AERONAUTICS

TECHNICAL REPORTOF THE

AERONAUTICAL RESEARCHCOMMITTEE

FOR THE YEAR 1 9 2 1 - 2 2 .

(With APPENDICES.)

VOL. I.

Model Experiments and Airscrews.

" L O N D O N :PUBLISHED BY HIS MAJESTY'S STATIONERY OFFICE.

To be purchased directly from H.M. STATIONERY OFFICE at the following addressesADATTRAI, HOUSE, KINCSWAY, LONDON, W.C, 2; 28, ABINGDON STREET, LONDON, S.W. 1 ;

YORK STREET, MANCHESTER; 1, ST. ANDREW'S CRESCENT, CARDIFFor 120, GEORGE STREET, EDINBURGH ,

or through any Bookseller,

1924.Price £1 Is. Net.

CONTENTS.

VOL. I.

Model Experiments and Airscrews.Page

Members of the Committee ... ... ... ... ... ... viiiReport of the Committee for the year 1921-22 ... ... ... 1

APPENDICES TO THE REPORT.Wind Tunnels :—

(i) Investigation of the Air Flow in the Duplex Wind Tunnel.—By E. F. Relf, A.R.C.Sc., T. Lavender and E. Ower,B.Sc., A.C.G.I. ... ... ... ... ... ... 53

Theoretical Work on Wing Sections :—(i) Some applications of the vortex theory of aerofoils.—By H.

Glauert, of the Royal Aircraft Establishment. Presentedby the Director of Research ... ... ... ... 56

(ii) Theoretical streamlines round a Joukowsky Aerofoil.—ByMiss M. Barker, B.Sc., Bathurst Student in Aeronautics,Newnham College, Cambridge ... ... ... ... 70

(iii) The calculation of the characteristics of tapered wings.—ByH. Glauert, of the R.A.E. Presented by the Director ofResearch. ... ... ... ... ... ... ... 76

Model Experiments on Wing Sections :—(i) Biplane investigation with R.A.F.15 Section.—By W. L.

Cowley, A.R.C.Sc., and C. N. H. Lock, M.A. ... ... 80(ii) A comparison between the aerodynamic properties of two

aerofoils of the same section, but with square and roundedwing tips respectively.—By W. L. Cowley, A.R.C.Sc.,and C. N. H. Lock, B.A. ... ... ... ... ... 95

(iii) Model tests of 64 Section biplane wings with flaps.—ByF. B. Bradfield, of the R.A.E. Presented by the Directorof Research ... ... ... ... ... ... ... 101

(iv) Cushioning effect on aeroplanes close to the ground.—ByW. L. Cowley, A.R.C.Sc., and C. N. H. Lock, B.A. ... 108

(v) Tandem aerofoils.—By J. L. Nayler and W. L. Le Page ... 116(vi) Wind tunnel tests on a Fokker Biplane.—By W. L. Cowley,

A.R.C.Sc. ... ... ... ... ... ... ... 126(vii) Tests on a model of the Dreadnought Postal Type Mono-

plane.—By E. Ower, A.C.G.I., B.Sc. ... ... ... 130

Stability and Control:—General:

(i) Report of the Accidents Investigation Sub-Committee onStability Terms ... ... ... ... ... ... 134

(ii) Some calculations dealing with the disturbed motion ofan aeroplane, with special reference to landing.—ByL. W. Bryant, B.Sc., A.R.C.Sc. ... ... ... ... 140

mExperimental Work: Page

(i) The determination of rotary derivatives.—By E. F.Relf, A.R.C.Sc., T. Lavender, and E. Ower, B.Sc.With an appendix on approximate formulae for rotaryderivatives.—By H. Glauert, of the R.A.E. ... ... 151

(ii) Experimental determination of tailplane characteristics.—By H. Glauert and I. L. Peatfield, of the R.A.E. Pre-sented by the Director of Research ... ... ... 166

(iii) The force on an aileron balanced by the " backwardhinge " method.—By H. B. Irving, B.Sc., and A. S.Batson, B.Sc. ... ... ... ... ... ... 184

(iv) Lateral control at large angles of incidence. Yawing androlling moments due to aileron movement on a com-plete model of S.E.5.A.—By A. S. Batson, B.Sc., andC. N. H. Lock, M.A. ... ... ... ... ... 187

( \ ) Lateral control at low speeds.—By F. B. Bradfield andI. L. Peatfield, of the R.A.E. Presented by the Directorof Research ... ... ... ... ... ... ... 200

vi) Lateral control of Bristol Fighter at low speeds. Measure-ment of rolling and yawing moments of model wings dueto rolling.—By F. B. Bradfield, of the R.A.E. Pre-sented by the Director of Research .„ ... ... 212

\i) Test of ten aerofoil sections for metal airscrews.—By I. L.Peatfield of the R.A.E. Presented by the Director ofResearch ... ... ... ... ... ... ... 233

n) An aerodynamic theory of the airscrew. By H. Glauertof the R.A.E. Presented by the Director of Research ... 238

in) The " Rotational Inflow Factor " in propeller theory.—ByG. I. Taylor, F.R.S. ... ... ... ... ... ... 256

iv) A consideration of airscrew theory in the light of data derivedfrom an experimental investigation of the distribution ofpressure over the entire surface of an airscrew blade, andalso over aerofoils of appropriate shapes.—By A. Fage,A.R.C.Sc., D.I.C., and R. G. Howard, B.Sc., A.M.I.C.E.... 264

(v) On the free transverse vibrations of airscrew blades.—ByR. V. Southwell and Barbara S. Gough ... ... ... 358

VOL. II.

Full Scale Work, Strength of Construction, Instruments.

Full scale work on Aeroplanes :—(i) The drag curve of R.A.F.14 B.E.2E. wings obtained by full

scale experiments with airscrew running and with airscrewstationary.—By the Aerodynamics Staff of the R.A.E.Presented by the Director of Research ... ... ... 369

(ii) Lift and Drag of B.E.2E. with R.A.F. 14 wings. Comparisonof full scale and model results.—By the Aerodynamics Staffof the R.A.E. Presented by the Director of Research ... 378

(iii) Lift and drag of B.E.2E. with R.A.F. 19 wings. Comparisonof full scale and model results—By H. M. Garner andF. B. Bradfield, of the R.A.E. Presented by the Directorof Research ... ... ... ... ... ... ... 382

iflT980) Wt. H9«»—T882(P.F.1154/7»I). 375. 12/24. Qp. 32.

IV

PageFull scale work on Aeroplanes—cont.

(iv) Experiments with a modified thrustmeter.—By the Aero-dynamics Stafi of the R.A.E. Presented by the Directorof Research ... ... ... ... ... ... ... 395

Fire Prevention on Aeroplanes :—(i) The prevention of fire in single-engined aeroplanes.—Report

of the Fire Prevention Sub-Committee ... ... ... 400(ii) The possible causes of fire in an aeroplane crash and the

means that can be taken to lessen the fire risk. Reportof the Fire Prevention Sub-Committee ... ... ... 421

Seaplanes :—(i) Seaplanes. Taking off and alighting.—By Flight Lieutenant

E. S. Goodwin, A.F.C. in charge of Test Depot, Marineand Armament Experimental Establishment, Isle ofGrain. Presented by the Director of Research... ... 449

(ii) Experiments with model flying boat hulls and seaplanefloats. Twenty-second series Report. Comparison ofthe Vigilant straight frame type and curved section flyingboats.—By E. M. Keary, A.I.N.A. ... ... ... ... 457

Strength of Materials :—(i) Some experiments on the fatigue of materials under

alternating torsion.—By H. J. Gough, M.B.E., B.Sc. ... 471(ii) Report on aluminium alloy rivets.—By Dr. W. Rosenhain,

F.R.S., and S. L. Archbutt, F.I.C. ... ... ... ... 483

Strength of Construction (aeroplanes) :—(i) Load Factors for Commercial Heavier-than-Air Craft.

Report of the Load Factor Sub-Committee... ... ... 490(ii) The calculation of stresses in a redundant structure by the

method of comparison of deflections, with examples of itsapplication to aeroplane design.—By W. S. Farren,M.B.E., M.A. (with preface by Dr. H. Lamb, M.A., F.R.S.) 499

& 501(iii) Tail loads in recovering from a vertical dive at terminal

velocity.—By John Case, M.A., and S. B. Gates. Pre-sented by the Director of Research ... ... ... ... 533

(iv) On the determination of the stresses in braced frameworks.Part II. The effect of shear upon a framework of uniformrectangular cross-section.—By R. V. Southwell ... ... 561

(v) A graphical method for the determination of the bendingmoments and deflection in an aeroplane spar.—ByBarbara S. Gough ... ... ... ... ... ... 575

Instruments t—(i) A directional hot-wire anemometer.—By A. Bailey, M.Sc.,

A.M.Inst.C.E. ... ... ... ... ... ... ... 583(ii) An electric motor of small diameter for use inside aeroplane

models.—By E. F. Relf, A.R.C.Sc. ... ... ... ... 587

PageOther papers :—

(i) The theory of initial motions and its application to theaeroplane. Being a sequel to R. & M. 689 on " Thecanonical forms of the equations of motion of an aeroplanein still "and gusty air."—By G. H. Bryan, Sc.D. ... ... 589

(ii) An investigation of the wind forces and moments actingon models, 1/50 scale, of the Caquot Kite Balloon.—ByL. F. G. Simmons, B.A., A.R.C.Sc., and H. Bateman,B.Sc., A.C.G.I., D.I.C. ... ... ... , ... ... 612

(iii) Report of tesis on the suitability of glycerin as a standardsubstance in viscometry.—By Guy Barr, B.A., D.Sc. ... 630

VOL. III.

Airships.GENERA.L INTRODUCTION TO VOL. III.

SECTION A.Full scale experiments :—

(i) Experiments on Rigid Airship R.32—Part I. Pressures onthe upper fin and rudder.—By J. R. Pannell, A.M.I.M.E.,R. A. Frazer, B.A., B.Sc., and H. Bateman, B.Sc.,A.C.G.I., D.I.C. ... ... ... ... ... ... 637

(ii) Experiments on Rigid Airship R.32—Part II. Controllabilityand turning trials.—By J. R. Pannell, A.M.I.M.E., R. A.Frazer, B.A., B.Sc., and H. Bateman, B.Sc., A.C.G.I.,D.I.C. ... ... ... ... ... ... ... ... 665

(iii) Experiments on Rigid Airship R.32—Part III. Measure-ments of resistance and airspeed.—By J. R. Pannell,A.M.I.M.E., R. A. Frazer, B.A., B.Sc., and H.Bateman, B.Sc., A.C.G.I., D.I.C. ... ... ... ... 682

(iv) Experiments on Rigid Airship R.32—Part IV. Note onmeasurements of airscrew thrust.—By R. A. Frazer, B.A.,B.Sc., and H. Bateman, B.Sc., A.C.G.I., D.I.C. ... ... 704

(v) Measurements of normal force and pitching moment onRigid Airship R.33.—By R. A. Frazer, B.A., B.Sc., andH. Bateman, B.Sc., A.C.G.I., D.I.C.... ... ... ... 712

(vi) Experiments on Rigid Airship R.38 (Z.R.2).—By R. A.Frazer, B.A., B.Sc., and H. Bateman, B.Sc., A.C.G.I., D.I.C. 729

SECTION B.Strength of construction (including experiments on pressure distri-

bution measurements) :—(i) Pressure plotting on fin and rudder of a model of R.32.—

By D. H. Williams, B.Sc., and A. H. Bell ... ... ... 771(ii) The pressure distribution over a model of the hull of Airship

R.33.—By R. Jones, M.A., and A. H. Bell ... ... 815(iii) The aerodynamic loading of airships.-^-By Professor L.

Bairstow, C.B.E., F.R.S. ... ... ... ... ... 849(iv) Aerodynamic pressure on an airship hull in curvilinear

flight.—By R. Jones, M.A. ... ... ... ... ... 855(v) Report on the accident to H.M. Airship R.38. — By the

Accidents Investigation Sub-Committee ... ... ... 864(vi) Report of the Airship Stressing Panel... ... ... ... 893

VI

PageSECTION C.

The equilibrium and stability of airships :—(i) The equilibrium of airships in curvilinear flight. An adden-

dum to R. & M. 716.—By R. Jones, M.A. ... ... 967fii) Acceleration derivatives in the case of a body moving in an

ideal fluid.—By R. Jones, M.A. ... ... ... ... 972(iii) The stability of airships.—By R. Jones, M.A., and D. H.

Williams, B.Sc. ... ... ... ... ... ... 978(iv) Experiments on a model of Rigid Airship R. 32, together with a

comparison with the results of full scale turning trials anda consideration of the stability of the ship.—By R. Jones,M.A..D. H.Williams, B.Sc., and A. H. Bell... ... ... 995

(v) The equilibrium of R.38 in circling flight.—By R. Jones,M.A. ... ... ... ... ... ... ... ... 1015

(vi) The motion of airships under certain imposed movementsof the rudders.—By R. Jones, M.A. ... ... ... 1020

(vii) Experiments on a model of rigid airship, R.38.—By R.Jones, M.A., and D. H. Williams, B.Sc. ... ... ... 1046

(viii) Experiments on model of a rigid airship of new design.—By R. Jones, M.A., D. H. Williams, B.Sc., and A. H.Bell ... ... ... ... ... ... ... ... 1067

(ix) The prediction of the resistance of rigid airship R.33.—ByR. A. Frazer, B.A., B.Sc., and A. G. Gadd ... ... 1097

INDEX TO SERIAL NUMBERS OF THE TECHNICAL REPORTS

Report No.it it

ti I i

11 »

it it

Jf » »

it it

it a

II >t

it t>

,,

„it it

it it

,,„II i»

it II

11 it

11 II

it it

,,n it

11 11

» it

„II 11

ft >»

11 11

11 »*

it 11

it i)

R. & M. 681717730731741743744745748749751752753754755756760761762763764765766767769770771772773774775776777

Page. . . 264 Report No.... 200... 130... 483... 575... 471... 589... 134... 972... 967... 978... 56... 612... 108... 630... 533... 184... 166... 378... 382... 729... 256... o58 tt i»... 76... 499... 369... 395... 101... 187... 80... 864... 490... 583

R. & M. 778779780781782784785786787788790794795796799800801802804805808809811812813814815816817818827

„ T.1573

Pag«... 587... 995... 855... 1020... 1015... 449... 457

238... 212

70... 561

849400

... 421

... 1046893

... 815

... 1067116140

... 771151637665682

... 704

... 71295126

... 233

... 109753

vm

MEMBERS OF THE COMMITTEE,MARCH, 1922.*

Professor Sir RICHARD GLAZEBROOK, K.C.B., F.R.S. (Chairman).Sir JOSEPH PETAVEL, K.B.E., D.Sc., F.R.S.ft (Vice-Ohairman).Brigadier-General R. K. BAGNALL-WILD, C.B.E., C.M.G.Professor L. BAIRSTOW, C.B.E., F.R.S.Wing-Commander W. D. BEATTY, G.B.E., A.F.O.Wing-Commander T. R. CAVE-BROWNE-CAVE, C.B.E.Professor J. D. CORMACK, C.M.G., C.B.E., D.Sc., M.Inst.C.E.Professor W. E. DALBY, M.A., B.Sc., F.R.S.Lieut.-Colonel E. GOLD, D.Sc., F.R.S.Professor B. M. JONES, M.A.Dr. HORACE LAMB, M.A., F.R.S.Mr. A. OGILVIE, C.B.E., M.I.Mech.E.fMr. J. D. SIDDELEY, C.B.E.$Sir HENRY WHITE SMITH, K.B.E.JMr. G. I. TAYLOR. M.A., F.R.S.Mr. H. T. TIZARD, M.A.ft

Secretary, Mr. J. L. NAYLER ;

Assistant Secretary, Mr. H. B. IRVING,National Physical Laboratory,

Teddington.

•Since this date Air Vice-Marshal Sir William H. G. Salmond, K.C.M.G.,C.B., D.S.O., on his appointment as D.G.S.R., has become a member ofthe Committee, and Wing-Commander Cave-Browne-Cave has retired ;otherwise the Committee remains as above for the year 1922-23.

•[•Representing the Royal Aeronautical Society.J Representing the Society of British Aircraft Constructors.•J"f Representing the Department of Scientific and Industrial Research.

REPORT FOR THE YEAR 1921-22,

May, 1922.

To Captain the Right Honourable F. E. GUEST, C.B.E., D.S.O.,M.P., Secretary of State for Air.

SIR,The Aeronautical Research Committee submit their report

for the year 1921-22.In accordance with previous practice the report gives a eum-

mary of the work of the past year. Reference is made to thevaried activities of the Committee and its Sub-Committees, themore special technical details being reserved for the Supplementwhich is appended.

In. order to co-ordinate the work of their numerous Sub-Committees the meetings of the Committee have been heldmonthly, with the exception of August. Questions of finance,general programmes of research, and the more important technicalquestions have received consideration by the main Committee,and it is with these that this report mainly deals.

Research in Aeronautics.—The Aeronautical Research Com-mittee deals primarily with those scientific questions relating toaeronautics which present unusual difficulty. In some cases thecauses of difficulty are unknown, whilst in others the cause isreasonably clear, but the remedy not in sight. An example ofthe latter type of problem appears in the loss of control which isexperienced with all aeroplanes when the stalling angle is exceeded.Accidents frequently arise from this and will continue to do sountil a remedy has been found, for the cause is inherent in theaeroplane as we now know it. The remedy at present is beyond theskill of the designer and carefully organised full scale and modelexperiments are required to enable the Committee to give a usefullead.

The loss of control at low flight speeds is one aspect of thesubject of stability and control, and the Committee are of opinionthat the study of that subject will conduce more than any otherinvestigation to the attainment of greater safety in flying. Anequally important line of research deals with the engine and itsinstallation ; in this case greater attention to detail offers theprospect of a real advance in the effort to produce what maybe called a fool-proof aeroplane.

Development in aircraft has, unfortunately, been intimatelyassociated with the investigation of accidents, dating from theenquiry into the safety of monoplanes by the DepartmentalCommittee in 1912 and extending to the Report on the failureof H.M. Airship B. 38 by the Accidents Investigation Sub-Com-mittee in 1921. The alternative method of systematic researchdirected to each element of the design appears to have been fol-lowed only in the case of a few aeroplanes such as B.E. 2,B.E. 1 and S.E. 5, but the example might be followed moregenerally with advantage.

In the method of procedure by accident investigation twoor three steps are normally taken. In the first place a Court ofInquiry is set up on the spot to take first evidence as to the causeof failure and the responsibility of personnel. Should moreinvestigation be needed the Accidents Branch of the Air Ministrycollects and analyses the relevant information. In the majorityof cases these two steps are sufficient. When, however, theyrequire supplementing on the scientific side the matter is referredto the Accidents Sub-Committee of the Aeronautical ResearchCommittee. The problems so referred are, therefore, in the normalcourse of events, of a difficult nature and the Sub-Committee hashitherto been able to refer to a trained and skilled staff, bothof flyers and experimentalists, at Farnborough and at Teddington,for the carrying out of the crucial experiments and for makingcalculations by which hypotheses can be verified so that theinvestigation can be brought to fruitful conclusions. The skillutilised is the outcome of experience gained in the past and notonly courage but a keen power of observation is called for underthe unusual conditions of flight imposed by such investigation.The Committee desire to express their appreciation of the valuablework of the Staffs both at the Royal Aircraft Establishment andthe National Physical Laboratory in connection with the problemsrelating to the design of a useful and safe aeroplane.

The Committee desire to put on record their sense of theserious loss to Aeronautical Science caused by the accident toH.M. Airship R. 38 and their deep sympathy with the relatives ofthose who lost their lives. Among those Mr. Campbell, Mr.Pannell, and Mr. Duffield were closely connected with the Com-mittee's work. Mr. Campbell had for some time been a memberof various Sub-Committees and had taken an active part in thework relating to airships. Mr. Pannell had been a member of thestaff of the National Physical Laboratory almost since its com-mencement in 1909 and for a number of years past had beenresponsible for the airship work. A large portion of our know-ledge of the aerodynamics of airships is due to his devotion andskill. He was continually pressing the need of further researchand his early death is a very real disaster. Mr. Duffield was amember of the Aeronautics Staff of the National Physical

Laboratory and had assisted in carrying out researches in thatDepartment. Latterly, his services had been devoted almostentirely to airship work.

The result of the investigation of the accident to B. 38 hasshown how much may be lost in life, experience and money bynot realising at an early stage that the Committee were in a posi-tion to give, and had published, advice, since proved to be usefuland correct. Experiments were planned, the results of whichWould have rendered obvious the danger of fast flight at lowheights in R. 38 ; failing these; it would still have been animportant safeguard had the Committee been put in a position tostudy the drawings and calculations relating to the design. Whilstit is probable that, as a result of the investigations of the Com-mittee, the same type of accident will not recur, it is clear thatthe design of an airship capable of high performance must bebased upon knowledge derived from scientific experiments on thefull scale. In view of this opinion the Aeronautical ResearchCommittee regret the decision to abandon such researches withairships.

The Committee believe that safety in aircraft and the com-mercial development attendant thereon is attainable only by acombination of organised research and technical application.To secure these it is essential to retain the services of the highlytrained staff to whom is due so much of our existing knowledge,and to free the Committee from the consideration of matters ofcurrent detail. Aeronautics is so much founded on direct experi-ment that discussion, however good, can in general only indicatethe best line of enquiry and not the positive solution of a newproblem. The whole of the work supervised by the AeronauticalResearch Committee costs about 1 per cent, of the vote for theRoyal Air Force and Air Ministry. The money which wouldhave come to this country had R. 38 been a success wouldhave maintained the research of the Committee in full activityfor a period of five years. In another way it may be stated that,should the work of the Committee lead to a reduction by one ofthe aeroplanes written off per year as a result of crashes, it wouldhave earned the cost to the Air Ministry of the fees paid to itsmembers.

Personnel.—Air Vice-Marshal Sir Edward Ellington hasduring the past year been succeeded as Director General of Supplyand Research at the Air Ministry by Air Vice-Marshal SirWilliam H. G. Salmond. Also in October, 1921, the Committeelost the services of Air Commodore Brooke-Popham, who resignedon being appointed Commandant of the Air Staff College. Briga-dier-General Bagnall-Wild, who has succeeded Air CommodoreBrooke-Popham as Director of Research at the Air Ministry andhas been appointed in the latter's place, is well known in connec-tion with the work of the Aeronautical Inspection Directorate.

Apart from the above there have been no changes in thepersonnel, as the members retiring on March 31st, 1921, werereappointed for a further term of three years.

Finance.—The Committee were faced with a difficult situa-tion in September last when, in consequence of the generalfinancial instability and urgent need for economy, they wereaaked to consider a serious curtailment of the activities of theAerodynamics Department of the N.P.L. While recognising theneed for economy, the Committee felt strongly that any con-siderable reduction of the programme of work was to be deplored,and urgent representations were made to the authorities con-corned that the fundamental research work on aerodynamics—so vital to the maintenance of the national status in the develop-ment of aeronautical science—should not seriously be interferedwith. The Committee attach the greatest importance to thiswork which is of that high quality belonging to all the aero-nautical research conducted since the early days of practicalflying in this country.

Arrangements have since been made for the AerodynamicsDepartment at the N.P.L. to be maintained, and the cost of thiswork will continue to be borne on the Air Ministry vote. Re-searches undertaken for the Committee at the N.P.L. at theinitiation chiefly of the Engine, and Materials and ChemistrySub-Committees, which are of value to other branches of engi-neering besides aeronautics, will, after consideration by theCommittee, be reported to the Co-ordinating Board for Engineer-ing Research of the Department of Scientific and IndustrialResearch, and will be financed by that Department. Otherinvestigations financed by other Government departments arealso included in the programme of work of the Committee.

Consideration has been given to possible means of lesseningthe expenditure of the Committee. Technical papers suitable forpublication will, when convenient, be dealt with direct by theChairman and Secretary of a Sub-Committee who may referthem to a Panel or to individual members. By this means areduction in the number of meetings of the Sub-Committeesbecomes possible. In addition, reports and illustrations will bereduced in quantity as much as possible. A saving will also beeffected by the action of the Society of British Aircraft Con-structors and their representatives, who no longer intend toapply for honoraria for attendance at meetings.

On account of the many specialised channels into which thework on aeronautics has been divided in the past, it was feltnecessary to have authorities on each subject and representativesof many departments on the respective Sub-Committees.* Withthe recent re-organisation of the various establishments it hasbeen possible to co-ordinate much of the work and consequently

* For membership, see end of report (p 13).

to reduce the number of official representatives during the comingyear. Economy will thus be obtained and some reduction of thenon-official membership will also be possible.

Publication of Reports.—The Committee have, throughoutthe past year, continued to recommend for publication accountsof researches containing scientific results of importance to aero-nautics. These are placed on sale by H.M. Stationery Officeand are embodied in the series of Reports and Memoranda.Distribution to Government Departments is under the controlof the appropriate branch of the Air Ministry. In addition, anumber of copies are sent in exchange to other GovernmentCommittees and laboratories abroad, with whom the Committeehas kept in close touch and with whose work it has, in some cases,co-operated.

Equipment for Experimental Work at the National PhysicalLaboratory and Royal Aircraft Establishment.—Full use has beenmade of the experimental equipment at the N.P.L. during thepast year, and the funds provided will be sufficient to meet theneeds of the coming year, although the equipment will not beused to quite the same extent as in the past. The number ofwind channels, &c., have not been increased and are the same asmentioned in the last annual report.

Full use has also been made of the experimental equipment atthe Royal Aircraft Establishment, but the Committee learn thatfinancial considerations have made it necessary to reduce appre-ciably the staff for running the wind channels. The necessity isregrettable. The full scale researches will, however, be maintainedon the same scale as in the previous year and provided theexisting highly skilled and fully trained squadron be retained,most valuable results should be obtained and the high standardalready set up for full scale research in this country be fullyrealised.

Tests on Proprietary Machines.—The procedure to be adoptedin regard to publication of tests on proprietary machines hasbeen carefully reconsidered. As a general rule, it has been agreedas heretofore that the results of all work undertaken at publiccost should be published unless some quite special reason existsto the contrary, and that the results of work paid for by anindividual should remain his property unless he gives permissionfor them to be published. In the case of work undertaken forGovernment Departments, publication would not take placewithout the consent of the Department having previously beenobtained.

Turning to the consideration of some of the technical questionsdiscussed by the Committee's organisation, mention should firstbe made of aerodynamics which constitutes the most importantsection of the Committee's work.

6

Aerodynamics.—Safety and economy form the two mostimportant subjects and the general researches on stability andcontrol of aeroplanes at low speeds have a direct bearing on them.Safety requires stable aeroplanes having satisfactory controls.Stability relieves the flyer of the fatigue of balancing the aero-plane under all conditions of weather, and good control at lowspeeds assists the pilot in making safer landings, particularly inan emergency. Researches on these subjects can be largelycarried out in wind channels, but final full scale teats in flight arealso necessary.

Two channels at the N.P.L. are now almost entirely devotedto lateral stability work. Much information on the longitudinalstability of an aeroplane is available, but in the case of lateralstability this is not so. The determination of the lateral rotaryderivatives on a model of the S.E. SA aeroplane is now beingmade and will be followed by the measurement of the full rangeof derivatives on models of the S.E. 5A and the Bristol Fighter,on which latter comparative full scale work is in hand at the R.A.E.In addition to model work at both establishments, the R.A.E.will shortly make full scale trials of several types of lateral controlon the same type of aeroplane so as to increase our knowledgeof the control of aeroplanes at low speeds.

The wind channel research at the various establishments stillprovides the ground work for further advances. In its applica-tion to full scale it is, however, necessary to know the correctionfactors when such are available. Some five years ago the AdvisoryCommittee for Aeronautics published a report of the Scale EffectSub-Committee in which an examination was made of existingdata to shew the amount of correction necessary to the results ofmodel work for application to full scale. With the accumulationof further knowledge on more modern types of machines, the timeis approaching when this work can usefully be reviewed. Acertain number of experiments are nearing completion, andwhen the results are available a further report can be prepared.The outstanding feature of such comparisons between modeland full scale tests is the uncertainty of the values of maximumlift coefficient on the full scale high lift wing section and of thedrag coefficient at small angles of incidence. With the moreusual forma of wing section the correction for maximum liftappears to be not considerable, the model value being generallysomewhat less than that obtained in the full scale ; but withcertain high lift wing sections prediction from model tests appearsto differ widely from the results of full scale tests. This lastis one of the matters which will receive due consideration in thepreparation of the report just mentioned.

A number of other general researches are in progress. TheN.P.L. are further devoting one channel to research on airscrewsboth in connection with a carefully planned scheme of work ona family of airscrews and with certain developments arising froir

the application of the Prandtl theory to airscrew problems.A number of experiments on the effect of the aeroplane bodieson the performance of an airscrew have still to be made, and theAirscrew Panel will shortly prepare a report on the whole seriesof tests for publication. Importance is also attached to thedevelopment at the B.A.B. of a thrust and torque meter for usewith engines of large horsepower, and to the pressure plottingexperiments on full scale airscrews in flight for comparison withthe results of the model work now published.

Wind channel tests have also been made on a number of aero-plane models for comparison with full scale, on a number of air-ship models with reference to the accident to H.M. Airship R. 38,and on the air flow over the deck of aeroplane carriers for theinformation of the Naval Construction Department of theAdmiralty.

Theoretical work on the flow of air over wings had receivedlittle attention until the publication, primarily by Prandtl and anumber of other workers at Gottingen, of the vortex circulationtheory. This is receiving consideration by a number of in-vestigators, who are continuing the theoretical work and alsomaking experiments for verification purposes. One applicationof this theory has been made to determine the aerodynamicperformance of an airscrew, and it will be described in a reportto be shortly issued.

Other experimental work includes the development of a smallwind channel along which the pressure drop will be zero : thisform of channel is particularly suitable for testing low resistanceforms which in ordinary channels need a large correction to themeasured force. A small high pressure wind channel is underconstruction and work on this will proceed during the next year.The William Froude Tank has conducted a number of tests onflying boats, including the Vickers " Vigilant " and the M.I forthe Air Ministry.

The international scheme under which standard models ofan aerofoil and of a good streamline airship are to be tested inthe various aeronautical laboratories of the world was referredto in the last report. An aerofoil and airship model has beendesigned and constructed at the N.P.L. ; a complete series oftests has since been made there and at the B.A.E., and reportsprepared. The models are now en route to the various participatinglaboratories.

A certain amount of theoretical work has been carried outon the stresses in aeroplane structures, and on a number of prob-lems dealing with fluid motion.

Engines.—A programme of research work on detonationproblems, initiated by Sir Dugald Clerk, is proceeding at theN.P.L. Thorough research has been made into the effect ofturbulence in producing detonation in hydrogen air mixtures.

8

and the general research has now been extended to other fuels,including various forms of liquid fuel. Attention is also beingdirected to the results ofj recent researches by Professor Boneand Mr. H. B. Ricardo, who have shown by different methodsthat the addition of small quantities of hydrogen to certainexplosive mixtures greatly accelerates the rate of combustion.

Development of high speed engines is essential to aeronautics,and on this a serious limitation is imposed by the excessive strainon the big end bearing. A joint Panel of the Engine Sub-Com-mittee and of the Engineering Board of the D.S.I.R. has beenappointed to direct experiments on big end bearings. Authorisa-tion has been obtained through the D.S.I.R. for the necessaryexpenditure on the construction of a testing machine which isnow nearly complete. The machine when completed and triedout will be re-erected at the N.P.L., where tests on various typesof bearing will be undertaken.

General research is being devoted to the use of a number offuels under varying conditions in aircraft engines. The AirMinistry have initiated a considerable programme, part of whichwill be carried out at the R.A.E. and part by the firm of Messrs.Ricardo, Ltd. The experiments will include an investigationinto the possibility of obtaining higher economy, the use of fuelsin supercharger units, and the possibility of using gases, other thanhydrogen, to accelerate the rate of combustion.

In addition to the work at the Government establishments,it is hoped during the coming year to carry out a certain amountof engine research at Universities in co-operation with the otherwork under the guidance of the Committee. Two Ricardo unitsfor engine experiment are being supplied—one to CambridgeUniversity and the other to the Armstrong College, Newcastle-on-Tyne. A further universal test bed is being supplied to theUniversity of Manchester. The Engine Sub-Committee haveprepared a scheme of researches to be carried out with the aidof this equipment.

The same Sub-Committee have considered fundamentalconditions of design of the Power Plant with the object of gettingaccessibility during flight. They have joined in the AccidentSub-Committee's request for statistics of engine failures, andthis having been acceded to by the Chief of the Air Staff, it ishoped to correct and modify weakness in design so far as suchpoints come generally under research. No detail is too small tocause repeated failures and, therefore, no such detail is too smallfor the consideration of the Engine Sub-Committee.

A special Panel was appointed to consider the causes of enginefailure, and have discussed a number of points. One of thedifficulties to which attention has been directed is the largenumber of sparking plugs annually employed, which suggests

their frequent failure. In co-operation with the Engine Sub-committee, the Ignition Department of the R.A.E. is carryingout investigations on the sparking plug to overcome thesedifficulties. In addition, this department is attacking the problemof obtaining increased electrical and mechanical efficiency of themagneto by studying the character of the spark, and it is thoughtthat a stage has been reached when the work may be broughtmore closely into bearing with the practical issues. The Committeehave requested that such aim be clearly defined.

The Engine Sub-Committee have also been kept informed ofthe engine researches in hand at the R.A.E. on a variety of enginesboth for pewer and economy tests. They learn that work isproceeding on the use of heavy oils in Diesel type engines and thisis not regarded as hopeful on account of the inherent heavy weightof this type of engine.

Meteorology.—Attention, has been directed more particularlyduring the past year to questions directly affecting aerial naviga-tion, which are assuming increasing importance in connectionwith aerial transport, particularly in the case of night flying.Bearing on this is a large amount of work carried out by theAir Ministry Establishment at Biggin Hill, and at CambridgeUniversity, on the accuracy of observations taken by sextants.It would now appear that the error in the use of gravity-controlledsextants used by skilled observers should not exceed about10'-20' in ordinary weather, while in disturbed weather the errorwill not be greater than 30'.

An increasing amount of meteorological information maynow be obtainable from daily flights of squadrons of aeroplanes.An example of what can be obtained in this way has been recentlybrought to the attention of the Committee by a report givinga record of the observations made by a pilot in a single seatermachine. He obtained measurements of air temperature in thevicinity of clouds, estimates of the wind direction and of theamount and height of cloud. A continuance of work of this kindshould assist greatly in increasing our knowledge of the upperatmosphere under all conditions.

Navigation.—The Air Ministry have submitted a number ofreports on instruments for the information of the Committee.This list of instruments so dealt with includes turn indicators,compasses, altimeters and leader cable gear. In connection withthe altimeter the Meteorology Sub-Committee have discussedthe adoption of a standard formula for calibration purposes,and it would appear that there is little to choose between anumber of recognised formulae including that standardised by theFrench authorities and based on a lapse rate of 6-5° C. per kilo-metre.

Fire Prevention in Aircraft.—A report has been issued to theAir Ministry during the past year on the precautions to beobserved in single engined aircraft to prevent fire on crash. This

(B7980) B

10

report summarises the existing position and is an advance on anearlier report issued some two years previously. The mainprecaution is the insertion between the engine and the rest of thecraft of a fireproof bulkhead, and one at least of the more recentBritish civil aircraft in operation on the cross-channel • service isso fitted. When this precaution is taken and when accumulatorsare not carried the chief remaining risk arises from the hot exhaustpipes ; steps are being taken to keep these below the criticaltemperature and a promising line of development appears to beto use carefully shaped exhaust pipes from each of the cylinders.Experiments on several such lines are proceeding at the R.A.E.by request of the Committee. Attention is also being paid tothe form of petrol systems on aircraft, which are found to becomplicated, and the notice of the Air Ministry has been drawnto this matter. It is hoped that future regulations for aeroplaneswill be so framed that great simplifications can be introduced.This observation applies in particular to twin engined aeroplanes,a matter into which the Fire Prevention Sub-Committee are en-quiring and on which they will report to the Air Ministry in duecourse.

Materials and Chemistry.—The scheme of researches to investi-gate the properties under fatigue of materials used in aeronauticalconstructional work, to which reference was made in the lastreport of the Committee, is now well in hand. Investigators havebeen appointed in various University centres, and although inmany cases the work is still in the preliminary stages, it is hopedthat reports will be available within the next few months. TheD.S.I.R. has made suitable provision for the continuance of thework during the next financial year and arrangements have beenmade for the supply of standard tesb materials to the variousinvestigators.

Amongst the work completed at the N.P.L., special attentionis directed towards new methods there developed for rapidlydetermining the fatigue limits of materials under alternatingtorsion and bending. These methods appear to give reliableresults and promise to make the determination of the fatigue limitsimpler than carrying out a tensile test instead of a matter re-quiring perhaps a week's time. The report on this investigationhas been published in the technical press as well as in the series ofCommittee reports.

Consideration has been paid to the use of standard materialsfor researches on fatigue. With this intention work was initiatedon nickel which has exhibited a number of striking properties.It is expected that these may throw considerable light on thenature of the changes which occur in the metal when it fails byfatigue.

The Light Alloys research at the N.P.L. has proceeded con-tinuously throughout the year, following the same lines as inprevious years. The Eleventh Report of the Alloys Research

11Committee of the Institution of Mechanical Engineers containsmany results of great value. Since the issue of this report theLaboratory has made tests on the effect of certain forms of treat-ment in the melting and re-melting of aluminium. It was foundthat neither exposure to an unduly high temperature duringmelting nor repeated re-melting of the same metal at ordinarymelting temperatures brought about any deterioration, providedthat care was taken to prevent the introduction of extraneousmatter. The purity of the aluminium in these tests was main-tained at the high percentage of about 99- 6.

Accidents Investigation Sub-Committee.—The Sub-Committeehave prepared and published the scheme of definitions of stabilityterms referred to in the last annual report. It is hoped that thesedefinitions will gradually be adopted, as they will prove ofassistance to pilots and will enable the designer to understand,and build to meet, the qualities desired by flyers.

The Sub-Committee was asked to investigate the technicalcauses of the disaster to H.M. Airship B. 38 and, following anexhaustive enquiry, a comprehensive report, which has since beenpublished, was presented to the Air Council. It is hoped thatthis report, prepared by experts in various aeronautical subjects,in addition to indicating the causes which led to the failure ofB. 38, may be of value in pointing out a number of conditions tobe complied with for security in future designs.

In the course of the investigation, it became evident thatthe airship designer has received very little assistance, of thekind which might be given by research, in the difficult task ofcalculating the stresses imposed upon his hull structure byaerodynamic and other forces. Authority was therefore obtainedfrom the Air Council for the appointment of a special Panel toinvestigate this problem : its terms of reference include :—

(a) an examination of the validity of the methods whichare at present in use, or which have been suggested,for calculating the strength of rigid airships, and

(b) the consideration of other methods which would enablea closer basis of design to be obtained.

This Panel is also considering all available evidence in regardto the aerodynamic loads which are likely to be imposed by normalmanoeuvres. Its report will be presented during the comingsummer.

The decision of the Government to discontinue airship researchis viewed by the Committee with considerable concern. Theyhave urged the importance of carrying out a quite limited schemeof research with one of the existing ships before she is completelydismantled or otherwise disposed of.

During the year the Sub-Committee has also issued reportsbo the Air Ministry on accidents to H.M. Airship B. 36 and to theTarrant " Tabor " Triplane.

Load Factors Sub-Committee.—As mentioned in the last annualreport, the Society of British Aircraft Constructors had askedthrough the Air Council that further consideration might, begiven to the question of load factors for commercial aircraft, witha view to the revision of certain parts of the Sub-Committee'sprevious report (B. & M. 673). Accordingly, the Load FactorsSub-Committee was reconvened in March, 1921, and severalmeetings have been held during the year.

A report has recently been presented to the Air Ministry, andit is hoped that this report will shortly be available to the public.In this report no considerable alteration in the method of specifica-tion has been made except as regards the specified conditions forthe centre of pressure in its most forward position, for the loadson fins and rudders, and for the strength of undercarriages.Provision has been made for altering the allowances on anymaterials which may come to be improved, or better known astime goes on.

Signed on behalf of the Committee,

R. T. GLAZEBROOK,

Chairman.

13

MEMBERSHIP OF SUB-COMMITTEES.

At May 1st, 1921, the membership of the Sub-Committeeswas composed as follows :—

Air Inventions Sub-Committee.—Sir R. T. Glazebrook, K.C.B.,F.R.S. (Chairman) ; Professor L. Bairstow, C.B.E., F.R.S. ;Wing Commander T. R. Cave-Browne-Cave, C.B.E. ; ProfessorB. M. Jones, M.A. ; Sir J. E. Petavel, K.B.E., F.R.S. ; Mr. G. I.Taylor, M.A., F.R.S. ; Major H. E. Wimperis, O.B.E., of theAir Ministry Laboratory.

Aerodynamics Sub-Committee.—Sir J. E. Petavel, K.B.E.,F.R.S. (Chairman) ; Professor L. Bairstow, C.B.E., F.R.S. ;Wing Commander T. R. Cave-Browne-Cave, C.B.E. ; ProfessorB. M. Jones, M.A. ; Dr. H. Lamb, M.A.. F.R.S. ; Mr. A. Ogilvie,C.B.E., MJ.Mech.E. ; Mr. G. I. Taylor, M.A., F.R.S. ; Sir H.White Smith ; Dr. J. D. Coales, Mr. R. J. Goodman-Crouchand Squadron Leader A. J. Miley, O.B.E., of the Air Ministry ;Mr. C. I. Campbell of the Royal Airship Works. Cardington ;Mr. R. V. Southwell, M.A. and Mr. E. F. Relf, A.R.C.Sc. of theNational Physical Laboratory ; Squadron Leader R. M. Hill andMr. R. McK. Wood of the Royal Aircraft Establishment ; Dr.A. J. Sutton Pippard, A.M.I.C.E., F.R.Ae.S. ; Captain W. S.Farren, M.B.E. ; Lieut.-Colonel M. O'Gorman, C.B. ; CaptainF. S. Barnwell and Mr. J. D. North, representing the Society ofBritish Aircraft Constructors ; Dr. H. 0. Watts, A.M.I.C.E, ;with the Chairman of the Aeronautical Research Committee (exofficio).

Engine Sub-Committee.—Professor W. E. Dalby, M.A., B.Sc.,F.R.S. (Chairman) ; Wing Commander T. R. Cave-Browne-Cave,C.B.E. ; Mr. A. Ogilvie, C.B.E., MJ.Mech.E.; Sir J. E. Petavel,K.B.E., F.R.S. ; Mr. J. D. Siddeley, C.B.E. ; Mr. H. T. Tizard,M.A. ; Squadron Leader B. C. Carter, Dr. J. D. Coales and Lieut.-Colonel L. F. R. Fell, D.S.O., O.B.E. of the Air Ministry ; MajorH. E. Wimperis. O.B.E. of the Air Ministry Laboratory ; Dr.T. E. Stanton of the National Physical Laboratory ; SquadronLeader G. H. Norman of the Royal Aircraft Establishment ;Brigadier General R. K. Bagnall-Wild, C.B.E., C.M.G. of theAeronautical Inspection Directorate ; Professor H. L. Callendar,F.R.S. ; Professor A. H. Gibson, D.Sc. ; Lieut.-Colonel M.O'Gorman, C.B. ; Mr. H. R. Ricardo ; Mr. T. B. Barrington andMr. A. H. R. Fedden, representing the Society of British AircraftConstructors ; with the Chairman of the Aeronautical ResearchCommittee (ex officio).

14

Materials and Chemistry Sub-Committee.—Professor C. F.Jenkin, C.B.E., M.A., M.Inst.C.E. (Chairman); Professor L.Bairstow, C.B.E., F.R.S. ; Professor W. E. Dalby, M.A., B.Sc.,F.R.S. ; Sir J. E. Petavel, K.B.E., F.R.S. ; Sir H. White Smith ;Mr. J. D. Siddeley, C.B.E. ; Mr. G. I. Taylor, M.A., F.R.S. ;Mr. H. T. Tizard, M.A. ; Mr. J. W. W. Dyer and Mr. S. Payneof the Royal Airship Works, Cardington ; Dr. L. Aitchison andMr. A. Young of the Air Ministry ; Dr. G. Barr, B.A., Dr. G. W.0. Kaye, B.A., Dr. W. Rosenhain, F.R.S., Mr. R. V. Southwell,M.A. and Dr. T. E. Stanton, F.R.S. of the National PhysicalLaboratory ; Mr. W. D. Douglas and Dr. J. E. Ramsbottom ofthe Royal Aircraft Establishment; Brigadier General R. K.Bagnall-Wild, C.B.E., C.M.G. of the Aeronautical InspectionDirectorate ; Professor F. C. Lea ; Dr. A. J. Sutton Pippard,M.B.E., A.M.I.C.E. ; Sir Robert Robertson, F.R.S. ; Mr. J. D.North and Captain G. S. Wilkinson, representing the Society ofBritish Aircraft Constructors ; with the Chairman of the Aero-nautical Research Committee (ex-officio).

Meteorology Sub-Committee.—Sir Napier Shaw, F.R.S. (Chair-man) ; Wing Commander T. R. Cave-Browne-Cave, C.B.E. ;Lieut.-Colonel E. Gold, D.S.O., F.R.S. ; Professor B. M. Jones,M.A. ; Dr. H. Lamb, M.A., F.R.S. ; Mr. G. I. Taylor, M.A.,F.R.S. ; Dr. G. C. Simpson, Colonel L. F. Blandy, D.S.O., FlightLieut. R. S. Capon and Squadron Leader G. G. H. Cooke, D.S.C.,A.F.C. of the Air Ministry ; Major H. E. Wimperis, O.B.E. of theAir Ministry Laboratory ; Dr. T. E. Stanton, F.R.S. of theNational Physical Laboratory ; Mr. G. L. Smith of the RoyalAircraft Establishment ; Mr. W. H. Dines, F.R.S. ; Mr. G. M. B.Dobson ; Professor F. A. Lindemann ; Mr. F. E. Smith, O.B.E.,F.R.S. ; Mr. C. T. R. Wilson, F.R.S. ; with the Chairman of theAeronautical Research Committee (ex officio).

Accidents Investigation Sub-Committee.—Lieut.-Colonel M.O'Gorman, C.B. (Chairman) ; Professor L. Bairstow, C.B.E.,F.R.S. ; Lieut.-Colonel E. Gold, D.S.O., F.R.S. ; Sir J. E.Petavel, K.B.E., F.R.S. ; Mr. G. B. Cockburn, O.B.E. ; Mr.M. A. Doyle and Squadron Leader Pritchard of the Air Ministry ;Squadron Leader R. M. Hill of the Royal Aircraft Establishment ;Dr. A. J. Sutton Pippard, M.B.E., A.M.I.C.E. ; with the Chairmanof the Aeronautical Research Committee (ex officio).

Fire Prevention Sub-Committee.—Lieut.-Colonel M. O'Gorman,C.B. (Chairman) ; Wing Commander T. R. Cave-Browne-Cave,C.B.E. ; Sir J. E. Petavel, K.B.E., F.R.S. ; Mr. G. B. Cockburn,O.B.E. ; Lieut.-Colonel L. F. R. Fell, D.S.O., O.B.E. of the AirMinistry ; Squadron Leader G. H. Norman and Dr. J. E. Rams-bottom of the Royal Aircraft Establishment ; Mr. F. M. Green,and Mr. R. K. Pierson, representing the Society of British AircraftConstructors ; with the Chairman of the Aeronautical ResearchCommittee (ex officio).

15

Load Factors Sub-Committee.—Sir R. T. Glazebrook, K.C.B.,F.R.S. (Chairman) ; Sir J. E. Petavel. K.B.E., F.R.S. ; ProfessorC. F. Jenkin, O.B.E., M.A., MJnst.C.E., Dr. T. E. Stanton, F.R.S.,and My. R. V. Southwell, M.A., representing the AeronauticalResearch Committee ; Wing Commander W. D. Beatty, C.B.E..and Mr. R. J. Goodman-Crouch, representing the Air Ministry ;Mr. F. Handley Page, Captain F. S. Barnwell, Mr. J. D. Northand Mr. 0. Short, representing the Society of British AircraftConstructors ; Lieut.-Colonel M. O'Gorman, C.B. and CaptainG. de Havilland, O.B.E., A.F.C., representing the Royal Aero-nautical Society.