Low-Level Wind Shear and Microbursts — Operational Procedures

This lesson covers the operational response to wind shear and microbursts. The meteorological background is detailed in Subject 050 Lesson "Low-Level Wind Shear and Microbursts".

Source: FAA AC 00-54 Pilot Windshear Guide (1988, still active); ICAO Doc 9817 Manual of Low-Level Wind Shear (3rd ed., 2005).

Wind shear definition

Wind shear is a vertical or horizontal change in wind speed and/or wind direction between two nearby points in the atmosphere. It occurs especially with:

Inversions (temperature inversion at low altitude — typical at night, early morning, or directly above cold surface air).
Thunderstorms — especially during downbursts/microbursts and at outflow boundaries.
Fronts (cold and warm) — abrupt wind change at frontal passage.
Jet streams and mountain waves — primarily at higher altitudes.

In low-altitude flight (take-off and approach) wind shear is life-threatening because no altitude is available to recover.

Detection in the cockpit

Indicators before encounter

METAR/SPECI with WS (wind shear) annotation.
TAF with WS for the active period.
ATIS with "wind shear advisory".
LLWAS / TDWR warning by ATC.
Visual cues: virga under cumulus, dust foot, abrupt cloud movement.
Preceding pilot PIREP "moderate to severe wind shear on final".

During encounter (approach)

Sudden IAS increase of 10–15 kt (headwind phase).
Followed by dramatic IAS loss (tailwind phase, wind reverses).
Altitude loss despite constant configuration.
Sink rate beyond plan.

Wind-shear cases on approach — table without correction

In a stabilised approach on glideslope at Vapp without pilot correction, the aircraft behaves as follows when the wind situation changes:

Wind change	Approach path	IAS	Reason
Decreasing headwind	below plan (low)	drops	less headwind → less lift → descends → IAS drops
Increasing headwind	above plan (high)	rises	more headwind → more lift → climbs → IAS rises
Decreasing tailwind	above plan (high)	rises	wind change acts like increasing headwind
Increasing tailwind	below plan (low)	drops	wind change acts like decreasing headwind

Rule of thumb: when the wind shifts so that effective headwind increases, the aircraft climbs above plan and IAS rises. When effective headwind decreases, the aircraft sinks below plan and IAS drops.

Operational response (approach)

Immediate go-around when:

IAS loss > 10 kt below Vapp within 5 sec.
Altitude loss > 100 ft below glideslope.
Pitch change > ±5° from trimmed approach.
Wind shift > 30° in direction.

Go-around procedure:

Throttle FULL immediately.
Pitch positive to best climb speed or to stick-shaker (extreme).
Flaps reduced gradually after speed gain.
Maintain configuration in extreme emergency — no flap/gear changes.
Inform tower: "Going around, wind shear."
Pattern again for another attempt or alternate.

Take-off with wind-shear warning

Do NOT take off when LLWAS warning active and no better conditions expected.
Runway choice: pick better wind line.
Take-off pause: wait 10–15 min — microburst lifetime 5–15 min.

Microburst-specific

Symptoms

Microburst symptoms (very acute):

IAS rise → IAS loss → descent — all within 20–40 sec.
On low approach (final): high ground-contact risk.

Microburst after lift-off — typical signs

Immediately after lift-off a much stronger than expected IAS rise is observed (headwind phase of the microburst).
Then: reduced climb rate and IAS loss — the aircraft has entered the microburst.

Recovery — microburst right after lift-off

When a microburst is encountered immediately after lift-off, the standard recovery (FAA AC 00-54) is:

Set max power — all available thrust.
Maintain present aircraft configuration — NO flap/gear changes (alters drag, costs energy).
Pitch to Vy (best rate of climb) — maximum altitude gain per time.
Pitch higher if needed up to stick-shaker (stall warning) — avoiding ground beats avoiding stall.
Hold full power until safely clear of the microburst.

Response to suspected microburst on final

Immediate go-around even in stable conditions when other aircraft report wind shear.
Pitch to Vy or stick-shaker — stall is survivable, ground collision is not.
Throttle FULL and hold.
Configuration: reduce flaps when safe (after speed gain, not in the acute phase).

Practical: pilot reaction time

Detection to reaction: typically 3–5 seconds.
In that window IAS can drop 20+ kt and altitude lose 100+ ft.
→ Anticipation: when in doubt, go around earlier rather than later.

Famous accidents recap

(Source: NTSB Final Reports)

Flight	Date	Place	Aircraft	Fatalities
Eastern 66	1975-06-24	JFK	B727	113
Pan Am 759	1982-07-09	New Orleans	B727	153
Delta 191	1985-08-02	DFW	L-1011	137
USAir 1016	1994-07-02	Charlotte	DC-9	37

These accidents led to LLWAS and TDWR at major airports, and to pilot wind-shear recovery training as mandatory for airline crews.