

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10
Q

Describe the terms isobaric, isochoric, isothermal, isentropic, polytropic - change of state.

A

Isobaric: Constant pressure.

Isochoric: Constant volume.

Isothermal: Constant temperature.

Isentropic: Adiabatic process

Polytropic: Realistic change of states

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11
Q

Which are the two main principles of driving the main rotor?

A

Tip drive.

Shaft drive.

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12
Q

Which are the main consequences arising from these principles?

A

Tip drive: No torque effect, high fuel consumption.

Shaft drive: Requires torque balancing.

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13
Q

Which anti-torque systems do you know? Name the advantages and disadvantages of these systems.

A

Conventional tail rotor:
+ work on all helicopter sizes
- Tip vortices (LTE)

NOTAR:
+ No tail drive shaft, really safe
- Can’t be used with heavy helicopters

Shrouded tail rotor (fenestron):
+ No LTE
- Need more pedal input

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14
Q

Explain the terms truss frame design, monocoque design, and semi-monocoque design.

A

Truss: Framework of supports.

Monocoque: Load supported by the skin.

Semi-monocoque: Combines both.

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15
Q

What are the names of the different axes of orientation for an aircraft? Name the associated movements.

A

Yaw (vertical)
Roll (longitudinal)
Pitch (lateral).

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16
Q

Which (helicopter) control device does initiate which type of movement?

A

Cyclic: Pitch and roll.
Collective: Vertical movement.
Pedals: Yaw.

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17
Q

Name and describe the two main assemblies of a swashplate.

A

Stationary: Transfers pilot inputs to the rotor system.
Rotating: Adjusts blade pitch as it rotates with the rotor.

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18
Q

Which inputs are transferred to the swashplate?

A

Cyclic and collective

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19
Q

How and where does the coning angle develop?

A

Develops due to lift and centrifugal force in rotor blades.
Where: between horizontal plane and TPP

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20
Q

How is forward flight initiated with a helicopter? Describe the entire procedure from the pilot’s input on the stick to the resulting movement of the helicopter.

A

Cyclic input tilts rotor disk forward, generating forward thrust.

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21
Q

Which physical phenomenon calls for the use of lead-lag hinges? Explain this phenomenon using an example from everyday life.

A

Conservation of angular momentum.

I.E: skater increases rotation by pulling arms towards the body.

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22
Q

Which other effect causes lead-lag of the rotor blades? Where does this effect always occur?

A

Hooke’s joint effect.
always occur at 3 and 9 o’clock

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23
Q

Explain the lead/lag position of a 4-bladed main rotor during forward flight (counterclockwise rotation).

A

Advancing blade is leading (3 o’clock)

Retreating blade is lagging (9 o’clock)

Blade at 12 o’clock is lagging

Blade at 6 o’clock is leading

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24
Q

How and by which control input is the pitch angle of the tail rotor blades changed?

A

Controlled by pedals.

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25
Q

Which components are required for the safe operation of a hydraulic system?

A

Reservoir
Consumer
Monitoring system
Valve
Pump
Fluid
Lines
Filters

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26
Q

Which helicopter systems are usually operated hydraulically?

A

Flight controls, landing gear, rotor brake, ramps,

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27
Q

Which hydraulically operated system is of particular importance to a helicopter pilot?

A

Flight control system.

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28
Q

Which type of reservoir should be used in an aircraft hydraulic system? What is its most important characteristic?

A

Enclosed system (prevents cavitation).

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29
Q

Which types of pumps are used in hydraulic systems? In what essential respects do these pumps differ from each other?

A

Gear Pump: Constant flow.
Radial Pump: Low pulsation.
Axial Piston Pump: Variable flow, high volume.

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30
Q

Which type of pump is primarily used for flight control purposes?

A

Axial piston pump.

31
Q

Where are the most important hydraulic pumps mounted? And why?

A

Near main gearbox
WHY: so the pump can be driven by the main rotor during engine failure

32
Q

Name the different types of rotor configurations! Name one German Army helicopter type each for every type of system.

A

Fully articulated (e.g., CH-53).

Semi-rigid (e.g., Bell 206).

Rigid (e.g., EC-135).

33
Q

Which movements must the rotor blades be able to perform?

A

Flapping, lead-lag, feathering.

34
Q

How are these movements allowed in the different rotor configurations?

A

Fully articulated rotor:
Through hinges and bearings

Semi-rigid:
Teetering, hinge and within the blade

Rigid:
Within the blade

35
Q

Name advantages and disadvantages of the different rotor configurations.

A

Fully articulated: Smooth ride, complex.
Semi-rigid: Simple, risk of mast bumping.
Rigid: Low maintenance, high stress.

36
Q

How is a tail rotor provided with a delta 3 hinge affected by flapping? How does this angle come about?

A

Minimizes flapping so the tail rotor can be moved closer to the fuslage/tail

37
Q

Why is the conventional tail rotor installed on a pylon?

A

To counteract the roll

Or,

Increases efficiency and reduces vibrations.
And for safety

38
Q

What is the purpose of the transmission system?

A

Transfer or transmit forces
Changing direction of forces
Changing RPM

39
Q

Name five components of the transmission system.

A

Main gearbox, tail rotor driveshaft, clutch, freewheeling unit, rotor brake

40
Q

When is a centrifugal clutch required in a helicopter?

A

Unloaded start, piston/single shaft gas turbine

or,

It is required for gradual rotor engagement.

41
Q

Why is a centrifugal clutch unsuitable for autorotation?

A

Can’t disengage quickly in emergencies.

42
Q

Which component is suitable for power-off landings? Describe this component’s design/structure and explain how it works.

A

Freewheeling unit (auto-rotation)
Clamp coupling principle
Placed = between main gearbox and engine

43
Q

Describe the design/structure of the main drive shaft.

A

A metal tube between the engine and the main gear box able to transfer/withstand the torque through moveable/flexible couplings.

or,

High-strength alloy, torsion resistant.

44
Q

How can offset and torsion of the tail rotor drive shaft be compensated for? What causes these offsets?

A

How: Flexible couplings and bearings
What causes: Gust, hard landings, vibrations and turbulence

45
Q

How is the main gearbox lubricated?

A

Wet sump lubrication system

46
Q

Which information on the lubrication oil circuit can be displayed in the cockpit?

A
  • Pressure
  • Temperature
  • Chips
47
Q

How is the final stage of the main gearbox often designed? Why?

A

Planetary gear system (compact design).
Why: High reduction of RPM

48
Q

How are forces transmitted from the rotor system to the airframe?

A

Thrust bearings and dampers.

Rotor mast -》Main Gear Box -》Fuselage

49
Q

Which auxiliary systems are usually driven by the transmission system?

A

Hydraulic pump, electrical generator, cooling fans and lubrication

50
Q

In simple words define the term “stress” and “strain.”

A

Stress: Force per unit area. F/A = stress

Strain: Change in length divided by the original length.

51
Q

Which types of stress do you know? State one example for each type!

A

Bending = Rotor blades
Shearing = Fuselage
Tension = Rotor blades being pulled apart
Compression = Landing gear
Torsion = Drive shaft
Buckling = Fuselage

52
Q

Name the 3 types of loads a helicopter could be subject to! Also, give an example of how you as a pilot could affect these loads!

A

Static loads: Weight of fuel or passengers.

Dynamic loads: Hard landings (G-forces).

Cyclic loads: Cyclic inputs

53
Q

Name the most commonly used materials in aircraft engineering! Give some examples where a specific material is used for a certain part/component of the helicopter (old vs. modern materials, e.g., gearbox is typically made out of…).

A

Old: Steel, wood, titanium.

Modern: Kevlar, carbon fiber, aluminum.

Example: Gearboxes are typically made of steel or aluminum.

54
Q

Out of which two parts is a so-called “composite” consisting?

A

Fiber and Matrix

55
Q

What is a “sandwich structure”?

A

A lightweight core material (e.g., foam) sandwiched between two stronger outer layers (e.g., aluminum).

56
Q

List two advantages as well as disadvantages of modern composite materials!

A

Advantages: High strength-to-weight ratio, corrosion resistance.

Disadvantages: Expensive, harder to detect damage.

57
Q

Name the design principles in aircraft engineering! State an example for each principle!

A

Safe life: Replace parts before failure (e.g., rotor blades).

Fail safe: Multiple wing spars.

Damage tolerance: Structures can carry loads even if damaged.

Crash safety: Crash absorbing seats

58
Q

List 6 typically used attachment methods in aviation! Explain why so many different methods are required!

A

Bolts, rivets, welds, adhesives, clamps, pins, screws

Different methods are used to address varying load conditions, materials, and maintenance needs.

59
Q

You are about to lift off in a helicopter with a counterclockwise rotating main rotor (as seen from above). Where will the aircraft yaw with increasing engine power? Wich countermeasure do you have to take?

A

It will yaw to the right with increasing power.

Counteract: Push left pedal and thereby increase thrust from the tail roter

60
Q

You are in a hover flight with a single-rotor helicopter. The rotor is turning counter-clockwise (as seen from above). What will happen if you push the left and the right pedal respectively?

A

Left pedal: The blade pitch on the tail rotor will increase. Increasing thrust and torque will make the helicopter yaw to the left.

right pedal: The blade pitch on the tail rotor will decrease. Decreasing thrust and torque, will make the helicopter yaw to the right.

61
Q

Which are the main differences between gas turbines and piston engines with regard to their working cycles (place and time)? What happens to the pressure during the combustion process?

A
  • A piston engine: Same place, different times.
  • Pressure increase
  • A gas turbine: Different place, same time
  • Slight decrease of pressure.
62
Q

How are the individual strokes of an internal combustion engine called?

A

Intake - compression - combustion - exhaust.

63
Q

Name the different types of jet engines!

A
  • Scramjet
  • Ramjet
  • Turbojet
  • Turbofan
  • Turboprop
  • Propfan
  • Rockets
    ▪ Solid fuel
    ▪ Liquid fuel
64
Q

Which main assembly groups does a turboshaft engine consist of?

A
  • Intake
  • Compressor
  • Combustion chamber
  • N1 turbine (compression)
  • N2 turbine (free power turbine)
  • Exhaust
65
Q

Which are the main differences between jet engines and turboshaft engines?

A
  • Jet engines produces thrust force.
  • Turboshaft engines produces shaft power.
66
Q

What is the purpose of a turboshaft engine’s compressor?

A

Increase static pressure to =
- Provide enough air for combustion
- Clear combustion direction

67
Q

Which main dangers are compressors exposed to? How can these dangers be avoided?

A
  • FOD (Foreign object damage)
    o I.e. sand erosion and glassing of the engines -> use filter
  • Compressor stall or surge – Avoid fast accelerations.
68
Q

Describe the principal structure/design of a compressor! How do pressure and temperature behave in the different stages?

A

A compressor consists of rotating blades (rotors) and stationary blades (stators) arranged in stages. Rotors increase air velocity, and stators convert this velocity into pressure.

Pressure: Increases with each stage.
Temperature: Rises due to compression.

69
Q

Name the different types of combustion chambers! Which type is the most common one used in helicopters? Why?

A

Types of combustion chambers:
- Annular Combustion Chamber
- Reversed Annular Combustion Chamber
- Tubular Combustion Chamber
- Reversed Tubular Combustion Chamber
- Combination Combustion Chamber

Most common in helicopters: Reversed Annular Combustion Chamber
Why: Compact, save space.

70
Q

Into which airflows does the airstream split up in the combustion chamber and what is the purpose of these airflows respectively?

A

Primary air (20-25% of the airflow):
- Ignition for the flame

Secondary air (75-80% of the airflow):
- Centering the flame.
- Provides a cooling “coating” for the flame.
- Flame cut off.

71
Q

Which turbine types are used in twin turboshaft engines? Which of the two turbines is first passed through by the airstream?

A
  • Compressor turbine (N1)
  • Free power turbine (N2)

”N1” is passed through first.

72
Q

Describe the design/structure of a turbine and explain how pressure and temperature behave within this type of turbine!

A
73
Q

Describe the design of the exhaust of turboshaft engines!

A

Air outlet = exhaust diffusor
- Low thermal detectability
- Pressure decrease
- Noise level

74
Q

What type of lubrication system is used in turboshaft engines?

A

Dry sump

Tyskland NOTES (21 decks)

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