flying machines-第14部分

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further　lessons。



Why　This　Rule　Prevails。



There　is　good　reason　for　this　precaution。　The　higher

the　altitude　the　more　rarefied　（thinner）　becomes　the　air；

and　the　less　sustaining　power　it　has。　Consequently　the

more　difficult　it　becomes　to　keep　in　suspension　a　given

weight。　When　sailing　within　30　feet　of　the　ground　sustentation

is　comparatively　easy　and；　should　a　fall　occur；

the　results　are　not　likely　to　be　serious。　On　the　other

hand；　sailing　too　near　the　ground　is　almost　as　objectionable

in　many　ways　as　getting　up　too　high。　If　the　craft

is　navigated　too　close　to　the　ground　trees；　shrubs；　fences

and　other　obstructions　are　liable　to　be　encountered。

There　is　also　the　handicap　of　contrary　air　currents

diverted　by　the　obstructions　referred　to；　and　which　will

be　explained　more　fully　further　on。



How　to　Make　a　Start。



Taking　it　for　granted　that　the　beginner　has　familiarized

himself　with　the　manipulation　of　the　machine；　and　especially

the　control　mechanism；　the　next　thing　in　order

is　an　actual　flight。　It　is　probable　that　his　machine　will

be　equipped　with　a　wheeled　alighting　gear；　as　the　skids

used　by　the　Wrights　necessitate　the　use　of　a　special

starting　track。　In　this　respect　the　wheeled　machine　is

much　easier　to　handle　so　far　as　novices　are　concerned

as　it　may　be　easily　rolled　to　the　trial　grounds。　This；

as　in　the　case　of　the　initial　experiments；　should　be　a

clear；　reasonably　level　place；　free　from　trees；　fences；

rocks　and　similar　obstructions　with　which　there　may　be

danger　of　colliding。



The　beginner　will　need　the　assistance　of　three　men。

One　of　these　should　take　his　position　in　the　rear　of　the

machine；　and　one　at　each　end。　On　reaching　the　trial

ground　the　aviator　takes　his　seat　in　the　machine　and；

while　the　men　at　the　ends　hold　it　steady　the　one　in　the　rear

assists　in　retaining　it　until　the　operator　is　ready。　In　the

meantime　the　aviator　has　started　his　motor。　Like　the

glider　the　flying　machine；　in　order　to　accomplish　the

desired　results；　should　be　headed　into　the　wind。



When　the　Machine　Rises。



Under　the　impulse　of　the　pushing　movement；　and　assisted

by　the　motor　action；　the　machine　will　gradually

rise　from　the　groundprovided　it　has　been　properly

proportioned　and　put　together；　and　everything　is　in　working

order。　This　is　the　time　when　the　aviator　requires

a　cool　head；　At　a　modest　distance　from　the　ground　use

the　control　lever　to　bring　the　machine　on　a　horizontal

level　and　overcome　the　tendency　to　rise。　The　exact

manipulation　of　this　lever　depends　upon　the　method　of

control　adopted；　and　with　this　the　aviator　is　supposed

to　have　thoroughly　familiarized　himself　as　previously

advised　in　Chapter　XI。



It　is　at　this　juncture　that　the　operator　must　act

promptly；　but　with　the　perfect　composure　begotten　of

confidence。　One　of　the　great　drawbacks　in　aviation　by

novices　is　the　tendency　to　become　rattled；　and　this　is

much　more　prevalent　than　one　might　suppose；　even

among　men　who；　under　other　conditions；　are　cool　and

confident　in　their　actions。



There　is　something　in　the　sensation　of　being　suddenly

lifted　from　the　ground；　and　suspended　in　the　air　that　is

disconcerting　at　the　start；　but　this　will　soon　wear　off　if

the　experimenter　will　keep　cool。　A　few　successful　flights

no　matter　how　short　they　may　be；　will　put　a　lot　of

confidence　into　him。



Make　Your　Flights　Short。



Be　modest　in　your　initial　flights。　Don't　attempt　to

match　the　records　of　experienced　men　who　have　devoted

years　to　mastering　the　details　of　aviation。　Paulhan；

Farman；　Bleriot；　Wright；　Curtiss；　and　all　the　rest　of

them　began；　and　practiced　for　years；　in　the　manner　here

described；　being　content　to　make　just　a　little　advancement

at　each　attempt。　A　flight　of　150　feet；　cleanly　and

safely　made；　is　better　as　a　beginning　than　one　of　400

yards　full　of　bungling　mishaps。



And　yet　these　latter　have　their　uses；　provided　the

operator　is　of　a　discerning　mind　and　can　take　advantage

of　them　as　object　lessons。　But；　it　is　not　well　to　invite

them。　They　will　occur　frequently　enough　under　the

most　favorable　conditions；　and　it　is　best　to　have　them

come　later　when　the　feeling　of　trepidation　and　uncertainty

as　to　what　to　do　has　worn　off。



Above　all；　don't　attempt　to　fly　too　high。　Keep　within

a　reasonable　distance　from　the　groundabout　25　or　30

feet。　This　advice　is　not　given　solely　to　lessen　the　risk

of　serious　accident　in　case　of　collapse；　but　mainly　because

it　will　assist　to　instill　confidence　in　the　operator。



It　is　comparatively　easy　to　learn　to　swim　in　shallow

water；　but　the　knowledge　that　one　is　tempting　death　in

deep　water　begets　timidity。



Preserving　the　Equilibrium。



After　learning　how　to　start　and　stop；　to　ascend　and

descend；　the　next　thing　to　master　is　the　art　of　preserving

equilibrium；　the　knack　of　keeping　the　machine　perfectly

level　in　the　airon　an　〃even　keel；〃　as　a　sailor　would

say。　This　simile　is　particularly　appropriate　as　all　aviators

are　in　reality　sailors；　and　much　more　daring　ones

than　those　who　course　the　seas。　The　latter　are　in　craft

which　are　kept　afloat　by　the　buoyancy　of　the　water；

whether　in　motion　or　otherwise　and；　so　long　as　normal

conditions　prevail；　will　not　sink。　Aviators　sail　the　air

in　craft　in　which　constant　motion　must　be　maintained　in

order　to　ensure　flotation。



The　man　who　has　ridden　a　bicycle　or　motorcycle

around　curves　at　anything　like　high　speed；　will　have　a

very　good　idea　as　to　the　principle　of　maintaining　equilibrium

in　an　airship。　He　knows　that　in　rounding　curves

rapidly　there　is　a　marked　tendency　to　change　the　direction

of　the　motion　which　will　result　in　an　upset　unless

he　overcomes　it　by　an　inclination　of　his　body　in　an　opposite

direction。　This　is　why　we　see　racers　lean　well

over　when　taking　the　curves。　It　simply　must　be　done

to　preserve　the　equilibrium　and　avoid　a　spill。



How　It　Works　In　the　Air。



If　the　equilibrium　of　an　airship　is　disturbed　to　an

extent　which　completely　overcomes　the　center　of　gravity

it　falls　according　to　the　location　of　the　displacement。

If　this　displacement；　for　instance；　is　at　either　end　the

apparatus　falls　endways；　if　it　is　to　the　front　or　rear；　the

fall　is　in　the　corresponding　direction。



Owing　to　uncertain　air　currentsthe　air　is　continually

shifting　and　eddying；　especially　within　a　hundred　feet　or

so　of　the　earththe　equilibrium　of　an　airship　is　almost

constantly　being　disturbed　to　some　extent。　Even　if　this

disturbance　is　not　serious　enough　to　bring　on　a　fall　it

interferes　with　the　progress　of　the　machine；　and　should

be　overcome　at　once。　This　is　one　of　the　things　connected

with　aerial　navigation　which　calls　for　prompt；

intelligent　action。



Frequently；　when　the　displacement　is　very　slight；　it

may　be　overcome；　and　the　craft　immediately　righted　by

a　mere　shifting　of　the　operator's　body。　Take；　for　illustration；

a　case　in　which　the　extreme　right　end　of　the

machine　becomes　lowered　a　trifle　from　the　normal　level。

It　is　possible　to　bring　it　back　into　proper　position　by

leaning　over　to　the　left　far　enough　to　shift　the　weight

to　the　counter…balancing　point。　The　same　holds　good　as

to　minor　front　or　rear　displacements。



When　Planes　Must　Be　Used。



There　are　other　displacements；　however；　and　these　are

the　most　frequent；　which　can　be　only　overcome　by　manipulation　of

the　stabilizing　planes。　The　method　of　procedure

depends　upon　the　form　of　machine　in　use。　The

Wright　machine；　as　previously　explained；　is　equipped

with　plane　ends　which　are　so　contrived　as　to　admit　of

their　being　warped　（position　changed）　by　means　of　the

lever　control。　These　flexible　tip　planes　move　simultaneously；

but　in　opposite　directions。　As　those　on　one　end

rise；　those　on　the　other　end　fall　below　the　level　of　the

main　plane。　By　this　means　air　is　displaced　at　one　point；

and　an　increased　amount　secured　in　another。



This　may　seem　like　a　complicated　system；　but　its

workings　are　simple　when　once　understood。　It　is　by

the　manipulation　or　warping　of　these　flexible　tips　that

transverse　stability　is　maintained；　and　any　tendency　to

displacement　endways　is　overcome。　Longitudinal　stability

is　governed　by　means　of　the　front　rudder。



Stabilizing　planes　of　some　form　are　a　feature；　and　a

necessary　feature；　on　all　flying　machines；　but　the　methods

of　application　and　manipulation　vary　according　to　the

individual　ideas　of　the　inventors。　They　all　tend；　however；

toward　the　same　endthe　keeping　of　the　machine

perfectly　level　when　being　navigated　in　the　air。



When　to　Make　a　Flight。



A　beginner　should　never　attempt　to　make　a　flight

when　a　strong　wind　is　blowing。　The　fiercer　the　wind；

the　more　likely　it　is　to　be　gusty　and　uncertain；　and　the

more　difficult　it　will　be　to　control　the　machine。　Even

the　most　experienced　and　daring　of　aviators　find　there

is　a　limit　to　wind　speed　against　which　they　dare　not

compete。　This　is　not　because　they　lack　courage；　but

have　the　sense　to　realize　that　it　would　be　silly　and　useless。



The　novice　will　find　a　comparatively　still　day；　or　one

when　the　wind　is　blowing　at　not　to　exceed　15　miles　an

hour；　the　best　for　his　experiments。　The　machine　will　be

more　easily　controlled；　the　trip　will　be　safer；　and　also

cheaper　as　the　consumption　of　fuel　increases　with　the

speed　of　the　wind　against　which　the　aeroplane　is　forced。







CHAPTER　XIII。



PECULIARITIES　OF　AIRSHIP　POWER。



As　a　general　proposition　it　takes　much　more　power　to

propel　an　airship　a　given　number　of　miles　in　a　certain

time　than　it　does　an　automobile　carrying　a　far　heavier

load。　Automobiles　with　a　gross　load　of　4；000　pounds；

and　equipped　with　engines　of　30　horsepower；　have　travelled

considerable　distances　at　the　rate　of　50　miles　an

hour。　This　is　an　equivalent　of　about　134　pounds　per

horsepower。　For　an　average　modern　flying　machine；

with　a　total　load；　machine　and　passengers；　of　1；200

pounds；　and　equipped　w