surfing aircraft vortices for energy (save) · wagner et. al, 2002 (t-38) nasa formation flight...

Copyright © 2011 Boeing. All rights reserved.

Engineering, Operations & Technology

Surfing Aircraft Vortices for Energy (SAVE) DARPA/AFRL Formation Flight for Efficiency Program



What are we trying to do?

Lead aircraft generates wake Trail aircraft positions near wake at over 3000 feet in trail

Wake flow-field results in substantial fuel savings

Demonstrate 10% trailing aircraft fuel burn reduction using enhanced C-17 autopilot guidance WITHOUT adversely effecting the airframe, engines, or aircrew.

Obtain data to mitigate remaining concerns associated with airframe, engines, and workload.

Understand system level opportunities and effects on transportation networks: military and commercial.

-60%

-40%

-40%

-20%

-20%

-20%

-10%-10%

-10%

0%

0%

0%

5%

5%

5%

5%

10%

10%

Relative Lateral Spacing (ft)

Rel

ativ

e Ve

rtic

al S

paci

ng (f

t)

-250 -200 -150 -100 -50 0-100

-50

0

50

100

2

Wake vortex

core

Benefit Map for 31,000 ft, 0.74 M Wake vortex

core

2



Benefits of formation flight are known and confirmed by numerous analytical and experimental studies

Only Hummel had success automating, all other efforts piloted Efforts have focused on benefits not the costs NASA/USAF effort in 2010 provided key data for program

What has been done before?

EOT_Template.ppt | 3

Hummel, 1996 (Do-28/Do-228)

Wagner et. al, 2002 (T-38)

NASA Formation Flight Program, 2002 (F-18)

NASA/USAF, 2010 (C-17)

3



What are we doing differently?


Large transport class aircraft Extended formations 3000-8000 ft (20-50 spans) Fully autonomous Comprehensive look at range of challenges

4



How is it done today?

Military Transports C-17 has the capability to fly

formation missions for airdrop using the C-17 Formation Flight System. Other aircraft, such as C-130, have

some capability via Station Keeping Equipment.

| 5

Military routinely plans and executes complex tanker missions involving large formations. Military makes use of Military Assumes

Responsibility for Separation Assurance (MARSA) to plan and execute formation missions.

Commercial Formation missions not flown.

5

http://www.google.com/imgres?imgurl=http://www.knowledgerush.com/wiki_image/a/a8/Usaf.f15.f16.kc135.750pix.jpg&imgrefurl=http://www.knowledgerush.com/kr/encyclopedia/United_States_Air_Force/&usg=__MDBTKfIF9BfjqHzN5PwgAOdCVzY=&h=475&w=750&sz=84&hl=en&start=3&zoom=1&tbnid=SFpppRNSz8T8aM:&tbnh=89&tbnw=141&ei=9Wh1TeaOMJLEsAP7vKCxBA&prev=/images?q=kc135&hl=en&gbv=2&tbs=isch:1&itbs=1



What are the SAVE opportunities?

Total USAF fuel use in 2010 was 2.5 billion gallons C-17 fuel use was approx.

$2 billion Just 1% reduction is $20

million a year Possibly double with

inclusion of other large transports.

6

Breakdown of USAF Aviation Fuel Usage by Aircraft Type, Fiscal Year 2010

6



7

What are the challenges? Five “showstoppers.”

We* will not be interested in Formation Flying for Aerodynamic Benefit if:

• It is unsafe

• It beats up the aircrew

• It beats up the aircraft

• It makes no business sense

• It makes no operational sense * Perspective provided by Air Mobility Command Chief

Scientist, Dr. Don Erbschloe.

7



What are the program focus areas?

Aerodynamic analyses

Flight test planning

Operational analysis

Sensing and control Data analysis

Simulation

Propulsion Structures Systems

8

8



+ VTRK

- VTRK

R100 R200

L100L200

+100

-100

R300

L300

(+300,R350)

A I

D CB

F GH

JKL

(+300,L350)

I

J K L

A

E-XTRK(Left)

+ XTRK(Right)E

+ VTRK

- VTRK

R100 R200

L100L200

+100

-100

T1-XTRK(Left)

+ XTRK(Right)

What were some of the tests conducted?

+ VTRK

- VTRK

R100 R200

L100L200

+100

-100

T2T1-XTRK(Left)

+ XTRK(Right)

L300L400

Wake Confirmation Tests

Demonstration and data gathering flight test included wide range of test points to met the program success criteria.

Wake Crossings

+ VTRK

- VTRK

R100 R200

L100L200

+100

-100

R300

L300

-200

+200

T2 T9T4 T8T6 T7T5T3 T10

+ XTRK(Right)

-XTRK(Left)

T1

Vertical Wake Passes

Dwells in Proximity to the Wake

9

9



Strain gage (13)

Accelerometer (8)

Program Addressed Safety Challenges

Demonstrated robust tracking of lead wake at separations of 4000-8000 ft.

View from cockpit, 5000 ft spacing. Indicated cross-track visible.

Airframe safety and engine operability from 40+ wake crossings reveal no concerns.

-100% -75% -50% -25% 0% 25% 50% 75% 100%

RH HOR STAB FS, UPR CAP STA RH HOR STAB FS, UPR CAP STA RH HOR STAB RS, UPR CAP STA RH HOR STAB RS, UPR CAP STA RH HOR STAB RS, UPR CAP STA PYLON 3 - STUB, UP INBD CAPPYLON 4 - STUB, UP INBD CAPRH WING, RS LWR CAPRH WING STA 4, FS LWR CAPRH WING STA 4, RS LWR CAPFS VERT STAB, CAP, Z=530FS VERT STAB, CAP, Z=812.5FS VERT STAB, CAP, Z= 713ENG 3 B FLANGE, FWD LATENG 4 B FLANGE, FWD LATRH WING STA 6, FS TIP - NORMRH WING STA 6, RS TIP - NORMFS VERT STAB, TIP LATRS VERT STAB, TIP LATRH HOR STAB FS, TIP NORMRH HOR STAB RS, TIP NORM

Stra

in g

ages

Acc

eler

omet

ers

Normalized peak responses over wake crossings.

10

10



NASA Ride Quality Metric for Lead and Trail 5 3 Flight card ratings

Median change in discomfort level from lead to trail.

Relative lateral spacing (ft)

Rel

ativ

e ve

rtic

al s

paci

ng (f

t)

Minor ride quality degradation for locations close to wake. Ride quality observations

strongly affected by turbulence.

Program Addressed Aircrew Challenges

Workload and ride quality assessed during flight test.

Enhanced Mission Computer enables fully automated and robust flight in close proximity to the wake.

11

Automated station-keeping performance from Sep. 2012 All points fully autonomous

Wake prevention engaged

Relative lateral spacing (ft)

Rel

ativ

e ve

rtic

al s

paci

ng (f

t)



Program Addressed Aircraft Challenges

No increase expected in engine wear due to SAVE. No significant increase in airframe wear due to SAVE.

Flight test, consisting of wake crossings and dwells, has substantially increased the aerodynamic, structural, and engine response database.

12

Trajectories during 20 inadvertent wake crossings

Database after 2012 Flight Tests

12



17 17.5 18 18.5 19 19.5 20 20.5 21

0.85

0.9

0.95

1

1.05

Time [hr]

Nor

mal

ized

fuel

flow

tota

l

Normalized fuel flow

Time [hr] L200ft XTRK ∆FF=6.4%

L170ft XTRK ∆FF=8.6%

L150ft XTRK ∆FF=9.4%

R200ft XTRK ∆FF=5.1%

Tares taken out of wake

Flight test analysis indicates 5-10% fuel flow reduction. Benefits consistent with predictions.

Subset of stable locations flown for extended duration (30 min each).

A B C

D

Program Confirmed Fuel Burn Savings

13

-60%

-40%

-40%

-20%

-20%

-20%

-10%-10%

-10%

0%

0%

0%

5%

5%

5%

5%

10%

10%

Relative Lateral Spacing (ft)

Rel

ativ

e Ve

rtic

al S

paci

ng (f

t)

-250 -200 -150 -100 -50 0-100

-50

0

50

100

Wake vortex

core

Wake vortex

core

A

B C

D

13



LTK: 7000 FT AVG XTK: L159, VTK: +26

DURATION: 30 MINS AVG FUEL SAVED: 10.7%

PHIK

KSUU

Surfing Aircraft Vortices for Energy (SAVE) Hickam to Travis Mission Demonstration: 07/11/2013

| 14

12000 FT

SKE COUPLED

TARE

TARE





LTK 7000 FT

HF RATING Satisfactory



HF RATING Very

Satisfactory

HUMAN FACTOR (HF) RATING

TARE Multiple human factors ratings taken on workload, ride quality, and fatigue – all satisfactory.

Substantial fuel burn savings observed, exceeding 10% over 90 min segment and totaling >4000lbs for the mission.

14



0

5

10

15

20

25

30

35

Total Number of FlightsFlights in a Formation

Num

ber o

f flig

hts

What difference will it make if successful?

Solo Formation

Average 60+% Formation Rate

Statistics over random sample of days Assuming C-17 flights remain in the same 24 hour window as historically flown, millions of gallons saved per year possible.

Program Addressing Operational Concerns

15

15



NORTHCOM C-17 Projected Fuel Savings

| 16

-250 -240 -230 -220 -210 -200 -190 -180 -170 -160 -1500

1

2

3

4

5

6

Cross-track position [ft]

Fuel

sav

ings

[Mill

ion

gallo

ns /

year

]

Expected cross-track

range

Estimated Yearly Fuel Savings C-17 NORTHCOM Route Network

12 hours schedule flexibility, 1000 NMi radius, standard reserves

Three aircraft

Two aircraft

1.9 to 2.6

Projected fuel savings [Million gallons / year]

1.7 to 2.3%

Percent fleet wide savings

Two aircraft results

2.8 to 3.9

Projected fuel savings [Million gallons / year]

2.5 to 3.5%

Percent fleet wide savings

Three aircraft results

Over the expected cross-track range, fleet fuel consumption benefits from 60+% of all C-17 flights joining a formation.

16



Summary

Technology has potential for substantial fleet wide savings

and can be obtained with a software change and operational flexibility.


Surfing Aircraft Vortices for Energy has demonstrated >10% fuel burn savings without adversely effecting the airframe, engines, or aircrew.

17

David Halaas [email protected]

206-544-4577 Stefan Bieniawski (PI)

[email protected] 206-544-4511

Contributions from many, including: Roger Clark, Steve Rosenzweig, Jeff Slotnick, Dave Halaas, Brian

Whitehead, Tristan Flanzer, Dan Tompkins, Rick Selder, Mike Cabot, Nam Chiang

Bill Blake (AFRL PM) [email protected] Aerospace Systems Directorate Air Force Research Laboratory Wright Patterson AFB OH 45433 DSN: 674-4006 (937)-904-4006



Wake Evolution Video


surfing aircraft vortices for energy (save) · wagner et. al, 2002 (t-38) nasa formation flight...

Documents