Met PPL exam

• Supercooled rain drops fall from cloud base to a/c = Ice formation
• Aircraft skin subzero temps, supercooled drops freeze
• Rapid build up of clear ice

Pilot action: DESCEND TO CRUISE BELOW FREEZING LEVEL.

• Prevent ice: Channel heat through electrical devices
• De-ice: Remove ice after formed by de-icing boots

Deicing boots:

• Flexible cells isntalled along L.E of eings
• Inflated to break ice + allow wind to shed it onto passing airflow.
  

• Frozen Dew
• Can disrupt airflow over wing (reducing lift)
• Preflight
• Can be removed by washing
  

• COLD SOAKING:
• When a/c crusing at high alt for few hours, airframe finally cools to same temp as outside air
• When cold soaked, a/c descends into layer of warm, humid air
• Water vapour can skip liquid state + turn to ice (DEPOSITION)
• This ice coat = HOAR FROST
• Little impact on a/c perf
  

Stage 1 (towering cumulus stage)

• Surface warming: uplift of warm air
• Rapid updrafts caused by release of latent ht/condensation
• VIrga
• Moderate/severe airframe icing
  

Stage 2 (mature stage)

• Convective cells form up/downdrafts
• Downdrafts - evaporation in falling raindrops
• latent ht absorbed from air
• cooling downdraft formed
• Attains highest altitude (top of troposphere)
• Rain+ hail well dvlped.
• Lightning
  

Stage 3 (dissipating stage)

• Downdrafts predominant over updrafts
• Microbursts (extremely strong downbursts)
• When temp of cloud = temp of environment, dissipation complete.