B737-Reduced Thrust Considerations

737.1

Reduced Thrust ConsiderationsReduced Thrust ConsiderationsTakeoff Performance MarginsTakeoff Performance Margins

Dick MaywardFlight Operations Engineering

Boeing Commercial AirplanesMay 2004

Dick MaywardFlight Operations Engineering

Boeing Commercial AirplanesMay 2004

737.2The Boeing Company

Common MisconceptionsCommon Misconceptions

• “If reduced thrust is used, then the airplane will not be able to clear the obstacles if an engine fails during takeoff.”

• “If the maximum allowable assumed temperature is used, then there will be no stopping margin left if the takeoff is aborted.”

• “If reduced thrust is used, then the airplane will not be able to clear the obstacles if an engine fails during takeoff.”

• “If the maximum allowable assumed temperature is used, then there will be no stopping margin left if the takeoff is aborted.”


Regulatory ComplianceRegulatory Compliance

Boeing AFM states: “Operations at reduced takeoff thrust based on an assumed temperature higher than the actual ambient temperature is permissible if the airplane meets ALL applicable performance requirements at the planned takeoff weight and reduced thrust setting.”

Boeing AFM states: “Operations at reduced takeoff thrust based on an assumed temperature higher than the actual ambient temperature is permissible if the airplane meets ALL applicable performance requirements at the planned takeoff weight and reduced thrust setting.”

AC/AMJ 25-13AC/AMJ 25-13


Regulatory Performance RequirementsRegulatory Performance Requirements

• Have sufficient runway length for:– 115% of all-engine takeoff distance– One engine inoperative takeoff distance– Accelerate-stop distance

• Achieve the one engine inoperative minimum climb gradient for:– First segment– Second segment– Final segment

• Clear all obstacles in the intended takeoff flight path

• Have sufficient runway length for:– 115% of all-engine takeoff distance– One engine inoperative takeoff distance– Accelerate-stop distance

• Achieve the one engine inoperative minimum climb gradient for:– First segment– Second segment– Final segment

• Clear all obstacles in the intended takeoff flight path


Effect of Temperature on True Airspeed and Thrust

Effect of Temperature on True Airspeed and Thrust

• Air density is lower at higher outside air temperature (OAT)

• For a given indicated airspeed (IAS), true airspeed (TAS) is higher at higher OAT

• For a given reduced engine power setting (N1 or EPR), lower air density (higher OAT) results in lower thrust

• Air density is lower at higher outside air temperature (OAT)

• For a given indicated airspeed (IAS), true airspeed (TAS) is higher at higher OAT

• For a given reduced engine power setting (N1 or EPR), lower air density (higher OAT) results in lower thrust


The Assumed Temperature MethodThe Assumed Temperature Method

• Dispatch takeoff performance must assume the higher true airspeed at the assumed higher temperature

• Takeoff thrust assumed is the rated thrust at that assumed temperature

• Dispatch takeoff performance must assume the higher true airspeed at the assumed higher temperature

• Takeoff thrust assumed is the rated thrust at that assumed temperature


Inherent Conservatism of the Assumed Temperature Method

Inherent Conservatism of the Assumed Temperature Method

• The actual thrust will be higher than the rated thrust at the assumed temperature, because the actual air density is higher

• The actual true airspeed will be lower, because the actual ambient temperature is lower

• The lower true airspeed combined with the higher thrust will result in a shorter ground distance

• The actual thrust will be higher than the rated thrust at the assumed temperature, because the actual air density is higher

• The actual true airspeed will be lower, because the actual ambient temperature is lower

• The lower true airspeed combined with the higher thrust will result in a shorter ground distance


The True Airspeed EffectThe True Airspeed Effect148148

146146

144144

142142

140140

True airspeed, kt

True airspeed, kt

Assumed temperature, °CAssumed temperature, °C

OAT – assumed temperature differenceOAT – assumed temperature difference

Assumed true airspeedAssumed true airspeed

Actual true airspeed at OAT, 15°CActual true airspeed at OAT, 15°C

3030 3232 3434 3636 3838 4040


737-800W W ITH CFM 56-7B27 ENG INES PRESSURE ALT ITUDE 0 FT

RUNW AY LENG TH 7000 FT , DRY NO O BSTACLES

FLAPS 5, A /C AUTO , STANDARD TAKEO FF SPEEDS M AXIM UM RATED THRUST (27K) 24K DERATE

O AT (C)

M TOW(KG )

PERFLIM

V1 VR V2 (KT)

M TOW (KG )

PERFLIM

V1 VR V2 (KT)

60 60400 FLD 134 135 140 55900 FLD 131 131 13455 62200 FLD 136 137 142 57700 FLD 133 133 13750 65000 FLD 138 139 146 59700 FLD 134 135 13945 67200 FLD 140 141 148 61900 FLD 136 137 14240 69300 FLD 141 143 150 64100 FLD 138 139 14438 70300 FLD 142 144 151 65000 FLD 139 140 14536 71100 FLD 142 145 152 65800 FLD 139 141 14634 72000 FLD 143 145 153 66700 FLD 140 141 14732 72900 FLD 143 146 154 67700 FLD 141 142 14830 73700 FLD 144 147 155 68600 FLD 141 143 14925 74300 FLD 144 147 156 69200 FLD 142 144 15020 75000 FLD 145 148 156 69800 FLD 143 144 15115 75600 FLD 146 149 157 70300 FLD 144 145 15110 76200 FLD 146 149 157 71000 FLD 144 146 152

Maximum AllowableAssumed Temperature 38°C


27K, OAT 15°CTakeoff Weight 70300 KG


The Assumed Temperature MethodThe Assumed Temperature Method


Margins Between Assumed and Actual Performance at the Maximum Allowable Assumed Temperature

Margins Between Assumed and Actual Performance at the Maximum Allowable Assumed Temperature

Parameter

V1 (KIAS / KTAS)

VR (KIAS / KTAS)

V2 (KIAS / KTAS)

Thrust per engine at V1, lb

Thrust per engine at VR, lb


One engine inoperative takeoff distance, ft

Accelerate-stop distance, ft

115% all-engine takeoff distance, ft

OAT 38°C OAT 15°Cassume 38°C

Extramargin

142 / 148

144 / 150

151 / 157

23855

19833

19857

7000

7000

6942

142 / 142

144 / 144

151 / 151

24061

20019

20034

6507

6507

6464

6

6

6

206

186

177

493

493

478


68006800

66006600

64006400

62006200

60006000

Field length, ftField length, ft


Runway lengthRunway length

Actual balanced field lengthActual balanced field length

3030 3232 3434 3636 3838 4040

Field Length Margin Increases With Lower Assumed Temperature Due to Higher ThrustField Length Margin Increases With Lower

Assumed Temperature Due to Higher Thrust• 737-800W / CFM56-7B27• Pressure Altitude 0 ft• Runway Length 7000 ft, Dry• Flaps 5, Standard Takeoff Speeds• OAT 15°C, Takeoff Weight 70300

kg72007200

70007000

2828

Field Length MarginField Length Margin

875 ft

493 ft


2550025500

2500025000

2450024500

2400024000

2350023500

Net thrust/engine at V1, lb



Rated thrustRated thrust

Actual thrustActual thrust

3030 3232 3434 3636 3838 4040

Thrust Margin Decreases With Lower Assumed Temperature

Thrust Margin Decreases With Lower Assumed Temperature

2600026000

2828

Rated Thrust Versus Actual ThrustRated Thrust Versus Actual Thrust• 737-800W / CFM56-7B27• Pressure Altitude 0 ft• Runway Length 7000 ft, Dry• Flaps 5, Standard Takeoff Speeds• OAT 15°C, Takeoff Weight 70300

kg

206 lb206 lb

139 lb139 lb


737-800W W ITH CFM 56-7B27 ENGINES PRESSURE ALTITUDE 0 FT

RUNW AY LENGTH 7000 FT, DRY NO O BSTACLES

FLAPS 5, A/C AUTO , STANDARD TAKEO FF SPEEDS M AXIM UM RATED THRUST (27K) 24K DERATE

O AT (C)

M TOW(KG )

PERFLIM

V1 VR V2 (KT)

M TOW (KG )

PERFLIM

V1 VR V2 (KT)


Lower Takeoff Weight May Permit Higher Maximum Allowable Assumed TemperatureLower Takeoff Weight May Permit Higher

Maximum Allowable Assumed Temperature


145145

140140

135135

130130

True airspeed, kt

True airspeed, kt


Assumed true airspeedAssumed true airspeed

Actual true airspeed at OATActual true airspeed at OAT

4040 4545 5050 5555 6060 6565

True Airspeed Effect Increases With Higher Assumed Temperature

True Airspeed Effect Increases With Higher Assumed Temperature

150150

3535

6 kt

10 kt

True Airspeed EffectTrue Airspeed Effect


2200022000

2100021000

2000020000

1900019000

1800018000




Rated thrustRated thrust

Actual thrustActual thrust

4040 4545 5050 5555 6060 6565

Thrust Margin Increases With Higher Assumed Temperature

Thrust Margin Increases With Higher Assumed Temperature

2300023000

3535

650 lb650 lb

• 737-800W / CFM56-7B27• Pressure Altitude 0 ft, OAT 15°C• Runway Length 7000 ft, Dry• Flaps 5, Standard Takeoff

Speeds

206 lb206 lb2400024000

2500025000

Rated Thrust Versus Actual ThrustRated Thrust Versus Actual Thrust


• 737-800W / CFM56-7B27• Pressure Altitude 0 ft, OAT 15°C• Runway Length 7000 ft, Dry• Flaps 5, Standard Takeoff

Speeds

66006600

64006400

62006200

60006000

58005800

Field length, ftField length, ft


Runway lengthRunway length

Actual balanced field lengthActual balanced field length

4040 4545 5050 5555 6060 6565

Field Length Margin Due to the True Airspeed Effect Increases With Higher Assumed Temperature

Field Length Margin Due to the True Airspeed Effect Increases With Higher Assumed Temperature

68006800

3535

493 ft

1035 ft

72007200

70007000

Field Length MarginField Length Margin


• If performance is limited by the one engine inoperative minimum climb gradient requirements, the higher actual thrust will result in a higher climb gradient

• If performance is limited by obstacle clearance, the higher climb gradient combined with the shorter takeoff distance will result in extra clearance margin

• If performance is limited by the one engine inoperative minimum climb gradient requirements, the higher actual thrust will result in a higher climb gradient

• If performance is limited by obstacle clearance, the higher climb gradient combined with the shorter takeoff distance will result in extra clearance margin

Extra obstacleclearance margins

Performance Margins in Flight Path With Assumed Temperature Reduced Thrust

Performance Margins in Flight Path With Assumed Temperature Reduced Thrust

Actual thrust and climb gradient

Rated thrust at the assumed temp


737-800W W ITH CFM 56-7B27 ENG INES PRESSURE ALT ITUDE 5000 FT

RUNW AY LENG TH 12000 FT , DRY NO O BSTACLES


O AT (C )

M TOW(KG )

PERFLIM

V1 VR V2 (KT)

M TOW(KG )

PERFLIM

V1 VR V2 (KT)

60 57300 CLB 133 133 136 49300 CLB 124 124 12655 59900 CLB 136 136 139 51500 CLB 126 126 12950 62500 CLB 138 139 142 53800 CLB 129 129 13245 65100 CLB 141 141 145 56200 CLB 132 132 13440 68100 CLB 143 144 148 58900 CLB 135 135 13835 71000 CLB 146 147 151 61700 CLB 138 138 14130 73900 CLB 148 150 154 64600 CLB 140 141 14425 75400 CLB 149 151 155 67600 CLB 143 144 14720 76400 CLB 150 152 156 70800 CLB 146 147 15115 76400 CLB 150 152 156 70900 CLB 146 147 15110 76500 CLB 150 152 156 71000 CLB 146 147 151





Thrust And Climb Gradient Margins At The Maximum Allowable Assumed TemperatureThrust And Climb Gradient Margins At The Maximum Allowable Assumed Temperature

Parameter


One engine inoperative climb gradient, %


Extramargin

20108

2.4

20355

2.54

247

0.14


• 737-800W / CFM56-7B27• Pressure Altitude 5000 ft• Runway Length 12000 ft, Dry• Flaps 5, Standard Takeoff Speeds• OAT 10°C, Takeoff Weight 71000 kg

2.82.8

2.62.6

2.42.4

2.22.2

Climb gradient, %

Climb gradient, %


Regulatory minimumRegulatory minimum

Actual gradientActual gradient

2020 2525 3030 3535 4040

3.03.0

1515

3.43.4

3.23.2

Climb Gradient Increases With Lower Assumed Temperature Due to Higher Thrust

Climb Gradient Increases With Lower Assumed Temperature Due to Higher Thrust

0.9 %

Climb Gradient MarginClimb Gradient Margin

0.14 %


737-800W W ITH CFM 56-7B27 ENGINES PRESSURE ALT ITUDE 5000 FT

RUNW AY LENGTH 12000 FT , DRY NO O BSTACLES


O AT (C)

M TOW (KG )

PERFLIM

V1 VR V2 (KT)

M TOW (KG )

PERFLIM

V1 VR V2 (KT)


Lower Takeoff Weight May Permit A Higher Maximum Allowable Assumed TemperatureLower Takeoff Weight May Permit A Higher Maximum Allowable Assumed Temperature


• 737-800W / CFM56-7B27• Pressure Altitude 5000 ft, OAT 10°C• Runway Length 12000 ft, Dry• Flaps 5, Standard Takeoff Speeds

Climb gradient, %

Climb gradient, %

Assumed temperature, °CAssumed temperature, °C3535 4040 4545 5050 55553030

Climb Gradient Margin Due to the True Airspeed Effect Increases With Higher Assumed Temperature

Climb Gradient Margin Due to the True Airspeed Effect Increases With Higher Assumed Temperature

6060 6565

2.62.6

2.42.4


Actual gradientActual gradient

0.25 %

0.14 %

2.32.3

2.52.5

2.72.7

Climb Gradient MarginClimb Gradient Margin


737-800W W ITH CFM56-7B27 ENGINES PRESSURE ALTITUDE 0 FT

RUNW AY 9000 FT, DRY OBSTACLE: 50 FT HT AT 1000 FT DIST FROM LIFTOFF END

FLAPS 5, A/C AUTO, STANDARD TAKEOFF SPEEDS MAXIMUM RATED THRUST (27K) 24K DERATE

OAT (C)

MTOW(KG)

PERFLIM

V1 VR V2 (KT)

MTOW (KG)

PERFLIM

V1 VR V2 (KT)

60 62900 OBS 138 138 143 57000 OBS 132 132 13655 65200 OBS 140 141 145 59200 OBS 134 134 13850 68600 OBS 142 144 149 61600 OBS 137 137 14145 71300 OBS 144 146 152 64200 OBS 139 140 14443 72400 OBS 145 147 153 65200 OBS 140 141 14541 73500 OBS 146 148 154 66300 OBS 141 142 14639 74600 OBS 147 149 155 67400 OBS 142 143 14837 75700 OBS 147 150 156 68400 OBS 143 144 14935 76700 OBS 148 151 157 69400 OBS 143 145 15030 79300 OBS 149 153 160 72200 OBS 146 147 15325 79800 OBS 150 153 160 72700 OBS 146 147 15320 80300 OBS 150 154 161 73100 OBS 147 148 15315 80800 OBS 151 154 161 73500 OBS 147 148 15410 81300 OBS 151 155 161 73900 OBS 147 149 154





Obstacle Clearance Margin at the Maximum Allowable Assumed Temperature

Obstacle Clearance Margin at the Maximum Allowable Assumed Temperature

Parameter

Net clearance


Extramargin

35 ft 61 ft 26 ft


• 737-800W / CFM56-7B27• Pressure Altitude 0 ft• Runway Length 9000 ft, Dry• Obstacle: 50 ft Ht at 1000 ft Dist from liftoff end• Flaps 5, Standard Takeoff Speeds• OAT 15°C, Takeoff Weight 73500 kg

8080

6060

4040

2020

Net clearance, ft

Net clearance, ft



Actual net clearanceActual net clearance

3030 3232 3434 3636 3838

100100

2828

120120

Obstacle Clearance MarginObstacle Clearance Margin

Net Clearance Margin Increases With Lower Assumed Temperature Due to Higher ThrustNet Clearance Margin Increases With Lower Assumed Temperature Due to Higher Thrust

26 ft

81 ft

4040 4242


737-800W WITH CFM56-7B27 ENGINES PRESSURE ALTITUDE 0 FT

RUNWAY 9000 FT, DRY OBSTACLE: 50 FT HT AT 1000 FT DIST FROM LIFTOFF END


OAT (C)

MTOW(KG)

PERFLIM

V1 VR V2 (KT)

MTOW (KG)

PERFLIM

V1 VR V2 (KT)


Lower Takeoff Weight May Permit Higher Maximum Allowable Assumed TemperatureLower Takeoff Weight May Permit Higher

Maximum Allowable Assumed Temperature


• 737-800W / CFM56-7B27• Pressure Altitude 0 ft, OAT 15°C• Runway Length 9000 ft, Dry• Obstacle: 50 ft Ht at 1000 ft Dist from liftoff

end• Flaps 5, Standard Takeoff Speeds

6060

4040

2020

Net clearance, ft

Net clearance, ft



Actual net clearanceActual net clearance

4545 5050 5555 60604040

8080

Obstacle Clearance MarginObstacle Clearance Margin

6565

Net Clearance Margin Due to True Airspeed Effect Increases With Higher Assumed Temperature

Net Clearance Margin Due to True Airspeed Effect Increases With Higher Assumed Temperature

58 ft69 ft


Issues With Takeoff SpeedsIssues With Takeoff Speeds

• Standard takeoff speeds depend on:

– Takeoff weight

– Flap setting

– Thrust (temperature, pressure altitude, and engine bleed configuration)

– V1 also depends on runway slope, wind, and surface condition (dry or wet)

• Takeoff speeds vary with thrust, therefore, they vary with assumed temperature

• Standard takeoff speeds depend on:

– Takeoff weight

– Flap setting

– Thrust (temperature, pressure altitude, and engine bleed configuration)

– V1 also depends on runway slope, wind, and surface condition (dry or wet)

• Takeoff speeds vary with thrust, therefore, they vary with assumed temperature


Increasing V1 and VR, typically resulting in lower V2, will re-balance field length

V1 = 140 V2 = 150VR = 145

Lower thrust

Proper takeoff speeds for a balanced field length

V2 = 155

Higher thrust

V1 = 135 VR = 140

Effect of Thrust on Takeoff Speeds (IAS)Effect of Thrust on Takeoff Speeds (IAS)


• 737-800W / CFM56-7B27• Pressure Altitude 0 ft• Flaps 5, Dry Runway, Standard

Speeds• OAT 15°C, Takeoff Weight 60400 kg

140140

135135

130130

125125

Takeoff speeds, KIAS

Takeoff speeds, KIAS


V1V1

VRVR

3030 3535 4040 4545 50502525

145145

Thrust Effect on Takeoff SpeedsThrust Effect on Takeoff Speeds

5555 6060

Takeoff Speeds (IAS) Vary With Assumed TemperatureTakeoff Speeds (IAS) Vary

With Assumed Temperature

V2V2

6565


Use the FMC or QRH to Obtain Proper Standard Takeoff SpeedsUse the FMC or QRH to Obtain Proper Standard Takeoff Speeds

T A K E O F F R E F 1 / 2 F L A P S

°2 6 K N 1

98. 8 / 98.8%C G T R I M

22.5% 5 . 2 5

R U N W A Y

< P E R F I N I T

Q R H V 1

V R

V 2

G W / T O W

S E L E C TQRH OFF>

— — — — — — — — — — — — — — — — — — — — — — — — — — —

— — — —

— — — —

— — — —

Standard Takeoff Speeds OnlyStandard takeoff speeds, plus adjustments for clearwayand stopway, slippery and contaminated runways, andinoperative system. No optimized V1 or improved climb.

Quick

Referen

ce

Handbo

ok


737-800W W ITH CFM 56-7B27 ENGINES PRESSURE ALT ITUDE 0 FT



O AT (C )

M TOW(KG )

PERFLIM

V1 VR V2 (KT)

M TOW (KG )

PERFLIM

V1 VR V2 (KT)






OverspeedOverspeedUse Speeds for the Maximum Allowable Assumed Temperature, Ignoring Thrust Effect on Speeds

Use Speeds for the Maximum Allowable Assumed Temperature, Ignoring Thrust Effect on Speeds


737-800W / CFM56-7B27Pressure Altitude 0 ft, OAT 15°CDry Runway, Standard Speeds

Flaps 5, Takeoff Weight 60400 kg

128 / 131 / 14315°C

131 / 133 / 14245°C

134 / 135 / 14060°C

V1 / VR / V2 (kt)

Assumed temperature

Proper Takeoff Speeds From QRHProper Takeoff Speeds From QRH



RUNW AY LENGTH 7000 FT, DRY NO O BSTACLES


O AT (C)

M TOW(KG )

PERFLIM

V1 VR V2 (KT)

M TOW (KG )

PERFLIM

V1 VR V2 (KT)






OverspeedOverspeedUse Speeds for the Lower Assumed Temperature,

Ignoring Weight Effect on SpeedsUse Speeds for the Lower Assumed Temperature,

Ignoring Weight Effect on Speeds


60006000

62006200

64006400

66006600

68006800

70007000

72007200

2828 3030 3232 3434 3636 3838 4040

• 737-800W / CFM56-7B27• Pressure Altitude 0 ft, OAT 15°C• Runway Length 7000 ft, Dry• Flaps 5, Takeoff Weight 70300 kg• Max Allowable Assumed Temp

38°C

Field length, ft

Field length, ft

Field Length Margin With OverspeedField Length Margin With OverspeedOverspeed Reduces Field Length MarginOverspeed Reduces Field Length Margin

Proper speeds

Runway length available

Overspeed– Max assumed

temp Overspeed– Lower assumed

temp



• 737-800W / CFM56-7B27• Pressure Altitude 5000 ft, OAT

10°C• Runway Length 12000 ft, Dry• Flaps 5, Takeoff Weight 71000 kg• Max Allowable Assumed Temp

35°C

Climb gradient, %

Climb gradient, %

Climb Gradient Margin With OverspeedClimb Gradient Margin With Overspeed

Proper speeds

Regulatory minimum

Effect of Overspeed on Climb GradientEffect of Overspeed on Climb Gradient

2.22.2

2.42.4

2.62.6

2.82.8

3.03.0

3.23.2

3.43.4

3.63.6

1515 2020 2525 3030 3535 4040


Overspeed– Lower assumed temp

Overspeed– Max assumed temp


• 737-800W / CFM56-7B27• Pressure Altitude 0 ft, OAT 15°C• Runway Length 9000 ft, Dry• Obstacle: 50 ft Ht at 1000 ft Dist from liftoff

end• Flaps 5, Takeoff Weight 73500 kg• Max Allowable Assumed Temp 41°C

Net clearance, ft

Net clearance, ft


Obstacle Clearance With OverspeedObstacle Clearance With Overspeed

Overspeed Reduces Obstacle Clearance Margin

Overspeed Reduces Obstacle Clearance Margin

2020

4040

6060

8080

100100

120120

2828 3030 3232 3434 3636 3838 4040 4242

Proper speeds

Regulatory minimum

Overspeed– Max assumed

tempOverspeed– Lower assumed

temp


Means to Maximize Thrust Reduction and Performance Margins

Means to Maximize Thrust Reduction and Performance Margins

• Takeoff configuration:– Flaps setting selection– No engine bleed for A/C packs

• Takeoff speeds options:– Improved climb– Optimized V1 (unbalanced)

• Goal: Increase the difference between the OAT and the assumed temperature, thus increasing the true airspeed effect.

• Takeoff configuration:– Flaps setting selection– No engine bleed for A/C packs

• Takeoff speeds options:– Improved climb– Optimized V1 (unbalanced)

• Goal: Increase the difference between the OAT and the assumed temperature, thus increasing the true airspeed effect.


7 3 7 -8 0 0 W W IT H C F M 5 6 -7 B 2 7 E N G IN E S P R E S S U R E A L T IT U D E 0 F T

R U N W A Y L E N G T H 7 0 0 0 F T , D R Y N O O B S T A C L E S

2 7 K , S T A N D A R D T A K E O F F S P E E D S O A T (C )

F L A P S 5 A /C A U T O

F L A P S 1 5 A /C A U T O

F L A P S 5 A /C O F F

6 0 6 0 4 0 0 6 0 8 0 0 6 1 3 0 0 5 5 6 2 2 0 0 6 3 4 0 0 6 3 2 0 0 5 0 6 5 0 0 0 6 6 1 0 0 6 6 0 0 0 4 5 6 7 2 0 0 6 8 2 0 0 6 8 1 0 0 4 0 6 9 3 0 0 7 0 5 0 0 7 0 3 0 0 3 8 7 0 3 0 0 7 1 4 0 0 7 1 1 0 0 3 6 7 1 1 0 0 7 2 3 0 0 7 2 0 0 0 3 4 7 2 0 0 0 7 3 2 0 0 7 2 8 0 0 3 2 7 2 9 0 0 7 4 1 0 0 7 3 6 0 0 3 0 7 3 7 0 0 7 5 0 0 0 7 4 4 0 0 2 5 7 4 3 0 0 7 5 7 0 0 7 5 0 0 0 2 0 7 5 0 0 0 7 6 3 0 0 7 5 6 0 0 1 5 7 5 6 0 0 7 6 9 0 0 7 6 2 0 0 1 0 7 6 2 0 0 7 7 6 0 0 7 6 9 0 0

Means to Maximize Thrust Reduction and Margin


OAT 15°CTakeoff Weight 70300 KG


Performance Limited by Field LengthPerformance Limited by Field Length


Assumed temperature

38°C

38°C

38°C

40°C

40°C

Field lengthrequired, ft

Extra margin, ft

6507

6314

6360

6416

6461

493

686

640

584

539

Field Length Margin With Optimum Takeoff Configuration

Field Length Margin With Optimum Takeoff Configuration

Takeoff configuration

Flaps 5, A/C Auto

Flaps 15, A/C Auto

Flaps 5, A/C Off

Flaps 15, A/C Auto

Flaps 5, A/C Off


7 3 7 -8 0 0W W IT H C F M 5 6 -7 B 2 7 E N G IN E S P R E S S U R E A L T IT U D E 5 0 0 0 F T

R U N W A Y L E N G T H 1 2 0 0 0 F T , D R Y N O O B S T A C L E S 2 7 K , A /C A U T O

O A T (C )

F L A P S 5 N O IM P C L B

F L A P S 1 N O IM P C L B

F L A P S 5 W IT H IM P C L B

6 0 5 7 3 0 0 5 9 3 0 0 6 0 6 0 0 5 5 5 9 9 0 0 6 2 0 0 0 6 3 2 0 0 5 0 6 2 5 0 0 6 4 7 0 0 6 5 7 0 0 4 5 6 5 1 0 0 6 7 4 0 0 6 8 3 0 0 4 0 6 8 1 0 0 7 0 5 0 0 7 1 1 0 0 3 9 6 8 7 0 0 7 1 1 0 0 7 1 6 0 0 3 7 6 9 9 0 0 7 2 4 0 0 7 2 5 0 0 3 5 7 1 0 0 0 7 3 1 0 0 7 3 4 0 0 3 0 7 3 9 0 0 7 4 0 0 0 7 5 3 0 0 2 5 7 5 4 0 0 7 4 8 0 0 7 6 5 0 0 2 0 7 6 4 0 0 7 5 5 0 0 7 7 3 0 0 1 5 7 6 4 0 0 7 6 1 0 0 7 7 7 0 0 1 0 7 6 5 0 0 7 6 8 0 0 7 8 1 0 0





Performance Limited by Climb or Obstacle ClearancePerformance Limited by Climb or Obstacle Clearance


Performance Margins With Optimum Takeoff Option

Performance Margins With Optimum Takeoff Option

Assumed temperature

35°C

35°C

39°C

40°C

Field lengthrequired, ft

Extra margin, ft

9086

9804

10153

10642

2914

2196

1847

1358

Takeoff option

Flaps 5, No Imp Climb



Flaps 5, Improved Climb

Climb gradient, %

2.54

2.93

2.58

2.58


The Takeoff Derate MethodThe Takeoff Derate Method

• Available for use on slippery or contaminated runways and with inoperative antiskid

• Can be combined with use of assumed temperature

• Available for use on slippery or contaminated runways and with inoperative antiskid

• Can be combined with use of assumed temperature





O AT (C)

M TOW(KG )

PERFLIM

V1 VR V2 (KT)

M TOW (KG )

PERFLIM

V1 VR V2 (KT)


Runway Length ConsiderationRunway Length Consideration




24K DerateOAT 15°C

27K assume 38°C

7000

22353

93.8

6507

24061

97.2

Parameter

Field Length Required, ft

Thrust per Engine at V1, lb

Takeoff N1 Setting

Using Derate Reduces Performance Margins




RUNWAY LENGTH 12000 FT, DRY NO OBSTACLES


OAT (C)

MTOW(KG)

PERFLIM

V1 VR V2 (KT)

MTOW (KG)

PERFLIM

V1 VR V2 (KT)


Climb ConsiderationClimb Consideration




24K DerateOAT 10°C

27K assume 35°C

2.4 2.54

Parameter

One Engine Inoperative Climb Gradient (%)





RUNWAY LENGTH 9000 FT, DRY OBSTACLE: 50 FT HT AT 1000 FT DIST FROM LIFTOFF END


OAT (C)

MTOW(KG)

PERFLIM

V1 VR V2 (KT)

MTOW (KG)

PERFLIM

V1 VR V2 (KT)


Obstacle Clearance ConsiderationObstacle Clearance Consideration




Using Derate Reduces Performance MarginsUsing Derate Reduces Performance Margins

24K DerateOAT 15°C

27K assume 41°C

35 61

Parameter

Net Clearance (ft)


9898

9696

9494

9393

N1N1

OAT, °COAT, °C

27K and max allowable assumed temp27K and max allowable assumed temp

24K Derate at OAT24K Derate at OAT

1515 2020 2525 3535 4545 5050

9999

1010

For Equivalent Performance, Using Derate Lowers N1 (RPM) and Achieves More Effective Thrust ReductionFor Equivalent Performance, Using Derate Lowers N1 (RPM) and Achieves More Effective Thrust Reduction

3030 4040

9797

9595


Other Advantages Of Takeoff DerateOther Advantages Of Takeoff Derate

• Permitted on slippery or contaminated runways, where the use of assumed temperature reduced thrust is prohibited

• Permitted with anti-skid system inoperative

• May increase maximum takeoff weight when performance is limited by VMCG

• May improve aircraft loadability, for some models, by extending aft takeoff CG limit

• Better trimmed for rotation and climbout for most models

• Permitted on slippery or contaminated runways, where the use of assumed temperature reduced thrust is prohibited

• Permitted with anti-skid system inoperative

• May increase maximum takeoff weight when performance is limited by VMCG

• May improve aircraft loadability, for some models, by extending aft takeoff CG limit

• Better trimmed for rotation and climbout for most models


Summary On Performance MarginsSummary On Performance Margins

• Extra performance margins are inherent in the Assumed Temperature method of reduced thrust, including at the maximum allowable assumed temperature

• Using those inherent margins for takeoff weight planning is prohibited!

• Extra performance margins are inherent in the Assumed Temperature method of reduced thrust, including at the maximum allowable assumed temperature

• Using those inherent margins for takeoff weight planning is prohibited!

B737-Reduced Thrust Considerations

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