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Part 2 > SYSTEMS PT2 > Flashcards

SYSTEMS PT2 Flashcards

1
Q

Torque

A

The ability of a force to produce a turning motion in an object

T (Nm) = F x D

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2
Q

Engine torque

A

The turning affect (torque) that the engine can produce on the crankshaft

Et turns the prop

It is produced in a pulsed manner during the power stroke (for a given cylinder)

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3
Q

Brake power

A

The actual power output from the crankshaft (the power delivered to the prop hub)

Brake Power = indicated power - friction power

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4
Q

Indicated power

A

The power developed inside the cylinders by combustion

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5
Q

Net indicated mean effective pressure (IMEP)

A

The average pressure during the power stroke minus the average pressure of the other three strokes

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6
Q

Friction power

A

Power lost in overcoming friction in the engine and driving engine accessories

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7
Q

Rated power

A

Brake power developed by an engine in good condition under standard conditions at the stated RPM (and MAP)

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8
Q

Rated or ‘critical’ altitude

A

The altitude where RP is developed at full throttle

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9
Q

Thermal efficiency

A

The ratio between the amount of heat energy contained in the fuel and the mechanical work it can create

Thermal loss through cooling, expulsion of gases, overcoming friction

Typical TE of a four-stroke engine may be as low as 20%

Largely determined by the materials used in the engine

Higher compression ratio - higher thermal efficiency (CR limited by the onset of detonation)

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10
Q

How does a shimmy damper work?

A

Hydraulic damping (piston type)

Case attached to upper shock strut cylinder, shaft attached to lower shock strut cylinder and piston inside shimmy damper. When the lower strut cylinder tries to shimmy, hydraulic fluid is forced through a bleed hole in the piston. The restricted flow through the bleed hole dampens the oscillation.

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11
Q

Volumetric efficiency

A

How efficiently the engine draws in the charge

  • drag of the charge from the walls/bends in manifold
  • increase in temp while passing from manifold into cylinder

Decreases the VE, aka the amount of charge inducted into the cylinder is less than the piston leaves room for.

Good VE occurs with the throttle open, good manifold/valve design, cool air, and proper valve timing.

Increasing RPM decreases VE.

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12
Q

Mechanical efficiency

A

Part of overall efficiency (Thermal efficiency)

Ratio between mechanical power input (indicated power) and power output (brake power)

Can approach 90% at most efficient RPM

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13
Q

Tyre bead

A

Embedded wire that anchors the tire to the carcass

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14
Q

Tyre Flippers/turn-ups

A

Layer of rubber/fabric around bead to insulate (heat) from the carcass

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15
Q

Tyre apex strips

A

Streamlined rubber strips around beads, good contact

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16
Q

Tyre chafers

A

Wrap around end of carcass piles and beads to prevent fitmet damage

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17
Q

Tyre breakers

A

Fabric plies under the tread to reduce shock and prevent direct carcass damage

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18
Q

Tyre belts

A

Circumferential plies between tread and carcass, reinforcement to add strength to tread

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19
Q

Tyre sidewall

A

Rubber from tread to bead, protects carcass

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20
Q

Tyre aspect ratio

A

Low aspect ratio for high speed
High aspect ratio for rough field ops

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21
Q

Tyre pressure

A

under 40 - unimproved soil/rough terrain
40-75 - improved airfields
75-125 - unlimited ops for large ac on improved surface rwy (concrete/asphalt)
over 125 - unsuitable for light a/c

22
Q

Cyclic ______ stress causes ______

A

Tensile, fatigue

23
Q

Torque on a component results in ____ stress

A

Shear

24
Q

Elastic limit

A

Stress beyond which the component will nor regain its initial shape following the removal of the applied load

25
Q

AFCS components

A

Gyros
Amplifier
Servos
Controller
Feedback

26
Q

AFCS

When the initial signal and feedback signal are equal in magnitude:

When the signal reaches a zero:

A

The servo stops moving

The feedback signal returns the control to a streamlined position

27
Q

Battery op

A

Dissimilar metals (electrodes) in a chemical solution (electrolyte), electrons attract to -ve electrode. When connected in circuit electrons flow -ve to tve.

Apx 2v per cell (12V bat, 6 cells)

28
Q

Primary cell

A

Dry (paste) cell, cannot be recharged.

29
Q

Secondary cell

A

Wet (liquid) or dry (paste), can be recharged.

Lead-acid or
Nickel-cadmium

30
Q

Ni-Cad

A

Low internal resistance
Voltage remains constant until discharged
High charge/discharge rates

31
Q

Thermal runway

A

Associated with Ni-Cad

High charge/discharge rates cause high temperature and breakdown within cell, current increases and more heating, creating a cycle.

32
Q

Li-Po

A

Rechargeable battery with semisolid polymer electrolyte instead of liquid, very lightweight.

Flammable electrolyte explosive hazard, becomes pressurised if damaged and if charged too quickly could short circuit.

33
Q

Is the impeller situated before or after the carb in a supercharger and in a turbocharger?

A

Supercharger - after (compresses charge)
Turbocharger - before (compresses air)

34
Q

Inlet manifold purpose

A

Duct charge from the carb, divide it, and deliver it to cylinders

35
Q

Leak in normally aspirated engine manifold effect

A

Weakening of mixture, possible detonation

36
Q

Leak in supercharged engine manifold effect

A

Loss of power, loss of MAP/charge at high power settings

37
Q

Exhaust manifold purpose

A

To collect products of combustion and discharge them into the airstream, must be well sealed. Leaks may result in toxic gases (co2) entering cabin and presents fire hazard.

38
Q

What is the purpose of supercharging

A

Increase the density of the charge prior to it entering the cylinder, maintain sea level power at higher altitude.

39
Q

Geared supercharger

A

Impeller driven by the engine (crankshaft) via a gear box. Mixture enters impeller and is accelerated centrifugally into the diffuser which slows down the mixture converting velocity to pressure. Mixture then goes to induction manifold and into cylinders.

MAP controlled by pilot, servo piston and aneroid capsule senses and controls throttle butterfly position to maintain MAP.

40
Q

Turbo charger

A

Exhaust gases drive turbine, turbine speed governed by position of waste gate. Principle same as geared but only air is fed through the impeller, FCU situated ahead.

Waste gate open - no supercharging
Waste gate closed - full supercharging

41
Q

What is the most important factor affecting shimmy

A

Trail

42
Q

Anti-icing heated air

A

Hot air from compressor bleed, or heated by engine exhaust or combustion heater, circulated through ducting (piccolo tube) in LE of wing and tail

43
Q

Anti-icing electric

A

Usually for static ports, pitot head, aoa vanes.
Windscreen may be heated by conductive wires embedded in the laminate.

44
Q

Napier system

A

Shaft driven by motor, as ice builds up the blade cuts it off. The more ice, the harder the motor needs to work to rotate the shaft.

45
Q

Chemical icing

A

anti-icing

Isopropyl alcohol or mix of alcohol and ethylene glycol
Lowers fz point of water, provides a slick surface

de-icing
on ground spraying heated fluid, followed with a thicker solution prior to t/o
in flight prop/LE sprayed

46
Q

De-icing boots

A

Internal airways fed by compressor bleed air, exhaust from vac pump, cylinder of compressed gas, engine driven compressor, allow boots to inflate cracking ice.

47
Q

Def of icing conditions

A

Less than +5C in visible moisture

48
Q

Centrifugal tacho

A

Flyweights convert rotation of drive cable into movement of pointer, increased RPM flyweights move outward.

49
Q

Drag cup tacho

A

Permanent rotating magnet on end of drive cable creates rotating magnetic field, sets up eddy currents in surrounding (but not touching) drag cup. Interaction causes torque on the drag cup which rotates it until balanced with tension in attached hairspring which links to a pointer.

50
Q

DC tacho

A

V produced by generator proportional to engine RPM and indicated by voltmeter which is calibrated to read in RPM.

If voltage lowers due to fault in system it will read incorrectly

51
Q

AC tacho

A

Generator produces 3 phase AC with a frequency proportional to RPM, this AC fed to synchronous system rotating it at same speed as generator. Motor then attached to drag cup which converts motor rpm to pointer against a spring.

52
Q
A

Part 2 (7 decks)

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