Weather 1 - Focus on Microbursts


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Weather 1 - Focus on Microbursts

  1. 1. Welcome Kevin McNulty, Aerospace Education Officer • Introduction • Module presentation approach • Program ideas • Feedback needed • Cadet experience and interests • Raise hands for unfamiliar terms
  2. 2. Welcome Kevin McNulty, Aerospace Education Officer • Email: • Home phone: 941-729-8928 • Cell phone: 941-737-8575 • Send me email if you would like a copy of this PowerPoint!
  3. 3. Welcome Module 3: The Air Environment Everyone always talks about the weather, but no one ever does anything about it.
  4. 4. Overview Module Learning Objectives Chapter 1 - Air Circulation • Describe how the Sun heats the Earth • Describe the Earth’s rotation and revolution and its effect on the seasons • Explain the various theories of circulation • Describe Coriolis Force • Define the jet stream (give three examples…just kidding)
  5. 5. Overview Module Learning Objectives Chapter 2 - Weather Elements • Define wind • Describe the Beaufort Scale • Define heat • Explain what temperature is and how it can be expressed • Describe what wind chill is and what it does • Describe how a microburst can affect a plane
  6. 6. Overview Module Learning Objectives Chapter 3 - Moisture and Clouds • Describe the condensation process • Describe how saturation occurs • Define dew point • Define what precipitation is and give some examples (not kidding this time) • Define fog • Define turbulence
  7. 7. Overview Module Learning Objectives Chapter 4 - Weather Systems and Changes • Define an air mass and their characteristics • Define a front and describe types of fronts • Describe hurricanes, thunderstorms, and tornadoes • Identify the stages of a thunderstorm • Outline safety precautions for thunderstorms and tornadoes
  8. 8. Basics Air, and why you need it
  9. 9. Basics The Atmosphere
  10. 10. Chapter one Air Circulation Causes of Air Circulation • Sun heats Earth via radiation and that heat is absorbed unevenly • Earth rotates on its axis and revolves around the sun. • Uneven heating plus the Earth’s movement is the cause of air movement and thus weather
  11. 11. Chapter one Air Circulation Radiation • 51% of sun’s radiation absorbed by Earth • Absorbed unevenly by land/water
  12. 12. Chapter one Air Circulation Convection • Warm air has lower pressure, weighs less, rises • Key cause of weather
  13. 13. Chapter one Air Circulation Revolution • Steep angle sun heats surface more than shallow angle • Summer in one hemisphere, winter in the other
  14. 14. Chapter one Air Circulation Rotation • Earth spins as air moves, deflecting longitudinal movement: The Coriolis Effect
  15. 15. Chapter one Air Circulation Jet Stream • Large temperature differences in the upper troposphere cause large pressure differences • Result is strong (120-150 mph) high wind known as the jet stream.
  16. 16. Chapter two Weather Elements Wind • A body of air in motion having a direction (use “from” direction) and speed • Measured in knots, mph, or on Beaufort Scale (see book) • Wind critically affects flight • Headwind increases lift • Tailwind increases speed • Differential winds cause turbulence • Wind shear causes erratic course changes
  17. 17. Focus on Microbursts A microburst is a type of windshear which is… … a very localized column of sinking air … typically associated with thunderstorms
  18. 18. Microburst Source
  19. 19. Microburst Effect on Flight A microburst can critically affect takeoff or landing
  20. 20. Microburst Delta Flight 191, August 2, 1985 Sequence of Events Leading up to Crash • As L-1011 approached DFW for landing, an isolated thunderstorm developed near the end of the runway. • Crew noticed storm cell ahead, but decided to proceed through it anyway, against company wx avoidance rules; they could not know the cell was spawning a microburst in their path. • At about 1500 feet AGL, First Officer Price reported seeing lightning in one of the clouds ahead.
  21. 21. Microburst Delta Flight 191, August 2, 1985 Sequence of Events Leading up to Crash • Unaware of microburst, DL191 entered leading edge of vortex ring headwinds. • At 800ft AGL, headwinds cause uncommanded pitch and acceleration from 149kt IAS to 173kt IAS. • Price was flying and tried to stabilize the aircraft's speed, but CPT Conners had recognized the speed increase as a sign of wind shear, warning Price to watch speed and telling him to “push up” (the throttles).
  22. 22. Microburst Delta Flight 191, August 2, 1985 Sequence of Events Leading up to Crash • As aircraft flew through headwinds to center of vortex ring, airspeed suddenly dropped from 173kt to 133kt, and Price pushed the throttles forward. • Hitting downdraft, airspeed suddenly dropped to 119kt and sink rate increased. On the CVR Conners can be heard saying "Hang on to the son of a bitch!” and instructing Price to push the throttles “way up!”
  23. 23. Microburst Delta Flight 191, August 2, 1985 Sequence of Events Leading up to Crash • Price tried to avoid a stall by pushing the nose down. • Nose-down attitude plus downdraft increased sink rate to 1,700 ft/min before impact. • The L-1011 first impacted the ground on a field about 6,300ft north of 17L and bounced back into the air. • While crossing Hwy 114 it came down again on top of a vehicle, killing its occupant. • Aircraft skidded onto the airfield, collided with two 4 mil gal water tanks at a speed of 220kt, and exploded.
  24. 24. First Impact: Microburst Delta 6300’ North Flight 191, August 2, 1985 Second Impact: H 114 wy Final Impact: W T ater anks 17L
  25. 25. Microburst Delta Flight 191, August 2, 1985 Compurer re-creation of microburst based on recorded NWS radar information
  26. 26. Microburst Delta Flight 191, August 2, 1985 Computer simulation based on flight recorder data Computer re-creation of crash
  27. 27. Microburst Delta Flight 191, August 2, 1985 Aftermath • Primary cause found to be pilot error for violating company wx avoidance rules and deciding to land in adverse conditions • Prior to crash, microbursts poorly understood • Because of crash, microbursts extensively studied and warning systems developed including ground and aircraft radar systems