Takeoff Thrust Setting

Takeoff Thrust Setting

Operational Liaison Meeting – Fly-By-Wire Aircraft 2004

Customer Services

Takeoff Thrust Setting © A

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Contents

• Introduction

• Rolling Takeoff

• Engine-Related Issues during Takeoff

• Power Check

• FADEC Logics during Takeoff (KOZ and MEASTO)

• Engine Thrust Loss ECAM Message on A340 CFM 56

• Conclusion


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Introduction

The Takeoff Thrust Setting Procedure…

• May differ, depending on engine type:4This is defined by Airbus and engine manufacturers

• Is a certified procedure, contained in the Aircraft Flight Manual (AFM)4And is associated with specific certified performance

• May differ, depending on wind conditions:4To minimize the risk of engine stall/surge

• Normally completed in two steps:4To avoid asymmetry due to different engine response


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Contents …

• Introduction

• Rolling Takeoff


• Power Check



• Conclusion


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Rolling Takeoff

• Definition of a Rolling Takeoff4Takeoff for which the thrust setting sequence is initiated

while the aircraft is moving. 4Thrust is not set under the brakes.

• What is considered to be a Rolling Takeoff?4The aircraft does not stop, when it enters the runway…4When the aircraft is aligned, the brakes released and

the thrust setting sequences are initiated.


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Rolling Takeoff …

• Advantages…4Less risk of FOD (less risk of ingestion)4Takeoff can be conducted earlier4Less risk of high power setting at low speeds (stall prevention)4Less brake wear4Smoother for passengers

• Disadvantages…4Engine response can differ (small dissymmetry)4Alignment on the runway axis may be longer

• Performance-wise, if the rolling takeoff technique is applied correctly, there will be no difference between a rolling takeoffand static takeoff.


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Rolling Takeoff …

• Airbus recommended Rolling Takeoff…4In the Standard Operating Procedures (SOP) -FCOM 3.03.12

– “Rolling takeoff is recommended, when possible”

• However:4This recommendation was sometimes considered too strong.

Some operators felt obliged to perform it systematically.4Rolling takeoff requires crew familiarization with the rolling

takeoff piloting technique4In some situations, the rolling takeoff technique is not

recommended (Engine Intermix operations).

• Therefore, the SOP (FCOM 3.03.12) will now reflect:4“Rolling takeoff is permitted”

Left up to the crew to decide whetheror not to perform a rolling takeoff


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Contents …

• Introduction

• Rolling Takeoff


• Power Check



• Conclusion


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Engine-Related Issues during Takeoff

• Engine Instability Phenomenon4Stall/Surge caused by:

– Reduced margin due to wear– Crosswind or tailwind

4Flutter caused by:– Resonance frequencies generated in under certain conditions (N1, EPR)

Application of adequate procedure: • Insufficiently accurate

• Increase crew workload

FADEC Logis automatically:• Respect certain parameters

• Avoid Resonance Zones


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Contents …

• Introduction

• Rolling Takeoff


• Power Check



• Conclusion


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Power Check

• Engines must reach the takeoff rating limit, established for thetakeoff conditions:

4Engines’ N1 or EPR must be equal to the rating limit value:– If one engine does not reach it, the takeoff should be rejected.

• In case of engine failure, takeoff performance is not guaranteed.

4Monitoring of engine parameters is done during takeoff:– N1/EPR, and EGT– In particular, the power check callout is done before 80 knots.

4What is the criteria/tolerance for aborting a takeoff:– For performance reasons, all engines should reach the rating limit– As a guideline, it is accepted that if a difference lower than:

• 1% N1• 0.01 EPR

– It is the crew’s decision

It is always the crew’s responsibility tocheck that the thrust is satisfactory for takeoff


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Contents …

• Introduction

• Rolling Takeoff


• Power Check



• Conclusion


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FADEC Logics during Takeoff (MEASTO)

• MEASTO A330 Rolls Royce (Trent 700)4 Modified Engine Acceleration Schedule for TakeOff

– High crosswind, tailwind or intake turbulence: Increase risk of fan stall

– The Fan stall risk zone is more significant at low speed.

– Engines automatically react against fan stall.• If a stall occurs: Engine power is reduced.

– Automatic and progressive thrust setting during takeoff:• Engine acceleration is controlled by a predefined EPR/second rate.• Function only active during the low speed phase of takeoff

(speed < 50 knots).• For RR T700 engines not fitted with this function,

this acceleration law had to be reproduced by the crew.

– It takes about 10 additional seconds to reach takeoff power.– For all flight conditions, takeoff thrust is achieved before 80 knots.– This function is only available on ground, and with forward thrust:

• Also available for ground maintenance tasks.


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FADEC Logics during Takeoff (MEASTO) …

• The engine acceleration rate for the fan stall margin, compared to the engine acceleration rate with the MEASTO function.

Normal Acceleration

Acceleration Rate of 0.04 EPR/second

Acceleration Rate of 0.02 EPR/second

I0

I5

I10

I15

I20

I25

I30 Time

1.6 -

1.4 -

1.2 -

1.0 -

EPR

Increased riskof fan stall

With the MEASTO Function


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• The thrust achieved progressively...Full takeoff thrust is reached:

4Within approximately 15 seconds

4Before reaching 80 knots

4Reduced acceleration rate with altitude,to compensate for the stall margin loss.

2 4 6 8 10 12 14 16 18

1.2

1.4

1.3

1.5

1.6

1.7

EPREPR

Time from thrustTime from thrustlever movementlever movement

-2000 feet

0 feet

4000ft

12500ftand above


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• MEASTO is:4Basically installed in production, an4Retrofit worldwide

• Simplification of the Takeoff Procedure, in the event of high crosswind or tailwind:4Rolling Takeoff no longer required4Step at 1.1 EPR is not required

• Reduced engine stall risk during takeoff

• Specific performance has been developedfor aircraft fitted with the MEASTO function…

Crew task reduction and simplification with this logic


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FADEC Logics during Takeoff (KOZ)

• The KOZ (Keep Out Zone) implemented on:4A330 Rolls Royce (Trent 700) 4A320/A319/A321 IAE (V2500 A5 series)4A340-500/600 Rolls Royce (Trent 500)

• To avoid fan flutter, the FADEC prevents stabilization in a certain EPR (N1) zone, depending on the engine type.

4For example, the KOZ for RR Trent 700 is between:– 1.16 to 1.28 EPR– The N1 interval changes, based on the temperature of the day.

• The max upper and min lower limit are: 51.4% and 73.6%

4The KOZ is active when:– Aircraft on ground, and– Low aircraft speed (M<0.15 or <80 knots), and– Forward thrust.


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FADEC Logics during Takeoff (KOZ) …

• During Engine Acceleration….4When the thrust lever is advanced through the KOZ, there is a

pause in the EPR command at the lower EPR command limit.

4The EPR command will remain at the lower command limit,until the thrust lever is advanced such that the corresponding EPR command exceeds the upper EPR command limit.

4Then, engine power will continue to increase with the thrust lever position.

KOZ is fully automatic

for the crew STABILIZATION


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FADEC Logics during Takeoff (KOZ IAE V2500 A5)

• To avoid cracking the fan blade root due to fan flutter, the FADEC prevents stabilization in a certain EPR (N1) zone.

• This automatic KOZ replaces the manual KOZ, applied by crews, to avoid operation in a specific fan speed range.

• In EPR mode, KOZ changes are based on the daily temperature.

• In N1, the Keep Out Zone is between61% to approx. 74%

• KOZ is transparent to the crew:4Not felt in the takeoff procedure4Low probability to reach this value during taxi

– With the exception of the Ice Shedding Procedure


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FADEC Logics during Takeoff (KOZ IAE V2500 A5) …

• Modification of the Takeoff Procedure for tailwind,or high crosswind:4Deletion of the 70% N1 step, which falls within the KOZ.

– Simplified Takeoff Procedure

4If tailwind or high crosswind:The performance impact is 25 meters in the takeoff distances

IDLEIDLE 1.05 EPR1.05 EPR 1.15 EPR1.15 EPR TO powerTO power

PRE-SCN17STEP

SUPPRESSED

IDLEIDLE 1.05 EPR1.05 EPR TO powerTO power

SCN17


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FADEC Logics during Takeoff (KOZ IAE V2500 A5) …

• IAE has considered the risk of fan flutter (for the pre-SCN17 procedure) to be acceptable, since the aircraft is alreadymoving and there is no stabilization.

4The main risk occurs during stabilization at low, or zero, aircraft speed:– For the Ice Shedding Procedure– For maintenance run-ups

4It is covered in the Airbus SOP.

• The engines are automatically protected, and the crewworkload is reduced.

• This feature is available with the SCN 17 Software4Airbus recommends embodiment of the SCN17 FADEC Software4This software is basically installed on the production line.


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Contents …

• Introduction

• Rolling Takeoff


• Power Check



• Conclusion


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Engine Thrust Loss ECAM Message on A340 CFM 56-5C

• A. ICE ENG X VALVE OPEN is triggered when:4There is a disagreement between the anti-ice valve,

and the pushbutton position:– The engine anti-ice has not been selected open, and– The anti-ice valve is open.

COMPARISON

PUSHBUTTON POSITION

ENG ANTI-ICE VALVE

POSITION

FWC

A.ICE ENG X VALVE OPEN

IFDISAGREE


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Engine Thrust Loss ECAM Message on A340 CFM 56-5C …

• Also, the current FADEC does not provide adequate thrust for takeoff:4Because takeoff thrust is computed by taking into account the position of

engine anti-ice valve (N1 decrement applied).

• Therefore, ENG THRUST LOSS triggers during takeoff.

PUSHBUTTON POSITION

ENG ANTI-ICE VALVE POSITION

ENG THRUST LOSS

FADEC

If DISAGREE

COMPARISON


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• To avoid this scenario, the FADEC C3J will compute takeoff thrust, based on the engine anti-ice pushbutton position.

• Therefore, ENG THRUST LOSS will not trigger during takeoff.

PUSH BUTTON POSITION ENG ANTI-ICE VALVE

POSITION

FADEC

IF DISAGREE No N1 decrement applied


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• With the FADEC C3J Standard -- If the crew selection disagrees with the actual position of the valve:

4The FADEC provides adequate thrust, and increases the EGT to compensate for the effect of engine anti-ice extraction.

4Only for engines with a low EGT margin, and for temperatures higher than the corner-point, will it lead to an EGT overlimit.

• Airbus recommends retrofitting the FADEC C3J Softwareon A340 aircraft with CFM 56-5C Engines:4To avoid rejected takeoffs

FADEC C3J Software


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Conclusion

• Rolling takeoffs may be advantageous in certain circumstances.4 However, it is up to the crew to apply this technique.

• The Takeoff Thrust Setting Procedure is standard for Airbus aircraft.4However, it may vary slightly from one engine to another,

and depends on wind conditions.

• Airbus is actively working on reducing crew workload during the Takeoff Setting Procedure:4MEASTO4KOZ4Avoidance of ECAM messages that lead to aborting a takeoff.

• Airbus recommends retrofitting the latest FADEC Software Standards in order to:4Further ensure safety4Ease the crew workload4Reduce maintenance costs.


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This document and all information contained herein is the sole property of AIRBUS S.A.S. No intellectual property rights are granted by the delivery of this document or the disclosure of its content. This document shall not be reproduced or disclosed to a third party without the express written consent of AIRBUS S.A.S. This document and its content shall not be used for any purpose other than that for which it is supplied.

The statements made herein do not constitute an offer. They are based on the mentioned assumptions and are expressed in good faith. Where the supporting grounds for these statements are not shown, AIRBUS S.A.S. will be pleased to explain the basis thereof.

AN EADS JOINT COMPANYWITH BAE SYSTEMS

Takeoff Thrust Setting

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