ATSC 231 - Quiz 11 review

What percent of aircraft weather related accidents are related to Icing for GA?

Induction icing = 8%

Structural = 2%

What percent of fatal aircraft weather related accidents are related to icing for GA?

Induction = 3%

Structural = 3%

What percent of aircraft weather related accidents are related to icing for part 121?

1%

What percent of aircraft weather related accidents are related to icing for part 135?

6% (no fatal accident stats)

Icing accidents from most to least

1. Part 91

2. Part 135

3. Part 121

4. Public use

What is induction icing?

All icing that affects powerplant operations

What are the common requirements for carb ice?

80 → 20 degrees F

High humidity

Low power setting

*Visible moisture doesn’t have to be present

What are the symptoms of carb ice?

• Fixed pitch

- Drop in RPM and engine roughness

• Constant speed

- Drop in MAP and engine roughness

What is the antidote for carb ice?

• Use full carb heat

• May tale minutes for power to return

What type of airplanes are subject to inlet icing?

• Reciprocating (carbureted and fuel injected)

• Turbine

What are the common conditions for Inlet icing?

• Visible moisture

• Temperatures less than 0 degrees C

What are the symptoms of inlet icing?

Fixed pitch

• Loss of RPM and Engine roughness

Constant speed

• Loss in MAP and Engine roughness

What are the hazards of Inlet icing for Turbine aircraft?

• FOD

• Balde damage

What are the antidotes for Inlet icing?

• Use alternate air

• Use carb heat

• Use anti-ice (turbine aircraft)

Where is High Ice Water Content (HIWC) found?

• High altitudes

• Tops of cumulonimbus clouds and anvils

• Temps -21 to -32 degrees C

What are the Hazards of HIWC?

• Turbine engine degradation

• Engine upset

• Engine damage from shedding

• Flameout and shutdown

Which CFR 14 part provides the icing envelopes for the certification of airplanes for ice protection?

Part 25 Appendix C

Water droplets in a subfreezing environment with diameters larger than 40 microns are known as supercooled ____ drops?

• Large

All aircraft are required to have ice protection for their propulsion systems in case of an inadvertent icing encounter.

True as per CFR part 23

The CFR 14 part 25 Appendic C does not provide for the certification of airplanes for ice protection in clouds with supercooled large drops?

True

What is the definition of Known Icing?

• Atmospheric condition in which the formation of ice is observed or detected in-flight

Regs for FIKI aircraft:

Part 23 → powerplant ice protection

Part 25 → Ice protection

• Appendix C = ice envelopes

• Appendic O = SLD

What is trace ice?

• Ice becomes noticeable

• Less than 1/4” per hour

What is light ice?

• occasional cycling of ice protection required

• 1/4” to 1” per hour

What is moderate ice?

• Frequent cycling of ice protection required

• 1” to 3” per hour

What is severe ice?

• Ice protection fails to remove ice

• By regs you must exit

• greater than 3” per hour

What is rime ice?

• rough, milky, opaque, brittle

• Rapid freezing of droplets

• Accretes along the stagnation line

• Conformal to shape of airfoil

What is Clear/ glaze ice?

• Hard, transparent, lumpy, “horns”

• Slow freezing of droplets

• Slow dissipation of heat fusion

• Clear and smooth

What is mixed ice?

• Combo of Glaze and rime

• Identification is difficult

• Forms in non-uniform clouds and temps than permit “moderate” freezing rate

What is intracycle ice?

• Ice that forms between actuation of deicing systems

What is residual ice?

• Ice that remains immediately after actuation of a deicing system

What is runback icing?

• Freezing or refreezing of water leaving protected surfaces and running back to unprotected surfaces

Who had the highest number of icing aircraft accidents per the NTSB from 2010 to 2014?

Part 91

What phase of flight do most icing accidents occur?

Cruise phase

Which states have the most icing accidents?

• California, Colorado, and Alaska

What type of certificate does most PIC’s hold in icing accidents?

• Commercial

For GA do most icing accidents occur with low to high time pilots?

• Low if it is specific to make and model

• High if it is just off total time

Which state in the US has the highest frequency of freezing rain and freezing drizzle?

Texas

Does freezing drizzle always indicate warmer air aloft?

No, it does not

What altitude is the peak occurrence for icing near?

10,000 ft MSL

What is liquid water content and its characteristics?

Mass of liquid (grams) in volume of cloud (cubic meters)

• Characteristics

- Highly variable in cloud

- Non-precipitating clouds

What are the requirements for structural icing?

• Temps less than 0 degrees C and visible moisture

*Most supercooled water drops 0 → -10 degrees C

What is supercooled liquid water?

Liquid water at temperatures below 0 degrees C

- Happens due to no ice nuclei

- Most found from temps 0 → -20 degrees C

What is collection efficiency?

• Ratio of water mass striking the airframe to the water mass in the free stream

Factors

- Drop size

- Geometry of collecting surface

- Airspeed

How does drop size effect collection efficiency?

Large drops = High collection

Small drops = Low collection

How does the geometry of the collection surface effect collection efficiency?

Thin airfoil → less curvature = high collection

Thick airfoil → more curvature = low collection

How does airspeed effect collection efficiency?

Fast airspeed = Greater collection efficiency

Slow airspeeds = lower collection efficiency

What are the factors that affect the thermodynamics of freezing?

• Temperature

• Liquid water content (LWC)

• Drop size

• Airspeed

How does temperature affect the thermodynamics of freezing?

Cold air (-20)

• Rapid freezing of droplets

• Trapped air

• Rime Ice

Warm air (-5)

• Slow freezing of droplets

• Water spreads

• Air escapes

• Glaze ice