formation flight presentation

7/21/2019 Formation Flight Presentation

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Motivation

Global air travel is expected togrow by 3 fold over the next 3 decades

Aviations contribution to global warming

is expected to grow to 20% by 2050

Source: Lee et al., Aviation and Global Climate Change in the 21stCentury ,2009


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1978 1983 1988 1993 1998 2003 2008

AircraftB

uilt

Airbus A330/A340 Development

Market penetration

Study

Launch

Delivery


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ObjectiveUse formation flight to improve the energy

efficiency and economic performance of todays aircraft


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Design Studies

Route Optimization

Conclusion

Formation Flight

Policy Considerations

Formation Flight


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Photo Source: John Benson, V is for Vamoose, Creative Commons

Bird Migration:

190 BPM when flying solo; 160 BPM when in formation

(Weimerskirch, Martin, Clerquin, Alexandre, andJiraskov, 2001)


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NASA Autonomous Formation Flight Experimentdemonstrated14-18% fuel savings (Ray et al. 2002)

Photo source: NASA


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Apply formation flight to an airline schedule anddemonstrate 7.7% fuel or 2.6% cost savings

Baseline ScheduleOptimized Formation

Flight Schedule

Xu, Ning, Bower, Kroo, Aircraft Route Optimization for Formation Flight, Journal of Aircraft, In Press


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When an aircraft produces lift it also createsenergetic and persistent wake vortices


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The wake vortices create regions ofdownwash and upwash

Ning, Aircraft Drag Reduction Through Extended Formation Flight,2011


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A trailing aircraft flying through the upwashcan reduce its drag at fixed lift

This can lead to reduced fuel burn or longer

range

(Lissaman, 1970, Weimerskirch et al. 2001, Blake and Multhopp, 1998)


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Wake vortices can persist for many miles beforebeing dissipated by viscous forces

Extended formation flight can achieve most ofthe savings of close formation flight

5 to 40 wing spans


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5 to 40 wing spans

Trailing aircraft see all of the savings

Wake evolution is an importantconsideration


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Design Studies

Route Optimization

Conclusion

Formation Flight


Route Optimization


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Mission Level

Continuous domain aircraft

mission performanceoptimization

Gradient-based method


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Mission Level

Continuous domain aircraft

mission performanceoptimization

Gradient-based method

System Level

Find the best schedule ofoptimized missions

Integer programing


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All possible solo and

formation missions

n candidate solo and

formation missions

Heuristic filter toeliminate bad routes

n optimized missions

Integer programming tooptimized schedule

Optimized schedule

Optimizemission 1

Optimizemission 2

Optimizemission 3

Optimizemission n

Flight schedule


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formation missions


formation missions




Optimized schedule

Optimizemission 1

Optimizemission 2

Optimizemission 3

Optimizemission n

Flight scheduleBaseline flight

schedule

Optimized formation

flight schedule


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formation missions


formation missions




Optimized schedule

Optimizemission 1

Optimizemission 2

Optimizemission 3

Optimizemission n

Flight schedule

Combinatorial set ofall possibleformations


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formation missions


formation missions




Optimized schedule

Optimizemission 1

Optimizemission 2

Optimizemission 3

Optimizemission n

Flight schedule

Reduce the size ofthe problem


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formation missions


formation missions




Optimized schedule

Optimizemission 1

Optimizemission 2

Optimizemission 3

Optimizemission n

Flight schedule

Gradient-basedmission

optimizations


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formation missions


formation missions




Optimized schedule

Optimizemission 1

Optimizemission 2

Optimizemission 3

Optimizemission n

Flight schedule

Integer programingto find the best

schedule of flights


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For n flights there are:

n solo routes

n(n-1) two-aircraft formation routes

n(n-1)(n-2) three-aircraft formation routes

NP-hard problem

But only a small subset of formations is practical Filters formations based on spatial and temporal

proximity


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Objectives Fuel burn Direct operating cost (DOC)

Variables (4-D trajectory) Altitudes, weight and Mach numbers Formation rendezvous longitudes, latitudes and altitudes Departure and arrival times

Constraints Rendezvous time and flight state compatibility Segment range Thrust margins Flight time


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Induced drag is sensitive to the offset between vortexand wing tip as well as the longitudinal position

Model accounts for wake roll-up and viscous decay

t i p

t i p


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Aircraft of different types are optimally arranged information according to relative weight and fuel

efficiency (Ning and Kroo, 2011, Xu, Ning, Bower andKroo , 2013)


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Drag buildup

Induced drag from the formation drag model andelliptic load assumptions

Parasite drag from modified flat plate methods

Compressibility drag from the method of Shevell

(1983)

Engine model included in the analysis


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Balance formation cost and fuel savings

Direct operating cost model (Liebeck et al.1995)

$/block hour (crew)

$/flight hour (airframe and engine maintenance) $/gal of fuel and $/lb of oil

Neglect landing fees, insurance and depreciation

C t i ft d f l fl d f t th 4 fli ht t t


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Compute aircraft drag, fuel flow and performance at the 4 flight states

I t t f th t i th B t ti


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Integrate for the segment range using the Breguet equation

The f el b rn objecti e falls o t of the eight


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The fuel burn objective falls out of the weight

Segments represent great circle routes


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Segments represent great circle routes

Middle segment is flown in formation


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gRendezvous and separation longitude and latitudes are design variables


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Formation Flight Fuel Reserve

Models the worst case scenario where an aircraft flies

the longer formation mission but gets no drag savings The aircraft must still carry enough fuel to reach its

destination

The additional weight from the reserve fuel cut

formation flight savings by 25%

Our conservative model of formation flightreduces the fuel burned, but not the fuel carried


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Find the best combination of individually optimalsolo and formation missions

Integer-programming solver with branch and

bound algorithms


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Objective: total fuel burn or cost for the entire flight schedule


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Variables: which solo and formations routes are flown


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Constraints: all scheduled flight must fly once


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Design Studies

Route Optimization

Conclusion

Formation Flight


Design Studies


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150 eastbound Star Alliance transatlantic flights

Airbus A330 and A340

Boeing 737,747,757,767 and 777


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Restrictive heuristic filters

The departure and arrival heading differences are lessthan 30 degrees

6 minutes of departure and arrival time flexibility

Optimize 2,500 of the 3.3 million possible

formations 1-week runtime on a laptop


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-6.9% Fuel-2.6% Cost

Minimum Cost Minimum Fuel

Solo Missions 37 23

2-Aircraft Formations 22 26


Distance in Formation 61.1% 67.5%

Change in Flight Time 4.9% 7.4%

Change in Departure Time 5.0% 4.8%


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-7.7% Fuel-2.2% Cost

Minimum Cost Minimum Fuel

Solo Missions 37 23



Distance in Formation 61.1% 67.5%

Change in Flight Time 4.9% 7.4%

Change in Departure Time 5.0% 4.8%


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Design Studies

Route Optimization

Conclusion

Formation Flight


Conclusion


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Formation flight can significantly reduce airlinefuel burn and cost:

7.7% fuel or 2.6% cost savings for a largetransatlantic alliance schedule

Results includes the effects of conservative fuelreserves


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Boeing 787


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Finalist, 2009 Airbus Fly Your Idea (FYI) Competition

Proposed formation flight at the 2009 Paris Airshow


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Inspire public interest and discussions on formation flight

and sustainable aviation


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Air Force/DARPA/NASA Experiment

Test flight from Edwards AFB to Hawaii in July,2013 demonstrated10% fuel savings at

longitudinal separations of 2000 to 6000 ftPhoto source: USAF

Pahle, et. al, A Preliminary Flight Investigation of Formation Flightfor Drag Reduction on the C-17 Aircraft, 2011


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Design Studies

Route Optimization

Conclusion

Formation Flight

Future WorkFuture Work


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Alternative formation reserve fuel requirements Cost sharing for multi-airline formations

Model multi-stage flights with delay

Incorporate wake tracking sensors constraints


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Formation flight can benefit from next

generation air traffic control systems Next Generation Air Transport System (NextGen)

Single European Sky ATM Research (SESAR)

Automatic Dependent Surveillance-Broadcast(ADS-B)


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Photo source: Boeing

GNSS provide high resolutionposition and velocity data


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Replaces legacy ground-basedradar tracking



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Ground-based transmissiontowers and data networks relayaircraft state and trajectory toATC

Replaces legacy voice-basedcoordination procedures


In-flight network share time-sensitivity spacing and collisionavoidance data



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avoidance data

Ground-based transmissiontowers and data networks relayaircraft state and trajectory toATC

Replaces legacy voice-basedcoordination procedures



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Formation flight can boost the policy argumentfor NextGen and SESAR

The FAA expects NextGen to reduce aviation fuelconsumption by 1.4 billion gallons by 2018

Formation flight can boost these savings by 800million gallons


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Design formation flight technology

demonstrations for NextGen and SESARAtlantic Interoperability Initiative to Reduce Emissions

(AIRE)

Incorporate formation flight requirements into

next generation ATC development


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The Department of Defense is the largestinstitutional petroleum user in the world

DoD requests $1.4 billion in FY2013 budget toimprove energy efficiency


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The Air Force accounts for 53% of DoDenergy consumption

The Air Mobility Command accounts for 64%of Air Force fuel consumption


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Boeing C-17

16-year, $40 billion program

C-X Concept Study: 1979First Flight: 1991IOC: 1995

Airbus A-400M

35-year, EUR 20 billion+ program

FIMA Concept Study: 1982First Flight: 1991

IOC: 2017+


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Air CargoMilitary Air Mobility


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Simplified missionplanning around major

hubs

Older air cargo fleetstand to benefit

No passengeracceptance issues

High quality station-keeping systems

High risk tolerance

Reduced ride qualityrequirement

Military Air Mobility Air Cargo Single Airlines


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High risk tolerance



hubs



No cost/benefit sharingissues

Depends on the successof next generation AirTraffic Control systems

Military Air Mobility Air Cargo Single Airlines Airline Alliances


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High risk tolerance



hubs



No cost/benefit sharingissues

Depends on the successof next generation AirTraffic Control systems

Institutional frameworkfor cost/benefit sharing

More flights; moresavings


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Use formation flight to moderate the design tradeoffsamong persistence, stealth and speed


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Use variable geometry to reconcile the conflicting

requirements posed by different flight segments


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MunksStagger TheoremThe induced drag of a lifting system is

unchanged as its elements move in thestreamwise direction*


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MunksStagger TheoremThe induced drag of a lifting system is

unchanged as its elements move in thestreamwise direction*


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Use virtual variable geometry to increasethe effective span of low observable UAVs


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Formation orbit

Individual and formationISR orbits


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Formation orbit



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Strike

Formation orbit



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Strike

Formation orbit

Pahle, J et. al, A Preliminary Flight Investigation of Formation Flight for Drag Reduction on theC-17 Aircraft, NASA Dryden Flight Research Center


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Ray, R. J., Cobleigh, B. R., Vachon, M. J., and John, C. S., Flight Test Techniques Used toEvaluate Performance Benefits During Formation Flight, TP-2002-210730, NASA, 2002

Bower, G. and Kroo, I., Multi-Objective Aircraft Optimization for Minimum Cost and EmissionsOver Specific Route Networks, ICAS Congress, 2008

Bower, G., Flanzer, T., and Kroo, I., Formation Geometries and Route Optimization forCommercial Formation Flight, AIAA Paper, 2009

Betz, A., Behavior of Vortex Systems, TM-713, NACA, 1933

Holzapfel, F., Probabilistic Two-Phase Wake Vortex Decay and Transport Model, Journal ofAircraft, Vol. 40, No. 2, March 2003

King, R. M. and Gopalarathnam, A., Ideal Aerodynamics of Ground Effect and Formation

Flight, Journal of Aircraft, Vol. 42, No. 5, September 2005 Ning, S. A., Aircraft Drag Reduction Through Extended Formation Flight, Ph.D. thesis, Stanford

University, 2011

Xu, J. Ning, A. Bower, G. Kroo, I. Aircraft Route Optimization for Formation Flight, Journal ofAircraft, In Press

Moshe, S. Blakeley, K. ORourke, R. Department of Defense Energy Initiatives: Backgroundand Issues for Congress, Congressional Research Service, 2012

Weimerskirch, H., Martin, J., Clerquin, Y., Alexandre, P., and Jiraskova, S., Energy Saving inFlight Formation, Nature, Vol. 413, No. 6857, 10 2001, pp. 697698, doi:10.1038/35099670.

David S. Lee, David W. Fahey, Piers M. Forster, Peter J. Newton, Ron C.N. Wit, Ling L. Lim,Bethan Owan, and Robert Sausen. Aviation and global climate change in the 21st century.

Atmospheric Environment, 43:35203537, 2009.

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