B737-Flying in Turbulence

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You should read the Flight In Severe Turbulence article in the SmartCockpit Flight Ops section (subsection Meteorology ). ). The turbulent air penetration speed is: - B737 Classics……….. 280 KIAS /.73 Mach - B737 NG …………….. 280 KIAS /.76 Mach

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Turbulent air penetration speeds provide high/low speed margins in severe turbulent air.

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Below 10,000 feet, a speed between 240 and 250 knots provides adequate buffet margin.

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Severe Severe turbulence turbulence should be avoided avoided if at all possible possible.. If severe turbulence turbulence cannot cannot be avoided, avoided, an increased buffet margin margin is recommended. This can be obtained by descending descending approximately approximately 4,000 feet below optimum attitude. On the weather radar, the most intense areas are displayed in red, lesser intensity in amber, and lowest intensity g reen. Turbulence is displayed in magenta. The turbulence mode displays normal precipitation and precipitation associated with turbulence. When the radar detects a horizontal flow of precipita precipitation tion with velociti velocities es of 5 or more meters meters per second second toward or away from the radar antenn ant enna, a, tha thatt target target displa display y become becomes s magent magenta. a. This This magen magenta ta area area is associ associate ated d with with hea heavy vy turbul turbulenc ence. e. The det detect ection ion of turbul turbulenc ence e is aut automa omatic ticall ally y limite limited d to a 40 nau nautic tical al mile mile range, range, regardless of the selected range. WX/TURB (turbulence) shows: weather radar returns / shows turbulence within 40 miles. Remember that turbulence detection requires presence of detectable precipitation. Clear air turbulence cannot be detected by radar.

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Turbulence at or near maximum altitude can momentarily increase the airplane’s angle-of attack and and acti activa vate te the the stic stick k shak shaker er.. When When flyi flying ng at spee speeds ds near near the the lowe lowerr am ambe berr band band,, any any maneuvering will increase the load factor and further reduce the margin to buffet onset and stick shaker. When descending in VNAV PTH, the FCC will disengage VNAV and switch to LVL CHG if actual speed becomes equal to or slightly less than the minimum speed, denoted by the underspeed limiti limiting ng symbol symbol in the MCP IAS/Ma IAS/Mach ch window window.. This This can also also hap happen pen in turbul turbulence ence or gusty gusty conditions when the minimum speed may momentarily increase due to G loading

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TURBULENCE PROCEDURE (According to Boeing 737NG FCOM)

PHASE OF FLIGHT

CLIMB

AIRSPEED

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CRUISE

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DESCENT

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B737 Classics……….. 280 KIAS /.73 Mach B737 NG …………….. 280 KIAS /.76 Mach

Use FMC recommended thrust settings. If the FMC is inoperative, refer to the Unreliable Airspeed page in the Performance-Inflight section for approximate N1 settings that maintain near optimum penetration airspeed.

B737 Classics Classics……….. ……….. .73 Mach / 280 / 250 KIAS B737 NG …………….. …………….. .76 Mach / 280 / 250 KIAS KIAS If severe turbulence is encountered at altitudes below 15,000 feet and the airplane gross weight is less than the maximum landing weight, the airplane may be slowed to 250 knots in the clean configuration.

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Take turbulence speed as soon as possible

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Select Continuous ignition ignition (FLT position) position) during severe turbulence.

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Disconnect autothrottle in severe turbulence and set thrust for penetration speed (FMS CRZ page: TURB N1). If the autopilot is engaged, leave it engaged unless airspeed, altitude or attitude deviations require use of manual control. During manual flight, maintain wings level and smoothly control attitude. Use the attitu attitude de indica indicator tor as the primar primary y instru instrumen ment. t. In extrem extreme e updra updrafts fts or dow downdr ndraft afts, s, large large altitude changes may occur. You can allow altitude and airspeed to vary and maintain attitude. Normally, Normally, no changes changes to cruise cruise altitude altitude or airspeed airspeed are required required when encounter encountering ing moderate moderate turbulence. If operating at cruise thrust limits, it may be difficult to maintain cruise speed. If this occurs, select a higher thrust limit (if available) or descend to a lower altitude. Mainta Main tain in clea clean n conf config igur urat atio ion n if hold holdin ing g in turb turbul ulen ence ce.. Flap Flap exte extens nsio ion n in an area area of know known n turbulence should be delayed as long as possible because the airplane can withstand higher gust loads with the flaps up. Advise Advise ATC if an increase increase in airspeed airspeed is necessary necessary due to turbulence turbulence,, if unable to accomplish accomplish any part of the holding procedure,

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Do not use sudden or large control inputs.

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After establishing the trim setting for penetration speed, do not change pitch trim.

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Do not allow allow the airspe airspeed ed to decrea decrease se and remain remain below below the turbulen turbulentt air pen penetr etrati ation on speed speed because stall/buffet margin is reduced. Avoid large thrust changes. Where possible avoid landing in tailwinds, on runways with negative slope, or on runways with less than normal braking conditions. Copyright 2006 SmartCockpit.com SmartCockpit.com

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