Transcript AFFSA ROADSHOW - e

WINDSHEAR
Lt Col Wally Emerson 15 April 2007
WHY STUDY WINDSHEAR?
744 Dead
287 Injured
CONUS Only
Since 1964
OBJECTIVE
Emphasize that the best defense against the hazards of low
altitude windshear is avoidance.
Give you key information to assist in recognizing and avoiding
windshear.
Discuss some precautions and techniques for improving
chances of surviving an inadvertent windshear encounter.
OBJECTIVE
Emphasize that the best defense against the hazards of low
altitude windshear is avoidance.
Give you key information to assist in recognizing and avoiding
windshear.
Discuss some precautions and techniques for improving
chances of surviving an inadvertent windshear encounter.
OBJECTIVE
Emphasize that the best defense against the hazards of low
altitude windshear is avoidance.
Give you key information to assist in recognizing and avoiding
windshear.
Discuss some precautions and techniques for improving
chances of surviving an inadvertent windshear encounter.
OVERVIEW
1) Windshear weather, particularly microbursts, and clues
which may indicate its presence,
2) Effects of windshear on airplanes
3) Windshear recognition cockpit, and avoidance,
4) Precautions to take when windshear is suspected,
5) Standard operating techniques related to windshear
6) Recovery techniques to an inadvertent windshear
encounter.
OVERVIEW
1) Windshear weather, particularly microbursts, and clues
which may indicate its presence,
2) Effects of windshear on airplanes
3) Windshear recognition cockpit, and avoidance,
4) Precautions to take when windshear is suspected,
5) Standard operating techniques related to windshear
6) Recovery techniques to an inadvertent windshear
encounter.
OVERVIEW
1) Windshear weather, particularly microbursts, and clues
which may indicate its presence,
2) Effects of windshear on airplanes
3) Windshear recognition cockpit, and avoidance,
4) Precautions to take when windshear is suspected,
5) Standard operating techniques related to windshear
6) Recovery techniques to an inadvertent windshear
encounter.
OVERVIEW
1) Windshear weather, particularly microbursts, and clues
which may indicate its presence,
2) Effects of windshear on airplanes
3) Windshear recognition cockpit, and avoidance,
4) Precautions to take when windshear is suspected,
5) Standard operating techniques related to windshear
6) Recovery techniques to an inadvertent windshear
encounter.
OVERVIEW
1) Windshear weather, particularly microbursts, and clues
which may indicate its presence,
2) Effects of windshear on airplanes
3) Windshear recognition cockpit, and avoidance,
4) Precautions to take when windshear is suspected,
5) Standard operating techniques related to windshear
6) Recovery techniques to an inadvertent windshear
encounter.
OVERVIEW
1) Windshear weather, particularly microbursts, and clues
which may indicate its presence,
2) Effects of windshear on airplanes
3) Windshear recognition cockpit, and avoidance,
4) Precautions to take when windshear is suspected,
5) Standard operating techniques related to windshear
6) Recovery techniques to an inadvertent windshear
encounter.
WINDSHEAR
Definitions
WINDSHEAR
Windshear is a generic term referring to any
rapidly changing wind currents.
GP: WIND SHEAR - A change in wind speed and/or wind
direction in a short distance, resulting in a tearing or shearing
effect. It can exist in a horizontal or vertical direction and
occasionally in both.
WINDSHEAR
WIND SHEAR
Vertical wind shear is the rate of change of
the wind with respect to altitude.
Horizontal wind shear is the rate of change
on a horizontal plane.
WINDSHEAR
WIND SHEAR
AC 00-54
Severe Windshear - A rapid change in
wind direction or velocity causing
airspeed changes greater than 15 knots
or vertical speed changes greater than
500 feet per minute.
WINDSHEAR
Wind shear can be encountered when flying
through a temperature inversion layer.
However, the dangerous wind shear we're
interested in is generally associated with a
frontal system, especially one which includes a
thunderstorm.
WINDSHEAR
Weather to look out for
WINDSHEAR
During a thunderstorm, a large column of cold, dense air rapidly
descends to the surface of the earth. This fast moving column can be
described as a downburst. Once the downburst reaches the surface of
the earth, it expands horizontally in all directions.
WINDSHEAR
Once the downburts spreads out horizontally, it undercuts the warmer
air outside the storm. This mixing of air produces a rolling vortex of
wind. The vortex then causes high velocity winds to surge in opposing
directions. These strong winds which makes up the gust front are also
known as horizontal wind shear.
WINDSHEAR
"Valley wind shear" is a name for another natural cause of wind shear
which results from a temperature inversion. This phenomena begins by
the cooling of the air in a valley. This cooling results in a stable air
mass on the valley floor. The wind blowing across the top of the
mountain pushes air down the mountain slope.
WINDSHEAR
The wind blowing across the top of the mountain pushes air down the
mountain slope. The air experiences heating during this descent.
However, when this air encounters the stable air mass on the valley
floor, it cannot penetrate it and flows over top of it. This results in a
layer of warmer air being pushed out over a layer of colder air, a
temperature inversion. Thus a wind shear is developed due to the air
flowing over the inversion, and stable air below it.
WINDSHEAR
As the valley floor air is warmed the next morning, it begins to rise
weakly. Air begins moving down the slope of the mountain downwind
to replace this rising air. As this continues and increases in strength, it
results in a rotary motion. This rotary motion is another form of wind
shear.
WINDSHEAR
Another way that mountains can create wind shear is by turbulence. As
the wind blows up one side of a mountain and reaches the top, it can
begin to mix turbulently. This turbulence on the lee (downwind) side of
the mountain is a form of wind shear. The same effect takes place
around the sides of buildings
MICROBURSTS
“The Granddaddy of all Windshears”
Microbursts: Dry or Wet
 Wet
microbursts are more common in
places like the Mississippi valley where
thunderstorm bases tend to be much lower.
 Dry
microbursts occur primarily in the high
plains/intermountain's where the
temperature/dew point spread is wide (30°
to 50°)
Downburst/Microburst Definition
 A downburst
is HEAVY COLD/MOIST air dropping
spilling out producing horizontal shears along a damage
path of 1-5 miles .
 A microburst is a downburst that covers an area less than
3 miles with peak winds that last 2–5 minutes.
Why are they important?
 Eastern Airlines
 August
Flight 66 crashed 24 June 1975
1983 near miss at Andrews AFB
 Fast
winds with rapidly shifting directions are bad for
planes trying to take off or land
 There
are typically 50–100 downbursts each year during
the convective season
Downdraft Formation
Two main mechanisms:
– Evaporation
 Cools
the air; cold air sinks
 Rain that evaporates before reaching the ground is called
virga
 Cold air can descend as fast as 40–60 m.p.h.
– Drag force
 Falling
precipitation drags air down with it, creating fast
descending air
 One raindrop is inconsequential but many drops have a
large effect on air flow
Downburst/Microburst
Structure
Weak environmental wind field
– Downburst is symmetrical
– Equal speed/damage on all sides
Weak environmental wind field or more stationary the front
Aircraft will experience equal headwinds and tailwinds
Downburst/Microburst
Structure
Strong environmental wind field
– Asymmetrical
– Strongest wind is downwind of
stagnation cone
– May produce a well-defined “foot”
shape to precipitation
Strong environmental wind field or fast moving front
Aircraft will experience bigger kick on the backside
Vortex Ring
WINDSHEAR
Evolution of a microburst. Microburst winds intensify for
about 5 min after ground contact and typically dissipate
about 10 to 20 min after ground contact.
DRY MICROBURST
In this example, air below a cloud base (up to approximately 15,000 feet
AGL) is very dry. Precipitation from higher convective clouds falls into
low humidity air and evaporates. This evaporative cooling causes the air
to plunge downward. As the evaporative cooling process continues, the
downdraft accelerates. Pilots are therefore cautioned not to fly beneath
convective clouds producing virga conditions.
WINDSHEAR
Greatest danger: Takeoff and landing
1. During landing, the pilot has already reduced
engine power and may not have time to increase
speed
2. During takeoff, an aircraft is near stall speed
General
Windshear, particularly low altitude windshear encounters, are
of significant importance because it can place the flight crew in
a situation where the maximum performance capability of the
aircraft is required. Windshear encounters below 500ft are the
most threatening because there is very little time or altitude to
respond and recover from an inadvertent encounter.
General
Knowledge of how windshear affects performance can be
essential to a successful recovery maneuver following an
inadvertent windshear encounter.
General
Windshear that improves performance will be first indicated in
the cockpit by an increased airspeed. Pilot reaction – reduce
thrust.
With power back you experience a shear in the reverse sense
that will decrease airspeed and degrade vertical flight path
performance.
General
The magnitude of the pitch change is a function of the following
- Aircraft configuration
- Weight
- Speed
- C of G
- Thrust
- Severity of airspeed change
General
If an attempt is made to regain lost speed by lowering the nose,
the combination of decreasing airspeed and decreasing pitch
attitude produces a high rate of descent. In some circumstances
as little as 5 seconds may be available to recognize and react to
a degrading vertical flight path.
General
INDICATORS OF WINDSHEAR:
•SIGMETS
•Visual signs (T-storms, black wall of death, tornados etc..)
•Unusual control forces required
•Significant changes in airspeed occur
•PIREPS
General
Crew Actions - Take-off Windshear Precautions
Maximum thrust should be used
If practical the longest suitable runway available should be used,
provided it is clear of areas of known windshear.
The flight director should not be relied upon during take-off in
suspected windshear conditions. The attitude director is the
primary reference for pitch attitude.
General
Crew Actions - Take-off Windshear Precautions
Crews should be alert for airspeed fluctuations during take-off
and initial climb. Such fluctuations may be the first indication of
windshear. Control forces may be different from those expected,
especially if airspeed is below the in-trim speed.
General
Crew Actions - Take-off Windshear Precautions
Crew co-ordination and awareness are very important. Close
monitoring of the flight instruments is imperative, and the nonhandling pilot should be especially aware of these and call out
any deviations from normal values.
General
Crew Actions - Take-off Windshear Precautions
The stick shaker must be respected at all times. If it is activated,
pitch attitude should be reduced just enough to stop the stick
shaker. Flight with intermittent stick shaker operation may be
required to maintain a positive rate of climb during a windshear
encounter.
MAX PERFORMANCE – just in and out of stick shaker
Effect on Airplanes
Windshear encounter during takeoff after liftoff.
(1) Takeoff initially appears normal.
(2) Windshear encountered just after liftoff.
(3) Airspeed decrease resulted in pitch attitude reduction.
(4) Aircraft crashed off departure end of runway 20 set after liftoff.
Effect on Airplanes
Windshear encounter during takeoff on runway.
1.
Takeoff initially appeared normal.
2.
Airspeed buildup slowed due to windshear.
3.
Airplane reached VR near end of runway, lifted off but failed to
climb.
4.
Airplane contacted obstacle off departure end of runway.
General
Crew Actions - Approach and Landing Windshear
Large thrust reductions or trim changes in response to a sudden
airspeed increase should be avoided as these may be followed
by a decrease in airspeed.
General
Crew Actions - Approach and Landing Windshear
In windshear conditions flight director commands should be
checked against ADI, and altimeters. These instruments are the
primary references for vertical flight path control.
Effect on Airplanes
Windshear encounter during approach.
1.
Approach initially appeared normal.
2.
Increasing downdraft and tailwind encountered at transition.
3.
Airspeed decrease combined with reduced visual cues resulted in
pitch attitude reduction.
4.
Airplane crashed short of approach end of runway.
General
Crew Actions - Windshear Recovery Maneuver
As a guide, marginal flight path control may be indicated by
uncontrolled changes from the normal steady state flight
conditions in excess of:
- 15 knots indicated airspeed
- 500 fpm vertical speed
- 5 degrees pitch attitude
- 1 dot glideslope displacement
General
Crew Actions - Windshear Recovery Maneuver
Whenever flight path control becomes marginal below 500ft
AGL, or when the "WINDSHEAR" or "PULL UP" warning
occurs, simultaneously:- Call "Windshear Go-around"
- Complete the rest of "Windshear" recall items (QRH)
General
Crew Actions - Windshear Recovery Maneuver
The call of "Windshear Go-around will advise the non-handling
pilot that the usual go-around procedure does not apply and that
speeds and pitch attitudes may not be normal for a go-around.
General
Crew Actions –
Windshears which exceed the performance capabilities of both
small and large aircraft have and will occur below 500ft. The
flight crew should search for any clues to the presence of
windshear along the intended flight path.
General
Crews should carefully review all available information such as
pilot reports of windshear or turbulence, low level windshear
reports and weather reports - especially thunderstorms and
'virga'.
General
Windshear that produces uncommanded airspeed changes of 15
knots or more is regarded as severe. Areas of known windshear
should be avoided and pilots should delay take-off or
discontinue an approach until conditions have improved
wherever necessary.
General
Windshear encounters should be reported precisely and
promptly to assist other pilots. Accurate pilot reports of
windshear can be a valuable clue as to the presence and severity
of windshear conditions.
General
Windshear Effects on Systems
Altimeters
During callouts and instrument scan in a windshear, use
of radio and/or barometric altimeters must be tempered by the
characteristics of each. Since radio altitude is subject to terrain
contours, the indicator may show a climb or descent due to
falling or rising terrain, respectively. The barometric altimeter
may also provide distorted indications due to pressure variations
within the microburst.
General
Windshear Effects on Systems
Vertical Speed Indicators
The vertical speed indicator (VSI) should not be solely
relied upon to provide accurate vertical speed information. Due
to instrument lags, indications may be several seconds behind
actual airplane rate-of-climb/descent and, in some situations,
may indicate a climb after the airplane has started descending.
Vertical speed indicators driven by an Inertial Reference Unit
(IRU) show significant improvement over other type
instruments but still have some lag.
General
Windshear Effects on Systems
Vertical Speed Indicators
In addition, gust induced pitot static pressure
variations within the microburst may introduce further VSI
inaccuracies. Due to such lags and errors, all vertical flight path
instruments should be cross-checked to verify climb/descent
trends.
General
Crew Actions - Windshear Recovery Maneuver
C-21 Windshear Recovery
Thrust
Aggressively apply necessary thrust (not less than go-around
thrust) to ensure adequate airplane performance. Avoid engine
over boost unless necessary to avoid ground contact. When
airplane safety has been ensured, adjust to maintain engine
parameters within specific limits.
General
Crew Actions - Windshear Recovery Maneuver
C-21 Windshear Recovery
Pitch
For a windshear encounter after liftoff or on approach, increase
or decrease pitch attitude as necessary, at a normal pitch rate,
toward an initial target attitude of 15 degrees.
General
Crew Actions - Windshear Recovery Maneuver
C-21 Windshear Recovery
Pitch
The all-engine pitch attitude may be maintained until either the
shear has been exited or stick shaker is encountered. Always
respect stick shaker. Use intermittent stick shaker as the upper
limit for pitch attitude.
General
Crew Actions - Windshear Recovery Maneuver
C-21 Windshear Recovery
Pitch
In a severe shear, stick shaker may occur below 10 degrees pitch
attitude. Rapidly changing vertical winds can also cause
momentary stick shaker at any attitude.
General
Crew Actions - Windshear Recovery Maneuver
C-21 Windshear Recovery
Pitch
Rapidly changing winds may cause rapid excursions in pitch
and roll with little or no pilot input. Control pitch in a smooth,
steady manner (approximately 2 degree increments) to avoid
excessive overshoot/undershoot of the desired attitude. Once the
airplane is climbing, and ground contact is no longer an
immediate concern, airspeed should be increased by cautious
reductions in pitch attitude.
General
Crew Actions - Windshear Recovery Maneuver
C-21 Windshear Recovery
Configuration
Do not change flap, gear, or trim position until terrain contact is
no longer a factor. However, stabilizer trim may be used to trim
out stick force due to thrust application. Although a small
performance increase is available after landing gear retraction,
initial performance degradation may occur when the landing
gear doors open for retraction.
General
Crew Actions - Windshear Recovery Maneuver
C-21 Windshear Recovery
Configuration
Extending flaps during a recovery after liftoff is not
recommended since the risk of moving the flaps in the wrong
direction or amount is considered a greater risk than
encountering a shear so great that a flap change is needed for
recovery.
Quick review
Downdraft up to 6000 feet/minute
Downdraft shaft 1
mile diameter
Up to 90 knots horizontal shear
1-3 miles in width
Downdraft up to 6000 feet/minute
Up to 90 knots horizontal shear
Duration 15 minutes or less…but once microburst activity starts
not uncommon for multiple microburst's
Downbursts
Approach to Prevention
Headwind increases –
experience increased
performance/pitches up
Headwind decreases until
downdraft – experience
decreased
performance/pitches down
Initiate go-around – experiencing
increasing tail wind and decreasing
performance
- 15 knots indicated airspeed
- 500 fpm vertical speed
- 5 degrees pitch attitude
- 1 dot glideslope displacement
SOLUTION
Detection
Equipment
–Ground-Based
–Airborne
Education
Ground-Based Detection
(NEXRAD)
Doppler Radar(6 Min)
(LLWAS) Low Level Windshear
Alerting System
– Barometric Pressure Jump Indicators
(TDWR)
Terminal Doppler
Weather Radar (2 Min)
AIRBORNE DETECTION
Predictive
– Alerts Crew Prior to Entry
Non-Predictive
– Alerts Crew That Windshear Has Been Entered
– “Test Probe”
AIRBORNE DETECTION
Predictive
– Alerts Crew Prior to Entry
– KC-135 (WXR-700X)
 PWS
(in auto) – automatic during T/O & Land
– +- 60*, 5 miles in front (microburst windshear detection)
– Gives warning, caution or advisory
WARNING
If a windshear warning alert occurs during final approach,
pilots should consider executing go-around procedures
AIRBORNE DETECTION
Non-Predictive
– Alerts Crew That Windshear Has Been Entered
– “Test Probe”
AIRBORNE DETECTION
SIGMETS
VISUAL CLUES
PIREPS
What Do We Have?
EDUCATION!
Examination of the worldwide windshear associated accidents and
incidents has shown that the majority of these have occurred in the
United States. The greater number of accidents results from the
combination of high convective activity and high air traffic density.
Many more windshear associated accidents and incidents have
probably occurred worldwide but have not been recorded as such.
Months & Time of Day
WEATHER FACTORS
Convective
65%
Fronts
15%
Other
20%
If you avoid any precipitation and
fronts, you avoid 80% of the threat!
Watch Out for Fronts If . . .
The
temperature differential exceeds
10 degrees Fahrenheit
The front is moving faster than 30
knots
Cold Fronts
Be
alert for windshear below 1,000
feet AGL 30 minutes to an hour after
frontal passage
Warm Fronts
Be
alert for windshear below 1,000
feet AGL six to twelve hours prior to
frontal passage
Warm front shears tend to be more
severe
Microburst Producers
High-Based
Thunderstorms
Small Rapidly-Developing Cells
Anything that Produces Convection
– Convection is Responsible for 90%
of Windshear-Related Accidents
Microbursts: Dry or Wet
 Dry
microbursts occur primarily in the high
plains/intermountains where the
temperature/dew point spread is wide (30°
to 50°)
 Wet microbursts are more common in
places like the Mississippi valley where
thunderstorm bases tend to be much lower.
A
Can you see
the micro
burst?
B
D
Can you see
the micro
burst?
C
E
Can you see
the micro
burst?
F
F
Can you see
the micro
burst?
http://www.cimms.ou.edu/~doswell/microbursts/Figure_17b.JPG
Can you see
the micro
burst?
B
http://www.cimms.ou.edu/~doswell/microbursts/Figure_13.JPG
Microburst
 About
5% of all thunderstorms produce
microbursts
 Wet
– Places like the Mississippi River Valley
 Convective
 Heavy
rain
activity with low bases
Dry Microbursts
Microburst
 Dry
– High plains/interior mountains
 Convective
activity forms at higher levels
– Thunderstorm base 10,000 - 15,000 MSL
 Dry
surface conditions
 Surface Temperature of 80+ degrees F
 Wide temp/dew point spread
– 30 - 50 degrees F
 Virga
Visual Identification (Dry)
- Virga :wisps or streaks of water or ice
particles falling out of a cloud but
evaporating before reaching the earth's
surface as precipitation. (NOAA 2001)
- Blowing dust/dust rings at surface
Dry Microbursts
The microburst is rendered visible by an expanding ring of dust
under a virga shaft descending from a high-based cumulonimbus.
The precipitation largely evaporates before reaching the surface,
so the surface rainfall is probably no more than a trace. As the
microburst pictured in the previous developed, the ring of dust
spread out over the surface
Here is a
time lapse
of a dry
microburst
Note the
difference
in wind
speed and
direction
Visual Identification (Wet)
Heavy precip
 Rain foot (Huh?)

http://www.cimms.ou.edu/~doswell/chasesums/chase97_18.JPG
C
MICROBURST WINDSHEAR PROBABILITY GUIDELINES
OBSERVATION
PROBABILITY
OF WINDSHEAR
PRESENCE OF CONVECTIVE WEATHER
NEAR INTENDED FLIGHT PATH:
With localized strong winds (Tower reports or
observed blowing dust, rings of dust,
tornado-like features, etc. ) ………………………………..HIGH
With heavy precipitation (Observed or radar
indications of contour, red or attenuation shadow) ………..HIGH
With rainshower ……………………………………………MEDIUM
With lightning………………………………………………MEDIUM
With virga…………………………………………………..MEDIUM
With moderate or greater turbulence (reported or
radar indications)……………………………………………MEDIUM
With temperature/dew point spread between
30 and 50 degrees Fahrenheit……………………………….MEDIUM
MICROBURST WINDSHEAR PROBABILITY GUIDELINES
OBSERVATION
PROBABILITY
OF WINDSHEAR
PRESENCE OF CONVECTIVE WEATHER
NEAR INTENDED FLIGHT PATH:
With localized strong winds (Tower reports or
observed blowing dust, rings of dust,
tornado-like features, etc. ) ………………………………..HIGH
With heavy precipitation (Observed or radar
indications of contour, red or attenuation shadow) ………..HIGH
With rainshower ……………………………………………MEDIUM
With lightning………………………………………………MEDIUM
With virga…………………………………………………..MEDIUM
With moderate or greater turbulence (reported or
radar indications)……………………………………………MEDIUM
With temperature/dew point spread between
30 and 50 degrees Fahrenheit……………………………….MEDIUM
MICROBURST WINDSHEAR PROBABILITY GUIDELINES
OBSERVATION
PROBABILITY
OF WINDSHEAR
PRESENCE OF CONVECTIVE WEATHER
NEAR INTENDED FLIGHT PATH:
With localized strong winds (Tower reports or
observed blowing dust, rings of dust,
tornado-like features, etc. ) ………………………………..HIGH
With heavy precipitation (Observed or radar
indications of contour, red or attenuation shadow) ………..HIGH
With rainshower ……………………………………………MEDIUM
With lightning………………………………………………MEDIUM
With virga…………………………………………………..MEDIUM
With moderate or greater turbulence (reported or
radar indications)……………………………………………MEDIUM
With temperature/dew point spread between
30 and 50 degrees Fahrenheit……………………………….MEDIUM
MICROBURST WINDSHEAR PROBABILITY GUIDELINES
OBSERVATION
PROBABILITY
OF WINDSHEAR
PRESENCE OF CONVECTIVE WEATHER
NEAR INTENDED FLIGHT PATH:
With localized strong winds (Tower reports or
observed blowing dust, rings of dust,
tornado-like features, etc. ) ………………………………..HIGH
With heavy precipitation (Observed or radar
indications of contour, red or attenuation shadow) ………..HIGH
With rainshower ……………………………………………MEDIUM
With lightning………………………………………………MEDIUM
With virga…………………………………………………..MEDIUM
With moderate or greater turbulence (reported or
radar indications)……………………………………………MEDIUM
With temperature/dew point spread between
30 and 50 degrees Fahrenheit……………………………….MEDIUM
MICROBURST WINDSHEAR PROBABILITY GUIDELINES
OBSERVATION
PROBABILITY
OF WINDSHEAR
PRESENCE OF CONVECTIVE WEATHER
NEAR INTENDED FLIGHT PATH:
With localized strong winds (Tower reports or
observed blowing dust, rings of dust,
tornado-like features, etc. ) ………………………………..HIGH
With heavy precipitation (Observed or radar
indications of contour, red or attenuation shadow) ………..HIGH
With rainshower ……………………………………………MEDIUM
With lightning………………………………………………MEDIUM
With virga…………………………………………………..MEDIUM
With moderate or greater turbulence (reported or
radar indications)……………………………………………MEDIUM
With temperature/dew point spread between
30 and 50 degrees Fahrenheit……………………………….MEDIUM
MICROBURST WINDSHEAR PROBABILITY GUIDELINES
OBSERVATION
PROBABILITY
OF WINDSHEAR
PRESENCE OF CONVECTIVE WEATHER
NEAR INTENDED FLIGHT PATH:
With localized strong winds (Tower reports or
observed blowing dust, rings of dust,
tornado-like features, etc. ) ………………………………..HIGH
With heavy precipitation (Observed or radar
indications of contour, red or attenuation shadow) ………..HIGH
With rainshower ……………………………………………MEDIUM
With lightning………………………………………………MEDIUM
With virga…………………………………………………..MEDIUM
With moderate or greater turbulence (reported or
radar indications)……………………………………………MEDIUM
With temperature/dew point spread between
30 and 50 degrees Fahrenheit……………………………….MEDIUM
MICROBURST WINDSHEAR PROBABILITY GUIDELINES
OBSERVATION
PROBABILITY
OF WINDSHEAR
PRESENCE OF CONVECTIVE WEATHER
NEAR INTENDED FLIGHT PATH:
With localized strong winds (Tower reports or
observed blowing dust, rings of dust,
tornado-like features, etc. ) ………………………………..HIGH
With heavy precipitation (Observed or radar
indications of contour, red or attenuation shadow) ………..HIGH
With rainshower ……………………………………………MEDIUM
With lightning………………………………………………MEDIUM
With virga…………………………………………………..MEDIUM
With moderate or greater turbulence (reported or
radar indications)……………………………………………MEDIUM
With temperature/dew point spread between
30 and 50 degrees Fahrenheit……………………………….MEDIUM
MICROBURST WINDSHEAR PROBABILITY GUIDELINES
OBSERVATION
PROBABILITY
OF WINDSHEAR
PRESENCE OF CONVECTIVE WEATHER
NEAR INTENDED FLIGHT PATH:
ONBOARD WINDSHEAR DETECTION SYSTEM ALERT (Reported
or observed)………………………………………………….HIGH
PIREP OF AIRSPEED LOSS OR GAIN:
-15 knots or greater…………………………………………..HIGH
-Less than 15 knots ………………………………………….MEDIUM
LLWAS ALERT/WIND VELOCITY CHANGE
- 20 knots or greater ………………………………………… HIGH
- Less than 20 knots ………………………………………… MEDIUM
FORECAST OF CONVECTIVE WEEATHER ……………..LOW
MICROBURST WINDSHEAR PROBABILITY GUIDELINES
OBSERVATION
PROBABILITY
OF WINDSHEAR
PRESENCE OF CONVECTIVE WEATHER
NEAR INTENDED FLIGHT PATH:
ONBOARD WINDSHEAR DETECTION SYSTEM ALERT (Reported
or observed)………………………………………………….HIGH
PIREP OF AIRSPEED LOSS OR GAIN:
-15 knots or greater…………………………………………..HIGH
-Less than 15 knots ………………………………………….MEDIUM
LLWAS ALERT/WIND VELOCITY CHANGE
- 20 knots or greater ………………………………………… HIGH
- Less than 20 knots ………………………………………… MEDIUM
FORECAST OF CONVECTIVE WEEATHER ……………..LOW
MICROBURST WINDSHEAR PROBABILITY GUIDELINES
OBSERVATION
PROBABILITY
OF WINDSHEAR
PRESENCE OF CONVECTIVE WEATHER
NEAR INTENDED FLIGHT PATH:
ONBOARD WINDSHEAR DETECTION SYSTEM ALERT (Reported
or observed)………………………………………………….HIGH
PIREP OF AIRSPEED LOSS OR GAIN:
-15 knots or greater…………………………………………..HIGH
-Less than 15 knots ………………………………………….MEDIUM
LLWAS ALERT/WIND VELOCITY CHANGE
- 20 knots or greater ………………………………………… HIGH
- Less than 20 knots ………………………………………… MEDIUM
FORECAST OF CONVECTIVE WEEATHER ……………..LOW
MICROBURST WINDSHEAR PROBABILITY GUIDELINES
OBSERVATION
PROBABILITY
OF WINDSHEAR
PRESENCE OF CONVECTIVE WEATHER
NEAR INTENDED FLIGHT PATH:
ONBOARD WINDSHEAR DETECTION SYSTEM ALERT (Reported
or observed)………………………………………………….HIGH
PIREP OF AIRSPEED LOSS OR GAIN:
-15 knots or greater…………………………………………..HIGH
-Less than 15 knots ………………………………………….MEDIUM
LLWAS ALERT/WIND VELOCITY CHANGE
- 20 knots or greater ………………………………………… HIGH
- Less than 20 knots ………………………………………… MEDIUM
FORECAST OF CONVECTIVE WEEATHER ……………..LOW
MICROBURST WINDSHEAR PROBABILITY GUIDELINES
OBSERVATION
PROBABILITY
OF WINDSHEAR
PRESENCE OF CONVECTIVE WEATHER
NEAR INTENDED FLIGHT PATH:
ONBOARD WINDSHEAR DETECTION SYSTEM ALERT (Reported
or observed)………………………………………………….HIGH
PIREP OF AIRSPEED LOSS OR GAIN:
-15 knots or greater…………………………………………..HIGH
-Less than 15 knots ………………………………………….MEDIUM
LLWAS ALERT/WIND VELOCITY CHANGE
- 20 knots or greater ………………………………………… HIGH
- Less than 20 knots ………………………………………… MEDIUM
FORECAST OF CONVECTIVE WEEATHER ……………..LOW
MICROBURST WINDSHEAR PROBABILITY GUIDELINES
OBSERVATION
PROBABILITY
OF WINDSHEAR
PRESENCE OF CONVECTIVE WEATHER
NEAR INTENDED FLIGHT PATH:
ONBOARD WINDSHEAR DETECTION SYSTEM ALERT (Reported
or observed)………………………………………………….HIGH
PIREP OF AIRSPEED LOSS OR GAIN:
-15 knots or greater…………………………………………..HIGH
-Less than 15 knots ………………………………………….MEDIUM
LLWAS ALERT/WIND VELOCITY CHANGE
- 20 knots or greater ………………………………………… HIGH
- Less than 20 knots ………………………………………… MEDIUM
FORECAST OF CONVECTIVE WEEATHER ……………..LOW
MICROBURST WINDSHEAR PROBABILITY GUIDELINES
OBSERVATION
PROBABILITY
OF WINDSHEAR
NOTE: These guidelines apply to operations in the airport vicinity (within
3 miles of the point of takeoff or landing along the intended flight
path and below 1000 feet AGL). The clues should be considered cumulative.
If more than one is observed the probability weighting should be increased, The
hazard increases with proximity to the convective weather, Weather assessment
should be made continuously.
CAUTION: CURRENTLY NO QUANTITATIVE MEANS EXISTS FOR
DETERMINING THE PRESENCE OR INTENSITY OF MICROBURST
WINDSHEAR, PILOTS ARE URGED TO EXERCISE CAUTION IN
DETERMINING A COURSE OF ACTION.
WINDSHEAR
There I was
Close Call for Reagan!
Strongest
microburst ever recorded
occurred at Andrews AFB on 1 Aug 83,
at 1410.
Air Force One had landed at 1404.
The wind difference between front and
back exceeded 214 knots!
Brush up time
Test
Brush up time
Winds. Wind information plotted uses the “Shaft-Barb-Pennant”
method The FROM direction which the wind is blowing is
represented by the “shaft” or a line. The wind speed is
represented by the barb or pennant. A short barb represents 5 knots
and a long barb represents 10 knots. Pennants are 50-knot winds.
Wind directions are plotted to the nearest 10 degrees relative to
true north.
1 Aug 83
300/015
330/065
300/110
“The Devil and Delta 191:
It Was No Act of God”
by J. Mac McClellan
Flying Magazine
January 1987
CVR from Delta 191 (DFW)
CP says
“There’s lightning comin’ out
of that one.” (6:04:18)
Captain is more concerned about his
malfunctioning DME (6:04:40)
CVR from Delta 191 (DFW)
Capt
says “Watch your speed.” CP
replies, “I’ve got ‘em in idle!”
(06:05:18)
Speed had increased from 150 KIAS
up to 173 KIAS
CVR from Delta 191 (DFW)
Capt
anticipates the windshear:
“You’re gonna lose it all of a sudden;
there it is.” (6:05:22)
Speed dropped from 173 KIAS to 129
KIAS; Vref = 137 knots
CVR from Delta 191 (DFW)
Capt
says, “Push it up; push it way up.
Way up. Way up--that’s it.” (6:05:24)
Sound of fans spooling up, then being
pulled back again (6:05:31)
AOA goes from 6 to 23 within 1
second; pitch +15.7 to - 8.5; over 5000
fpm VVI; 2Gs to -0.3Gs
CVR from Delta 191 (DFW)
GPWS
begins to sound (6:05:43)
Capt commands “TOGO!” (6:05:45)
CP says “Push it way up!” (6:05:47)
“Oh, #%$!” (6:05:53)
Hit the water tanks doing 200 KIAS
AIRCREW ACTIONS
AVOID!
Analyze
the weather
Select the most appropriate runway
Use the appropriate flap setting
Consider using max power
Be ready to use the escape maneuver
Consider a Go-Around . . .
+/-
15 KIAS
+/- 500 fpm VVI
+/- 5 degrees of pitch
+/- one dot on glide slope
Unusual throttle position for
an extended period of time
Critiques