wakenet3- urope evaluation of wake encounter flight...

29 FEBRUARY 2012A380 WakeVortex - Evaluation of wake encounter flight tests in support of defining safe A380 separations - EYCDR - Ref. LxxPR1203140 - Issue 1

W k N t3 E

Evaluation of wake encounter flight tests in t f d fi i f A380 ti

WakeNet3-Europe

support of defining safe A380 separations4th Major Workshop, DFS Langen, Germany, 28 & 29 February 2012

Presented byAndreas REINKE / Task Leader Turbulence Hazards – Stability & Control


Presentation outline

• Background & Introduction

• Direct Wake Impact Method(DWIM)

• Summary & Outlook

© AIRBUS Operations S.A.S. All rights reserved. Confidential and proprietary document.

Background & Introduction


g

• During 2005 - 2010, Airbus has conducted more than 1.400 real wake vortex encounters in flight trials• various generator aircraft (A380, B747, A340) • various encountering aircraft (A380, A340, A300, A320, A318)

diti t ti f i fli ht ll h• conditions representative of cruise flight as well as approach

Thi i th l t i d t d t i ti t• This is the largest campaign ever conducted to investigate all aspects of the wake vortex characteristics• to establish safe separation minima for A380 operations• to establish safe separation minima for A380 operations• to advance knowledge of the wake turbulence phenomenon,

aiming at reducing separations when safe to do soaiming at reducing separations when safe to do so




g

• The wake vortex encounter hazard chain• Complex chain of events with many influencing factors

CAUSECAUSE CONSEQUENCECONSEQUENCECAUSECAUSE CONSEQUENCECONSEQUENCE




g

• A380 Wake Vortex Safety Case (2008)

• Relative safety assessment versus Heavy (B744, B773) reference aircraftaircraft

• Primarily based on vortex circulation measured by LiDAR


y y



g

• A380 Wake Vortex Safety Case (2008)

• ICAO recommendation to add 2 NM separations behind A380 approach operations for Heavy Medium and Light follower aircraftapproach operations for Heavy, Medium and Light follower aircraft compared to other Heavy leader aircraft

• Today's strange situation:• A light aircraft can fly 6 NM behind a B747A light aircraft can fly 6 NM behind a B747• A B747 has to remain 6 NM behind the A380

• First encounter flight tests have been performed by Airbus in 2006 (cruise) and 2007 (approach). Raw upset data and pilots impression showed no difference between A380 and A340-600 at equal separation distances ...




g

• Updated A380 Wake Vortex Safety Case (expected 2012)

• Relative safety assessment versus Heavy (A346) reference aircraft

• Primarily based on measured wake impact from encounter flight tests


Direct Wake Impact Method (DWIM)


p ( )

• In order to measure wake impact from encounter flight tests, Ai b h d l d th Di t W k I t M th dAirbus has developed the Direct Wake Impact Method.

DWIM d i f & t i ti th t i i ft• DWIM derives forces & moments impacting the encountering aircraft ..

… and which are a direct result of the wake encounter.




p ( )

• If an aircraft enters a region of wake vortex flow:

• The vortex flow field interacts in a complex way with the structure p yand the aerodynamic surfaces of the aircraft.

• This complex aerodynamic• This complex aerodynamic interaction exerts forces &moments on the aircraftmoments on the aircraft.

• All further aircraft reactions are a consequence of these forces & moments.




p ( )

• Background: How to simulate a wake vortex encounter ?

• Wake encounter simulations have beenperformed for many years e gperformed for many years, e.g.

• Offline simulations• Offline simulations

• Piloted wake encounter simulations• Piloted wake encounter simulations(WaveEnc & S-WAKE projects)

• Airbus Vortex Encounter Severity Assessment (VESA) method

TUB / ZFB




p ( )


1)Define a vortex velocity flow field using a modelusing a model

2)Establish local flow velocities2)Establish local flow velocities(wind kinematics)




p ( )


3) Apply a suitable multi-point aerodynamic aircraft modelaerodynamic aircraft model

• E.g. Strip Method• E.g. Panel Methodg

4)Use a standard flight dynamic simulation loop




p ( )

• Background: How to simulate a wake vortex encounter ?Standard 6-DoF Flight Simulation

tt M,F

Aerodynamic d l

Sum forces & tVelocities Eq. of motion

A l tiIntegrations

Attit d fli ht th

WKA VVV −= kK,V Ω&&kkkK X,,,V ΘΩ

BackgroundWi d

WV

model moments Accelerations Attitude, flight path

Flight simulation loop (simplified)

Wind




p ( )

• Background: How to simulate a wake vortex encounter ?Wake Encounter Flight Simulation

tt M,F bb M,F wvwv M,F

Aerodynamic d l

Sum forces & tVelocities Eq. of motion

A l tiIntegrations

Attit d fli ht th

Background Wind

model moments Accelerations Attitude, flight path

Flight simulation loop (simplified)Multi-point

Vortex model


paero model



p ( )

• How to measure wake impact from a wake vortex encounter ?

Flight test i ft

Wake Encounter Flight Test

aircraft

Unknown wake vortex flow field

• Five steps are required to derive wake impact from flight tests.

© AIRBUS Operations S.A.S. All rights reserved. Confidential and proprietary document. Flight simulation loop



p ( )


Flight test i ft


aircraft


1) Derive total forces and moments




p ( )

• How to measure wake impact from a wake vortex encounter ?1) Derive total forces and moments from measured aircraft dynamics

10

20

30

/s]

Roll rateFlight test example

-10

0

10

Roll

rate

[deg

/

0 10 20 30 40 50 60

-30

-20

R

Measurements

0 10 20 30 40 50 60Time [sec]

kkkK X,,,V ΘΩ




p ( )

• How to measure wake impact from a wake vortex encounter ?1) Derive total forces and moments from measured aircraft dynamics

[kNm

]

Total MxFlight test example

ing

mom

ent

0 10 20 30 40 50 60

Roll

Sum forces & t Eq. of motion Measurementstt M,F

0 10 20 30 40 50 60Time [sec]

moments qtt,




p ( )


Flight test i ft


aircraft


tt M,F

2) Identify wake encounter time segment




p ( )

• How to measure wake impact from a wake vortex encounter ?2) Identify wake encounter time segment from measured winds

10

15

/s]

Vertical windRegion of

wake influenceFlight test example

0

5

tical

win

d [m

/ wake influence

-10

-5

Mea

sure

d ve

rt

Region of no wake influence Region of no wake influence

0 10 20 30 40 50 60-15

Time [sec]

M

Region of no wake influenceprior to the encounter

Region of no wake influence following the encounter




p ( )


Flight test i ft


aircraft


tt M,F

3) Identify the background wind




p ( )

• How to measure wake impact from a wake vortex encounter ?2) Identify the background wind from measurements prior and after the

wake encounter (for all three axes)Background wind

Vw

Background wind

10

15

/s]

Vertical windRegion of

wake influenceFlight test example

0

5

10

tical

win

d [m

/ wake influence

-10

-5

Mea

sure

d ve

rt

Region of no wake influence Region of no wake influence

0 10 20 30 40 50 60-15

Time [sec]

M

Region of no wake influenceprior to the encounter

Region of no wake influence following the encounter




p ( )


Flight test i ft


V

Background wind

aircraft Vw


tt M,F

4) Derive base forces & moments




p ( )

• How to measure wake impact from a wake vortex encounter ?4) Derive base forces & moments from known aircraft behaviour

applied to recorded aircraft attitudes and background wind

10

20

30

/s]

Roll rateFlight test example

-10

0

10

Roll

rate

[deg

/

0 10 20 30 40 50 60

-30

-20

R

Measurements

kkkK X,,,V ΘΩ

BackgroundWi d

WV

0 10 20 30 40 50 60Time [sec]

Wind




p ( )

• How to measure wake impact from a wake vortex encounter ?4) Derive base forces & moments from known aircraft behaviour

applied to recorded aircraft attitudes and background wind

[kNm

]

Base MxFlight test example

ing

mom

ent

0 10 20 30 40 50 60

Roll

Aerodynamic d l

Sum forces & tVelocities Measurements

WKA VVV −= kkkK X,,,V ΘΩ

BackgroundWi d

0 10 20 30 40 50 60Time [sec]

bb M,F

WV

model momentsWind bb,




p ( )


Flight test i ft


V

Background wind

aircraft Vw


tt M,F bb M,F

5) Subtract base and total forces & momentsWake impact is the difference between measured (total) effects andWake impact is the difference between measured (total) effects and effects resulting from aircraft movement versus the background wind




p ( )

• How to measure wake impact from a wake vortex encounter ?5) Subtract base and total forces & moments

[kNm

]

Total MxBase Mx

Flight test example

ing

mom

ent

0 10 20 30 40 50 60

Roll

0 10 20 30 40 50 60

Time [sec]

tt M,F bb MFM,F tt M,F bb M,Fwvwv M,F




p ( )

• How to measure wake impact from a wake vortex encounter ?5) Subtract base and total forces & moments

[kNm

]

Wake-induced MxFlight test example

ing

mom

ent

0 10 20 30 40 50 60

Roll

0 10 20 30 40 50 60

Time [sec]

Example of a double tt M,F bb MFM,F

vortex encountertt M,F bb M,Fwvwv M,F




p ( )


Flight test i ft


V

Background wind

aircraft Vw

tt M,F bb M,F tt M,F bb M,F wvwv M,F

Outside the vortex influence, the total forces & moments equal the

base forces & moments

Under the wake influence, the total forces & moments differ fromthe base forces & momentsbase forces & moments. the base forces & moments.

The difference is the Direct Wake Impact.




p ( )


• Five step process:1 Derive total forces and moments1. Derive total forces and moments 2. Identify wake encounter time segment3 Identify the background wind3. Identify the background wind4. Derive base forces & moments5 Subtract base and total forces & moments5. Subtract base and total forces & moments

• This processp• Makes no assumptions on the vortex flow field• Does not require a model of aircraft-wake interaction• Allows to perform tests with control surface movements

without this biasing the result




p ( )

• Application• All Airbus back-to-back wake encounter flight tests (2007, 2010) have

been evaluated using the Direct Wake Impact Method• From all wake induced forces & moments the peak value of the• From all wake-induced forces & moments, the peak value of the

rolling moment is the key severity metric.

]

Wake-induced MxFlight test example

mom

ent [

kNm

]Ro

lling

m

0 10 20 30 40 50 60Time [sec]




• Comparison of peak roll impact with independently identified t i l ti h l t ff t f diff t t

p ( )

vortex circulations shows a relevant effect of different vortex core sizes – in line with theory.

2010 WVE F/T di ti di t2010 WVE F/T - diverse separation distances

F/T

Maximum wake-induced

Same rolling moment

|MXw

v| max

F

rolling momentMXwv

A320 b hi d A380

Different circulations

ΓB-H

A320 behind A380A320 behind A346

00

Identified total vortex circulation


Summary


y

• Wake encounter flight tests have been performed by Airbus in order to define safe wake turbulence minima for A380 operations

• Flight tests are evaluated using the DWIM which derives peak wake-induced roll impacts acting on an encountering aircraftp g g

• DWIM makes no simplifying assumptions about the structure of the vortex flow field or its interaction with the encountering aircraftvortex flow field or its interaction with the encountering aircraft.

• DWIM assesses the impact of a vortex on the follower instead of only the circulation characteristics of a wakeonly the circulation characteristics of a wake

• Wake impact in roll not only depends on vortex circulation but t i l l t l llvortex core size plays a relevant role as well.


Outlook


• Airbus is currently updating the A380 Safety Case & Safety Assessment Report together with EASA, ECTL and FAA

• Primary evidence comes from wake encounter flight tests

• The Direct Wake Impact Method is used to assess these tests

• Reduced wake turbulence separations behind A380 operations versus the 2008 Safety Case are expected.

• Encounter flight test results allow validating wake impact models i t f th f t t t i tiin support of other safety assessments, e.g. recategorisation



© AIRBUS Operations S.A.S. All rights reserved. Confidential and proprietary document. This document and all information contained herein is the sole property of AIRBUS Operations S.A.S. No intellectual propertyrights 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 Operations S.A.S. Thisdocument 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 expresseddocument 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 expressedin good faith. Where the supporting grounds for these statements are not shown, AIRBUS Operations S.A.S. will be pleased to explain the basis thereof.AIRBUS, its logo, A300, A310, A318, A319, A320, A321, A330, A340, A350, A380, A400M are registered trademarks.


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