Hazards Flashcards
Wind shear
Best described as a change in wind direction and/or speed within a very short distance
Vertical gust
●Changes angle-of-attack.
May introduce damaging flight loads.
Rising gust increases angle-of-attack.
●Too many G’s
●Stall
Falling air decreases angle-of-attack.
●Decrease in lift – recovery altitude?
Horizontal gust
●Change in airspeed.
Most important at slow airspeeds.
Induces a pitching moment to return the airplane to trimmed speed.
Induces new drag and lift values for new airspeed.
Microburst
Produced by precipitation drag due to evaporation and melting of precipitation particles
As the microburst reaches the ground, it disperses laterally, causing the wing to roll upward along its outer boundary; This is known as a Vortex Ring
Last no longer than 15 min
Ground icing
Caused by freezing rain, freezing drizzle and wet snow
Induction icing
Carbureted Engines
●Ice may form on the venturi walls and throttle plate, restricting airflow to the engine
●This may occur at temperatures between 20° F (-7° C) and 70° F (21° C)
Solution
●Carburetor Heat
Injected Engines
●Fuel-injected aircraft engines usually are less vulnerable to icing but still can be affected if the engine’s air source becomes blocked with ice
Solution
●Alternate Air Source
Turbofan Engines
●In the area of reduced pressure at the inlet, which lowers the temperature below that of the surrounding air
●This reduction in temperature may be sufficient to cause ice to form on the engine inlet, disrupting the airflow into the engine
●Another hazard occurs when ice breaks off and is ingested into a running engine, which can cause damage to fan blades, engine compressor stall, or combustor flameout
●Another problem in turbine engines is the icing of engine probes used to set power levels
Can lead to erroneous readings of engine instrumentation operational difficulties or total power loss
Structural icing
Accumulation of ice on the aircraft exterior
Skin temperature equal to or less than zero
Small and/or narrow objects are the best collectors of droplets and ice up most rapidly
An aircraft’s tailplane is a better collector than its wings, because the tailplane presents a thinner surface to the airstream
Tailplane icing induced stall
Rarely encountered during cruise flight
●Horizontal stabilizer isn’t working hard
Typically encountered when configuring for landing… i.e. lowering flaps
●Induces a larger downwash off the wings
●Induces larger angle of attack on the horiz stab
●Makes horizontal stab work harder…leads to a tailplane stall
Tailplane stall warning signs
●Visible icing
●Lightening of stick forces
Easy to move yoke nose-down…hard to pull up
●Buffeting of controls…but not the airframe
●Difficulty trimming your aircraft
●Rapid nose down pitching
Often during or after lowering flaps
Tailplane stall recovery
Opposite for wing stall
Aggressively lower the nose
●Excessive force may be necessary
Undo the last configuration change
●May need to totally retract the flaps
Judicious use of power
●Increasing airspeed my make your situation worse
Icing process
Icing occurrence, type, and severity depends on three basic parameters:
●Temperature
●Liquid Water Content
●Droplet Size
Icing temperatures
Icing Type OAT Range
Clear 00 C to -50 C
Clear or Mixed -50 C to -100 C
Mixed or Rime -100 C to -150 C
Rime -150 C to -200 C
Ice effects on coefficient of lift
•A significant reduction in CL-MAX and a reduction in the angle of attack where stall occurs can result from a relatively small ice accretion
•A reduction of CL-MAX by 30 percent is not unusual, and a large horn ice accretion can result in reductions of 40 percent to 50 percent
•Drag tends to increase steadily as ice accretes. An airfoil drag increase of 100 percent is not unusual, and for large horn ice accretions, the increase can be 200 percent or even higher
Other effects of ice
Ice can partially block or limit control surfaces
If extra weight caused by ice accumulation is too great:
●The aircraft may not be able to become airborne
●If in flight, the aircraft may not be able to maintain altitude
•Another hazard of structural icing is the possible uncommanded and uncontrolled roll phenomenon, referred to as roll upset, associated with severe in-flight icing
•Roll upset may be caused by airflow separation (aerodynamic stall), which induces self deflection of the ailerons and loss of or degraded roll handling characteristics
High density altitude
Density Altitude is pressure altitude corrected for non standard temperature
If a chart in not available, the DA can be estimated by adding 120 feet for every degree Celsius above the ISA
Braking action
GOOD: No degradation of braking action.
FAIR: Somewhat degraded braking conditions.
POOR: Very degraded braking conditions.
NIL: No braking action.
Cold climate hazards
•Difficult to function efficiently
•Takeoffs on snow or ice will experience “sticky” conditions
•Visibility problems
•Whiteout
•Hot to Cold, look out below
•6000 ft w/ OAT of -280 C, true alt is 840 lower than indicated
