The Engine

Question 1

Valve overlap increases the ______ of charge induced into the cylinder, improves ______ of the waste gases, and aids ______ of the upper parts of the cylinder.

Answer 1

weight (or amount); scavenging; cooling

Question 2

The onset of combustion at too early a point in the cycle through pre-ignition can lead to a loss of ______ and to serious engine ______.

Answer 2

power; damage

Question 3

The heat energy from the combustion process causes the ______ of the gases in the confined space of the cylinder to rise suddenly, which pushes the piston down in the cylinder.

Answer 3

pressure

Question 4

A two-stage energy conversion process is involved in the piston engine. ______ energy in the fuel is first converted to ______ energy by combustion, and then to ______ energy by the action of the piston.

Answer 4

Chemical; heat; mechanical

Question 5

In aero engines, two ______ ______ are fitted to each cylinder to ignite the mixture at the right time.

Answer 5

spark plugs

Question 6

In a typical piston aero-engine, the fuel-air mixture is ignited by ______ ______ situated on opposite sides of the cylinder head.

Answer 6

spark plugs

Question 7

The pistons are normally cast from______ ______. Steel piston ______ seal the piston within the cylinder, preventing both the loss of combustion pressure and the passage of ______ into the combustion chamber.

Answer 7

aluminium alloy; rings; oil

Question 8

Diesel engines use (compression / spark ignition). A typical system of preheating the combustion chamber to facilitate ignition when starting is to use ______ plugs.

Answer 8

compression; glow

Question 9

The horizontally-opposed piston engine has its cylinders arranged (on each side of / above / below) the crankshaft?

Answer 9

on each side of

Question 10

Valve lag involves the ‘late’ closing of the ______ valve on the induction stroke.

Answer 10

inlet

Question 11

The camshaft rotates at (half / twice) the speed of rotation of the crankshaft.

Answer 11

half

Question 12

Valve overlap involves the period when both valves are open for a short period around TDC at the end of the ______ stroke and at the beginning of the ______ stroke.

Answer 12

exhaust; induction

Question 13

In the compression stroke, both valves are closed. The fuel-air charge becomes compressed and as a result its ______ rises considerably.

Answer 13

temperature

Question 14

Cylinder heads are fitted at the top of each cylinder to enclose the ______ space. They are normally constructed of ______ alloy and also have a large number of ______ fins.

Answer 14

combustion; aluminium; cooling

Question 15

During the induction stroke, the inlet valve is (closed / open). As the piston descends, pressure in the cylinder is (increased / lowered) and the fuel-air mixture flows in because the pressure in the intake manifold is (higher / lower).

Answer 15

open; lowered; higher

Question 16

Valve lag allows more time for the fuel-air ______ to enter the cylinder.

Answer 16

charge

Question 17

The piston engine burns a mixture of ______ and ______ in the combustion chambers.

Answer 17

fuel and air

Question 18

One complete cycle of a four-stroke engine requires (one / two / four) complete revolutions of the crankshaft.

Answer 18

two

Question 19

Detonation causes wildly oscillating ______ fluctuations within the cylinder and can lead to (overheating / overcooling), deterioration of ______ surfaces, and a (loss of / gain in) power.

Answer 19

pressure; overheating; bearing; loss of

Question 20

In broad terms, a diesel aero engine can be expected to produce the same power as an (AVGAS / AVTUR) engine of more than (twice / three times / four time) its cylinder capacity.

Answer 20

AVGAS; twice

Question 21

Cylinder barrels are normally constructed of ______ and have a large number of closely-spaced external cooling ______.

Answer 21

steel; fins

Question 22

The connection between the connecting rod and the crankshaft is made through a (big end / main) bearing. The crankshaft is held in place by, and runs in, (big end / main) bearings.

Answer 22

big end; main

Question 23

Pre-ignition is the ignition of the charge by some means (before / after) normal ignition is timed to occur.

Answer 23

before

Question 24

The ideal spark advance will be somewhere between 45 and 5 degrees before TDC depending on a number of factors. To cope with these variables, most light aircraft engines have a fixed spark advance set at an optimum point of about ______ degrees before TDC.

Answer 24

25 degrees

Question 25

When they are not held open by the camshaft, the valves are held closed by strong ______ to provide an ______ tight seal.

Answer 25

springs; air

Question 26

Valve lead involves the ‘early’ opening of the ______ valve on the power stroke.

Answer 26

exhaust

Question 27

Valve lead assists scavenging of the ______ gases by giving them more time to escape, and by utilising pressure left in the cylinder to force them out in a process called ______.

Answer 27

waste (or exhaust); blowdown

Question 28

Taken together, valve lag, lead and overlap enable the engine to ‘______’ better and produce more power for a given weight of fuel in the mixture.

Answer 28

breathe

Question 29

The function of the inlet valve is to open at the right time to admit the ______ ______ mixture. The function of the exhaust valve is similarly to provide an outlet for the ______ gases.

Answer 29

fuel/air; exhaust

Question 30

The main function of the camshaft is to operate the ______ at the right time.

Answer 30

valves

Question 31

The ‘most effective’ crankshaft angle is when the connecting rod and the crank web are at ______ degrees to one another. This occurs typically when the piston is at 62 to 72 degrees crank ______. Peak cylinder pressure, however, is normally about 15 to 20 degrees (after / before) TDC.

Answer 31

90 degrees; angle; after

Question 32

Most light aircraft have the propeller directly connected to the crankshaft. The power generated in the engine is therefore transmitted to the propeller by the rotating engine crankshaft and the propeller produces a (lift / weight / thrust / drag) force.

Answer 32

thrust

Question 33

Detonation is the spontaneous combustion (or ______ ) of a part of the charge (before / after) normal ignition has taken place.

Answer 33

explosion; after

Question 34

Detonation and pre-ignition have the potential to cause ______ to an engine if they are allowed to continue when they occur.

Answer 34

damage

Question 35

Each valve operates (once / twice) in every two revolutions of the engine. This means that for an engine running at 2,000 rpm, the valves open and close ______ times a minute.

Answer 35

once; 1000

Question 36

Name the four strokes of the four-stroke cycle.

Answer 36

Induction; Compression; Power; Exhaust

Question 37

So that the peak cylinder pressure is developed at the right place in the cycle, the timing of the ignition must normally be (advanced / retarded).

Answer 37

advanced

Question 38

A four cylinder engine therefore delivers ______ power impulses in every single revolution of the engine. A six cylinder engine delivers ______ power impulses per revolution.

Answer 38

two; three

Question 39

The piston is connected to the crankshaft by a ______ rod, which converts the reciprocating motion of the piston into a ______ motion of the crankshaft.

Answer 39

connecting; rotary (or turning)

Question 40

Diesel engines (do / do not) have a carburettor. In a diesel aero-engine, the air required for combustion is typically processed through a ______ charger and an ______ before passing to the cylinders. Both of these measures increase the ______ of the charge, therefore increasing the ______ produced by the engine.

Answer 40

do not; turbo; intercooler; density; power

Question 41

Prior to completion of the power stroke, the ______ valve is opened.

Answer 41

exhaust

Question 42

Diesel engines (are / are not) susceptible to knock. Because of this, it is unlikely that diesel engines will be designed to operate with a compression ratio of more than ______.

Answer 42

are; 20:1

Question 43

The (RPM / POWER) output of diesel engines is controlled basically by varying the amount of ______ being ______ into successive air charges. In a modern engine, once the pilot sets the power lever this control is achieved through a unit called the (ECU / waster gate).

Answer 43

POWER; fuel; injected; ECU

Question 44

The basic differences between a turboprop and a reciprocating engine are:

a) . Power production in the turboprop is ______ while that of the reciprocating engine is ______.
b) . For engines of a given size, the turboprop is (heavier / lighter), and produces (more / less) power.
c) . While they are more expensive, turboprops are (more / less) reliable, and have longer mean times between ______.

Answer 44

a) . continuous; intermittent
b) . lighter; more
c) . more; overhaul