# AC 00-54: Pilot Windshear Guide - Type: Advisory circular (guidance, not mandatory unless a rule or AD requires it) - Status: Historical - Approved: November 25, 1988 - Last reviewed: September 13, 2024 - This change: AC 00-54 is canceled. - Family: AC 00-54 - 14 CFR parts: 1 - Pages: 64 - PDF: https://openairdocs.org/files/sha256/1f/78/1f786f723daa86d2608130cb8c9b822237095e529f4064e757de31ccb076e8c1 - FAA DRS: https://drs.faa.gov/browse/excelExternalWindow/B3FB7DD636FB870B862569BA0068920B.0001 - DRS record last changed: November 21, 2025 - Page: https://openairdocs.org/ac/00-54 ## Versions - [AC 00-54](https://openairdocs.org/ac/00-54) (Historical), approved Nov 25, 1988, 64 pages. AC 00-54 is canceled. ## Text Each page's text from the PDF; open the PDF at a page with #page=N. This is OCR from the scanned FAA advisory circular. OCR can misread letters and numbers. ### Page 1 (OCR) Advisory of Transportation U.S. Department Circular Federal Aviation Administration Subject: Date: 11/25/88 AC No: 00-54 PILOT WINDSHEAR GUIDE Initiated by: AFS- 200 Change: PURPOSE. This advisory circular communicates key windshear information relevant to flightcrews. Appendix 1 of this advisory circular is the Pilot Windshear Guide, which is only one section of the two-volume Windshear Training Aid. RELATED READING MATERIAL. The other components of the Windshear Training Aid are the Windshear Overview for Management, Windshear Substantiating Data, Example Windshear Training Program, and two training videos. These additional publications may be purchased from the National Technical Information Service, 5285 Port Royal Road, Springfield, VA 22161, telephone (703) 487-4650. A multimedia package, including video tapes, slides, and the Windshear Training Aid, may be purchased from the National Audiovisual Center, 8700 Edgeworth Drive, Capitol Heights, MD 20743-3701, telephone (301) 763-1896. 3. BACKGROUND. In 1985, the Federal Aviation Administration (FAA) contracted with a consortium of aviation specialists from the Boeing Company, United Air Lines, McDonnell Douglas, Lockheed California, Aviation Weather Associates, and Heliwell, Inc., to study windshear. As a result, the Windshear Training Aid was developed. The Windshear Training Aid presents an effective means of training flightcrews to minimize the windshear threat through avoidance, cockpit recognition, and recovery techniques. In order to make the Pilot Windshear Guide section of the Windshear Training Aid available to a wide aviation audience, the guide is reprinted as appendix 1 to this advisory circular. 4. UPDATING PROCEDURE. In order to ensure that the Pilot Windshear Guide is kept up-to-date, the FAA will host meetings for the purpose of reviewing new information on the subject of windshear. These meetings will be held approximately every 18 months and will be announced in the Federal Register. Technical assistance will be solicited from representatives of the original contract team, as well as from other qualified industry sources, in proposing and evaluating changes. As improvements and changes to the Pilot Windshear Guide occur, they will be distributed as a change to this advisory circular. DCBcauditle D. C. Beaudette Acting Director, Flight Standards Service ### Page 3 (OCR) Appendix 1 APPENDIX 1. PILOT WINDSHEAR GUIDE ### Page 4 (OCR) Appendix 1 Pilot Windshear Guide-- Disclaimer and Indemity Notice The following disclaimer is required by virtue of the contract between the Federal Aviation Administration and the Boeing Commercial Airplane Company. DISCLAIMER AND INDEMNITY NOTICE and its companion documents, Windshear stantiating "A Windshear Avoided" andỗạWindshear What the Crew Can Do" were prepared pursuant to Federal Aviation Administration Prime Contract DFTAOl- 86-C-00005 with The Boeing Company as a training aid for flight in windshear conditions. The information contained erein and in the companion material: was derived from information originally developed for the Boeing 727, and with additional recommendating, Doug- veloped and approved by Boeing, provides a base-line training program las or Lockheed for their respective might be adapted for use in specific adapted for use in specific commercial transport aircraft manufac- OF THIS PILOT WINDSHEAR GUIDE AND ITS COMPANION VIDEO PRESENTATIONS ỊA WIND- SHEAR AVOIDED" AND "WINDSHEAR - WHAT THE CREW CAN DO" FOR ANY PURPOSE RE- **LATED TO AIRCRAFT OR CONDITIONS OTHER** **THAN THOSE SPECIFIED ABOVE IS NOT** **AUTHORIZED AND MAY RESULT IN IMPROPER** **AIRCRAFT OPERATION, LOSS OF AIRCRAFT** **CONTROL, INJURY AND LOSS OF AIRCRAFT AND LIFE. ANY USE, ADAPTATION AND/OR** **USE AFTER ADAPTATION OF THE MATERIAL** **IN THIS PILOT WINDSHEAR GUIDE AND ITS** COMPANION VIDEO PRESENTATIONS A WIND- SHEAR AVOIDED" AND "WINDSHEAR - WHAT THE CREW CAN DO" BY ANY ENTITY FOR ANY **PURPOSE RELATED TO AIRCRAFT, CONDI-** **TIONS OR TO TRAINING PROGRAMS OTHER** **THAN THOSE SPECIFIED ABOVE SHALL BE** **COMPLETELY AT THE RISK OF THE ENTITY** **RESPONSIBLE FOR USING, ADAPTING AND/OR** **USING THE ADAPTATION OF THIS PILOT** WINDSHEAR GUIDE AND ITS COMPANION VID- EO PRESENTATIONS "A WINDSHEAR AVOIDED" AND "WINDSHEAR - WHAT THE CREW CAN ADAPTATION AND/OR USE AFTER ADAPTATYON SUCH ENTITY BY SUCH USE, †1 **ASSUMES SUCH RISK AND WAIVES AND RE-** **LEASES ALL CLAIMS IT MAY HAVE AGAINST** THE BOEING COMPANY, MCDONNELL DOUGLAS ASSOCIATE SUSSIARES. CORPORATION, LOCKHEED AVIATION CORPORATION, WEATHER THEIR **THN TOES NO THAN ES THE NY CON AFFILIATES** **BILITY WHATSOEVER, WHETHER BASED** **CONTRACT (INCLUDING BUT NOT LIMITED** **TO EXPRESS AND IMPLIED WARRANT** **CLAIMS), TORT (INCLUDING BUT NOT LIM** **ITED TO NEGLIGENCE AND STRICT LIABIL-** ITY CLAIMS) OR OTHERWISE, ARISING FROM SUCH ADAPTATION. ANY SUCH ENTITY (IN- ADAPTATION AND/OR USE OF **CLUDING WITHOUT LIMITATION ANY MANU-** **FACTURER OF OTHER AIRCRAFT OR OPERATOR** **WITH ANOTHER TRAINING PROGRAM BUT NOT** **THE UNITED STATES GOVERNMENT) WHICH** **USES THIS PILOT WINDSHEAR GUIDE AND** ITS COMPANION VIDEO PRESENTATIONS A WINDSHEAR WHAT THE CREW CAN DO" OR ADAPTS AND/OR AVOIDED" Ạ&WINDSHEAR **USES AN ADAPTATION THEREOF WITH RE-** **SIONS OR TRAINING PROGRAM THEREBY TRAINING PROGRAM** AGREES TO INDEMNIFY AND HOLD HARMLESS THE BOEING COMPANY, McDONNELL DOUGLAS **CORPORATION, CORPORATION,** **DIVISIONS, SUBSIDIARIES AND AFILTATES** **SUBCONTRACTOES ANO PILOTES FROM MAY** **LIABILITY WHATSOEVER, WHETHER BASED ON (INCLUDING BUT NOT LIMITED** **CLAIMS), TORT (INCLUDING BUT NOT LIM-** **ITED TO NEGLIGENCE AND STRICT LIABIL-** **ITY CLAIMS) OR OTHERWISE, ARISING FROM** **ADAPTATION AND/OR USE OF SUCH ADAPTATION.** Notwithstanding any other provision of this contract to the contrary, the FAA shall accept the items delivered hereunder with the disclaimer affixed by Contractor and agrees not to remove such disclaimer for any reason whatsoever. ### Page 5 (OCR) Appendix 1 **PILOT WINDSHEAR GUIDE** **TABLE OF CONTENTS** **SECTION DESCRIPTION PAGE** **2.0 INTRODUCTION** **2.1 OBJECTIVES 1** **2.2 WINDSHEAR WEATHER 2** **2.3 LESSONS LEARNED FROM WINDSHEAR ENCOUNTERS 14** **2.3.1 ENCOUNTER DURING TAKEOFF - AFTER LIFTOFF 15** **2.3.2 ENCOUNTER DURING TAKEOFF - ON RUNWAY 19** **2.3.3 ENCOUNTER ON APPROACH 22** **2.3.4 WINDSHEAR EFFECTS ON AIRPLANES AND SYSTEMS 24** **2.3.5 DEVELOPMENT OF WIND MODELS 28** **2.4 MODEL OF FLIGHT CREW ACTIONS 29** **2.4.1 EVALUATE THE WEATHER 30** **2.4.2 AVOID KNOWN WINDSHEAR 35** **2.4.3 CONSIDER PRECAUTIONS 38** **2.4.3.1 TAKEOFF PRECAUTIONS 38** **2.4.3.2 APPROACH PRECAUTIONS 41** **2.4.4 FOLLOW ESTABLISHED STANDARD OPERATING TECHNIQUES 43** **2.4.5 WINDSHEAR RECOVERY TECHNIQUES 45** **2.4.5.1/3 ENCOUNTER DURING TAKEOFF - AFTER LIFTOFF AND** ENCOUNTER ON APPROACH ... … 45 2.4.5.2 ENCOUNTER DURING TAKEOFF - ON RUNWAY … 49 2.5 SUMMARY … 56 iii ### Page 7 (OCR) Appendix 1 2.0 INTRODUCTION Aid is to reduce windshear related accidents and incidents by modifying During the period from 1964 to 1986, flight crew behavior through education at least 32 accidents and incidents and training. have occurred in which windshear was identified as a contributing These accidents and incidents resulted 2.1 OBJECTIVES in over 600 fatalities and nearly 250 The objective of the Pilot Windshear injuries. There is evidence to sug- Guide is to summarize and communicate gest that if undocumented "close key windshear information relevant to calls and general aviation statistics flight crews. It is intended to be were included, these figures would be provided to pilots during windshear much higher. ground training and to be retained as a windshear information reference for serious nature of this future use. problem, the National Research Council was commissioned to study the wind- Avoidance is emphasized as the best shear issue. One finding of the Coun- defense against the hazards of low algeneral lack of effective titude windshear. Information to astraining programs The Council made recommenda- shear is provided. sist in recognizing and avoiding wind- However improving precautions regarding further efforts needed tions and techniques for to improve the training of pilots to chances of surviving an inadvertent recogniZe windshear avoid, and cope with inad- windshear encounter are also disencounters. cussed. Specifically, the Pilot Windresult of these recommendations, the shear Guide presents key findings re- Federal Aviation Administration garding: sored development of a comprehensive Windshear Training Aid. 1) Windshear weather, particularly microbursts, and clues which may The Pilot Windshear Guide is one of indicate its presence, several parts of the Windshear Training Aid. The other components are the 2) Effects of windshear on airplanes, Windshear Overview for Management, Windshear Substantiating Data, Example 3) Windshear recognition from the Windshear Training Program, and two cockpit, and avoidance, Training Videos. 4) Precautions to take when windshear The educational material and training is suspected, recommendations provided in the Wind- Training Aid were developed 5) Standard operating techniques rethrough an extensive review process to lated to windshear, and achieve a wide air transport industry consensus. The goal of the Training 6) Recovery techniques to be used in an inadvertent windshear encounter. ### Page 8 (OCR) Appendix 1 2.2 WINDSHEAR WEATHER Decreasing Headwind Shear - Windshear in which headwind decreases causing an Wind variations at low-altitude have airspeed loss. Tong been recognized as a serious hazard to airplanes during takeoff and Decreasing Tailwind Shear - Windshear approach. These wind variations can in which tailwind decreases causing an result from a large variety of meteor- airspeed increase. ological conditions such as: topographical conditions, temperature in- Increasing Tailwind Shear - Windshear versions, sea breezes, frontal sys- in which tailwind increases causing an tems, strong surface winds, and the airspeed loss. most violent forms of wind change--the thunderstorm and rain shower. Examination of airplane accident and incident reports from 1959 1983 Throughout this document several terms identified 51 windshear-related are used when discussing low altitude events. These events are summarized wind variations. in Figure 1. fined as follows: In order to avoid further windshear Windshear - Any rapid change in wind encounters, pilots must learn to direction or velocity. recognize conditions producing windshear. As Figure 1 indicates, 2 out Severe Windshear - A rapid change in of every 3 windshear events were rewind direction or velocity causing lated to convective storms. For this airspeed changes greater than 15 knots reason, the primary focus of the Pilot or vertical speed changes greater than Windshear Guide is directed toward 500 feet per minute. windshear associated with convective weather conditions: thunderstorms, Increasing Headwind Shear - Windshear and in particular the most hazardous in which headwind increases causing an form of windshear, the microburst. airspeed increase. Weather System Windshear Events* Number of Convective Storms 33 (Thunderstorms, Rain/ Snow Showers) Front Strong Surface Winds 2 Unstable (Turbulent) Air 2 Strong Winds on Top of Temperature Inversion Sea Breeze Front Mountain Wave Unknown Total 51 *Event - accident or incident Figure 1. Windshear events by weather system (1959 to 1983). ### Page 9 (OCR) Appendix 1 o The Thunderstorm beginning of the mature stage and presence of a downdraft. After ap- There are two basic types of thunder- proximately an hour, the heated upstorms: airmass and frontal. Airmass draft creating the thunderstorm is cut thunderstorms appear to be randomly off by rainfall. Heat is removed and distributed in unstable air and devel- the thunderstorm dissipates. Many op from localized heating at the thunderstorms produce an associated earth's surface (Figure 2). The heat- cold air gust front as a result of the ed air rises and cools to form cumulus downflow and outrush of rain-cooled clouds. As the cumulus stage contin- air. These gust fronts are usually ues to develop, precipitation forms in very turbulent and can create a serihigher portions of the cloud and ous threat to airplanes during takeoff falls. Precipitation signals the and approach. Cumulus Stage Mature Stage Dissipating Stage - Gust Front 5x85 Rain Light Rain Surface Heating Localized T = Airflow/Circulation Cooling Surface Figure 2. Airmass thunderstorm life cycle. ### Page 10 (OCR) Appendix 1 Frontal thunderstorms are usually as- (speed and direction) at different sociated with weather systems like altitudes in the thunderstorm. This fronts, converging winds, and troughs causes the severe thunderstorm to be aloft. Frontal thunderstorms form in vertically tilted (Figure 3). Precipsquall lines, last several hours, itation falls away from the heated upgenerate heavy rain and possibly hail. draft permitting a much longer storm and produce strong gusty winds and development period. Resulting airpossibly tornadoes. The principal flows within the storm accelerate to distinction in formation of these more much higher vertical velocities which severe thunderstorms is the presence ultimately result in higher horizontal of Targe horizontal wind changes wind velocities at the surface. Anvil Wind Updraft Downdraft / Airflow Circulation 53355 Surface Heating - Heavy Rain and Hail Figure 3. Severe frontal thunderstorm anatomy. ### Page 11 (OCR) Appendix 1 The downward moving column of air, or downdratt, of a typical thunderstorm is fairly large, about 1 to 5 miles ir and tornadoes make it critical that pilots avoid thunderstorms. Figure 4 shows average annual worldwide thunderdiameter. Resultant outflows may pro- storm days. duce large changes in wind speed. Certain areas can readily be seen to Though wind changes near the surface have a high potential for windshear occur across an area sufficiently Decause of the high level of conveclarge to lessen the effect, thunder- tive activity. Due to the lower frestorms always present a potential haz- quency of air traffic in the highest ard tO airplanes. Regardless of threat areas (the tropics), fewer acwhether a thunderstorm contains wind- cidents have been reported in these shear however, the possibility of regions. heavy rain, hail, extreme turbulence, Figure 4. Average annual worldwide thunderstorm days. Note that the highest windshear threat occurs in the tropics. ### Page 12 (OCR) Appendix 1 Examination of the worldwide windshear- high convective activity and high air associated accidents and incidents in traffic density. Many more windshear- Figure 5 shows that the majority of associated accidents and incidents these have occurred in the United have probably occurred worldwide but States. The greater number of acci- have not been recorded as such. dents results from the combination of var • Edmonton Detroil . *New York City * Chicago Tucson • Chihuahua • New Orleans Mexico City Pago Pago A Microburst-related accident/incident Figure 5. Worldwide microburst-related airplane accidents/incidents. High frequency of air traffic in North America combined with a high number of thunderstorm days leads to concentration of windshear-related accidents/incidents in United States. ### Page 13 (OCR) Appendix 1 In fact, closer examination of the derstorm activity and a number of United States (Figure 6) shows a cor- accidents. relation between areas of high thun- 10 20 30 40 30 30 20 10 10 20 30 40 40 80 • Microburst-related accident/incident 30 80 30 80 Figure 6. Average annual continental U.S. thunderstorm days. Correlation exists between regions of higher thunderstorm activity and windshear-related accidents incidents. ### Page 14 (OCR) 11/25/88 AC 00-54 Appendix 1 o The Microburst as a Windshear Threat Downdrafts associated with microbursts are typically only a few hundred to Identification of concentrated, more 3,000 feet across. When the downdraft powerful downdrafts--known as micro- reaches the ground, it spreads out bursts--has resulted from the inves- horizontally and may form one or more tigation of windshear accidents and horizontal vortex rings around the from meteorological research. Micro- degion is typically 6,000 to 12,000 downdraft (Figure bursts can occur anywhere convective weather conditions (thunderstorms, feet across. The horizontal vortices rain showers, virga) occur. Observa- may extend to over 2,000 feet AGL. tions suggest that approximately five percent of all thunderstorms produce a microburst. Cloud Base 1000 ft Approx Virga or Scale Rain 1000 ft - Downdraft Outflow Front - Horizontal Vortex Outflow Figure 7. Symmetric microburst. An airplane transiting the microburst would experience equal headwinds and tailwinds. ### Page 15 (OCR) Appendix 1 Microburst outflows are Therefore, not not always may be much less than the subsequent symmetric (Figure 8). airspeed loss experienced when exiting significant airspeed increase may the microburst. occur upon entering the outflow, or Cloud Base 1000 ft Approx Virga or Scale Rain • • 1000 ft Downdraft Horizontal Vortex Wind Outflow Front- Outflow Figure 8. Asymmetric microburst. An airplane transiting the microburst from left to right would experience a small headwind followed by a large tailwind. ### Page 16 (OCR) Appendix 1 More than one microburst can occur in the same weather system. Pilots are therefore cautioned to be alert for additional microbursts if one has already been encountered or observed. If several microbursts are present, a series of horizontal vortices can form near the ground due to several microbursts being embedded in one another (Figure 9). Conditions associated with these vortices may produce very powerful updrafts and roll forces in addition to downdrafts. 500 ft Approx Series of Horizontal Scale Microburst Vortices 500 ft Microburst Figure 9. Horizontal Vortices. A series of horizontal vortices can form near the ground due to microbursts imbedded in one another. ### Page 17 (OCR) Appendix 1 Wind speeds intensify for about 5 minutes after a microburst initially contacts the ground (Figure 10). An encounter during the initial stage of microburst development may not be considered significant but an airplane following may experience an airspee change two to three times greater. Microbursts typically dissipate within 10 to 20 minutes after ground contact. Maximum Initial Ground Shear Dissipation Downdraft Contact Intensity Begins Cloud base as high as 15,000 ft 10 15 Elapsed Time (min) Figure 10. 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. ### Page 18 (OCR) AC 00-54 Appendix 1 Doppler radar wind measurements indicate that the wind speed change a pilot might expect when flying through the average microburst at its point of peak intensity is about 45 knots (Figure However, microburst windspeed differences of almost 100 knots have been measured. In fact, a severe event at Andrews Air Force Base (Camp Spring, Maryland) on August 1, 1983 11/25/88 indicated headwind/tailwind differential velocities near 200 knots. IT IS VITAL TO RECOGNIZE THAT SOME EStEPED WITH ANY KNOWN SUCCESSFULLY MICROBURSTS CANNOT TECHNIQUES! Note that even windshears which were within the performance capability of the airplane have caused accidents. • Maximum windshear capability of jet transports at heavy weight, for a shear encounter at a critical location, is 40 to 50 knots windspeed change Number of Measured Microbursts (500 ft JAWS Doppler Radar Data) 20 30 40 50 60 70 80 90 100 JFK MSYDENOÃD DEN DFW DEN - Accident/ Incident Windspeed Maximum Horizontal Windspeed Change (kt) Changes Figure 11. Microburst frequency versus intensity. Accidents have occurred in windshears within performance capability of airplane. Some windshears cannot be escaped successfully! ### Page 19 (OCR) Appendix 1 Microbursts can be associated with In this example, air below _a cloud both heavy rain, as in thunderstorm base (up to approximately 15,000 feet conditions, and much lighter precipi- tation associated with convective higher AGL) is very dry. convective clouds Precipitation from falls into relatively virga clouds. Microbursts have occurred in dry conditions of light evaporative cooling causes the air to low humidity air and evaporates. This rain or (precipitation that plunge downward. As the evaporative evaporates before reaching the earth's Tore cautione not to fly bene there- cooling process continues, downsurface). The formation of a dry microburst is illustrated in Figure 12. vective clouds producing virga conditions. Cloud Base (As high as 15,000 ft) 1000 ft Approx Virga or Scale Dry Light Rain - 1000 ft Air - Downdraft Outflow Front / Cold Horizontal Air ||| Vortex Plunge Outflow Figure 12. Dry microburst formation. Evaporation of rain below cloud base (virga) causes intense cooling of rainshaft air and subsequent cold air plunge. ### Page 20 (OCR) Appendix 1 2.3 LESSONS LEARNED FROM WINDSHEAR Windshear Recognition **ENCOUNTERS** • Recognition of windshear encounter Analysis of past windshear accidents is difficult and is usually comand incidents has taught valuable les- plicated by marginal weather regarding windshear recognition and flight path control. Engineering • Time available for recognition and and flight simulator recovery is short (as little as 5 tions have been conducted as well to seconds) additional intormation. resulting lessons learned form a basis o Flight crew coordination is essenrecommended precautions and tial for prompt windshear recognitechniques in this document. tion and recovery The primary lesson learned is that the Pilot Technique best defense against windshear is to avoid it altogether. This is espe- o Flight path must be controlled cially important because shears wil with pitch attitude (unusual stick exist which are beyond the capability forces may be required as a result) of any pilot or airplane. In most windshear accidents, several. clues-- o Lower than normal airspeed may LLAAS alerts, weather reports, visual have to be accepted to counter signs--were present that would have lift loss alerted the flight crew to the presence of a windshear threat. In all In reaching these conclusions, three instances, however, these clues were types of windshear encounters which either not recognized or not acted have resulted in an accident or inciupon. Flight crews must seek and heed dent were examined: an encounter dursigns alerting them to the need for ing takeoff after liftoff, an encounavoidance. ter during takeoft on the runway, and an encounter during approach. Details Other lessons were also learned re- of these encounters and the lessons garding windshear recognition Tearned are described in Sections pilot technique should the avoidance 2.3.1 through 2.3.3. Following this process fail. These lessons are sum- Section 2.3.4 presents the lessons marized as follows: learned regarding effects of windshear on airplanes and airplane systems. Section 2.3.5 describes the impact of these lessons on simulator training. ### Page 21 (OCR) Appendix 1 2.3.1 ENCOUNTER DURING TAKEOFF - AFTER off the runway (Figure 13). For the LIFTOFF first 5 seconds after liftoff the takeoff appeared normal, but the air- In a typical accident studied, the plane crashed off the end of the runairplane encountered increasing way about 20 seconds after liftoff. tailwind shear shortly after lifting Microburst Runway Figure 13. Windshear encounter during takeoff after liftoff. (1) Takeoff initially appeared normal. (2) Windshear encountered just after liftoff. (3) Airspeed decrease resulted in pitch attitude reduction. (4) Aircraft crashed off departure end of runway 20 sec after liftoff. ### Page 22 (OCR) Appendix 1 In many events involving after-liftoff required on some airplanes). correcwindshear encounters, early trends in tive action, however, was too late to airspeeand altitude appeared normal. pitch attitude, vertical prevent ground contact since the downspeed ward flight path was well established. In this example, the airplane encountered windshear before stabilized Reducing pitch attitude to regain lost climb was established which caused airspeed, or allowing attitude to dedifficulty in detecting onset of crease in response to lost airspeed, shear. As the airspeed decreased, is the result of past training emphapitch attitude was reduced to regain sis on airspeed control. Successful trim airspeed (Figure 14). By reduc- recovery from an inadvertent windshear ing pitch attitude, available perform- encounter requires maintaining or inance capability was not utilized and creasing pitch attitude and accepting the airplane lost altitude. As ter- Tower than usual airspeed. Unusual rain became a factor, recovery to ini- and unexpected stick forces may be retial pitch attitude was initiated. quired to counter natural airplane This required unusually high stick pitching tendencies due to airspeed force (up to 30 pounds of pull may be and lift loss. Lift Normal Flight Path Normal Climb Pitch Down Descending Microburst * Lift Flight Path →--^ Figure 14. Windshear effects on flight path. Microburst reduces airspeed and lift at normal attitude which results in pitch down tendency to regain airspeed. ### Page 23 (OCR) Appendix 1 To counter the loss of airspeed and flight path degradation be prevented lift resulting from windshear, pitch (Figure te from the intended flight Once the airplane begins attitude must not be allowed to fall to deviate below the normal range. Only by prop- path and high descent rates develop, erly controlling pitch attitude and it takes additional time and altitude accepting reduced airspeed can to change flight path direction. Pitch Down Descending Flight Lift Path Microburst- Lack of Proper Pitch Control Improved Flight Path Microburst Controlled Pitch Attitude Figure 15. Pitch control effects on flight path. Control of pitch attitude and acceptance of reduced airspeed results in improved flight path. ### Page 24 (OCR) Appendix 1 In the windshear encounter cited ear- Only 5 to 15 seconds may be available Capability may not have been used bee available airplane performance to recognize and respond to a windshear encounter (Figure 16). It is cause of two factors: lack of timely therefore of great importance that a recognition and inappropriate or in- windshear encounter be recognized as adequate response. Rapidly deterio- soon as possible. Timely recognition rating climb performance may not De of windshear requires effective crew apparent to the crew unless all appro- coordination and appropriate callouts priate vertical flight path instru- by the pilot not flying. ments are closely monitored. 300 200 Normal Altitude (ft) Typical Accidents/Incidents 100 5 10 15 20 25 Time From Liftoff (sec) Figure 16. Time available to respond to windshear encounter. Takeoff initially appeared normal. Additional time is required to arrest descent. Result: only 5 to 15 sec may be available for recognition and recovery. ### Page 25 (OCR) Appendix 1 2.3.2 ENCOUNTER DURING TAKEOFF - ON increasing tailwind shear however, the RUNWAY airplane did not reach VR As the until nearing the end of the runway. Analysis of a typical accident where airplane lifted off, the tailwind conan increasing tailwind shear was en- tinued increasing, preventing any furcountered during takeoff ground roll ther airspeed increase. The airplane showed that initial indications ap- contacted an obstacle off the deparpeared normal (Figure 17). Due to the ture end of the runway. Microburst Runway Figure 17. Windshear encounter during takeoff on runway. (1) Takeoff initially appeared normal. (2) Airspeed buildup slowed due to windshear. (3) Airplane reached Vp near end of runway, lifted off but failed to climb. (4) Airplane contacted obstacle off departure end of runway. ### Page 26 (OCR) Appendix 1 windshear encounter, ift Less-than-normal airspeed, resulted in re- due to takeoff attitude (Figure 18). turn, inability lift off soon In duced available at normal enough to clear obstacles resulted. Runway Normal Takeoff Microburst* Lift Runway Windshear Encounter Figure 18. Windshear effects on liftoff. Microburst reduces airspeed and lift at normal attitude that results in inability to lift off. ### Page 27 (OCR) 11/25/88 AC 00-54 Appendix 1 An additional factor is the difficulty If there is insufficient runway left of recognizing deteriorating airplane to accelerate to normal takeoff speed, performance. Timely recognition of a and inadequate runway to stop, liftoff windshear encounter on the runway may and safe climb may require rotation at be difficult since the only indication speeds less than normal rotation speed may be a slower than normal airspeed (Vp). In this case, additional pitch increase. The presence of gusts may attitude may De required to achieve mask abnormal airspeed build-up. Time sufficient lift (Figure 19). In traavailable to respond effectively to a ditional training, crews are frequentwindshear may be as little as ly cautioned not to rotate at speeds seconds from the initial encounter. less than vp to avoid high pitch at- Effective crew coordination, particu- titudes that could result in aft bod larly standard callouts, is essential contact. In a windshear encounter in routine operations to develop habit otation toward normal takeoff pitch patterns required to ensure timely attitude at lower than normal airspeed recognition of degrading performance. may be required to lift off in the remaining runway. This may result in Full thrust may be required to provide additional performance, particularly advertent aft body contact. To deal with an in- windshear encounter, tech- the if reduced thrust takeoff procedures pilot must be prepared to apply have been used. niques which differ from those ordinarily used. Lift Microburst• Runway Normal Takeoff Attitude Lift Microburst" Runway Increased Pitch Attitude Figure 19. Pitch attitude effects on liftoff. Increased pitch attitude generates lift required for liftoff. ### Page 28 (OCR) Appendix 1 2.3.3 ENCOUNTER ON APPROACH along the approach flight path (Figure 20). airplane lost airspeed, Analysis of a typical windshear en- dropped below the target glidepath, counter on approach provided evidence and contacted the ground short of the of an increasing downdraft and tailwind runway threshold. Microburst Glide Slope Instruments Visual Runway Figure 20. 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. ### Page 29 (OCR) Appendix 1 Reduced airspeed, as the airplane encountered the windshear, resulted decreased lift. This loss of lift increased the descent rate (Figure 21). The natural nose-down pitch response of the airplane to low airspeed caused additional altitude loss. Pitch attitude increase and recovery initiation were not used soon enough to prevent ground contact. Lack of timely and appropriate response--affected by weather conditro limited recognition time was a inadequate crew coordination significant factor in delaying re- Gradual applicathrust during have masked the initial decreasing airspeed trend. complicated the approach. from instruments to exterior references may have detracted from instrument scan. Inadequate crew coordination may have resulted in failure to be aware of flight path degradastabilized approach clearly defined callouts is essential to aid in recognition of unacceptable flight path trends and the need to initiate recovery. Glide Path Lift Flight on Glide Path Runway Normal Approach Glide Path Pitch Down Microburst* Descending Below Glide Path Runway Windshear Encounter Figure 21. Windshear effects on flight path on approach. Microburst reduces airspeed and lift at normal attitude which results in pitch down tendency to regain airspeed. ### Page 30 (OCR) Appendix 1 2.3.4 WINDSHEAR EFFECTS ON AIRPLANES headwind shears must not be relied AND SYSTEMS upon to provide early indications of subsequent tailwind shears. Be prepared. Windshear Effects on Airplanes In contrast to shears which increase o Headwind/Tailwind Shear Response airspeed, an increasing tailwind (or decreasing headwind) shear will de- The various components of windshear crease indicated airspeed and performhave unique effects on airplane per- ance capability. Due to airspeed for the shear depts ot the flight loss, the airplane may tend to pitch of the shear depends down to regain trim speed. path through the microburst. • Vertical Windshear Response an increasing headwind (or decreasing tailwind) shear increases indicated Vertical winds exist in every microairspeed and thus increases perform- burst and increase in intensity with ance. The airplane will tend to pitch Such winds usually up to regain trim airspeed. An addi- peak intensity at heights greater than tional consideration is that this type 500 feet above the ground. of shear may reduce normal decelera- speeds greater than 3,000 feet tion during flare which could cause per minute can exist in the center of overrun. a strong microburst. The severity of the downdraft the airplane encounters Any rapid or large airspeed increase, depends on both the altitude and latparticularly near convective weather eral proximity to the center of the conditions, should be viewed as a possible indication of a forthcoming airspeed decrease. Thus a large airspeed Perhaps more critical than sustained increase may be reason for discontinu- downdrafts, short duration reversals ing the approach. However, since mi- in vertical winds can exist due to the crobursts are often asymmetric and the horizontal vortices associated with headwind may not always be present, microbursts. This is shown in Figure 22. 500 ft Microburst Approx Series of Horizontal Scale Vortices 500 ft Microburst Flight Path Figure 22. Encounter with microburst horizontal vortices. Rapid updraft downdraft variations due to horizonta/ vortices can cause uncommanded pitch changes and may result in momentary stick shaker activation well above normal stick shaker speeds. ### Page 31 (OCR) 11/25/88 AC 00-54 Appendix 1 An airplane flying through horizontal input to counteract the roll and mainvortices as shown on the previous page tain aircraft control experiences alternating updrafts and downdrafts causing pitch changes with- • Turbulence Effects out pilot input. These vertical winds result in airplane angle-of-attack Turbulence may be quite intense in Fluctuations which, if severe enough, weather conditions associated with may result in momentary stick shaker windshear. Effects of turbulence can actuation or airframe shudder at mask changing airspeed trends and speeds well above normal. delay recognition of severe windshear. Turbulence may also tend to vertical winds, like those associated discourage use of available airplane vortices the recovery pitch attitude during a recovery by sidered in development of causing random stick shaker activity. significant These effects can significantly increase pilot workload and distraction. to increase pilot workload The higher work- • Rain Effects load results from attention to momentary stick shaker actuation and uncom- Accident investigations and the study manded pitch of windshear have shown that some rapid changes in vertical wind. forms of windshear are accompanied by high rates of rainfall. NASA research • Crosswind Shear Response is underway to determine if high rainfall rates contribute to a loss of A crosswind shear tends to cause the airplane pertormance. The results airplane to roll and/or yaw. Large available to date are inconclusive. crosswind shears may require large or However, because rain may serve as a rapid control wheel inputs. These warning of sevent wie avoided! areas of shears may result in significantly in- heavy rain should be High creased workload and distraction. In rates of rainfall also cause signifiaddition, if an aircraft encounters a cant increases cockpit noise horizontal vortex, severe roll forces levels, making crew coordination and may require up to full control wheel pilot concentration more difficult. ### Page 32 (OCR) Appendix 1 • Basic Aerodynamics tudinal stability characteristics tend to pitch the airplane up with increas- The pilot has direct control over air- ing airspeed and down with decreasing plane pitch attitude which in turn airspeed. Thrust changes in response acts to change the flight path. The to these airspeed variations may also angle-of-attack will change with pitch affect stability. In airplanes with attitude resulting in modified underwing-mounted engines, there is an flight path angle. These three angles additional tendency to pitch up as are related as follows: thrust increases, and pitch down as thrust decreases. This tendency may Attitude = Angle of * path Angle Pitch Flight become more pronounced at low speeds. Attack o Stall and Stall Warning • Airplane Performance Airplane stall occurs when further in- Transport category airplanes have con- creases in angle-of-attack produce no siderable climb capability at speeds further increase in lift. In order to below normal reference values. As prevent inadvertent _entry. into this seen in Figure 23 for typical takeoff flight region, stall warning devices climb performance, a rate-of-climb of (stick shakers, stick pushers, stall 1500 FPM is possible even at stick warning horns) are installed on airshaker speeds. planes. In addition, having clean, smooth wing leading edges will help o Airplane Stability prevent both early onset of stall buffet as well as rolloff tendency prior As mentioned earlier, typical longi- to stall. 2500 Rate-of- Climb (ft/min) 1500 Stick Shaker 130 150 Airspeed (kt) Figure 23. Typical takeoff rate-of-climb capability. Significant climb capability exists even at stick shaker airspeeds. ### Page 33 (OCR) Appendix 1 Windshear Effects or. Systems provide accurate vertical speed information. Due to instrument lags, • Altimeters indications may be several seconds behind actual airplane rate of climb/ During callouts and instrument scan in descent and, in some situations, may a windshear, use of radio and/or baro- indicate a climb after the airplane metric altimeters must be tempered by has started descending (Figure 24). the characteristics of each. Since vertical speed indicators driven by an radio altitude is subject to terrain Inertial Reference Unit (IRU) show contours, the indicator may show a significant improvement over other climb or descent due to falling or type instruments but still have some rising terrain, respectively. The 1ag• barometric altimeter may also provide distorted indications due to pressure In addition, gust-induced pitot static variations within the microburst. pressure variations within the microburst may introduce further VSI in- • Vertical Speed Indicators accuracies. Due to such lags and errors, a11 vertical flight path The vertical speed indicator (VSI) instruments should be crosschecked to should not be solely relied upon to verify climb/descent trends. 1200 Actual Vertical Speed ,, inertial- Instruments Referenced VSI Lag and 800 - Air Data Indicate Climb Erroneousiy System VSi Vertical 400 Speed (ft/min) Takeoff Roll -400 Airplane Is Descending 008- 8 12 16 20 24 28 32 36 40 44 48 Time (sec) Figure 24. VSI error during takeoff windshear encounter. VSI may lag actual flight path changes. ### Page 34 (OCR) AC 00-54 Appendix 1 • Stick Shaker Stick shaker is activated by angle of attack. Consequently, rapidly changing vertical winds or maneuvering will vary the attitude and airspeed at properly functioning system alpha vanes, stick shaker will normally activate providing a warning prior to stall. below the stall angle of attack thus • Cockpit Angle of Attack Indicators useful of attack indicators do provide indications of margin to stick shaker; however, they may not provide effective guidance in a windshear ensince angle of attack is attitude adjustments where controlled indirectly through pitch In an actual winaging veerical winds cause padly angle of attack fluctuations independenter pilet fangte the attack direts its usefulness as a guiding parameter. 11/25/88 2.3.5 DEVELOPMENT OF WIND MODELS The lessons learned from windshear accident investigations, engineering analyses, and flight simulator studies have provided insight for development of simulator windshear models for pilot training. Through these efforts it was determined that the essential elements which must be taught include: 1) Recognition of windshear encounter, 2) Flight at speeds significantly less than those speeds typically exposed to in training, and 3) Use of pitch attitude rather than airspeed control to recover. A simple model presenting a significant windshear threat requiring use of prompt corrective attitude control is sufficient to teach these elements. Once the basics of recognition and recovery are understood, more complex models may be useful. ### Page 35 (OCR) Appendix 1 2.4 MODEL OF FLIGHT CREW ACTIONS dealing with the situation. The model of flight crew actions must be incor- Due to the serious threat imposed by porated into day-to-day operations to infrequent windshear encounters, an ensure such actions are available and orderly set of actions is necessary to easily recalled when needed. increase flight crew awareness of weather conditions that produce wind- The recommended procedures in this shear (Figure 25). Additionally, cer- section have been developed for tain operating practices have been de- Boeing, Douglas, and Lockheed jet veloped that improve the chances of transport airplanes. Use of these surviving a windshear encounter. procedures for other types of airpast windshear accidents, certain of planes is not appropriate until verithese actions were frequently missing, fied with the respective airframe thereby reducing crew effectiveness in manufacturer. Evaluate the Weather No Any Signs o Windshear? Yes Avoid Known Windshear Is It Safe No ro Continue? Yes Consider Precautions Follow Standard Operating Techniques Windshear Recovery Technique (Report the Encounter Figure 25. Model of flight crew actions. ### Page 36 (OCR) Appendix 1 2.4.1 EVALUATE THE WEATHER 1) Terminal Forecasts The weather evaluation process that An examination of terminal forefollows was developed after careful casts is recommended. Study o. analyses of several windshear-related the following two terminal foreaccidents. accident casts demonstrates what to look occurred, several potential windshear for: indicators were present, but a clear, definitive choice to divert or delay YNG FT AMD 1 101815 1820Z C45 BKN was not made. The windshear indica- 80 OVC 2018G35 LLWS ONL C20 OVC tors are meant to be cumulative. The SEAL TO OVE 08z" C25 OVC 3214G25 more indicators present, 2RW-/TRW-. 09Z IFR crews should consider delaying depar- CIG RA TRN WND. ture or approach. Only through an increased awareness of potential wind- FT AMD 2 COR 101815 1745Z C30 shear indicators and a proper weather" BKN 2020G35 OCNL C12 OVC 3TRW CHC evaluation routine will flight crews C4 X 1/2T+RW+AG55. - 22Z C18 OVC be best prepared to avoid microburst 2420G30 windshear. (1/2TRW+G50. 01Z C16 OVC 2918G28 04Z C18 BKN 3016 BKN Every windshear accident has occurred OCNL SCT. 09Z VFR.. on a typical day, to a typical crew, on a typical takeoff or approach. TOO Note that for Youngstown, Onio the many times a number of clues were forecast is calling for LLWS--1 OW present, acknowledged by the crew, but level (altitude) windshear. While not accepted as potential of windshear. The weather evaluation indicators cast, tional "LLWS" clue. given an addi- thunderstorms exist in the fore- pilots are process must continue during the takeoff and climbout and throughout the approach and landing. If some of the In the terminal forecast for Terre indicators are present, this continual Haute, Indiana, LLWS does not searching may lead to early recogni- However, the chance of tion of the potential for a windshear severe heavy rain encounter. 55 knots, suggest the potential If convective cloud conditions are for microbursts if actual thunderpresent and/or if thunderstorms appear storm conditions are encountered. likely, the potential for windshear and microburst activity exists. Dry microbursts are somewhat more if there are only subtle signs of con- difficult to recognize. vective weather, such as weak cumulus ing in regions of low humidity riy if the near the surface, any convective particularly cloud is a likely microburst producer. Examination of the terminal forecast for convective activ- The following weather information ity--rain, thunderstorms, etc.--is should be examined for any potential good practice. windshear conditions affecting the flight: ### Page 37 (OCR) Appendix 1 2) Hourly Sequence Reports provide a strong indication that windshear may be present. Hourly sequence reports should be inspected thunderstorms, The temperature and for windshear rainshowers, clues-- or MSO 007/83/45/1715G30/974 VSBY W3 ST/2 SA 2152 50BKN 800VC 12TBD Dlowing dust. ed for large differences, indicat- dew point spread should be examin- 1.e. 30 3) Severe Weather Watch Reports to 50 degrees Fahrenheit, A check for issuance of an aviaing Tow humi dity. Additional tion severe weather watch should signs such as warming trends, be made. In the following examgusty winds, cumulonimbus clouds, ple, a line of thunderstorms apetc., should be noted. proaching severe limits are forecast. Severe convective weather In the example shown below, evi- is a prime source for microbursts. dence of blowing dust, large temperature/dewpoint spread, gusting ISTMS FCST TO APCH SYR LIMITS THIS winds, and thunderstorms (without AFTN AND ERY EVE TO THE RT OF A LN rain) is present. These signs FM YUM IPL RIV BUR 15 W SDB BFL IYK EED YUM. ### Page 38 (OCR) Appendix 1 4) LLWAS Reports LLWAS in its present form has some limitations: LLWAS (Low Level Windshear Alert System) - Presently installed at A) shear magnitude may be serious- 110 airports in the U.S., this ly underestimated, system is designed to detect wind B) trees, buildings and other surshifts between outlying stations face obstructions may disrupt and a reference centerfield sta- (Figure 26) by or limit the flow of air near tion If an LLWAS the sensors, alert (triggered wind speed C) location and spacing of sensors occurs, it indicates the presence and/or direction differential) may allow microburst develop- ment to go entirely in undesomething shear-like, though tected--particularly the not necessarily indicative of mag- early stages (Figure 26), nitude or location. However, the D) because the sensors are on the absence an alert does not ground, microburst development necessarily indicate that it is which has not yet reached the safe to proceed! surface will not be detected, and LLWAS information is available by E) LLWAS coverage only exists near request anytime, but will be pro- the runways and typically does vided by controllers whenever an not extend beyond the middle LLWAS alert is in progress. marker. WINDSHEAR ALERTS. 2 QUADRANTS. Even with these limitations, LLWAS CENTERFIELD WIND 210 AT 14. WEST can provide useful information BOUNDARY WIND 140 AT 22. NORTH- about winds around the airport. **EAST BOUNDARY WIND 270 AT 24.** LLWAS Stations • Runways Microburst 3 nmi 2 nmi 1 nmi Figure 26. Undetected microburst due to wide LLWAS station spacing. ### Page 39 (OCR) Appendix 1 5) SIGMETS ring of blowing dust or localized dust in general, flying debris, SIGMETS, particularly CONVECTIVE virga, a rain core with rain di- SEvE STrang worms of scattared provide essential verging away horizontally from the clues. (fun i clouds, to tornadose tures (funne) tornados). embedded thunderstorms, light, lightning may be the onl reaching level 5 intensity, indi- isual clue. Pilots must become cating a potential for windshear. aware that these visual clues are often the only means to identity ATTENTION ALL AIRCRAFT. CONVECTIVE the presence of severe windshear. **SIGMET CHARLIE ONE FROM THE VICIN- TTY OF ELMIRA TO PHILLIPSBURG. 7) PIREPS** SCATTERED EMBEDDED THUNDERSTORMS MOVING EAST AT ONE ZERO KNOTS. PIREPS are extremely important in- FEW INTENSE LEVEL FIVE CELLS, MAX- dicators in microburst windshear IMUM TOPS FLIGHT LEVEL FOUR FIVE Reports of sudden ZERO. irspeed changes in the airport approach or landing corridors pro- 6) Visual Clues from the Cockpit vide indication of the presence of windshear. The value of recognizing microbursts by visual clues from the Mountered wingshear fin final, cockpit cannot be overemphasized. encountered final, Pilots must remember that micro- loss of 20 knots at 300 feet apbursts occur only in the presence proaching middle marker runway 27 of convective weather indicated by right, Douglas MD-80." cumulus-type clouds, and virge. thunderstorms that other types of wind- rain showers, In international weather reports, (Note windshear observations or reports shear can occur in the absence of from pilots may be included at the convective weather.) end of routine and special weather reports. Microburst windshear can often be identified by some obvious visual ON ANCH RY 347A7 16EORTED MOD MS clues such as heavy rain (in a dry or moist environment). This is particularly true if the rain is In the above example, a Boeing 727 accompanied by curling outflow, a on approach to Runway 34 reported moderate windshear at 1610 hours. ### Page 40 (OCR) Appendix 1 8) Airborne Weather Radar Another significant aspect of weather radar use is attenuation. The use of airborne weather radar Attenuation is caused by heavy to detect convective cells should rainfall reducing the ability of De considered a matter of rou- the radar signal to penetrate, tine. Weather radar provides causing the radar to present an extremely useful information for incomplete picture of the weather the avoidance of thunderstorms in area. In the terminal area, comthe airport terminal area, but parison of ground returns to cannot directly detect windshear. weather echoes is a useful tech- Pilots have become adept at avoid- nique to identify when attenuation ing thunderstorms while enroute is occurring. Tilt the antenna and at altitude. However, rela- down and observe ground returns tively little emphasis has been around the radar echo. With very placed on their use near the heavy intervening rain, ground reterminal area. Most heavy rain turns behind the echo will not be De thunderstorms near the airport can detected with conventional peturns is referred to as a shadow This area lacking ground weather radar by a careful use of and may indicate a larger area of tilt control to scan above the precipitation than is shown on the intended flight altitude (15,000 indicator. Areas of shadowing to 20,000 feet). The subject of should be avoided. the proper use of tilt control for this purpose should be studied in Turbulence Doppler radars starting available radar manuals and to become available to flight bulletins. crews provide an additional clue to the presence of microbursts. Pilots should understand that If, in the departure/arrival segneavy precipitation, as seen on ment of the airport vicinity, turtheir radar and associated with bulence indications are present in onvective clouds indicates the mid-levels of convective cloud ossibility of microbursts; now- systems (e.g., 15,000 to 20,000 ever, the absence of strong re- feet) and low humidity conditions indicate a safe situation. turns must not be depended upon to Poten- spread), the situation is pilots exist (large temperature/dewpoint prime tially hazardous dry microburst for microburst formation. conditions may only produce weak should be particularly cautious radar returns. when they observe this indication. ### Page 41 (OCR) 11/25/88 2.4.2 AVOID KNOWN WINDSHEAR The importance of avoiding severe windshear and microbursts cannot be over-emphasized. Microburst windshears have been measured which are beyond the capability of transport category airplanes and the most highly skilled pilots. Recall from Figure 11 that even windshears which were within the performance capability of the airplane have caused accidents. Avoidance may only involve delaying departure or approach for 10 to 20 minutes since this is the typical time required for microburst dissipation. Even though significant emphasis on simulator training is recommended in ilot training curriculums, avoidance nust be the first line of defense. Simulators are valuable for teaching windshear recognition and recovery. However, pilots are cautioned not to develop the impression that real-world windshear encounters can be successfully negotiated simply because they AC 00-54 Appendix 1 have received simulator training. In an airplane, complicating factors (l.e. turbulence, precipitation noise, instrument errors, etc.) may make shears much more difficult than in a simulator. In addition, simulator motion systems are limited in their capability to reproduce all the dynamics of an actual windshear encounter. Remember, some windshears cannot be escaped using any known techniques. Therefore, above all, AVOID, AVOID, AVOID: Unfortunately, there are no universal quantitative windshear avoidance criterno-go thecision guidelineambiquere assured detection and warning system in operation which can measure windshear intensity along a specific the weather evaluation factors which factors which can be helpful in avoiding windshear is shown in Table 1 on the following Page 35 ### Page 42 (OCR) 11/25/88 AC 00-54 Appendix 1 TABLE 1 **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 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 WEATHER LON NOTE: These guidelines apply to operations in the airport vicinity (within patien de ere he d is oved the prostity ed ring 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. ### Page 43 (OCR) 11/25/88 AC 00-54 Appendix 1 Table 1, designed specifically for in off pates surel convective weather (thunderstorm, terms path, such enraves evaluation of roarious suerva- counters may present other significant evaluation various observa- weather related risks. Pilots are tional clues to aid in making appro- therefore urged to exercise cautior priate real time avoidance decisions. The observation weighting is categor- when determining as course of actione Use of Table should not replace ized according to the following scale: sound judgement in making avoidance decisions. HIGH PROBABILITY: Windshear clues should be considered Critical attention need be given to cumulative. The probability for each this observation. A decision to avoid single observation is given. However, (e.g. divert or delay) is appropriate. if more than one windshear clue is observed, the total probability rating MEDIUM PROBABILITY: may be increased to reflect the total set of observations. Consideration should be given to avoiding. Precautions are appropriate. Example: LOW PROBABILITY: Nearing destination based clouds over VIRGA is seen descending from high Consideration should be given to this the airfield (MEDIUM PROBABILITY). observation, but a decision to avoid Commencing approach, a PIREP is reis not generally indicated. ceived indicating that another flight just experienced a 10 knot airspeed The guidelines in Table 1 apply to airport (MEDIUM approach loss on final to the same operations in the airport vicinity PROBABILITY). There- (within 3 miles of takeoff or landing tore, it would be appropriate to raise along the intended flight path below the total avoidance decision weighting 1000 feet AGL). Although encountering to HIGH PROBABILITY (indicating a weather conditions described in Table decision to avoid is appropriate). ### Page 44 (OCR) Appendix 1 2.4.3 CONSIDER PRECAUTIONS altitude available for recovery if required. Lastly, full thrust takeoffs Avoidance is the best precaution. may eliminate resetting thrust in a However, there are situations when recovery, thereby maximizing accelerawindshear clues do not clearly dictate tion capability and reducing crew delaying, but can be interpreted to workload. mean that conditions are right for windshear activity. In these in- • Runway Selection stances, pilots should consider the next step of flight crew actions, the Use the longest suitable runway that use of precautions. avoids suspected areas of windshear. The choice of a suitable runway in- A number of precautionary techniques volves consideration of exposure to have been developed which crews can obstacles after liftoff and crosswind take to lessen the effect of windshear and tailwind limitations. should an unsuspected severe windshear sures maximum runway available to acbe encountered on takeoff or ap- celerate to rotation speed and may reproach. These precautions include sult in more ground clearance at the consideration of thrust setting, run- end of the runway and during the climb way selection, flap selection, air- profile. Should the decision be made speed, use of autopilot, autothrottle to reject the takeoff, more runway is and flight director. They were devel- available on which to stop the airoped by detailed analysis and piloted plane. simulation of several microburst windshear encounters. In many cases, • Takeoff Flap Selection tradeoffs were involved and no "best" recommendation for all conditions The choice of takeoff flap setting is could be developed. dependent on the airplane type. The following flap settings should be con- Use of precautions along with even the sidered unless limited by obstacle best recovery piloting skills cannot clearance and/or climb gradient: guarantee a successful escape from any microburst windshears. It is im- Airplane Takeoff ortant to realize that the recom- Type Flap Setting mended precautions each have a relatively small effect on the outcome of B727 15 an inadvertent windshear encounter. B737 5 to 15 Therefore, use of precautions should B747 20 not replace sound pilot judgment in B757 20 deciding whether or not it is safe to B767 20 proceed. Use of precautions should not bias a go/no-go decision in the go 10 or 20 direction. DC-9-20, -30,-40,-50 5 or 15 MD-80 5 to 15 2.4.3.1 TAKEOFF PRECAUTIONS DC-10 5 to 20 • Thrust Setting L-1011 10 to 22 Maximum rated takeoff thrust should be Studies of available takeoff flap setused for takeoff. This shortens the tings showed that the greater flap takeoff roll and reduces overrun ex- setting provided best performance for posure. Full thrust also provides the windshear encounters on the runway. best rate of climb, thus increasing However, lesser flap settings showed Page 38 ### Page 45 (OCR) Appendix 1 the best performance for in-air wind- 1) Determine 'actual and Vz shear encounters. The takeoff flap speeds for airplane settings in the table offered somewhat gross weight and flap setting. better performance over a wide range Set airspeed bugs to these of conditions; however, it must be values in the normal manner. pointed out that the performance difference between flap settings is small. 2) Determine field length limit maximum weight and correspondo Increased airspeed ing Vp for selected runway. Increased airspeed rotation 3) If field length limit VR is proves the ability of the airplane to greater windshear weight VR, after liftoff. Increased airspeed im- Vr lup to 20 knots in excess proves the flight path, reduces poten- actual weight VR) flight takeot be Airseted speeds, and reduces pilot work- should to the higher speeds. Delaying rotation to a higher airspeed 4) Rotate to normal initial climb may appear to increase the risk of attitude at the increased attitude. VR overrunning available runway. How- and maintain this ever, Decause of the manner in which This technique produces increased rotation speed is calcu- higher initial climb speed lated, it is simply using the runway which slowly bleeds off to the as if the aircraft was loaded to the normal initial climb speed. field length limit weight for that runway limit conditions, If the takeoff is at field WARNING: If windshear is encountered length the risk of beyond the actual overrunning the available runway is gross weight (bug) YR, do increased because there is no extra not attempt to accelerate to runway available. The overrun expo- the increased VR, but rosure is also increased if the wind- tate without hesitation. In shear reduces the airspeed below the no case should rotation be minimum airspeed required for liftoff delayed beyond 2,000 feet at the maximum available (body con- from the end of the usable tact) attitude. However, initiating runway surface. ( See Secrotation no later than 2000 feet from tion 2.4.5 Recovery Techthe end of the usable runway surface niques) reduces the probability of overrun and liftoff. maximizes the available energy after If increased than normal accelerating liftoff, airspeed was not used airspeed If increased Vp is to be used, the Reducing technique for scheduling and using in- pitch attitude creased rotation airspeed is: windshear is encountered. ### Page 46 (OCR) Appendix 1 • Flight Director rectors must be disregarded if a recovery is required not use speed-referenced flight and, time permitting, directors unless they equipped switched off by the Pilot with windshear recovery guidance. Not Flying (PNF). WARNING: speed-referenced flight Some flight directors are equipped director which does not have with a selectable pitch attitude windshear recovery guidance mode. feature, the If normal procedures utilize may command a pitch attitude this selectable pitch change to follow target attitude mode may be effectively used airspeeds regardless of in a windshear encounter provided the flight path degradation. selected attitude is within the ac- This guidance may be in ceptable range. However, if an atticonflict with the proper tude other then the selected attitude procedures for windshear becomes necessary, the flight director recovery. Such flight di- should be disregarded, and time permitting, switched off by the PNF. Takeoff Precautions • Use maximum rated takeoff thrust • Use longest suitable runway • Consider using recommended flap setting • Consider using increased rotation airspeed • Do not use speed referenced flight director Page 40 ### Page 47 (OCR) Appendix 1 2.4.3.2 APPROACH PRECAUTIONS considered: • Stabilized Approach Airplane Landing During some normal operations achieved stabi- Type Flap Setting lized prior to 500 feet AGL. environment, approaches However, in a B727 B737 30 30 potential windshear a B747 25 or 30 stabilized approach should be estab- B757 30 lished no later than 1,000 feet AGL to B767 30 improve windshear recognition capability. DC-9 * MD-80 28 • Thrust Management DC-70 35 Minimize thrust reductions. L-1011 33 than immediately compensating for an airspeed increase by reducing * Minimum flap setting authorized for a brief pause to evaluate speed trends particular model. occurs and recovery is initiated, thr is prudent. Studies of windshear encounters using additional airspeed and earlier avail- a11 available landing flap settings ability of thrust (due to engines ac- showed that the flap settings recomcelerating from a higher RPM) will be mended above provided the best overall advantageous. recovery performance for a wide range assure inappropriate thrust of windshears. reductions do not occur. sence of a tailwind shear, • Increased Airspeed cedure may result in a higher Increased airspeed on approach imto be accounted for on landing. proves climb performance capability and reduces the potential for flight • Runway Selection at stick shaker during recovery from an inadvertent windshear encounter. avoids the area of suspected windshear If available landing field length perand is compatible with mits, airspeed may be increased up to A longer runway a maximum of 20 knots. This increased provides the greatest margin for in- fouchdown must emar wathin the flamai speed should be maintained to creased ground roll due pated winds and speed Possible to unantici- resulting touchdown zone--do not allow the airplane to float down the runway. (instrument) other aids to glide path monitoring As many variables are involved, it is (VASI, etc.) are desirable as not practical to provide exact guidthey can enhance windshear recognition ance on the effect of 20 knots extra providing timely, speed actual stopping distance. path deviation information. Wind can be a major factor since stopping distance is affected by ground- • Landing Flap Selection speed rather than airspeed. If increased airspeed is used and an in- The choice of landing flap setting is creasing performance shear is encoundependent on airplane туре. The tered, a go-around may be necessary following flap settings should be due insufficient landing field Page 41 ### Page 48 (OCR) Appendix 1 length for the higher approach speed. 25 percent and in some cases Furthermore, if a pilot can be reason- may exceed brake energy ably certain that wind changes (due to limits. topography or unique local conditions) will not result in decreasing perform- • Flight Director and/or Autopilot ance, it may be inappropriate and Autothrottles increased approach speed. During approach it is desirable to Other factors affecting stopping dis- utilize the flight director, autopilot tance such as availability and effec- and autothrottles to the maximum extiveness of thrust reversers, tire and tent practical. These systems may rebrake condition, runway surface conditions, etc., must also be taken into crew more time to monitor instruments consideration. On a dry runway with and weather conditions. field length may accorresete 20 knots of autoflight systems, and in particuthe autothrottle, only extra speed benefits if properly monitored. cases greater field length may be absence of proper monitoring, in doubt, these systems may mask onset of shear longest suitable runway which does not awareness of expose the airplane to greater hazard control inputs being made. from possible shear. Furthermore, not all autoflight sys- WARNING: Increased touchdown tems perform well in gusty or turbuincrease stopping distance. lent conditions. The autopilot and/or additional knots at the autothrottle should be discontouchdown can increase stop- nected when continued use appears ping distance by as much as counter-productive. Approach Precautions • Stabilize approach no later than 1000 ft AGL • Minimize thrust reductions • Use most suitable runway • Consider using recommended flap setting • Consider using increased approach speed • Use autoflight systems during approach Page 42 ### Page 49 (OCR) 11/25/88 AC 00-54 Appendix 1 2.4.4 FOLLOW ESTABLISHED STANDARD shears that proved to be most deadly OPERATING TECHNIQUES are those which caught crews by surprise. In an effort to aid crews with the early recognition of a windshear en- Crews should be aware of normal verti- Care formulateres were series of recommendations under the general cal windshear induced deviations are more flight path indications so that On takeoff, rate, heading niques (SOT's). of Standard Operating These SOT's fall into Tech- would readily recognized. include attitude, on approach, climb this two general headings of crew awareness and airspeed buildup. and crew coordination. airspeed, attitude, descent rate and throttle position provide valuable in- The need for emphasis on SOT's came formation. Awareness of these indicafrom recognition that in most takeoff tions assures that flight path degradation is recognized as soon as pospitch attitude was reduced below the sible. attitude that would maintain level flight. This was done when the air- During takeoff and approach, be alert plane was already descending toward for airspeed fluctuations. Such flucthe ground tuations may be the first indication flight path awareness on the part of of windshear. Control column forces the crews involved. This lack of significantly different than those exwas also observed during pected during a normal takeoff or piloted simulator studies of windshear go-around may result if airspeed is encounters. Traditional training pro- below target or airspeed buildup is grams and routine flying may not have low during rotation and liftoff. Verreinforced proper flight path control tical flight path displays should be for altitude loss. used to crosscheck flight director commands. focus when dealing with During takeoff while at relatively low ADHERENCE TO AIRSPEED MUST BE MODIFIED altitude (below 1000 feet), the SOT': IN FAVOR OF MAINTAINING FLIGHT PATH BY equire awareness and use of norma CONTROLLING PITCH ATTITUDE. climbout pitch attitude and less em- The SOT's that follow emphasize flight Rhow the all engine initial climb all-engine initial climb path and pitch attitude for operations pitch attitude. Rotate at the normal near the ground. Following SOT's re- rotation rate to this attitude for all sults in better crew performance dur- takeoffs. Minimize pitch attitude reing day-to-day operations, as well as ductions in response to low airspeed case an ordination ding viest until terrain and obstruction clearance is assured. for timely windshear recognition, par- On approach, avoid large thrust reducticularly at night or in marginal tions or trim changes in response to weather conditions. airspeed increases as an airspeed decrease follow. o Crew Awareness monitor vertical flight path instruments, such as vertical speed, altime- It is important for crews to remain ters and glideslope displacement. alert for any change in conditions, addition, comparison of groundspeed remembering that windshear can be and airspeed indications can provide quick to form and to dissipate. The additional information Page 43 ### Page 50 (OCR) Appendix 1 windshear recognition. When potential asses judgment to determine the sarent assessing the situation for windshear exists, achieve a stabilized approach no later than 1,000 course of action. feet AGL. • Crew Coordination High workload and distractions in the approach phase, particularly in mar- The PF should focus attention on flyginal weather, attention ing the airplane. In a windshear eninstruments provide counter, appropriate action should be early recognition of flight path de- taken in response to callouts. terioration. Additionally, application of thrust on approach may The PNF should focus attention on airmask a decreasing airspeed trend. speed, vertical speed, altitude, pitch attitude,,& any sionificant deviations glidepath deviation and Crews should be prepared to execute thrust. the recommended recovery procedure im- from normal indications are detected, mediately if deviations from target the PNF should immediately call out conditions in excess of the following the deviation. Callouts in the cockoccur: pit should be standardized and easy to understand to ensure timely recogni- Takeoff/Approach tion. 1) +15 knots indicated airspeed EXAMPLE: 2) +500 FPM vertical speed low. " decreasing--glideslope "Vertical speed 1200 down--airspeed one dot 3) +5° pitch attitude Approach STANDARD OPERATING TECHNIQUES SUMMARY 1) +l dot glideslope displacement • Takeoff 2) Unusual throttle position for a significant period of time. o Know normal attitudes, climb rates, airspeed build-uP initial • Know/use ail-engine These values should be considered as climb attitude. guidelines only. • Make continuous rotation at certain in- normal rate. significant • Crosscheck flight director cominitiate recover me ore necessary the recovery before any of o Minimize pitch attitude reduc- mands. are exceeded. tions. situations may exist where brief ex- • Monitor vertical flight path particularly in airspeed, instruments, call out deviafrom known or anticipated tions (PNF). local wind effects may not be an indi- o Know recovery decision guidesignificant lines. pilot flying (PF) is responsible for Page 44 ### Page 51 (OCR) Appendix 1 o Approach initial target pitch attitude for both takeoff and approach. Additional o Know normal attitudes, descent vantages of 15 initial target pitch rates airspeeds, throttle attitude are that it is easily reosition. called in emergency situations and it • Crosscheck flight director com- is prominently displayed on attitude mands. director indicators. Avoid large thrust reductions. Monitor vertical flight path Note: 1) L-1011 target attitudes: instruments, call out devia- Takeoff = 17.5° tions (PNF). Approach = 15° o Know recovery decision guidelines. 2) Operators lated target pitch attitudes such as all-engine attitude 2.4.5 WINDSHEAR RECOVERY TECHNIQUE takeoffs go-arounds may use these at- The primary recovery technique objec- titudes in place of the rective is to keep the airplane flying as ommended initial target relong as possible in hope of exiting covery attitude. the shear. A wide variety of techniques were considered to establish While other more complex techniques the one best meeting this objective. may make slightly better use of air- The best results were achieved by plane performance, these techniques do itching toward an initial target at not meet simplicity and ease of recall titude while using necessary thrust. requirements. Evaluations showed that Several factors were considered in the recommended technique provides a developing this technique. simple, effective means of recovering from a windshear encounter. Studies show windshear encounters occur infrequently and that only a few A detailed discussion of the recomsuccessful seconds are recovery situations available to initiate a Additionally, Recovery both recovery during takeoff technique during high stress pilot and during approach is disinstrument scan typically becomes very cussed together in the following seclimited--in extreme cases, to only one tion since the technique for both sitinstrument. Lastly, recovery skills uations is identical. The recovery will not be exercised on a day-to-day technique for encounters during takebasis. These factors dictated that off on runway is presented later. the recovery technique must not only be effective, but simple, easily re- 2.4.5.1/3 ENCOUNTER DURING TAKEOFF - called, and have general applicability. AFTER LIFTOFF and Extensive analysis and pilot evalua- ENCOUNTER ON APPROACH conducted. Al though range of recovery attitudes (including Windshear recognition is crucial to and the range of all-engine ini- making a timely recovery decision. tial climb attitudes) provides good The recommended recovery procedure recovery capability for a wide variety should be initiated any time the of windshears, 15 was chosen as the flight path is threatened below 1000 Page 45 ### Page 52 (OCR) 11/25/88 AC 00-54 Appendix 1 feet AGL on takeoff or approach flight required to avoid ground contact. guidelines unacceptable When airplane safety has been ensured, path degradation are repeated below: adjust thrust to maintain engine parameters within specified limits. o Takeoff/Approach • PITCH 1) +15 knots indicated airspeed The pitch control technique for re- 2) +500 FPM vertical speed covery, stose a windshear encounter or on approach is as 3) +5° pitch attitude follows: o Approach o At a normal pitch rate, increase or decrease pitch atti- 1) +l dot glideslope displacement tude as necessary toward an initial target attitude of 2) Unusual throttle position for a director Should be turned off autopilot/flight significant period of time. by the PNF unless specifically again. these should be considered as designed for operations in guidelines since exact criteria cannot windshear, or unless using a e established. In every case, it is pitch selectable flight direche responsibility of the pilot flying tor with desired attitude comto assess the situation and use sound manded. judgement in determining the safest course of action. In certain in- • Always respect stick shaker. stances where significant rates of Use intermittent stick shaker change occur, it may be necessary to as the upper pitch limit. In a initiate recovery before any of the secure sow 15 pitch atten day severe above are exceeded. If windshear inadvertently o If attitude has been limited to immediately initiate the rec- less than 15° increase to stop attitude stick ert tettenue to land! as soon as stick shaker stops. (However, if on approach and an inperformance shear is encoun- • If vertical flight path or altered, a normal go-around, rather than titude loss is still unaccepta the recovery maneuver, may be accom- ble after reaching 15' › Turther increase pitch attitude smoothly in small increments. recovery from a windshear encounter after liftoff or o Control pitch in a smooth, during approach is the same for both steady manner (in approximately cases. This technique is described as 2 degree increments) to avoid follows: excessive overshoot/undershoot of desired attitude. • THRUST o Once the airplane is climbing Aggressively apply necessary thrust to and ground contact is no longer ensure adequate airplane performance. an immediate concern, airspeed Disengage the autothrottle if neces- should be increased by cautious sary. Avoid engine overboost unless reductions in pitch attitude. ### Page 53 (OCR) Appendix 1 • CONFIGURATION for windshear recovery. Such systems must be disre- Maintain flap and gear position until garded if recovery is reterrain clearance is assured. AT- ouired and, time permitting, though a small performance increase is switched off by the PNF. available after landing gear retraction, initial performance degradation Use of autopilot control wheel steermay occur when landing gear doors open ing (CWS) has not been fully evaluated for retraction. While extending flaps for its effectiveness in a windshear during a recovery after liftoff may encounter. One consideration regardresult in a performance benefit, it is ing CWS is that it is usually a single not a recommended technique because: channel autopilot mode and as such has authority. 1) Accidentally retracting flaps case, if CWS is used during a wind- (the usual direction of move- encounter, should be ment) has a large adverse im- discontinued if it produces difficulty pact on performance. in achieving the desired attitude. 2) If landing gear retraction had been initiated prior to recognition of the encounter, extending flaps beyond a takeoff rap setting might result in a continuous warning horn which distracts the crew. ADDITIONAL CONSIDERATIONS Some flight directors are equipped selectable pitch If normal procedures this feature, the selectable pitch attitude mode may be effectively used in a windshear encounter provided the selected attitude is within the acceptable range: However, if an attitude other than the selected attitude becomes necessary, the flight director If autopilot/flight director systems should be disregarded, and time perspecifically designed for operation in mitting, switched off by the PNF. windshear are engaged during approach, they should be used during the re- Avoid stabilizer trim changes in recovery maneuver. These systems may sponse to short term windshear-proaid in recovery from an inadvertent duced airspeed/stick force changes. windshear encounter However, due to However, stabilizer trim should be limited time available to recognize used to trim out stick force due to and respond, do not engage the auto- thrust application. pilot or autothrottle if these systems were not engaged prior to recovery. hroughout recovery the PNF should all out vertical flight path devia Totator sir sprople for example, for operation in windshear may command a pitch attitude "sinking 500, 300, etc." altitude 200, climbing change to follow target air- 400, altitude speeds or a fixed pitch attitude regardless of flight Operators of airplanes requiring a degradation. flight engineer may incorporate the may be in conflict second officer into the callout with the proper procedures process. ### Page 54 (OCR) Appendix 1 Racist changing winds may cause rapid 2) Altitude at which shear was enexcursions pitch countered little or no pilot input as well as varying the attitude for stick shaker 3) Location of shear with respect to activation. runway in use As soon as possible, report the en- 4) Airplane type counter to the following may not have the performance 5) Use the term PIREP to encourage rebroadcast of the report to other windshear encounter. aircraft increasing in intensity must be aware that their timely. ac- dangerous. controllers Critical remarks are also helpful in establishing windshear ...maximum thrust required", severrity"...al- le.g• may prevent a pending disas- most contacted terrain", etc.). ter--SECONDS ilot report for windshear encounter. EXAMPLE: nould contain the following informa tion: iSan Francisco Tower, PIREP, Flight 126 encountered windshear on final 1) Maximum loss or gain of airspeed loss of 20 knots at 300 feet approaching middle marker runway 27 right, Douglas MD-80. After Liftoff/On Approach Windshear Recovery Technique • THRUST • Apply necessary thrust • PITCH • Adjust toward 15° • Increase beyond 15° if required to ensure acceptable flight path • Always respect stick shaker • CONFIGURATION • Maintain existing configuration Page 48 ### Page 55 (OCR) Appendix 1 2.4.5.2 ENCOUNTER DURING TAKEOFF - The go/no-go criteria based on engine ON RUNWAY failure decision speed (V]) may not be valid for windshear conditions Recognition of windshear is difficult since groundspeed can be much higher during takeoff roll since airspeed is than airspeed (Figure 27). It therechanging rapidly. In addition to fore may not be possible to stop the visual clues described previously, un- airplane on the runway during a reusual airspeed fluctuations, slow or jected takeoff. The ability to lift erratic airspeed build-up may be indi- off is a function of airspeed; the cations of a windshear encounter. ability to stop is largely a function of ground speed. Indicated Microburst Airspeed Reaches V1 V. = 130 kt Insufficient Stopping Distance Remains! A/S = 80 kt AS = 120 k1 AS = 130 k1 Runway G/S = 80 kt G/S = 130 kt G'S = 170 kt Normal V, Distance Figure 27. Windshear effects on go/no-go decision point. Vy decision speed may not be attained until insufficient runway remains to abort takeoff. ### Page 56 (OCR) Appendix 1 Prior to Vi NOT sufficient to offset the effects Overboost however, The takeoff should be rejected if un- of an inadvertent windshear enacceptable airspeed variations occur counter. Proper pitch attitude conbelow indicated V1 and the pilot trol is the most important factor in decides that there is sufficient run- recovery from windshear. way remaining to stop the airplane. • PITCH After Y1 When Vp is reached, rotate at normal toward 15° pitch attitude. The takeoff must be continued if V1 severe windshear encounters, has been reached. VR might not be reached and the reject the takeoff may • THRUST If this is the case, rotation must be initiated no later than 2,000 Aggressively apply necessary thrust to feet from the end of the usable ensure adequate airplane performance. face (Figure 28). Avoid engine overboost unless sary to ensure airplane safety. Note: Transport category airplanes airplane safety has been ensured, ad- typically can lift off 5 to 10 just thrust to maintain engine param- knots prior to VRIiFt (except eters within specified limits. 727, which cannot Off prior to VR). Microburst Approximately 2000 ft Required To Rotate and Lift off! - Attempt To Stop Results in Overrun Runway May Be Less Than Vp F Indicated Airspeed - 2000 ft• Figure 28. Windshear effects on rotation decision. Windshear effects may force rotation at speeds below Vp. Rotation should begin no later than 2000 ft from runway departure end. ### Page 57 (OCR) Appendix 1 Pitch attitude and rotation rate in the available runway Liftoff Re- Once airshould not be restricted to avoid aft borne, follow the After body contact since all available pitch covery Technique discussed earlier. attitude may be required to lift off Takeoff (On Runway) Recovery Technique • THRUST • Apply necessary thrust • PITCH • Rotate toward 15° (no later than 2000 ft remaining) • Increase beyond 15° if required to lift off Note: After liftoff follow after liftoff recovery technique Page 51 ### Page 58 (OCR) Appendix 1 The runway remaining during takeoff Another indication of runway remaining can be identified on runways having may be the runway lighting. FAA/ICAO appropriate marking and lighting. precision approach runways (Figure 29) While the markings discussed are usu- ally to assist landing aircraft, they rather than white for the last 2,000 lights which can also be used to determine runway feet of runway when viewed in the remaining during a takeoff. takeoff direction. In addition, centerline lighting can be used to iden- Figure 29 illustrates the markings and ify the amount of runway remaining lighting typical of FAA and ICAO pre- The crew in an airplane taking of cision approach runways. For an air- from left to right in the figure would plane departing from left to right in see white centerline lights until the figure, the first pair of single 3,000 feet from the end of the runway hash marks on either side of the cen- (1,000 feet until rotation must take terline indicates 3,000 feet of runway place). From 3,000 feet to the 1,000 remaining (i.e. 1,000 feet until rota- feet remaining point the centerline tion must be initiated). As takeoff lights alternate white and red. The continues, the 2,000 feet remaining centerline lights are all red for the point is denoted by the first pair of last 1,000 feet of runway. A line of double hash marks encountered. Note red lights perpendicular to the runway that the spacing of all hash marks is indicate the end of usable runway surin 500 foot intervals from the depar- face. ture end threshold. Centerline and Edge Lighting • White Nighttime - Approximate Feet Remaining • Red 3000 2000 1000 • Yellow • • • • • ..•.o ... Daytime - Approximate Feet Remaining Figure 29. FAA ICAO precision approach runway markings and lighting. ### Page 59 (OCR) Appendix 1 Figure 30 illustrates the markings on the runway threshold pilot _ For runways an FAA non-precision approach runway. with these markings, judgement The main indicator of distance remain- and/or familiarity with specific feaing on these runways is the fixed dis- tures along the runway are required to tance markings on either side of cen- estimate the 2,000 feet remaining terline approximately 1,000 feet from point. Centerline and Eage Lighting O White •Red Approximate Feet Remaining 1000 • • 0070 Figure 30. FAA nonprecision approach runway markings and lighting. ### Page 60 (OCR) 11/25/88 AC 00-54 Appendix 1 Runway markings and lighting on an centerline at intervals of approxi- ICAO non-precision runway are shown in mately 500 feet (150 meters) starting Figure 31. This figure represents the from the runway threshold. Fixed disoptimum configuration that might ap- tance markers may also be present appear. Most ICAO non-precision ap- proximately 1,000 feet (300 meters) proach runways would include some, but from the threshold. In addition, runnot necessarily all of these features. way edge lights may be color coded similar to precision approach runways ICAO non-precision runways have single with yellow rather than white lights hash marks on either side of runway for approximately the last 2,000 feet (600 meters) of the runway. Centerline and Edge Lighting O White Nighttime - Approximate Feet Remaining • Red .......... • Yellow • • • • • • 3000 2000 1000 Daytime - Approximate Feet Remaining Figure 31. ICAO nonprecision approach runway markings and lighting. ### Page 61 (OCR) Appendix 1 • Other Recovery Techniques • Use of inertial reference speed emphasizes control of round speed Many windshear recovery techniques which is contrary to the recomwere evaluated while establishing the mended recovery technique. technique recommended above. The addition, this technique is oritechniques below are NOT recommended ented toward compensating for the since they may reduce the chances for windshear and continuing the apsurviving a windshear encounter. proach rather than immediately initiating the recovery maneuver. Attempting to maintain target air- While this technique is not approspeed does not utilize full climb priate for microburst encounters, capability of the airplane. it may De suitable for use in other types of windshears. Attempting to pitch directly to stick shaker does not maximize use Use of "dive" technique (lowering of available airplane energy, and airplane nose in attempt to acceland increased exposure to stallpath results in a degraded flight erate then pull up at some predetermined minimum altitude) exposes the airplane to potentially higher • Attempting to fly at best intensity duces lower minimum recovery apti- Lift/Drag angle-of-attack does not utilize the short-term maximum tudes, requires high pitch rates gradient capability of the air- and complicates the recovery proplane. cedure. • Retracting flaps during approach Again, best recovery results are recovery (per the normal go-around achieved by properly controlling pitch procedure) reduces margins to attitude 'in conjunction with thrust stick shaker and has an adverse application. impact on initial climb capability of the airplane. ### Page 62 (OCR) Appendix 1 2.5 SUMMARY Behavior changes are also necessary. These changes involve appropriate This document has presented the latest pilot technique should the windshear air transport industry findings on avoidance process fail. with any learning, however, it windshear education and training. must As was discussed in this Pilot Windchanges in attitude and be- shear Guide, some of the techniques havior if it is to be effective. presented regarding pitch attitude and airspeed control differ from those Changes in attitude are necessary to ordinarily used. However, the recomheighten crew awareness of clues which mended techniques have been rigorously indicate the presence of windshear. studied and evaluated for their effec- In past windshear accidents, signifi- tiveness. Pilots must be prepared to cant clues apparently went unnoticed. apply these techniques and take deci- Recall again that the best defense sive action should the need arise. against the low altitude windshear hazard is to avoid it altogether. It is recognized that the value of This is especially important since this training will be challenged giver shears exist that are beyond the capa- the infrequency of its required use. bility of any pilot or airplane. Like many other piloting skills, wind- Since present weather information shear training will not be exercised infallibly detect windsnear the sig- sources and detection systems cannot flight will be required to maintain profici- daily and periodic recurrency training crews must be ever alert for ency. Through this process the knownals which will permit avoidance. ledge and skills pertaining to windshear recognition, avoidance, and recovery will be available and ready for use when required. Page 56 DU.S.GOVERNMENT PRINTING OFFICE:1990-717-000/03921 ### Page 64 (OCR) U.S. Department Postage and Fees Paid Federal Aviation of Transportation Administration Federal Aviation DOT 515 Administration USMALL® 800 Independence Ave., S.W. 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