the aeroplane speaks-第7部分

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＇＇13＇＇　Box…kite。　The　first　crude　form　of　biplane。


Now　the　Pilot　decides　to　change　the　straight　gliding　descent　to　a　spiral　one；　and；　obedient　to　the　Rudder；　the　Aeroplane　turns　to　the　left。　But　the　Momentum　（two　tons　at　100　miles　per　hour　is　no　small　affair）　heavily　resents　this　change　of　direction；　and　tries　its　level　best　to　prevent　it　and　to　pull　the　machine　sideways　and　outwards　from　its　spiral　coursethat　is；　to　make　it　‘‘side…skid''　outwards。　But　the　Pilot　deflects　the　Ailerons　and　‘‘banks''　up　the　planes　to　the　correct　angle；　and；　the　Aeroplane　skidding　sideways　and　outwards；　the　lowest　surfaces　of　the　planes　press　up　against　the　air　until　the　pressure　equals　the　centrifugal　force　of　the　Momentum；　and　the　Aeroplane　spirals　steadily　downwards。

Down；　down；　down；　and　the　air　grows　denser；　and　the　Pilot　gulps　largely；　filling　his　lungs　with　the　heavier　air　to　counteract　the　increasing　pressure　from　without。　Down　through　a　gap　in　the　clouds；　and　the　Aerodrome　springs　into　view；　appearing　no　larger　than　a　saucer；　and　the　Pilot；　having　by　now　got　the　‘‘feel''　of　the　Controls；　proceeds　to　put　the　Aeroplane　through　its　paces。　First　at　its　Maximum　Angle；　staggering　along　tail…down　and　just　maintaining　horizontal　flight；　then　a　dive　at　far　over　flying　speed；　finishing　with　a　perfect　loop；　then　sharp　turns　with　attendant　vertical　‘‘banks''　and　then　a　wonderful　switchback　flight；　speeding　down　at　a　hundred　and　fifty　miles　an　hour　with　short；　exhilarating　ascents　at　the　rate　of　two　thousand　feet　a　minute！

All　the　parts　are　now　working　well　together。　Such　wires　as　were　before　in　undue　tension　have　secured　relief　by　slightly　elongating　their　loops；　and　each　one　is　now　doing　its　bit；　and　all　are　sharing　the　burden　of　work　together。

The　Struts　and　the　Spars；　which　felt　so　awkward　at　first；　have　bedded　themselves　in　their　sockets；　and　are　taking　the　compression　stresses　uncomplainingly。

The　Control　Cables　of　twisted　wire；　a　bit　tight　before；　have　slightly　lengthened　by　perhaps　the　eighth　of　an　inch；　and；　the　Controls　instantly　responding　to　the　delicate　touch　of　the　Pilot；　the　Aeroplane；　at　the　will　of　its　Master；　darts　this　way　and　that　way；　dives；　loops；　spirals；　and　at　last；　in　one　long；　magnificent　glide；　lands　gently　in　front　of　its　shed。

‘‘Well；　what　result？''　calls　the　Flight…Commander　to　the　Pilot。

‘‘A　hundred　miles　an　hour　and　a　thousand　feet　a　minute；''　he　briefly　replies。

‘‘And　a　very　good　result　too；''　says　the　Aeroplane；　complacently；　as　he　is　carefully　wheeled　into　his　shed。

　　　　　　

That　is　the　way　Aeroplanes　speak　to　those　who　love　them　and　understand　them。　Lots　of　Pilots　know　all　about　it；　and　can　spin　you　wonderful　yarns；　much　better　than　this　one；　if　you　catch　them　in　a　confidential　moodon　leave；　for　instance；　and　after　a　good　dinner。



PART　IV

'CROSS　COUNTRY

The　Aeroplane　had　been　designed　and　built；　and　tested　in　the　air；　and　now　stood　on　the　Aerodrome　ready　for　its　first　'cross…country　flight。

It　had　run　the　gauntlet　of　pseudo…designers；　crank　inventors；　press　‘‘experts；''　and　politicians；　of　manufacturers　keen　on　cheap　work　and　large　profits；　of　poor　pilots　who　had　funked　it；　and　good　pilots　who　had　expected　too　much　of　it。　Thousands　of　pounds　had　been　wasted　on　it；　many　had　gone　bankrupt　over　it；　and　others　it　had　provided　with　safe　fat　jobs。

Somehow；　and　despite　every　conceivable　obstacle；　it　had　managed　to　muddle　through；　and　now　it　was　ready　for　its　work。　It　was　not　perfect；　for　there　were　fifty　different　ways　in　which　it　might　be　improved；　some　of　them　shamefully　obvious。　But　it　was　fairly　sound　mechanically；　had　a　little　inherent　stability；　was　easily　controlled；　could　climb　a　thousand　feet　a　minute；　and　its　speed　was　a　hundred　miles　an　hour。　In　short；　quite　a　creditable　machine；　though　of　course　the　right　man　had　not　got　the　credit。

It　is　rough；　unsettled　weather　with　a　thirty　mile　an　hour　wind　on　the　ground；　and　that　means　fifty　more　or　less　aloft。　Lots　of　clouds　at　different　altitudes　to　bother　the　Pilot；　and　the　air　none　to　clear　for　the　observation　of　landmarks。

As　the　Pilot　and　Observer　approach　the　Aeroplane　the　former　is　clearly　not　in　the　best　of　tempers。　‘‘It's　rotten　luck；''　he　is　saying；　‘‘a　blank　shame　that　I　should　have　to　take　this　blessed　'bus　and　join　X　Reserve　Squadron；　stationed　a　hundred　and　fifty　miles　from　anywhere；　and　just　as　I　have　licked　my　Flight　into　shape。　Now　some　slack　blighter　will；　I　suppose；　command　it　and　get　the　credit　of　all　my　work！''

‘‘Shut　up；　you　grouser；''　said　the　Observer。　‘‘Do　you　think　you're　the　only　one　with　troubles？　Haven't　I　been　through　it　too？　Oh！　I　know　all　about　it！　You're　from　the　Special　Reserve　and　your　C。O。　doesn't　like　your　style　of　beauty；　and　you　won't　lick　his　boots；　and　you　were　a　bit　of　a　technical　knut　in　civil　life；　but　now　you've　jolly　well　got　to　know　less　than　those　senior　to　you。　Well！　It's　a　jolly　good　experience　for　most　of　us。　Perhaps　conceit　won't　be　at　quite　such　a　premium　after　this　war。　And　what's　the　use　of　grousing？　That　never　helped　anyone。　So　buck　up；　old　chap。　Your　day　will　come　yet。　Here's　our　machine；　and　I　must　say　it　looks　a　beauty！''

And；　as　the　Pilot　approaches　the　Aeroplane；　his　face　brightens　and　he　soon　forgets　his　troubles　as　he　critically　inspects　the　craft　which　is　to　transport　him　and　the　Observer　over　the　hills　and　far　away。　Turning　to　the　Flight…Sergeant　he　inquires；　‘‘Tank　full　of　petrol　and　oil？''

‘‘Yes；　sir；''　he　replies；　‘‘and　everything　else　all　correct。　Propeller；　engine；　and　body　covers　on　board；　sir；　tool　kit　checked　over　and　in　the　locker；　engine　and　Aeroplane　logbooks　written　up；　signed；　and　under　your　seat；　engine　revs。　up　to　mark；　and　all　the　control　cables　in　perfect　condition　and　tension。''

‘‘Very　good；''　said　the　Pilot；　and　then　turning　to　the　Observer；　‘‘Before　we　start　you　had　better　have　a　look　at　the　course　I　have　mapped　out。

‘‘A　is　where　we　stand　and　we　have　to　reach　B；　a　hundred　and　fifty　miles　due　North。　I　judge　that；　at　the　altitude　we　shall　fly；　there　will　be　an　East　wind；　for　although　it　is　not　quite　East　on　the　ground　it　is　probably　about　twenty　degrees　different　aloft；　the　wind　usually　moving　round　clockways　to　about　that　extent。　I　think　that　it　is　blowing　at　the　rate　of　about　fifty　miles　an　hour；　and　I　therefore　take　a　line　on　the　map　to　C；　fifty　miles　due　West　of　A。　The　Aeroplane's　speed　is　a　hundred　miles　an　hour；　and　so　I　take　a　line　of　one　hundred　miles　from　C　to　D。　Our　compass　course　will　then　be　in　the　direction　AE；　which　is　always　a　line　parallel　to　CD。　That　is；　to　be　exact；　it　will　be　fourteen　degrees　off　the　CD　course；　as；　in　this　part　of　the　globe；　there　is　that　much　difference　between　the　North　and　South　lines　on　the　map　and　the　magnetic　North　to　which　the　compass　needle　points。　If　the　compass　has　an　error；　as　it　may　have　of　a　few　degrees；　that；　too；　must　be　taken　into　account；　and　the　deviation　or　error　curve　on　the　dashboard　will　indicate　it。

‘‘The　Aeroplane　will　then　always　be　pointing　in　a　direction　parallel　to　AE；　but；　owing　to　the　side　wind；　it　will　be　actually　travelling　over　the　course　AB；　though　in　a　rather　sideways　attitude　to　that　course。

‘‘The　distance　we　shall　travel　over　the　AB　course　in　one　hour　is　AD。　That　is　nearly　eighty…seven　miles；　so　we　ought　to　accomplish　our　journey　of　a　hundred　and　fifty　miles　in　about　one　and　three…quarter　hours。

‘‘I　hope　that's　quite　clear　to　you。　It's　a　very　simple　way　of　calculating　the　compass　course；　and　I　always　do　it　like　that。''

‘‘Yes；　that's　plain　enough。　You　have　drafted　what　engineers　call　‘a　parallelogram　of　forces'；　but　suppose　you　have　miscalculated　the　velocity　of　the　wind；　or　that　it　should　change　in　velocity　or　direction？''

‘‘Well；　that　of　course　will　more　or　less　alter　matters；''　replies　the　Pilot。　‘‘But　there　are　any　number　of　good　landmarks　such　as　lakes；　rivers；　towns；　and　railway　lines。　They　will　help　to　keep　us　on　the　right　course；　and　the　compass　will；　at　any　rate；　prevent　us　from　going　far　astray　when　between　them。''

‘‘Well；　we'd　better　be　off；　old　chap。　Hop　aboard。''　This　from　the　Observer　as　he　climbs　into　the　front　seat　from　which　he　will　command　a　good　view　over　the　lower　plane；　and　the　Pilot　takes　his　place　in　the　rear　seat；　and；　after　making　himself　perfectly　comfortable；　fixing　his　safety　belt；　and　moving　the　control　levers　to　make　sure　that　they　are　working　freely；　he　gives　the　signal　to　the　Engine　Fitter　to　turn　the　propeller　and　so　start　the　engine。

Round　buzzes　the　Propeller；　and　the　Pilot；　giving　the　official　signal；　the　Aeroplane　is　released　and　rolls　swiftly　over　the　ground　in　the　teeth　of　the　gusty　wind。

In　less　than　fifty　yards　it　takes　to　the　air　and　begins　to　climb　rapidly　upwards；　but　how　different　are　the　conditions　to　the　calm　morning　of　yesterday！　If　the　air　were　visible　it　would　be　seen　to　be　acting　in　the　most　extraordinary　manner；　crazily　swirling；　lifting　and　dropping；　gusts　viciously　collidinga　mad　phantasmagoria　of　forces！

Wickedly　it　seizes　and　shakes　the　Aeroplane；　then　tries　to　turn　it　over　sideways；　then　instantly　changes　its　mind　and　in　a　second　drops　it　into　a　hole　a　hundred　feet　deep；　and　if　it　were　not　for　his　safety　belt　the　Pilot　might　find　his　seat　sinking　away　from　beneath　him。

Gusts　strike　the　front　of　the　craft　like　so　many　slaps　in　the　face；　and　others；　with　the　motion　of　mountainous　waves；　sometimes　lift　it　hundreds　of　feet　in　a　few　seconds；　hoping　to　see　it　plunge　over　the　summit　in　a　death…diveand　so　it　goes　on；　but　the　Pilot；　perfectly　at　one　with　his　mount　and　instantly　alert　to　its　slightest　motion；　is　skilfully　and　naturally　making　perhaps　fifty　movements　a　minute　of　hand　and　feet；　the　former　lightly　grasping　the　‘‘joy…stick''　which　controls　the　Elevator　hinged　to　the　tail；　and　also　the　Ailerons　or　little　wings　hinged　to　the　wing…tips；　and　the　latter　moving　the　Rudder　control…bar。

A　strain　on　the　Pilot？　Not　a　bit　of　it；　for　this　is　his　Work　which　he　loves　and　excels　in；　and　given　a　cool　head；　alert　eye；　and　a　sensitive　touch　for　the　controls；　what　sport　can　compare　with　these　ever…changing　battles　of　the　air？

The　Aeroplane　has　all　this　time　been　climbing　in　great　wide　circles；　and　is　now　some　three　thousand　feet　above　the　Aerodrome　which　from　such　height　looks　absurdly　smal