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ATPL - [Mod 2] AGK - Engines > 07. Piston Engine Power Augmentation > Flashcards

07. Piston Engine Power Augmentation Flashcards

1
Q

Normal aspirated engine

The charge mass that can enter the cylinder is dependant on what 2 things regarding air within the inlet manifold

A
  1. DENSITY
  2. PRESSURE

Pg 165

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2
Q

Density varies with which 3 things

A
  1. Temperature
  2. Altitude
  3. Humidity

Pg 166

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3
Q

Density varies with ____, ____, and ____, so the best means to determine engine power is by what

A
  1. TEMPERATURE
  2. ALTITUDE
  3. HUMIDTY
  4. DENSITY ALTITUDE

DA = PA + ((Actual Temp - ISA temp) x 118)

Pg 166

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4
Q

What is the density altitude formula

A

Density altitude = Pressure altitude + (Diff. between actual & ISA Temp x 118)

DA = PA + ((Actual - ISA) x 118)

EXAMPLE:
An aircraft plans to take off from an airfield at an altitude of 4000ft.
The OAT is 21℃.
The ISA temp for 4000 ft should be 7℃
ISA temp = 15 - (alt x 2) ⋉ 15 - (4 x 2) ⋉ 15 - 8 = 7℃
21 - 7 = 14
4000 + (14 x 118) ⋉ 4000 + 1652 = 5,652 ft
This means the max power produced by the engine at this airfield on this day is equivilant to an engine operating at almost 5,700 ft

Pg 166

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5
Q

Engines produce the most power when they are HOT & HIGH or when they are LOW & COLD

A

LOW and COLD

Idea would be winter sea level conditions when air is cold, dry, and dense

Pg 166

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6
Q

Complete the following graph that shows a Normally Aspirated Engine Performance
LINK HERE

A
  1. Performance available - Sea Level
  2. Performance available - Altitude
  3. TAS
  4. Power

LINK HERE

Pg 167

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7
Q

Piston Engine Power & Performance

When considering power output, the efficiency of which component of the engine must be taken into account

A

PROPELLER

Pg 167

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8
Q

At high atmospheric densities, the engine produces more power and needs MORE or LESS power to turn the propeller

A

MORE

Pg 167

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9
Q

Propeller efficiency varies significantly with ____ as well as density

A

AIRSPEED

Pg 167

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10
Q

What are the 3 operational descriptions of power output

A
  1. Take-off
  2. Rated
  3. Cruise

  1. Take-off - is the max power the engine can produce
  2. Rated - Power available under specific conditions
  3. Cruise - Expressed normally as a percentage of max power

Pg 168

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11
Q

Normally aspirated engines mass of charge entering the cylinder will INCREASE or DECREASE with increasing density altitude

A

DECREASE

Read “increasing density altitude” as increase in altitude and not as density increasing.
Density increasing means thicker, denser air, where as altitude increasing means a decreasing density.
Remember - Density Altitude is just a point in the sky (altitude) at which the aircraft is at

Pg 169

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12
Q

By ____ ft, a normally aspirated engine will have lost ____% of its power

A
  1. 20,000 ft
  2. 50%

Pg 169

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13
Q

Supercharging

What type of system helps maintain normal power output during the climb

A

COMPRESSOR SYSTEM

Altitude boosted supercharger

Pg 169

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14
Q

Supercharging

A compressor system that helps maintain normal power output during the climb is known as what

A

ATLTITUDE BOOSTED SUPERCHARGER

Pg 169

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15
Q

What are the 2 types of supercharging devices

A
  1. Supercharger
  2. Turbocharger

Pg 169

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16
Q

A superchargers compressor is driven by what

A

BELT from the CRANKSHAFT

Pg 169

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17
Q

A turbochargers compressor is driven by what

A

EXHAUST GAS

Pg 169

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18
Q

What does MAP stand for

A

MANIFOLD ABSOLUTE PRESSURE
(MAP)

MAP guage is a gauge that measures the manifold absolute pressure

Pg 170

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19
Q

What does a MAP GAUGE measure

A

AIR PRESSURE in INLET MANIFOLD

Gauge measures the pressure of the air being supplied by turbocharger into the inlet manifold

Pg 170

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20
Q

What is the difference in terms of measurements between a boost gauge and a manifold absolute pressure gauge (MAP)

A

BOOST - measures pressure relative to standard sea level
BOOST - can be negative or positive
MAP - pressure displayed as an absolute pressure

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21
Q

If the MAP and boost gauges indicate atmosopheric pressure whens stopped on the ground, what is this known as

A

STATIC BOOST

Pg 170

22
Q

Static boost is a term used to describe what

A

Engine stopped on the ground
MAP and BOOST gauges indicate atmospheric pressure

Pg 170

23
Q

What does a turbocharger unit comprise of

A

TURBINE linked to IMPELLER

Pg 172

24
Q

What drives the turbine in a turbocharger engine

A

EXHAUST GAS

Exhaust gas drives the turbine, which then drives the impeller

Pg 172

25
Q

How does an impeller in a turbocharger engine impart energy to the air.

A

ACCELERATES AIR to CIRCUMFERENCE

Pg 172

26
Q

Impeller vanes are designed to CONVERGE or DIVERGE air

A

DIVERGE

Pg 173

27
Q

As air diverges to the impeller circumference, the air increases in what 3 things

A
  1. Velocity
  2. Pressure
  3. Temperature

Pg 173

28
Q

What is the name of the component which trades velocity for a further increase in pressure and temperature in a turbochargerd engine

A

DIFFUSER

Pg 173

29
Q

How does a diffuser function in a turbocharger engine

A

Trades VELOCITY for increase in PRESSURE & TEMPERATURE

Usually formed by an expanding duct

Pg 173

30
Q

Some turbochargers use what to cool air before entering the cylinder

A

INTERCOOLERS

Pg 173

31
Q

What are 2 key advantages of a turbocharger

A
  1. NO ENGINE POWER
  2. RPM BOOST

Engine Power - No power is taken from the engine to drive the turbocharger
As RPM increases, velocity of exhaust gas increases, which increases the impeller speed, thus icnreasing the amount of boost

Pg 173

32
Q

What is 1 key disadvantage of a turbocharger

A

SPOOL TIME

Turbo lag

Turbine is driven by exhaust gases. When RPM increased, it takes a finite amount of time to spool up the turbocharger

Pg 173

33
Q

What is turbo lag

A

LAG in BOOST DELIVERED

Turbine is driven by exhaust gases. When RPM increased, it takes a finite amount of time to spool up the turbocharger

Pg 173

34
Q

If the amount of exhaust gas output is not controlled to drive the turbine, what can this lead to

A

OVER BOOSTING

Excessive mass of charge is pumped into the cylinders

Pg 175

35
Q

A sophisticated method of boost control is what

A

WASTE GATE SYSTEM

Pg 176

36
Q

What happens to the exhaust gases when the waste gate system is open and when it is closed

A

OPEN - Exhaust gases go to atmosphere
CLOSED - Exhaust gases to go turbine

Pg 176

37
Q

The waste gate system is fitted PARALLEL or IN SERIES to the turbocharger.
The waste gate system is fitted UPSTREAM or DOWNSTREAM to the turbocharger

A
  1. PARALLEL
  2. UPSTREAM

Pg 176

38
Q

What is the name of the component that constantly controls and maintains the right amount of boost to the turbocharger

A

WASTE GATE CONTROLLER

Pg 177

39
Q

What does the waste gate controller do

A

MAINTAINS and CONTROLS BOOST

Maintains the right amount of boost across a range of ambient conditions

Pg 177

40
Q

As altitude increases and air density decreases, the waste gate controller will OPEN or CLOSE

A

CLOSE

Closes to try and maintain the optimum level of boost delivered to the cylinders

Pg 177

41
Q

What is the term given to the point where the waste gate controller has completely closed

A

CRITICAL ALTITUDE

Pg 177

42
Q

At critical altitude what will happen to MAP pressure and engine power

A

REDUCES

Pg 177

43
Q

On a supercharger engine, the equivilant of critical altitude is known as what

A

FULL THROTTLE HEIGHT

Pg 177

44
Q

What is a disadvantage of reaching critical altitude in terms of exhaust gases

A

BACK PRESSURE
VOLUMETRIC EFFICIENCY

Volumetric efficienty in the cylinder due to back pressure

All exhaust gas is directed towards the turbine, which causes back pressure
THis means some exhaust lags, this remaining in the cylinder, reducing the volumetric efficiency

Pg 177

45
Q

What is the waste gate position for each of the following stages of flight, and any other significant considerations;

  1. Engine start
  2. Idle Power
  3. Take off
  4. Climb
  5. Critical Altitude
  6. Above critical altitude
A
  1. HELD OPEN - spring pressure
  2. FULLY CLOSED - MAP pressure low as little exhaust gas
  3. PARTIALLY OPEN
  4. CLOSED - Turbine RPM increases
  5. FULLY CLOSED - Turbine at max speed
  6. FULLY CLOSED - Max value of MAP reduces

Pg 178

46
Q

In a supercharger system how does the intercooler cool the air entering the engine

A

COLD RAM AIR

Ducted from atmosphere and passed over induction manifold

Pg 179

47
Q

What is rated power

A

MAX POWER at which engine can be operated CONTINUOUSLY

Pg 180

48
Q

What is rated boost

A

MANIFOLD PRESSURE allowed for RATED POWER

Pg 180

49
Q

Supercharger

If an aircraft climbs at rated boost to the full throttle height, it is said to have reached what

A

RATED ALTITUDE

Rated altitude is the maximum altitude at which maximum continous power can be maintained on a supercharged engine

Pg 180

50
Q

What is a supercharged engine at significant risk from with rapid throttle movements

A

THERMAL SHOCK

Pg 180

ATPL - [Mod 2] AGK - Engines (23 decks)

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