The evolution of construction techniques and the use of metal in wings is presented. Drag is discussed along with the fuselage and tail. The interaction of these parts is also investigated

Toussaint, A

English

NASA Technical Reports Server

..
NATIONAL
. r, -.. .-. ... -,,,.1 - .
.
*.
ADV130RY (XMMITTEEFOR AEROILAUTICS.
. . . ..- ,-. ,.. ,.. .fi . .
,
EVOLUTIONOF MODERN AVIATIONAND EXPERI’XHJTAL
AND TECHNICAL
.
RESEARCHESIN AERODYNAMICLABORATORIES.
From ~LfAerophile,m November‘1-15,1921.
,
.?: ..- . .
~.l -,%. -- .-. ~-- ...,.. -----
“i;......
April, 1922.
&
.,
.
https://ntrs.nasa.gov/search.jsp?R=19930081292 2020-03-17T04:08:36+00:00Z
.—
: IlllllllirllimiimlllllllI “
~_31176014405043 J
EVOLUTIONOF MODERN AVIATIONAND EXE%RIMENTAL
,- ..,... #l@e~~IOAL ~SEARCHES IN AERODYNAMICLABORATORIES.*
.. ,-------,.-.
-,-,.,.., -~+-,
...
By A. Toussaint,
, Direotorof the AeroteohnioInstituteof Saint @r.
The art of oonstruotingairplanesIS now In .%11 evolution,
not to aay revolution, This trahafokmationIs stillproceeding
slowly,but for miziy builderswho have not hesltated to leave
the beaten traok,this slowness”haabgen due to diffloultiesof m
financialor materialrather than of a teohnloalorder.
This evolutionaffeotsvery differentpoints, suoh as the
generalshape and dimensionsof airplanes,the materlaisused in
their oonstruotion,eto. These considerationsare, moreover,mu-
tually related. We know, in faot, that the exolusiveuse of metal
depends
We
of ‘this
on the size of the airplaneand the shape of its wings,
propose to examinehere only
evolution,that arisingfrom
theoretloalstudiesIn aerodynamioal
winuQ l
one of the essentialoauses
eqerlmental researchesand
laboratories.
Modern airplanewings have seotionsand shapes olearlydeduoed
f~om the most reoent discoveriesof aerodynamics.
Let-usfirst”oonsider.wingseotions. A good wing seotion
..
must offer the minimump~aslte resistanceend be ospableof pro-
.duoingconsiderableliftingforoes.
* Taken from “L’Aerophile,wI?ov”ember1-15, 1921,
..
.— --- —. -- - . - —-- —— . --
-2-
1
.
The drag of a wing seotlon
,,~..~ . 1. Thp_resistancedue to
----
......
-,
mhole susfaoe;
2. The reslstame due to
geneaally oomprises two parts:
the friotionof the air on its
,.x
-. ...-
impaotand to the separatIon of
air from wing, wltt the consequentparas+.tiorortioes.
The drag of good modern wing seotionsis reduoedalmcst en-
.tirelyto the first kind of reslstame, that 1s, to friotion.
This constitutesa oonslderabledegree of progress,whioh the
‘laboratorieshave been able to put Into ~ffeo%,as a reeult of .
improvementsin their equipment. Henoe the oontourof these
wing sectionsis suoh that the moleoulesof air eaoounteredby
the wing follow its surfaoeiwithout impaot or separation The
air “aots~perfeotlyon these wing seotlons,ltke fluids on the
blade of a turbine. Of coursethis maximum improvementonly cov-
ers the range of the angles of attaok employed In aviation,
whioh, however,already constitutesquite an extensivedomain.
The impaotand separationof the air streamsare always experi-
enced, even on very good wing sections,wheneverthe ~gle of at-
taok is very muoh abwe or below its normal range.
It is well to note that a long seriesof these good wing
seotionehas been designedIn acoordemoewith the theory of the
motion of perfeot fluids. Thie had previouslybeen determined
for the best shapes of airshipsend streamlinedrchimled bodies.
~~ e to the Yrl.otionof the Air.
The friotionof the air on the wings is not a negligible
.-.
~1.11 I . 1 1 1 mm 1 ,-- , .,, .-. .. . ---
-3-
Wantity. Many experimenterskava determinedIts laws of v&-la-
tion.~~h the -~eed and surfaoeareas. We thus find that the frio-
.,.- ....-..,,,.
-!.!.., .,.”...
tion does not Inoreaseexaotlyas the squareof tie v’elooitynor
as the araa of the stiaoe. This means that the frictionon one
squaremeter of firfaoetill be just so mush 1sss, for a given
speed,as ths squ”e meter under considerationfmzns past of a W“-
ger surfaoe. In the same way, equal speedaooelerationsdo not
correspondto equal incrementsof friotion.
The laws of friotlon,of the tir on plane surfaoes,are wall
known and oan be appliedwith just so muoh oloserapproximation,
as there is less
ern contours. We
ing s~aue on a
separationof the fluid moleoulesfrom the nod-
aooordinglyfind that one squaremeter of llft-
airplaneflying 100 m/sao (360km/hr) would re-
quire about 8 HP to overoomefriotionalone, assumingthe surfaoe
to be well mollgbeds This figuremight be doubledwith a less
perfeotpollsh. For the airplanebuilt only for speed,like those
partiolpatingin the Deutsoh oontest,the lifting
12.5 square meters, for exaqple,tha enginapower
frlotion on the wing alone would be about 100 HP.
surfaoebeing
absorbedby the
To this must
be added the powar absorbedby
er parts of the airplane.
Aoourateknowledgeof the
the friotionof the air on the oth-
resistanoedue to the friotionof
the air, therefore,requiresthat the oonstruotorvarnish and pol-
. .
ish, with the greatestoare, all the exteriorsurfaoesof his air- .
planes. We lamw, moreover,that another objeot of this varnishing
.
—
-4”
smd ‘dopi~g~Is to shrink the fabrio ooverlngof the wings. vitil
- progressIn.oonstruo.tioq,.Jfabrionded not be oonsidersd;but the
,. ,.-.+ ,.~
.
wood or metal oovexingsreplaclng.tkemmust be oarefullypolished
if there la to be an ~rovement urer the small ooeffiolentsof
friotiohof the
Oi ooume,
not so great in
tiarnlshe~fabrio surfaoesnow &aploye&
the amoutitof the power absorbedby frlotionis
an airplaneof medium speed (qommerolal),”though
the inoreasedfriotiondue to its larger dimensionspartiallyoff-
sets the diminutionof friotiondue to lower speed.
Dr&K Due to Llf*.
Unfortunately,the drag of a wing due to friotionIs not the
only drag. There is also the drag due to the lift, r@@.red to
offset the weight of the airplane. This has been
portlonalto the ~uare of the lift. The cost of
quently Increasesvery rapidlywith the magnitude
But the
other faotor
“ lift depends
coefflolentof proportionality,that
found to be pro-
the lift conse-
of the drag.
is to cay, the
whioh enters into the value of the drag due to the
only on the shapesad dispositionof the airplane.
It seems thereforethat the ~effloient oould be made very smll,
if the means of oonstruotion,atour disposalenable the reali~
tion of the best shapesand dispositions. Experlenoehas, In
fact, mown that increasingthe aspect ratio and the -p is the
P=wer me~s of diminishingthe &-a& due to lift.
As a result of the experimentalresearchesand theoretical
studiesin aerod-lo laboratories,the constructingengineer
..— —
-5-
oan now determineIn advanoe the &vantages or dlsaihmntagesln-
1
.. ..herentin_all the shapes and dispositionssuggestedto hlm by the
...-,..~._ . ,., ..=
.... ....,,
requirementsof construotion. He can definitely-~eterminewheth-
er he must employa singlewing (monoplane)sor a bip”laneor multi-
p~e cell and the best proportionsto give th-
~ , Tall p~eB ~ d OtherAiKOaneParts.
The laWS of the resistanceof the atz to the fise~ge are
likewiseacxmratelydeterminedexperimentally.In truth,.a fuse-
lage shuuldhave the shape of a revolvi~gSOlidwtth the least
head resistance. We can determineIn advancethe Cor=eotoutline
followedby the fluid moleculesin air withoutviscosity. For
suoh an outline,especiallyapplicableto alrshlphulls, the head
resistanceis almost entirely tie to the friotionof the air.
The smount due to &ad and separationof the fluid streamsis
very small on SUti IIUIISand frequentlyties not exoeed one-tMrd
of the total drag.
But for airplanefuselagae,the necessitiesof oonstruotlon,
conditionsof Inhabitability m“ equipment, and ccmmunloatlonwith
other parts often necessitatemodificationsof the ideal outlines.
Nevertheless,the praoticalfuselageforms are tested in aerody-
IWIliClaboratories,whioh c!ietgmingall thgir oharacterlstiosand
,.
also the Influenoe.ofthe.partlcu@r dispositionsdue to the @lu@-
...
.-
ment or to the oommunioationswith the otksr parts.
In the same way, the aerodynamicpropertiesof the tail plane%
taken singlyor in conjunctionwith other parts, have been studied
..
r
n m-mm n m — , .. ——,-. -— - ‘-- - - ‘- ‘-— -- ‘—
—.. -
.
-6-
e“~erlmeatally in great detai1.
.. .Theease is the same with resistances..,..--”
-..FW-, L..-,.,
... ..
externalfittings,eto. For these
&tory has shown that the values of
smallmodels are rarely applicable
due to knding gears,
parts in p&t~oularj”the lakor-
the reslstanoesmeasuredon
to the full size. Fortunately,
tha e~erimental a~aratus has been sufficientlyimprovedto ek-
able the direot testingof these pats in full si~e- It is the
resultsof thesemeasurements that the engineermust apply in his
oaloulations.
.
~nteraoticnof AlrpJ.ana -~
~ Interaotlonis meant the reciprocal”aotion of two or more
pa&s of an airplaneor other a,,lroraft,a reclprooalaotion”whioh
modifies, to a greateror 1SSS degrees the aerodynamicproperties
of eaoh part taken separately.
Certainof these interactionshave been
and Oa
parts.
anoe of
biplane
be oaloulatedin advanoefor various
accuratelydetemined
combinationsof two
These inolude,for example,the interactionor gap resist-
two or more wings sup&posed in suoh manner as to”forma
or.multiplane08110
The interactionsof the wings
likewisebean determinedby a very
and horizontal.
oomp~etestudy
tail planes have
of the magnitude
and direotionof the downwashbehind a wing..
. ...
Other tnteraotionsare of a more oomplexnature and oan only
be determinede~erimentally in eadh particularease. Suoh are,
for example,the reoiprooalaotions of the wings and fuselages,
—
-’7-”
exteriodfittings,the graund, eto. Lastly;as we shall se3 fur-
.,
--ther,along,,the-prop~ller”itselfreaots on the vartouaparts of
. . ,.-+,-+
..
the airplane.
The total drag of an airplaneoan thereforebe oaloulated
from the Individualresistuoes amd interaotlons.
Propellershave been the objsot02 a considerablenumbe% of
systematicexperimentalresearoheso It may be said that the oon-
struotlngengineeraan surelyfind in this aooumulationof doou-
ments the most suitablepropellerfor solvinghis particularprob-
lem. Moreover,generalruleshave besn establlshed wnloh still
furtherextend the field of applloationof the experimentalre-
sult s,
Lastly, the Interaotlons of two tandem
between one or two propellersand the wings
propellersand those
and fuselagesof an
alrplsaehave been determinede~erlmentally. Rules have been
enunolatedwhioh render it possibleto establishwith aertalnty
the oomplexengine-propellergroupsof oertaintypes of giant air-
planes. lhme~ou”sand varied data enable us to oaloulatethe lnte~-
aotlon of propellerand airpleme.
Al~lane In its EntIretti, Evolutionof Shameq.
Either by the sum of the individualresistamoesand titerao-
tions of its parts or by testinga smallmodel, the aerodynamic
propertiesof a o~lete airplanehave been determinedIn aerody-
namlo laboratories.
.—.
The enginesraocordlzglyhas In hand all the data for oaloti-
.latlnghis ainlane and for dete-ning its perfomaaoes, degreer,
.,,-.-.=---,.#._ _.A
.,,..
of stabllity~maneuverability~eto;”--He MOWS the -rod-o
price, that is to say, the share of the total drag borne by each
part, &NI omsequ%ntly the enginepower requiredfor predetermined
pezformanoes.
Under these oonditione,he oan work out the structuralde-
tails with more confidence. It must be ncted that the study of
peaoe-timeairplanesmd especiallyof large modern airplanesne-
cessitateslarge expenditures. The oonstruotion,followed by final
adjustmentsand trials,requiresconsiderablecapital. It is
thereforeImportantto leave nothing to ohanoeand to prevent faiJ.-
ure at any crest.
Knowledgeof the aerodynamiccharacteristlosof airplanes has
dram the attentionof investigatorsto the great Importance of
parasite resistanoeeand interactionsbetween essentialparts,
namely, the wings and tail planes. One of the most marked tmpro~e-
ments In modern airplanesoonelstsin obtainingairplaneforms for
whioh theseparasite resistancesare zero or as nearly so as possi-
ble. By utilizingmodern wing seotions,Whioh, aside from their.
aerodynamlo~ualities, have the advantageof being relatively
.thiok,engineershave been enabledto pl.aoenearly all braolng,
engines,eto., insidethe wing, so that the alrplaqetends toward
a flyingwing, equippedwith one or more fuselagesfor supporting
the tall planes and landinggear.
II
‘i. -
I
,
I
~
I
----
-9-
One of the essentialfaotors In modern progreesazulmolutiou
of aviationevolvesthereforefrom the experimentalreseamhes
.
.- .-, .,-,,
and.theoretical
—
-,-s. - ,.
inve6tlga*io&3of tikiodybamid WboTatoriee.
The teohnioaldata alreadyobtainedby the experimentersof
the differentoountriesis considerable,but the problemsare co~-
ooattnua13yohanglngand inoreaslng.
It ts thereforeImportaatfor our aerodynamlokboratories
to be providedwith the neoessarymaterialand means for perforn+
Ing the immensetask devolvingupon them. It ~as, in faot, by
Inoreaeing
remarkable
Perhaps by
It is
the efflolenoytofthe experimentalapparatusthat tke
propertiesof modeLm wing seotionswere disomered.
tomorrowthese means mill be insufficient,
import=t, espeoiallyfor the present,to utilize to
the fullest extent the experimentalequipmentof existinglabora-
tories. This is simplya que5tion
paying the indispensabletechnioal
Investlgation is not simplymaking
of sufficientappropriationsfor
experimenters. An e~erlmental
more or less aoourateweighings
or measurements,but it necessitatesa thorou@”study of the prob-
lem presented,of previousdooumentsszxlof the oauses of error,
a judioialand oritioalmalysis aP the data obtainedand the mak-
ing of dsduotiqns”htherefrom,This work Is of an
leotualthm materialand constitutesthe reason
ly be entrustedto oompetenttntelleats. Suoh a
order more’ lntel-
why it shouldon-
seleotpersonnel
merits meterlal recompensecorrespondingto the nature of its work-
.-
-lG -
In this oonneotion,tkeoaetioal.investigationsare desirald.e
and shoulLe-.=tipzsoe~e W ezparimefits.It IG remarkablethat
?zostof +Ae good mode= wing seotioasweze designedbY pu-eQ
t~e~reti~e,lmethods, Tne teaohingof theoretio~ aerodynamics
shouldbe systematizedin this respeot,not simplybeoause it con-
stitutesa soienoeof generaloultw-e (generalmotion of fluids),
but also beoause suoh instructionwill directmany of OU- future
professorsand soholarstoward the teohnloalproblemsof aerial
Mx30motion.
kernmsnt a~ropriatione and private donationsto this work
will constitutean investmentof the first order, for scienoe
pays dividen& in the form of discoverieswhose far-reaohingmor-
al and finamial effeotsare inoa@ulable. Aerodynamicsis no
exceptionto this rule.
.
It muld, moreover,be extremelydangerousfor our future
safetyto fall behind certainother oo~tries In this respeot,.
whioh, unfortunately,is now the ease. Nevertheless,we have in
Franoe, everythingneoessaryfor conduotlng
in oertainrespeds, we even Fossessbetter
than aay other oountry. Let us beware lest
.
these rese~ches snd,
e2qerimenteJapparatus
our failure,for the ,
sake of economy,to provide for the appointmentof a few addi-
tional englneers:~y oost us very dearly in the future.
.
Translatedby the NationalAdvisory Committeefor Aeronautics.
.
. . .- - . .. - . -- . ... .- -- - - .. . .



Evolution of modern aviation and experimental and technical researches in aerodynamic laboratories

Abstract

Similar works

Full text

Available Versions

NASA Technical Reports Server