Met 2 Flashcards
What are the effects of icing on an aeroplane?
Aerodynamics Weight Engine blockage Undercarriage jammed Control surfaces jammed Pitot tubes blockage Communications aerial icing Vision -canopy icing Vibration
What factors affect the severity of icing?
Cloud droplet variables: - size (larger droplet, more severe icing) - concentration - temperature Aircraft varaibles: - Shape (more streamlined, more icing) - Speed (higher speed, more icing)
What situation causes most icing on aircraft?
When a sub-zero aircraft strikes super-cooled water droplets.
In what temperature range is icing most common?
-15 to 0 degrees C more super cooled droplets close to zero
What are the two types of icing in cloud?
Clear Ice Rime Ice
Describe clear ice
1) Clear 2) Dense 3) Adhesive 4) large super cooled droplets 5) temps close to zero 6) slow freezing
Describe rime ice
1) White 2) Low density 3) Brittle 4) small super cooled droplets 5) very low temps 6) rapid freezing traps air
Other forms of icing (not incl rime and clear ice)?
1) Packed snow 2) Rain ice 3) Hoar frost 4) Engine ice
What are the 2 ways that kinetic heating occurs?
1) Increased pressure at LE 2) Friction between aircraft skin and atmosphere
Give 1 advantage and 1 disadvantage of kinetic heating
Advantage: Raises temp above 0 degrees = no icing Disadvantage: Raises temp from very cold to close to 0 degrees = more severe icing
How long does it take for 0.5cm of ice to build up in light, moderate and severe icing conditions?
Light = 15-60mins Moderate = 5-15mins Severe = <5mins
What are the conditions for a thunderstorm?
1) Deep untable layer - preferably unstable up to tropopause 2) Trigger action - heating, mountains, fronts 3) High moisture content - high dew point
What two weather conditions are assumed to occur in CB?
Sever icing and moderate turbulence
What are the hazards associated with thunderstorms?
WHISTLER Weather - heavy precip Hail severe Icing Squall/strong winds severe Turbulence Lightning severe Electrical/magnetic effects Rapid pressure changes
What are the common indicators of thunderstorm activity?
Cloud type - convective (towering CU, CB, Castellanus, Mammatus) Hail or Heavy precepitation Lightning Radio Crackle Radar returns/echos St Elmos Fire across canopy
What is Meteorological visibility?
The greatest horizontal distance at which known objects can be seen and recognised by an observer on the ground with normal eyesight and under conditions of normal daylight illumination.
What is Prevailing visibility?
The visibility value, as per met vis, which is reached or exceeded within at least half the horizon circle or within at least half of the surface of the airfield.
What is the Runway Visual Range (RVR)?
The maximum distance in the direction of take-off or landing at which the runway, or lights delineating the runway, can be seen from a height corresponding to the average eye-level of the pilot at touchdown.
How is RVR measured?
By an observer (or automatically) from a 15ft high tower near to the runway.