Engine Performance

Question 1

Which of the following reduce volumetric efficiency: throttling back, increased rpm or heating of the inlet air (e.g. carburettor heat).

Answer 1

all of them do

Question 2

Indicated power = P.L.A.N.K. What do the letters in this formula stand for?

Answer 2

P = net IMEP
L = length of stroke
A = area of top of piston
N = speed of engine
K = number of cylinders

Question 3

Power is the ______ of doing work. It is measured by force times distance over ______.

Answer 3

rate; time

Question 4

Indicated Mean Effective Pressure (IMEP) must be measured to be able to calculate the indicated power of an engine. Net IMEP is the average cylinder pressure during the power stroke, less the average pressure during ______ ______ ______ ______.

Answer 4

the other three strokes

Question 5

The power output of light aircraft piston engines is measured in horsepower (HP). One HP is equivalent to ______ ft lb of work per second and equals approximately ______ of a kilowatt (kW).

Answer 5

550; 3/4

Question 6

Mechanical efficiency is brake power divided by ______ power, expressed as a percentage. At the most efficient operating rpm, mechanical efficiency approaches ______%.

Answer 6

indicated; 90%

Question 7

At higher speeds, a maximum of about ______% of the brake power delivered to the propeller by the engine, will be converted into thrust power by the propeller.

Answer 7

80%

Question 8

In low pressure/high temperature and humidity conditions, a normally-aspirated engine (may not / will always) be able to develop its rated power.

Answer 8

may not

Question 9

The brake power of a piston aircraft engine is the (actual / indicated) power output at the (propeller hub / inside of the engine).

Answer 9

actual; propeller hub

Question 10

How are brake power, indicated power and friction power related?

Answer 10

Brake power = indicated power - friction power

Question 11

Torque is a force that produces (or tends to produce) a ______ or ______ motion in an object. It is measured by the force times the ______ distance between it and the pivot point.

Answer 11

twisting or turning; perpendicular

Question 12

Friction power (includes / does not include) the power required to drive engine accessories.

Answer 12

includes

Question 13

Engine torque is the amount of turning effect the engine can produce on the crankshaft. Propeller torque is the force that (aids / resists) this turning motion. At constant rpm, propeller torque is equal and (opposite to / in the same direction as) engine torque.

Answer 13

resists; opposite to

Question 14

Thermal efficiency is the ratio between the amount of useful work done by the engine and the amount of heat energy consumed from the fuel. The thermal efficiency of a four-stroke engine is in the order of (80% / 50% / 20%).

Answer 14

20%