Aviation Turbulence飞机颠簸
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2. 7 October 1981; NLM CityHopper F28-4000; Moerdijk, Netherlands: Shortly after takeoff, the aircraft entered an area of severe thunderstorm activity. The aircraft apparently had a catastrophic in flight structural failure due to severe turbulence because it was seen to emerge from the clouds with one of its wings broken away. All four crew members and 13 passengers were killed.
• Moderate Chop: Causes rapid bumps or jolts without appreciable changes in aircraft altitude or attitude
• Severe Turbulence: Causes large, abrupt changes in altitude or attitude; usually causes large variations in indicated airspeed. Aircraft may be momentarily out of control.
• Moderate Turbulence: Similar to light turbulence but of greater intensity. Changes in altitude and/or attitude occur but the aircraft remains in positive control at all times; usually causes variations in indicated airspeed.
Boundary Layer
Continental Boundary layer diurnal cycle
Boundary layer profiles from DOE ARM SODARs (acoustic sounders)
Turbulence profile
Vertical wind profile
• Occurs due to surface obstructions i.e. terrain or buildings
• Surface wind speed and stability play major factors in turbulence development
Clear Air Turbulence (CAT)
Pilots report turbulence as
follows:
• Light Turbulence: Momentarily causes slight, erratic changes in altitude and/or attitude (pitch, roll, yaw)
• Light Chop: Causes slight, rapid, and somewhat rhythmic bumpiness without appreciable changes in altitude or attitude
thermal wind shear)
Ellrod Index Strengths
• Easy to compute, easy to understand. • Has a good track record of defining
existence of turbulence (but not strength). • Widely available.
Aviation Turbulence
US-China Aviation Cooperation Program (ACP)
Embry-Riddle Training Debbie Schaum
AMS Turbulence Definition
• aircraft turbulence—Irregular motion of an aircraft in flight, especially when characterized by rapid up-anddown motion, caused by a rapid variation of atmospheric wind velocities. This can occur in cloudy areas (particularly towering cumulus and lenticular clouds) and in clear air. Turbulence is the leading cause of nonfatal passenger and flight attendant injuries.
• Ri typically .5 to 10 near where turbulence is observed.
• The lower the Ri, the better chance of having turbulence.
Ellrod Index
• Based on observations that Clear Air Turbulence (CAT) is frequently found near:
3. 16 August 1982; China Airlines 747; near Hong Kong: The aircraft encountered severe in flight turbulence. Two of the 292 passengers were killed.
4. 3 October 1990; Eastern DC9-31; Florida, USA: The aircraft clear air turbulence at 31,000 feet. One injured passenger died three weeks later.
5. 5 September 1996; Air France 747-400; near Ouagadougou, Burkina Faso: Severe turbulence associated with a weather front seriously injured three of the 206 passengers. One of the three passengers later diedBaidu Nhomakorabeaof injuries caused by an in flight entertainment screen.
6. 28 December 1997; United Airlines 747-100; over Pacific Ocean near Japan: The aircraft encountered severe turbulence during cruise about two hours after departing Japan. One of the 346 passengers was killed. None of the 23 crew members were killed but three sustained serious injuries.
Common Forms of Turbulence
• Boundary Layer Turbulence • Clear Air Turbulence • Mountain Wave Turbulence • Cloud Updrafts (Thunderstorms) • Wake Turbulence
g
Ri
z V 2
z
Lapse rate Wind shear
Kelvin Helmholtz Wave
Breakdown
• For Ri less than .25, flows become turbulent.
• Seldom observe Ri=.25 in atmospheric flows.
• Extreme Turbulence: Aircraft is violently tossed about and is practically impossible to control; may cause structural damage or injury.
Fatal Turbulence Events Since 1980
• The following are events involving in flight turbulence where at least one jet airliner passenger was killed.
1. 10 May 1980; Indian Airlines 737-200; near Rampur Hat, India: The aircraft experienced severe en route turbulence. Two of the 132 were killed.
Wind Shear
• Vertical wind shear can cause instability that curls the air around a horizontal axis.
Kelvin Hemholtz Turbulence
Richardson Number
• Richardson number Ri =stability over wind shear squared.
1. Vertical wind shear 2. Horizontal wind shear 3. Convergence 4. Horizontal deformation (i.e. fronts) 5. Lapse rate discontinuities (i.e. inversions) 6. Strong horizontal thermal gradients (i.e.
Mechanical Boundary Layer Turbulence
• Influenced by terrain, stability and wind speed.
Mechanical Turbulence Near Ground
Boundary Layer Turbulence Guidance
• Clear Air Turbulence Index Forecasts • EMC/NCEP SREF home page
Other Factors in CAT
• Classical Kelvin Helmholtz waves may not account for all observed CAT.
• Use analysis of surface lapse rate and winds
Boundary Layer Turbulence Summary
• Occurs due to surface heating and convection so most prominent during heat of the day
• None available on web that I know of.
• Rules of thumb are widely used, such as if have winds over 30 knots in boundary layer with unstable lapse rate, then forecast turbulence.
• Moderate Chop: Causes rapid bumps or jolts without appreciable changes in aircraft altitude or attitude
• Severe Turbulence: Causes large, abrupt changes in altitude or attitude; usually causes large variations in indicated airspeed. Aircraft may be momentarily out of control.
• Moderate Turbulence: Similar to light turbulence but of greater intensity. Changes in altitude and/or attitude occur but the aircraft remains in positive control at all times; usually causes variations in indicated airspeed.
Boundary Layer
Continental Boundary layer diurnal cycle
Boundary layer profiles from DOE ARM SODARs (acoustic sounders)
Turbulence profile
Vertical wind profile
• Occurs due to surface obstructions i.e. terrain or buildings
• Surface wind speed and stability play major factors in turbulence development
Clear Air Turbulence (CAT)
Pilots report turbulence as
follows:
• Light Turbulence: Momentarily causes slight, erratic changes in altitude and/or attitude (pitch, roll, yaw)
• Light Chop: Causes slight, rapid, and somewhat rhythmic bumpiness without appreciable changes in altitude or attitude
thermal wind shear)
Ellrod Index Strengths
• Easy to compute, easy to understand. • Has a good track record of defining
existence of turbulence (but not strength). • Widely available.
Aviation Turbulence
US-China Aviation Cooperation Program (ACP)
Embry-Riddle Training Debbie Schaum
AMS Turbulence Definition
• aircraft turbulence—Irregular motion of an aircraft in flight, especially when characterized by rapid up-anddown motion, caused by a rapid variation of atmospheric wind velocities. This can occur in cloudy areas (particularly towering cumulus and lenticular clouds) and in clear air. Turbulence is the leading cause of nonfatal passenger and flight attendant injuries.
• Ri typically .5 to 10 near where turbulence is observed.
• The lower the Ri, the better chance of having turbulence.
Ellrod Index
• Based on observations that Clear Air Turbulence (CAT) is frequently found near:
3. 16 August 1982; China Airlines 747; near Hong Kong: The aircraft encountered severe in flight turbulence. Two of the 292 passengers were killed.
4. 3 October 1990; Eastern DC9-31; Florida, USA: The aircraft clear air turbulence at 31,000 feet. One injured passenger died three weeks later.
5. 5 September 1996; Air France 747-400; near Ouagadougou, Burkina Faso: Severe turbulence associated with a weather front seriously injured three of the 206 passengers. One of the three passengers later diedBaidu Nhomakorabeaof injuries caused by an in flight entertainment screen.
6. 28 December 1997; United Airlines 747-100; over Pacific Ocean near Japan: The aircraft encountered severe turbulence during cruise about two hours after departing Japan. One of the 346 passengers was killed. None of the 23 crew members were killed but three sustained serious injuries.
Common Forms of Turbulence
• Boundary Layer Turbulence • Clear Air Turbulence • Mountain Wave Turbulence • Cloud Updrafts (Thunderstorms) • Wake Turbulence
g
Ri
z V 2
z
Lapse rate Wind shear
Kelvin Helmholtz Wave
Breakdown
• For Ri less than .25, flows become turbulent.
• Seldom observe Ri=.25 in atmospheric flows.
• Extreme Turbulence: Aircraft is violently tossed about and is practically impossible to control; may cause structural damage or injury.
Fatal Turbulence Events Since 1980
• The following are events involving in flight turbulence where at least one jet airliner passenger was killed.
1. 10 May 1980; Indian Airlines 737-200; near Rampur Hat, India: The aircraft experienced severe en route turbulence. Two of the 132 were killed.
Wind Shear
• Vertical wind shear can cause instability that curls the air around a horizontal axis.
Kelvin Hemholtz Turbulence
Richardson Number
• Richardson number Ri =stability over wind shear squared.
1. Vertical wind shear 2. Horizontal wind shear 3. Convergence 4. Horizontal deformation (i.e. fronts) 5. Lapse rate discontinuities (i.e. inversions) 6. Strong horizontal thermal gradients (i.e.
Mechanical Boundary Layer Turbulence
• Influenced by terrain, stability and wind speed.
Mechanical Turbulence Near Ground
Boundary Layer Turbulence Guidance
• Clear Air Turbulence Index Forecasts • EMC/NCEP SREF home page
Other Factors in CAT
• Classical Kelvin Helmholtz waves may not account for all observed CAT.
• Use analysis of surface lapse rate and winds
Boundary Layer Turbulence Summary
• Occurs due to surface heating and convection so most prominent during heat of the day
• None available on web that I know of.
• Rules of thumb are widely used, such as if have winds over 30 knots in boundary layer with unstable lapse rate, then forecast turbulence.