Exercise 3 - Ancillary Controls

Question 1

Mixture Control - What is it?

Answer 1

• Allows pilot to adjust mixture of fuel and air to adapt to changing conditions

Question 2

Mixture Control - Why We Need It

Answer 2

• Air density decreases
• proper combustion requires a correct mixture by mass

Question 3

Mixture Control - How it Works

Answer 3

• “leaning” the mixture by adjusting out will reduce fuel mass
• good for efficient cruise at higher altitudes and higher humidity
• “enriching” the mixture will increase the fuel mass
• good for maximum power at low altitudes

Question 4

Mixture Control - Factors Affecting Air Density

Answer 4

• Altitude, density decreases with increase in altitude
• Temperature, density decreases with increase in temperature
• Humidity, density decreases with increase in humidity
• Carburetor Heat increases temperature, reducing density

Question 5

Mixture Control - How We Use It

Answer 5

• POH contains detailed instructions
  In General:
• Mixture should be slightly lean of full rich for taxi (1-2 twists)
• Full rich for takeoff
• Full rich for climb
  -“rich best power” for cruise, lean to maximum RPM
• Progressively rich the mixture for descent
• Full rich for landing
• Generally better to be slightly on the rich side

Question 6

Mixture Control - Too Rich (Excessive Fuel)

Answer 6

• Will not develop full power
• Will run unevenly
• May operate cooler than desirable
• Fuel is wasted
• Spark plug fouling may occur
• Range is Reduced

Question 7

Mixture Control - Too Lean (Excessive Air)

Answer 7

• Power will be lost
• Will run rough/vibrate
• May operate hotter than is desirable
• Damage may occur from prolonged operation

Question 8

Carburetor Heat - Why We Need It

Answer 8

• May not need it
• Fuel injected aircraft do not have carburetors, meaning they don’t need a carburetor heat system
• Air is cooled up to 30º as it passes through the throttle (pressure drops and fuel vaporization both cause cooling)
• This can cause ice to form and eventually block airflow to the engine

Question 9

Carburetor Heat - What it Does

Answer 9

• Allows us to direct hot air into the carburetor, melting ice

Question 10

Carburetor Heat - How it Works

Answer 10

• Air that has beed heated by the exhaust system is directed into the carburetor
• Any ice that is present will be melted and new ice will not form

Question 11

Carburetor Heat - Carburetor Ice

Answer 11

• Formation is a function of environmental conditions and power setting
• Forms in high humidity conditions between -5ºC and 30ºC
• Formation is most severe between -5ºC and 15ºC
• Low Power significantly increases risk due to restriction of the throttle package
• Ice buildup reduces engine power (visible in RPM indications)
• Must be vigilant because ice can develop rapidly

Question 12

Carburetor Heat - Proper Use

Answer 12

• Carb Heat should be on anytime the RPM is outside of the normal operating range (green arc) in flight
• Applying carb heat first when reducing power is key (might not work if engine is already too cool)
• Set carb heat cold last when increasing power
• When carb heat is turned on and there is a decrease in RPM, there is no icing
• When carb heat is turned on and there is no change or an increase in RPM there is icing

Question 13

Carburetor Heat - Use Considerations

Answer 13

• Carb heat is unfiltered, minimize use on ground
• Hot air is less dense and enriches mixture so RPM will reduce when carb heat is hot
• Carb heat can raise the temperature into the carb icing range in extremely cold conditions

Question 14

Cabin Heating and Cooling - Why We Need It

Answer 14

• Windshield defogging
• Pilot Comfort

Question 15

Cabin Heating and Cooling - What It Does

Answer 15

• Supplies fresh air to cabin (either hot or cold)

Question 16

Cabin Heating and Cooling - Cabin Heat

Answer 16

• Outside air is ducted past the engine exhaust pipes, then into the cabin
• Cracks in muffler shroud can allow carbon monoxide into the cabin so pay attention to indicators

Question 17

Cabin Heating and Cooling - Fresh Air

Answer 17

• Outside air is vented directly into cabin in multiple places
• Pilot controls how much of each is entering the cabin, allowing some control over final temperature

Question 18

Cabin Heating and Cooling - Windshield Defoggers

Answer 18

• Vents on the Glareshield
• Formation is a function of environmental conditions and power setting
• forms in high humidity conditions