02 Derate takeoff by cfm

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04/02/2006RXCF

THE POWER�OF FLIGHTDERATE TAKE OFFDERATE TAKE OFF

(( ASSUMED TEMPERATURE METHOD )ASSUMED TEMPERATURE METHOD )

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REDUCE TAKE OFF THRUST

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WHY REDUCE TAKE OFF THRUST ?WHY REDUCE TAKE OFF THRUST ?

You will reduceTakeoff EGT

Substantial costs may be savedby extension of engine parts life time.

When REAL GW < MAX LIMITING GWMax Thrust is not any more necessary!

You will improveflight safety

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You will improveflight safety

REDUCE TAKE OFF THRUST

IMPROVE ENGINE INTEGRITY BY REDUCTIONOF ENGINE DETERIORATION.

PROBABILITY OF ENGINE FAILURE

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You will reduceTakeoff EGT

TAKE OFF IMPACTTAKE OFF IMPACTVsVs

FLIGHT COSTFLIGHT COST

Flight Leg

1

0.8

0.6

0.4

0.2

00.5 1.5 2.5 321

T/O

CLIMB

CRUISE

% of cost

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Substantial costs may be savedby extension of engine parts life time.

EGT MARGIN WILLDECREASE SLOWLY KEEP SFC AT LOW RATE

TOTAL ENGINE PERFORMANCERETENTION WILL BE BETTER

LONGER ENGINE LIFE ANDINCREMENT OF SHOP VISIT RATE

REDUCTION OF MAINTENANCE COSTSREDUCTION OF MAINTENANCE COSTS( material, man power, services ... )( material, man power, services ... )

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• RUNWAY (Length, Altitude, slope…)•TEMPERATURE, QNH, wind,…• FLAPS SETTING• OBSTACLES HEIGHT & DISTANCE• AIRPLANE CONDITION• RUNWAY CONDITION

For

At • MAX TAKEOFF THRUST SETTING

There’s 1 LIMITING GW

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THRUSTT/Off GW

T°

Flat Rated T°

Real T°

TodayMax Thrust

TodayMax GWTodayReal GW

TodayReduced Thrust

Assumed T°

IF REAL GW < MAX LIMITING GW

A T° called “assumed T°” can be computed that would limit the performanceof the airplane to the real GW.

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04/02/2006RXCF

THE POWER�OF FLIGHTHOUSTON,

We've got a problem here!

It looks like the assume temperaturewe took: – 55° wasn’t the right one !

Could you confirm ?!?

?!?

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The accuracy of the OATis essential to optimize :

• TAKEOFF GROSS WEIGHT

• ASSUMED TEMPERATURE

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DOES THE ASSUMED TEMPERATURE METHODALWAYS CONSERVATIVE ?

YES, because of T° effect on performance.

Air T° = 10°& TAS = 138.5 KtsV1 CAS = 140 Kts

The Speed used tocomply with the

performancecalculations!

The Speed you will have...

Assumed T° = 45°& TAS = 148.5 KtsV1 CAS = 140 Kts

Example:

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Since the V1 are the same for both:

• The actual T°&• The assumed T°

The acceleration distances to V1 are always lessbecause the True Airspeed values are always lower.

TAS = CASTAS = CAS ++//-- 1% 1% 55°°c / Stdc / Std

++ if Tif T°° > Std> Std-- if Tif T°° < Std< Std

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Distance from start of roll

V1 CAS = 140 Kts

V1 TAS = 138.5 Kts

Air TAir T°° = 10= 10°°cc

V1 CAS = 140 Kts

V1 TAS = 148.5 Kts

Air TAir T°° = 45= 45°°cc

AIRCRAFT PERFORMANCE MARGINAIRCRAFT PERFORMANCE MARGINWITH REDUCED TAKEOFF THRUSTWITH REDUCED TAKEOFF THRUSTIS ALWAYS CONSERVATIVE.IS ALWAYS CONSERVATIVE.

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AIRCRAFT PERFORMANCE MARGINAIRCRAFT PERFORMANCE MARGINWITH REDUCED TAKEOFF THRUSTWITH REDUCED TAKEOFF THRUST

IS ALWAYS CONSERVATIVE.IS ALWAYS CONSERVATIVE.

You compute atYou compute at T = 45T = 45°°butbut

You fly atYou fly at T = 10T = 10°°

Distance from start of roll

Air T° = 45°cAir T

° = 10°cV1 CAS=

140 KtsV1 TAS = 138.5 Kts

V1 TAS = 148.5 Kts

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TAKE OFF DATA ASSOCIATED WITHTAKE OFF DATA ASSOCIATED WITHA PARTICULAR AMBIENT TEMPERATUREA PARTICULAR AMBIENT TEMPERATURE

IS ALWAYS CONSERVATIVEIS ALWAYS CONSERVATIVEFOR ANY LOWER TEMPERATUREFOR ANY LOWER TEMPERATURE

WITHIN THRUST REDUCTION LIMIT.WITHIN THRUST REDUCTION LIMIT.

You know what ?

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AIRLINEAIRLINEIS FULLY INVOLVED FORIS FULLY INVOLVED FORENGINE CHOICE ENGINE CHOICE ……

CREWSCREWSARE THE MAIN CONTRIBUTORS FORARE THE MAIN CONTRIBUTORS FORSAVING THE ENGINE !SAVING THE ENGINE !

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THE ENDTHE END

THANKS FOR YOURTHANKS FOR YOURATTENTION !ATTENTION !