Engines

Question 1

What setting does mixture need to be set at sea level?

Answer 1

Full rich

Question 2

What happens to the mixture as an airplane increases altitude?

Answer 2

The mixture becomes more rich as air density decreases with altitude because fuel flow remains the same.

Question 3

What happens to an engine running too rich?

Answer 3

It runs roughly and loses power

Question 4

For takeoff and climb in a Skyhawk, what altitude can the mixture be leaned for smoother operation?

Answer 4

3000 feet

Question 5

At cruise, the EGT is used for leaning the engine at what percentage throttle (or less)?

Answer 5

75%

Question 6

What happens to EGT as the mixture is leaned?

Answer 6

It will rise until it reaches a peak

Question 7

What happens to fuel flow as the mixture is leaned?

Answer 7

It will decrease

Question 8

What happens to EGT as the mixture is leaned past its peak?

Answer 8

It will start to decrease

Question 9

What is the recommended leaning technique/temperature?

Answer 9

Once EGT peak is reached, lean the mixture to 50 degrees rich of peak EGT

Question 10

What is the recommended leaning technique for best economy?

Answer 10

Leave the mixture set to peak EGT.

Question 11

What needs to be done with mixture anytime the throttle or altitude is changed?

Answer 11

It needs to be reset/adjusted

Question 12

How is proper leaning set during cruise without an EGT instrument?

Answer 12

Lean the engine until it starts to run roughly, then enrich until it runs smoothly.

Question 13

Why should you never lean at high power settings?

Answer 13

Serious engine damage can occur if leaning over 75% power

Question 14

What should always do with the mixture before increasing the power?

Answer 14

Enrich

Question 15

What are two problems that can cause abormal combustion in an engine?

Answer 15

Detonation and pre-ignition

Question 16

When does detonation occur?

Answer 16

When the air/fuel mixture in the cylinder is exposed to excessive temperature and spontaneously combusts

Question 17

How does a pilot know if detonation has occured?

Answer 17

A loud jolt or sound, and a sudden decrease/loss of engine power

Question 18

What is pre-ignition? What causes pre-ignition?

Answer 18

The uncontrolled ignition of the fuel/air mixture before the spark plug fires.
Excessively hot exhaust valves or spark plug ends can cause pre-ignition

Question 19

What is the best way to deal with detonation and pre-ignition?

Answer 19

Reduce power, increase mixture, and open cowl flaps