fokker 100 wake vortex encounterwakenet.eu/fileadmin/wakenet2-europe/wakenet2/past events/2004...

1

1All information contained in this document is Copyright (C)2004 USE2ACES b.v. - All rights reserved

Fokker 100 Wake Vortex EncounterWakenet 2-Europe, WG5, first Workshop:Wake Vortex Encounters in Flight and Flight Simulation Airbus Hamburg, May 10 and 11, 2004

Wim Huson Experimental Test Pilot

USE2ACES b.v. - the Netherlands


USE2ACES b.v.

Address Houtsnip21902 KK Castricumthe Netherlands

Phone & Fax +31-251-654-458Mobile Phone +31-6-5066-4000Email [email protected]

Internet www.use2aces.com

2


Overview

• Circumstances of the encounter

• Crew observations

• Crew reactions

• Analysis by NLR

• Lessons learned

• Questions & discussion


Objectives

• Reporting a low altitude wake encounter during approach in tailwind operations

• Are there still lessons to be learned for wake detection, avoidance and training?

3


DXXX-3 A

• 110 passengers• 45 Tons Maximum Take off Mass• 2 Rolls Royce Tay engines• Exceeds stage 4 noise rules by 6,5 dB

Fokker 100 Characteristics


Circumstances of the encounter

• Autoland trials of the Fokker 100 • Fully instrumented prototype• Crew mixed Fokker / CAA-NL• Wake effects between 300 and 90 ft agl.• Wake encounter between 190 and 90 ft agl.• Leading aircraft: B-747 5 NM ahead• Tail wind component 7 Kt.• Light LH crosswind on during approach appr. 2

Kt.

4


Crew observations (1)

• Autocoupled approach for autoland measurement• Visual conditions, unlimited visibility• B-747 vacated Amsterdam runway 06• Until 300 ft really still air, no turbulence at all• From 300 ft to 190 ft “washboard ride”• At 190 ft suddenly

• large aileron movements (still autocoupled) • perceived sinking (<1 g for app. 4 s.)


Crew observations (2)

• The “Flight Test Result Summary” reported:

• “Go-around was initiated at 150 ft *) above the runway with initial conditions as follows: AFCAS: LAND3, flap 42, Vref+5 due to wake turbulence around 200 ft test was cancelled.”

• *) Go-around initiated at approximately 95 ft

5


Crew reactions

• At 300 ft noticed sudden “washboard ride”• Did not yet associate it with a wake vortex• At 190 ft large aileron deflections, banking &

sinking feeling• Disconnected autopilot• Applied firewall thrust • Manual go-around


Analysis by NLR (1)• Assumed vortex strength

of preceding B-747 is 813 m2/s

• The distance of the F100 behind the B-747 was approximately 5nm.

• At this location the roll-up of the wake vortices is completed.

-60

-40

-20

0

20

40

60

0 20 40 60 80 100 120 140y(m)

span of B-747

vertical speed(m/s)

vortex strength:813 m2/score radius:2.51 m

6


Analysis by NLR (2)

• Strength of wake vortex calculatedwith induced rolling motion

• Wind conditions were reconstructed• It is assumed that wake decay has occurred to

18 % of the original strength. [ 813 -> 147 m2/s ]• The Fokker 100 traverses the left wing tip wake

of the B-747 at an angle of 6 degrees


Angle of attack vane RH• Three distinct areas in time

history• Until 300 ft (time 153 s) still

air, no turbulence• 300 ft to 190 ft (until time

160 s) “washboard ride”• From 190 ft (from time 160

s) the encounter-10

-8

-6

-4

-2

0

2

4

6

8

130 140 150 160 170 180

AAV2(dg)

t(s)

encounter

7


Angle of roll• The encounter can be

observed clearly from the roll angle excursions during the time frame 160s -170s (equivalent with altitude bracket 190 ft to 90 ft)

• Remember: autocoupled in high gain autoland mode -10

-8

-6

-4

-2

0

2

4

6

8

10

130 140 150 160 170 180

ARIRS(dg)

t(s)

encounter


- 1 5

- 1 0

- 5

0

5

1 0

1 5

2 0

1 5 0 1 5 5 1 6 0 1 6 5 1 7 0 1 7 5 1 8 0

D A 2 ( d g )

t( s )

f l i g h t

-50

-40

-30

-20

-10

0

10

20

150 155 160 165 170 175 180

ARIRS(dg/s)

t(s)

flight

Bank angle analysis

- 1 5

- 1 0

- 5

0

5

1 0

1 5

2 0

1 5 0 1 5 5 1 6 0 1 6 5 1 7 0 1 7 5 1 8 0

D A 2 ( d g )

t( s )

s i m u l a t i o n• Using identical aileron

inputs roll response in free air was calculated

-50

-40

-30

-20

-10

0

10

150 155 160 165 170 175 180

ARIRS(dg/s)

t(s)

simulation

• Vortex strength was determined using difference in response

8


Body roll rate• Three distinct areas in time

history• Remember: autocoupled in

high gain autoland mode

-15

-10

-5

0

5

10

15

130 140 150 160 170 180

RRBIRS(dg/s)

t(s)

encounter


- 1 5

- 1 0

- 5

0

5

1 0

1 5

2 0

1 5 0 1 5 5 1 6 0 1 6 5 1 7 0 1 7 5 1 8 0

D A 2 ( d g )

t( s )

f l i g h t

-25

-20

-15

-10

-5

0

5

10

15

20

150 155 160 165 170 175 180

RRBIRS(dg/s)

t(s)

flight

Roll rate analysis

-15

-10

-5

0

5

10

15

20

150 155 160 165 170 175 180

DA2(dg)

t(s)

sim ulation• Using identical aileron

inputs roll response in free air was calculated

-25

-20

-15

-10

-5

0

5

10

15

20

150 155 160 165 170 175 180

RRBIRS(dg/s)

t(s)

simulation

• Vortex strength was determined using difference in response

9


Normal load factor• Three distinct areas in time

history• Until 300 ft (time 153 s) still

air, no turbulence• 300 ft to 190 ft (until time

160 s) “washboard ride”• At 190 ft suddenly (from

time 160 s) the encounter• large aileron movements

and • perceived sinking (<1 g for

4 s.)

0.8

0.9

1

1.1

1.2

1.3

1.4

130 140 150 160 170 180

nz(g)

t(s)

encounter


Radio height

0

100

200

300

400

500

600

130 140 150 160 170 180

RHBIN1(ft)

t(s)

encounter

10


Wake vortices - approachLight tailwind


-3000

-2000

-1000

0

1000

2000

3000

4000

-200 -100 0 100 200

xrw(m)

yrw(m)

rw 06

w ind

vortex of left w ing tip B-747

path of aircraftintercept angle

vortex of right w ing tip B-747

11


Wake vortices - landing Touchdown point

No windLight quartering tailwind


Encounter during cruise flight• MD-11 5NM behind a B-747

in the OTS around FL 350• Suddenly “washboard ride”

upon leg change into the wind

• Deviating 1/10th of a NM (FMS function) resolved it

12


Phenomena before encountering upset• Wake turbulence training aid appendix 4A page

78 quoting ASRS data: • “We began to encounter light wake turbulence ../..

Aircraft began to roll to right, full opposite aileron was applied.....”

• Washboard ride experienced by us in both encounters

• Low altitude: Fokker 100 5NM behind B-747• Cruise Flight: MD-11 5NM behind B-747


Lessons learned (1): Is radar separation really sufficient?

• Wake turbulence training aid chapter 3-A5.1: • Radar separation provided by FAA has been successful in preventing

wake-turbulence encounters• NLR report TP 2001-003 “Safety aspects of tailwind operations”:

• In a tailwind, the wake may be blown back onto the glide slope• In a quartering tailwind such as was present in the F100 vortex

encounter the wake can be present in the touchdown zone• 5 NM separation between heavy and medium / large category

aircraft in tailwind conditions is not sufficient in all cases

• Should more separation be applied in tailwind operations?

13


Lessons learned (2)

• The “washboard ride” pre-alerted the crew in both cases!

• ASRS shows more cases of pre-encounter phenomena

• Are “washboard ride” characteristics always present?

• Can “washboard” be used as an input for o/b multi-sensor warning computation? (supplementing lidar etc.)

• Pre-alerting is useless if not trained for


Lessons learned (3)

• Recognising pre encounter phenomena very important

• “Washboard characteristics” can be presented in simulator

• Training is essential for awareness • Awareness should result in earlier avoidance

14


Lessons learned (4) • At 190 ft such an encounter should result in a go-around

• Best option • If no go-around is flown: hard landing or worse

• In IMC reduction in situational awareness• No visual contact with leading aircraft (Callsign incl. “Heavy”

known?)• Spatial disorientation due unexpected high roll rate movement • Invoked roll angle close to the ground

• Wake turbulence training aid appendix 3C page 32: • Encountering wake-turbulence at low altitudes is much more

hazardous than in cruise or early in the approach• Low altitude encounter is rated as extremely hazardous


Acknowledgements

• Fokker Services • Dirk van Os

[email protected]• Rudi den Hertog

[email protected]

• NLR• Ton Nieuwpoort

[email protected]• Gerard van Es

[email protected]

15


Questions & Discussion

fokker 100 wake vortex encounterwakenet.eu/fileadmin/wakenet2-europe/wakenet2/past events/2004...

Documents