flying machines-第15章

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feet　to　forty…four　degrees；　Fahrenheit　at　5；000　feet；　at

which　altitude　the　wind　had　a　velocity　of　43　miles　an

hour；　in　clouds　of　a　cirro…cumulus　nature；　a　landing　finally

being　made　near　Tannersville；　New　York；　in　the

Catskill　mountains；　after　a　voyage　of　five　and　one…half

hours。



〃I　have　no　knowledge　of　a　recorded　trip　of　this　distance

and　duration；　maintained　in　practically　a　straight

line　from　start　to　finish。〃



This　wind　disturbance　is　more　noticeable　and　more

difficult　to　contend　with　in　a　balloon　than　in　a　flying

machine；　owing　to　the　bulk　and　unwieldy　character　of

the　former。　At　the　same　time　it　is　not　conducive　to

pleasant；　safe　or　satisfactory　sky…sailing　in　an　aeroplane。

This　is　not　stated　with　the　purpose　of　discouraging

aviation；　but　merely　that　the　operator　may　know　what　to

expect　and　be　prepared　to　meet　it。



Not　only　does　the　wind　change　its　horizontal　course

abruptly　and　without　notice；　but　it　also　shifts　in　a　vertical

direction；　one　second　blowing　up；　and　another

down。　No　man　has　as　yet　fathomed　the　why　and　wherefore

of　this　erratic　action；　it　is　only　known　that　it　exists。



The　most　stable　currents　will　be　found　from　50　to　100

feet　from　the　earth；　provided　the　wind　is　not　diverted

by　such　objects　as　trees；　rocks；　etc。　That　there　are

equally　stable　currents　higher　up　is　true；　but　they　are

generally　to　be　found　at　excessive　altitudes。



How　a　Bird　Meets　Currents。



Observe　a　bird　in　action　on　a　windy　day　and　you　will

find　it　continually　changing　the　position　of　its　wings。

This　is　done　to　meet　the　varying　gusts　and　eddies　of　the

air　so　that　sustentation　may　be　maintained　and　headway

made。　One　second　the　bird　is　bending　its　wings；　altering

the　angle　of　incidence；　the　next　it　is　lifting　or　depressing

one　wing　at　a　time。　Still　again　it　will　extend

one　wing　tip　in　advance　of　the　other；　or　be　spreading　or

folding；　lowering　or　raising　its　tail。



All　these　motions　have　a　meaning；　a　purpose。　They

assist　the　bird　in　preserving　its　equilibrium。　Without

them　the　bird　would　be　just　as　helpless　in　the　air　as　a

human　being　and　could　not　remain　afloat。



When　the　wind　is　still；　or　comparatively　so；　a　bird；

having　secured　the　desired　altitude　by　flight　at　an　angle；

may　sail　or　soar　with　no　wing　action　beyond　an　occasional

stroke　when　it　desires　to　advance。　But；　in　a

gusty；　uncertain　wind　it　must　use　its　wings　or　alight

somewhere。



Trying　to　Imitate　the　Bird。



Writing　in　_Fly_；　Mr。　William　E。　White　says：



〃The　bird's　flight　suggests　a　number　of　ways　in　which

the　equilibrium　of　a　mechanical　bird　may　be　controlled。

Each　of　these　methods　of　control　may　be　effected　by

several　different　forms　of　mechanism。



〃Placing　the　two　wings　of　an　aeroplane　at　an　angle　of

three　to　five　degrees　to　each　other　is　perhaps　the　oldest

way　of　securing　lateral　balance。　This　way　readily　occurs

to　anyone　who　watches　a　sea　gull　soaring。　The

theory　of　the　dihedral　angle　is　that　when　one　wing　is

lifted　by　a　gust　of　wind；　the　air　is　spilled　from　under　it；

while　the　other　wing；　being　correspondingly　depressed；

presents　a　greater　resistance　to　the　gust　and　is　lifted

restoring　the　balance。　A　fixed　angle　of　three　to　five　degrees；

however；　will　only　be　sufficient　for　very　light　puffs

of　wind　and　to　mount　the　wings　so　that　the　whole　wing

may　be　moved　to　change　the　dihedral　angle　presents

mechanical　difficulties　which　would　be　better　avoided。



〃The　objection　of　mechanical　impracticability　applies

to　any　plan　to　preserve　the　balance　by　shifting　weight

or　ballast。　The　center　of　gravity　should　be　lower　than

the　center　of　the　supporting　surfaces；　but　cannot　be

made　much　lower。　It　is　a　common　mistake　to　assume

that　complete　stability　will　be　secured　by　hanging　the

center　of　gravity　very　low　on　the　principle　of　the

parachute。　An　aeroplane　depends　upon　rapid　horizontal　motion　for

its　support；　and　if　the　center　of　gravity　be　far

below　the　center　of　support；　every　change　of　speed　or

wind　pressure　will　cause　the　machine　to　turn　about　its

center　of　gravity；　pitching　forward　and　backward　dangerously。



Preserving　Longitudinal　Balance。



〃The　birds　maintain　longitudinal；　or　fore　and　aft　balance；

by　elevating　or　depressing　their　tails。　Whether

this　action　is　secured　in　an　aeroplane　by　means　of　a

horizontal　rudder　placed　in　the　rear；　or　by　deflecting

planes　placed　in　front　of　the　main　planes；　the　principle

is　evidently　the　same。　A　horizontal　rudder　placed　well

to　the　rear　as　in　the　Antoinette；　Bleriot　or　Santos…Dumont

monoplanes；　will　be　very　much　safer　and　steadier

than　the　deflecting　planes　in　front；　as　in　the　Wright　or

Curtiss　biplanes；　but　not　so　sensitive　or　prompt　in　action。



〃The　natural　fore　and　aft　stability　is　very　much

strengthened　by　placing　the　load　well　forward。　The

center　of　gravity　near　the　front　and　a　tail　or　rudder

streaming　to　the　rear　secures　stability　as　an　arrow　is

balanced　by　the　head　and　feathering。　The　adoption　of

this　principle　makes　it　almost　impossible　for　the　aeroplane

to　turn　over。



The　Matter　of　Lateral　Balance。



〃All　successful　aeroplanes　thus　far　have　maintained

lateral　balance　by　the　principle　of　changing　the　angle

of　incidence　of　the　wings。



〃Other　ways　of　maintaining　the　lateral　balance；　suggested

by　observation　of　the　flight　of　birds　areextending

the　wing　tips　and　spilling　the　air　through　the　pinions；

or；　what　is　the　same　thing；　varying　the　area　of　the

wings　at　their　extremities。



〃Extending　the　wing　tips　seems　to　be　a　simple　and

effective　solution　of　the　problem。　The　tips　may　be　made

to　swing　outward　upon　a　vertical　axis　placed　at　the　front

edge　of　the　main　planes；　or　they　may　be　hinged　to　the

ends　of　the　main　plane　so　as　to　be　elevated　or　depressed

through　suitable　connections　by　the　aviator；　or　they　may

be　supported　from　a　horizontal　axis　parallel　with　the

ends　of　the　main　planes　so　that　they　may　swing　outward；

the　aviator　controlling　both　tips　through　one　lever

so　that　as　one　tip　is　extended　the　other　is　retracted。



〃The　elastic　wing　pinions　of　a　bird　bend　easily　before

the　wind；　permitting　the　gusts　to　glance　off；　but　presenting

always　an　even　and　efficient　curvature　to　the

steady　currents　of　the　air。〃



High　Winds　Threaten　Stability。



To　ensure　perfect　stability；　without　control；　either　human

or　automatic；　it　is　asserted　that　the　aeroplane　must

move　faster　than　the　wind　is　blowing。　So　long　as　the

wind　is　blowing　at　the　rate　of　30　miles　an　hour；　and　the

machine　is　traveling　40　or　more；　there　will　be　little　trouble

as　regards　equilibrium　so　far　as　wind　disturbance

goes；　provided　the　wind　blows　evenly　and　does　not　come

in　gusts　or　eddying　currents。　But　when　conditions　are

reversedwhen　the　machine　travels　only　30　miles　an

hour　and　the　wind　blows　at　the　rate　of　50；　look　out　for

loss　of　equilibrium。



One　of　the　main　reasons　for　this　is　that　high　winds

are　rarely　steady；　they　seldom　blow　for　any　length　of

time　at　the　same　speed。　They　are　usually　〃gusty；〃　the

gusts　being　a　momentary　movement　at　a　higher　speed。

Tornadic　gusts　are　also　formed　by　the　meeting　of　two

opposing　currents；　causing　a　whirling　motion；　which

makes　stability　uncertain。　Besides；　it　is　not　unusual

for　wind　of　high　speed　to　suddenly　change　its　direction

without　warning。



Trouble　With　Vertical　Columns。



Vertical　currentscolumns　of　ascending　airare

frequently　encountered　in　unexpected　places　and　have　more

or　less　tendency；　according　to　their　strength；　to　make

it　difficult　to　keep　the　machine　within　a　reasonable

distance　from　the　ground。



These　vertical　currents　are　most　generally　noticeable

in　the　vicinity　of　steep　cliffs；　or　deep　ravines。　In　such

instances　they　are　usually　of　considerable　strength；　being

caused　by　the　deflection　of　strong　winds　blowing

against　the　face　of　the　cliffs。　This　deflection　exerts　a

back　pressure　which　is　felt　quite　a　distance　away　from

the　point　of　origin；　so　that　the　vertical　current　exerts　an

influence　in　forcing　the　machine　upward　long　before　the

cliff　is　reached。







CHAPTER　XV。



THE　ELEMENT　OF　DANGER。



That　there　is　an　element　of　danger　in　aviation　is

undeniable；　but　it　is　nowhere　so　great　as　the　public

imagines。　Men　are　killed　and　injured　in　the　operation

of　flying　machines　just　as　they　are　killed　and　injured　in

the　operation　of　railways。　Considering　the　character　of

aviation　the　percentage　of　casualties　is　surprisingly

small。



This　is　because　the　results　following　a　collapse　in　the

air　are　very　much　different　from　what　might　be　imagined。

Instead　of　dropping　to　the　ground　like　a　bullet　an

aeroplane；　under　ordinary　conditions　will；　when　anything

goes　wrong；　sail　gently　downward　like　a　parachute；

particularly　if　the　operator　is　cool…headed　and　nervy　enough

to　so　manipulate　the　apparatus　as　to　preserve　its　equilibrium

and　keep　the　machine　on　an　even　keel。



Two　Fields　of　Safety。



At　least　one　prominent　aviator　has　declared　that　there

are　two　fields　of　safetyone　close　to　the　ground；　and

the　other　well　up　in　the　air。　In　the　first…named　the　fall

will　be　a　slight　one　with　little　chance　of　the　operator

being　seriously　hurt。　From　the　field　of　high　altitude　the

the　descent　will　be　gradual；　as　a　rule；　the　planes　of　the

machine　serving　to　break　the　force　of　the　fall。　With　a

cool…headed　operator　in　control　the　aeroplane　may　be

even　guided　at　an　angle　（about　1　to　8）　in　its　descent　so

as　to　touch　the　ground　with　a　gliding　motion　and　with

a　minimum　of　impact。



Such　an　experience；　of　course；　is　far　from　pleasant；

but　it　is　by　no　means　so　dangerous　as　might　appear。

There　is　more　real　danger　in　falling　from　an　elevation

of　75　or　100　feet　than　there　is　from　1；000　feet；　as　in　the

former　case　there　is　no　chance　for　the　machine　to　serve　as

a　parachuteits　contact　with　the　ground　comes　too

quickly。



Lesson　in　Recent　Accidents。



Among　the　more　recent　fatalities　in　aviation　are　the

deaths　of　Antonio　Fernandez　and　Leon　Delagrange。　The

former　was　thrown　to　the　ground　by　a　sudden　stoppage

of　his　motor；　the　entire　machine　seeming　to　collapse。

It　is　evident　there　were　radical　defects；　not　only　in　the

motor；　but　in　the　aeroplane　framework　as　well。　At　the

time　of　the　stoppage　it　is　estimated　that　Fernandez　was

up　about　1；500　feet；　but　the　machine　got　no　opportunity

to　exert　a　parachute　effect；　as　it　broke　up　immediately。

This　would　indicate　a　fatal　weakness　in　the　structure

which；　under　proper　testing；　could　probably　have　been

detected　before　it　was　used　in　flight。



It　is　hard　to　say　it；　but　Delagrange　appears　to　have

been　culpable　to　great　degree　in　overloading　his　machine

with　a　motor　equipment　much　heavier　than　it　was

designed　to　sustain。　He　was　65　feet　up　in　the　air　when

the　collapse　occurred；　resulting　in　his　death。　As　in　the

case　of　Fernandez　common…sense　precaution　would