The American Society ofMechanical Engineers

WRIGHT FIELDFIVE-FOOT WIND TUNNEL

A National HistoricMechanical Engineering Landmark

United States Air ForceWright-Patterson Air Force Base

Dayton, OhioMarch 22, 1995

IntroductionThe Wright Field Five-Foot Wind Tunnel is anoutstanding example of an early aerodynamictesting facility that remains active today. The 5ft(1.52m) dimension refers to the diameter of thetest section where the model to be tested islocated. The tunnel was well known from theearly 1920s to the late 1950s for its aerodynamictesting, contributions to aeronautical researchand the development of nearly every major air-craft and associated hardware used by the U.S.Air Force and its predecessor the Army Air Ser-vice. It was conceived, designed, and built whenvery little aerodynamic theory or test data wasavailable that could be used as a baseline for itsdesign. The wind tunnel is a remarkable wood-working job and was considered an importantmoney-saving device guiding the construction ofearly aircraft. It is a unique specimen of a highlysophisticated wind tunnel and is one thatremains today. In a sense, it represents an exten-sion of the Wright brothers’ principle of apply-ing wind tunnel testing as a technique to developaerodynamic parameters and as a vital step in theairplane development cycle. Early wind tunnelsshowed the way for the first successful poweredflights. They enabled the establishment of aero-nautics as an exact science by allowing the mea-surement of lift and drag coefficients. Airplanedevelopment would have been more costly, dan-gerous, and slow if the five-foot wind tunnel hadnot been available for use prior to flight testing.The Air Force Institute of Technology todaymaintains and uses this facility as a teaching andresearch tool, and it remains a part of aviationhistory.

Facility History and Signifi-

The five-foot wind tunnel was constructed atMcCook Field in Dayton Ohio during the 1921-1922 time period and was housed in a standardsteel hanger. It was moved to its current site,

cance

Area B at Wright-Patterson Air Force Base dur-ing the 1928-1929 time period.

The five-foot wind tunnel was conceived by AirService Engineering Division personnel atMcCook Field based partially upon contactsthey had with National Advisory Committee forAeronautics (NACA) personnel in the early1920s, their earlier constructed high speed 14 in(35.6 cm) tunnel, and their general knowledge ofother facilities. The 14-in tunnel had beendesigned using the tunnel in the laboratory ofOrville Wright as a basis for size and other char-acteristics. Prior to initiating the design of thefive-foot tunnel, they had numerous contracts

Five-Foot Wind Tunnel Test (Early 1920's)McCook Field

with the Massachusetts Institute of Technology(MIT) for testing models of early aircraftdesigns in the MIT 4-foot tunnel. Engineers atMcCook Field originally designed an 8 ft (2.44m) diameter tunnel but compromised to a 5 ftone due to air flow requirements and characteris-tics, speed range, cost, and portability require-ments. It was projected during design that thetunnel would move to a permanent location atWright Field in the near future.

The design and technical specifications leadingto the construction of the tunnel were prepared

by personnel of the Engineering Division, AirService. The tunnel components were plannedand fabricated by McCook Field workmen. Itwas completed in 1922, and the final inspectionteam included Orville Wright.

The tunnel is the oldest operating wind tunnel inthe country and represents a significant part ofaviation history. It is an early example of a mod-ern wind tunnel as well as a rare artifact thatremains from McCook Field which was the pre-decessor of Wright Field. The tunnel is nowlocated in Building 19, Area B, Wright Fieldwhich is a historically significant structure dueto its age and that the building has not changedsince it was built (Ref 8). The tunnel wasplanned as a research tool and also for engineer-ing development. The tunnel was also used forvarious types of testing in the 1920s, 1930s,through World War II and beyond. In 1958, themanagement of the facility was turned over tothe Air Force Institute of Technology (AFIT)where it is still used as a teaching and researchtool.

The Wright Field Five-Foot Wind Tunnel is cur-rently operational. It is supervised by the AirForce Institute of Technology. It is not generallyopen or available to the public. However, spe-cial arrangements can be made to tour the tunnelarea by calling the AFIT Office of Public Affairs(513) 255-2216 or 9314.

Technical Background andDescriptionThe five-foot wind tunnel can test models withwings spans up to 40 in (1.02m). It is a semi-open-circuit-type tunnel: room air is mixed withdischarged air and drawn through the airstraightener into the rounded 10 ft (3.05m)intake bell. The cutaway view of the tunnel(inside front cover) shows the air straightenerpulled back from the tunnel air inlet, for illustra-tion only, to show the tunnel inlet shape. Thetunnel then tapers in diameter to the 5 ft test sec-tion. After the test section, the diffuser graduallyincreases in diameter to its maximum of 12 ft(3.66 m). At this point, the air enters the first

Five-Foot Wind Tunnel in Bldg 19, Wright Field

fan, then passes through the counter-rotatingsecond fan before being discharged into theroom. The two-fan design was developed foreconomic considerations. The tandem fanarrangement was a compromise between power,fan diameter and fan speed available (Ref 2).Four Sprague dynamometers, rewired as electricmotors, were available as surplus from anotherprogram. Conserving electric power and lowinitial costs were considered important designgoals.

Considerable effort was expended in conductingmodel tests to achieve smooth, efficient air flow.The diffuser allows an interchange of potentialand kinetic energy of the fluid flow. One goalwas to develop a diffuser design where the totalenergy of air moving at the downstream end ofthe diffuser end was within ten per cent of itsvalue at the inlet end. No thorough analysis ofthe aerodynamic characteristics of this inter-change of energy had been previously perfected,and the design of the five-foot tunnel was basedupon model tests. When built, it was consideredthe most efficient wind tunnel in the world (Ref1). Other tunnel components such as the intakebell and air straightener were designed in a simi-

Five-Foot Tunnel Air Flow Straightener

GENERAL SPECIFICATIONS

FIVE-FOOT WIND TUNNEL

Type Operation Continuous

Stagnation Pressure 1 ATM (1.01 x 105N/m2)

Power (4 Motors) 1600 HP (1193 KW)

Mach No. Range 0 - 0.3 (Approx)

Maximum Reynolds No. 1 X 106

lar manner to produce smooth air flow. The tun-nel centerline was elevated above the floor suchthat the volume above and below the tunnel cen-terline were in the optimum relationship to max-imize return air.

A honeycomb type of structure was inserted intothe throat of the intake bell for low speed tests.The air-flow straightener is on rails to facilitatethe installation or removal of this honeycomb(Ref 7). It was also necessary to generate uni-form air flow in the test section to add an aero-dynamic fairing in front of the fan hub. Aprotective screen and air diversion cone werealso placed before the first fan. Air diversionfins were located radially around a cylindricalcore corresponding to the hub size and extendingbetween the fans. The air passageway in theannular space has a constantly increasing areaand air flow reaches its minimum velocity justbefore entering the first fan.

The intake bell, cylindrical tube, and diffusersections of the tunnel were constructed fromwood. Outer rings were built up by gluingtogether a number of segments to a thickness ofabout four inches and a depth of about sixinches. To make the individually curved seg-ments, large square boards were first gluedtogether and the segments cut out to the propercurvature. Narrow staves of seasoned PortArthur cedar were cut in a four-sided molderwith tongue-and-grove joints. These were then

GENERAL DIMENSIONS

FIVE-FOOT WIND TUNNELLength Diameter

Section Ft M Ft M

Tunnel Proper 96 29.26 Max at Fans 12 3.66

Intake Bell 5 1.52 Lip 10 3.05

Throat 5 1.52

Test Section 18 5.49 5 1.52

Diffuser 48 14.63 Entrance 5 1.52

Exit 12 3.66

Fan Section 25 7.62 Intake 12 3.66

Fan 12 Blades 11.92 3.63

Hub 8.67 2.64

Longitudinal Axis 9.92 ft (3.02m) above floor

REYNOLDS NUMBER VS MACH NUMBER

FIVE FOOT WIND TUNNEL

MACH NUMBER

DESIGN

E. N. Fales was an aeronautical engineer, AirCorps, Materiel Division, Dayton, Ohio. Heresearched many of the existing aerodynamictesting facilities available after World War I bothin the United States and Europe, and it isbelieved that this information was used todevelop the characteristics and design of thefive-foot tunnel. Many of the early technicalreports and literature written describing the five-foot tunnel, its performance, design, and impactupon airplane development were authored byFales.

CONSTRUCTION

Construction of the tunnel was under the directsupervision of R. J. Myers, Foreman of theWood Shops and a 40 year wood working vet-eran. He came to McCook Field during WorldWar I and was one of the very early personnel ofthe Engineering Division. It was reported in1923 that the wind tunnel was planned and con-structed without special design drawings orspecifications. This was evidence of the skill ofMcCook Field’s wood workers.

R. J. Myers

Five-Foot Tunnel Wooden Construction Five-Foot Tunnel Test Section and Observa-

tion Windows

placed inside the circumferential rings and gluedand screwed together. Each section of the tunnelwas therefore a rigid unit. These units were thenbolted together at the flanges to form the tunnelwalls. Sections were supported from the floorby cradles under alternate rings.

Models were supported in the test section bywires connected to the measuring balances. Twoforce balances were provided for the tunnel. Forlow speed work, a standard National PhysicsLaboratory (NPL) type balance was used tocompare data with earlier tests. For high speedwork, a balance of the Wright type, which stillexists today, was used. This balance was a newfeature, that eliminated velocity fluctuations andallowed the operator to directly read the lift todrag ratio. Today, a full six-component straingage balance measures aerodynamic forces, andthe model is mounted at the front of a beam(sting) which is supported downstream from thetunnel walls or floor to reduce or eliminate airturbulence on the model. Models were installedor removed from the tunnel through two smalldoors located in the top of the tunnel test section. Five-Foot Tunnel Drive Motors and Fan Section

Facility ContributionThe Wright Field Five-Foot Wind Tunnel madesignificant contributions to the development ofearly aviation in the 1920s and continues todayto provide students with a basic understanding ofwind-tunnel testing procedures. It retains itsability to test complete scale models of an actualairplane and to conduct tests in support ofresearch on the general principals of aeronautics.

The tunnel was considered advanced for its timebecause of its power, speed range, and combinedfeatures which were not available in any othersingle facility. These features were the airstraightening vanes, intake bell, and deceleratingcone. At McCook Field, two interchangeabletest sections were also available.

The five-foot tunnel contributed to the develop-ment of methods to measure aerodynamic per-formance factors including lift, drag, andstability on a model and convert these data tothe full-scale airplane. In its early existence,over a five-year period, approximately 50 tests

were conducted on projects valued at severalmillion dollars. A 1/70 scale model of theXNBL-1 Barling Bomber was one of the air-planes tested in this facility during the early1920s. The tunnel provided critical data on theperformance and stability of this 20-ton airplanewhich had six engines and was the largest builtat the time. It contained many novel and untriedfeatures. The stabilizer setting needed for stabil-ity was predicted by wind tunnel tests and wasfound to be correct during its initial flight (Ref3). Other five-foot tunnel tests conducted onscaled models during this same time period wereon the Curtis P-1 Pursuit airplane and the ArmyNight Observation airplane. Testing was alsoconducted to determine the general effectivenessof ailerons on airplane control. In the 1930’s and1940’s, the five-foot tunnel contributed dataimportant to the solution of flutter problems thatcould lead to catastrophic failures. After WorldWar II, aircraft that have benefited from tests inthe five-foot tunnel include the F-15, F-4C,C-130, EC-135 and many missile systems.Recently, research flutter testing was conductedin the tunnel.

Barling Bomber

Bibliography1. “Building the Five-foot McCook Field WindTunnel,” The Slipstream, Vol 4, No. 8A, Sep-tember 1923.

2. Fales, E. N., “Description of McCook Field5-foot Wind Tunnel,” Air Service InformationCircular, Vol IV, No. 341, May 15, 1922.

3. Fales, E. N., “The Wind Tunnel and Its Con-tribution to Aviation,” Aviation, October 21,1927.

4. Fales, E. N., “The McCook Field Five-FootWind Tunnel,” The Slipstream, Vol 4, No. Janu-ary 1923.

5. Borden, D. M., “Calibration Constant ofWright Field Five-Foot Wind Tunnel,” AirCorps Information Circular, Vol VII, No. 643,March 1, 1930.

6. “A Little Journal to the Home of the Engi-neering Division, Army Air Service,” McCookField, Dayton Ohio, pp. 4,5.

7. Technical Orders No. 23, Air Service Infor-mation Circular, Vol IV, No. 348, Mar 1922, pp.28 & 29.

8. Skywriter, August 23, 1992, p. 16.

9. Skywriter, October 18, 1992, p. 16.

10. Building 19, 5-foot Wind Tunnel, HAERNO. OH-79-B; Received Apr 1, 1992.

Text of the Wright FieldFive-Foot Wind Tunnel Plaque

NATIONAL HISTORICMECHANICAL ENGINEERING LANDMARK

WRIGHT FIELD FIVE-FOOT WIND TUNNEL1922

WIND TUNNEL TESTING OF AIRCRAFT MODELS IS ESSEN-TIAL TO DETERMINE AERODYNAMIC PARAMETERSSUCH AS LIFT AND DRAG. THIS EARLY EXAMPLE OF THEMODERN WIND TUNNEL WAS CONCEIVED AND BUILT BYTHE AIR SERVICE ENGINEERING DIVISION WHEN LITTLEAERODYNAMIC THEORY OR DATA EXISTED AS A BASISFOR ITS DESIGN. YET, WHEN COMPLETED, THISWOODEN TUNNEL WAS CONSIDERED THE MOST EFFI-CIENT IN THE WORLD AND PROCUDED VERY SMOOTHAIR FLOW. THE FINAL INSPECTION TEAM INCLUDEDORVILLE WRIGHT.

THE MODEL IS MOUNTED IN A TEST SECTION FIVE-FEETIN DIAMETER. AIR FLOW IS PROVIDED BY TWO FANSDRIVEN BY ELECTRIC MOTORS TOTALING 1600 HP. THETUNNEL STILL IS USED FOR TEACHING AND RESEARCH.

THE AMERICAN SOCIETY OF MECHANICAL ENGINEERS

1995

The ASMEThe American Society of Mechanical Engineers, founded in 1880, is a worldwide engi-neering society focused on technical, educational, and research issues. It conducts one ofthe world’s largest technical publishing operations, holds technical conferences, and setsmany industrial and manufacturing standards.

The American Society of Mechanical EngineersPaul J. Torpey, PresidentJohn B. Kitto, Jr., P.E., Vice President, Region VWilliam B. Weber, P.E., Chair, Region V History and LandmarksJohn R. Parker, Senior Vice President, Public AffairsErwin Fried, P.E., Vice President, Public InformationDavid L. Belden, P.E., Executive DirectorArthur W. Ebeling, Director, Midwest Regional Office

The ASME History and Heritage CommitteeJ. Lawrence Lee, P.E., ChairmanRobert M. Vogel, SecretaryWilliam DeFotisBurton DichtRobert B. GaitherR. Michael Hunt, P.E.William J. Warren, P.E.Euan F. C. Somerscales, EmeritusRichard S. Hartenberg, P.E., EmeritusDiane Kaylor, Staff Liaison

The ASME Dayton SectionGeorge F. Tirome, P. E., ChairmanHarry J. Moresi, Vice ChairmanVincent R. Miller, TreasurerJeffrey P. Bacso, SecretaryNelson D. Wolf, P. E., History and Heritage

Air Force Institute of Technology (AFIT)The Air Force Institute of Technology contains the graduate engineering school for theU.S. Air Force located at Wright-Patterson Air Force Base, Ohio. They maintain andoperate the five-foot wind tunnel which is located in the Area B part of the base and is thehome of Aeronautical Systems Center.

Air Force Institute of Technology (AFIT)Col. Ronald D. Townsend, CommandantDr. Robert Calico, Dean, Graduate School of Engineering

Aeronautical Systems CenterLt. General Richard Scofield, Commander

AcknowledgmentThe ASME Dayton Section gratefully acknowledges the assistance of the Air Force Insti-tute of Technology for the use of their sketch (front cover) and photographs. Specialthanks also to the Historic American Engineering Record, National Park Service for theuse of their drawing.

The History and Heritage Program of the ASMEThe ASME History and Heritage Recognition Program began in September 1971. Toimplement and achieve its goals, ASME formed a History and Heritage Committee, ini-tially composed of mechanical engineers, historians of technology and curator (emeritus)of mechanical engineering at the Smithsonian Institution. The Committee provides a pub-lic service by examining, noting, recording, and acknowledging mechanical engineeringachievements of particular significance. The History and Heritage Committee is part ofthe ASME Council of Public Affairs and Board of Public Information. For further infor-mation please contact Public Information, American Society of Mechanical Engineers,345 East 47th Street, New York, NY 10017-2392, (212) 705-7740.

DesignationThe Wright Field Five-Foot Wind Tunnel isthe 114th National Historic MechanicalEngineering Landmark to be designated.Since the ASME Historic Mechanical Engi-neering Recognition Program began in 1971,170 Historic Mechanical Engineering Land-marks, 6 Mechanical Engineering HeritageSites, and 6 Mechanical Engineering Heri-tage Collections have been recognized. Eachreflects its influence on society, either in itsimmediate locale, nationwide, or throughoutthe world.

An ASME landmark represents a progres-sive step in the evolution of mechanicalengineering. Site designations note an eventor development of clear historical impor-tance to mechanical engineers. Collectionsmark the contributions of a number ofobjects with special significance to the his-torical development of mechanical engineer-ing.

The ASME Historical Mechanical Engineer-ing Recognition Program illuminates ourtechnological heritage and serves to encour-age the preservation of the physical remainsof historically important works. It providesan annotated roster for engineers, students,educators, historians, and travelers. It helpsestablish persistent reminders of where wehave been and where we are going along thedivergent paths of discovery.

The Nominator and Author

Nelson D. Wolf, P.E. is a section chief in theWright Laboratory at Wright-Patterson AirForce Base, Ohio. He is an ASME memberand currently Chairman of the Dayton Sec-tion History and Heritage Committee. In thelate 1950’s, he worked as an engineer in amechanical instrumentation group that ser-viced the five-foot wind tunnel. This Land-mark brochure is the result of his research ofdocuments found in the Wright Field techni-cal library.