aeroplanes-第10章

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_Fig。　15。　Utilizing　Momentum。_



CUTTING　OFF　THE　POWER。This　curve；　A；　may

reach　that　point　where　momentum　has　ceased　as

a　forwardly…propelling　factor；　and　the　machine

now　begins　to　travel　rearwardly。　（Fig。　16。）　It

has　still　the　entire　supporting　surfaces　of　the

planes。　It　cannot　loop…the…loop；　as　in　the　instance

where　the　planes　are　fixed　immovably　to　the　body。



Carefully　study　the　foregoing　arrangement；　and

it　will　be　seen　that　it　is　more　nearly　in　accord　with

the　true　flying　principle　as　given　by　nature　than

the　vaunted　theories　and　practices　now　indulged

in　and　so　persistently　adhered　to。



The　body　of　a　flying　machine　should　not　be　oscillated

like　a　lever。　The　support　of　the　aeroplane

should　never　be　taken　from　it。　While　it　may　be

impossible　to　prevent　a　machine　from　coming

down；　it　can　be　prevented　from　overturning；　and

this　can　be　done　without　in　the　least　detracting

from　it　structurally。



_Fig。　16。　Reversing　Motion。_



The　plan　suggested　has　one　great　fault；　however。

It　will　be　impossible　with　such　a　structure

to　cause　it　to　fly　upside　down。　It　does　not　present

any　means　whereby　dare…devil　stunts　can　be　performed

to　edify　the　grandstand。　In　this　respect

it　is　not　in　the　same　class　with　the　present　types。



THE　STARTING　MOVEMENT。Examine　this　plan

from　the　position　of　starting；　and　see　the　advantages

it　possesses。　In　these　illustrations　we

have　used；　for　convenience　only；　the　monoplane

type；　and　it　is　obvious　that　the　same　remarks　apply

to　the　bi…plane。



Fig。　17　shows　the　starting　position　of　the　stock

monoplane；　in　position　1；　while　it　is　being　initially

run　over　the　ground；　preparatory　to　launching。

Position　2　represents　the　negative　angle　at　which

the　tail　is　thrown；　which　movement　depresses　the

rear　end　of　the　frame　and　thus　gives　the　supporting

planes　the　proper　angle　to　raise　the　machine；

through　a　positive　angle　of　incidence；　of　the　plane。



_Fig。　17。　Showing　changing　angle　of　body。_



THE　SUGGESTED　TYPE。In　Fig。　18　the　suggested

type　is　shown　with　the　body　normally　in　a　horizontal

position；　and　the　planes　in　a　neutral　position；

as　represented　in　position　1。　When　sufficient

speed　had　been　attained　both　planes　are

turned　to　the　same　angle；　as　in　position　2；　and

flight　is　initiated　without　the　abnormal　oscillating

motion　of　the　body。



But　now　let　us　see　what　takes　place　the　moment

the　present　type　is　launched。　If；　by　any　error　on

the　part　of　the　aviator；　he　should　fail　to　readjust

the　tail　to　a　neutral　or　to　a　proper　angle　of　incidence；

after　leaving　the　ground；　the　machine　would

try　to　perform　an　over…head　loop。



The　suggested　plan　does　not　require　this　caution。

The　machine　may　rise　too　rapidly；　or　its

planes　may　be　at　too　great　an　angle　for　the　power

or　the　speed；　or　the　planes　may　be　at　too　small　an

angle；　but　in　either　case；　neglect　would　not　turn

the　machine　to　a　dangerous　position。



These　suggestions　are　offered　to　the　novice；　because

they　go　to　the　very　foundation　of　a　correct

understanding　of　the　principles　involved　in　the

building　and　in　the　manipulation　of　flying　machines

and　while　they　are　counter　to　the　beliefs　of

aviators；　as　is　shown　by　the　persistency　in　adhering

to　the　old　methods；　are　believed　to　be　mechanically

correct；　and　worthy　of　consideration。



THE　LOW　CENTER　OF　GRAVITY。But　we　have　still

to　examine　another　feature　which　shows　the　wrong

principle　in　the　fixed　planes。　The　question　is

often　asked；　why　do　the　builders　of　aeroplanes

place　most　of　the　weight　up　close　to　the　planes？

It　must　be　obvious　to　the　novice　that　the　lower

the　weight　the　less　liability　of　overturning。



FORE　AND　AFT　OSCILLATIONS。The　answer　is；

that　when　the　weight　is　placed　below　the　planes　it

acts　like　a　pendulum。　When　the　machine　is　traveling

forward；　and　the　propeller　ceases　its　motion；

as　it　usually　does　instantaneously；　the　weight；　being

below；　and　having　a　certain　momentum；　continues

to　move　on；　and　the　plane　surface　meeting

the　resistance　just　the　same；　and　having　no　means

to　push　it　forward；　a　greater　angle　of　resistance　is

formed。



In　Fig。　19　this　action　of　the　two　forces　is　illustrated。　The

plane　at　the　speed　of　30　miles　is　at

an　angle　of　15　degrees；　the　body　B　of　the　machine

being　horizontal；　and　the　weight　C　suspended　directly

below　the　supporting　surfaces。



The　moment　the　power　ceases　the　weight　continues

moving　forwardly；　and　it　swings　the　forward

end　of　the　frame　upwardly；　Fig。　20；　and　we　now

have；　as　in　the　second　figure；　a　new　angle　of　incidence；

which　is　30　degrees；　instead　of　12。　It　will

be　understood　that　in　order　to　effect　a　change　in

the　position　of　the　machine；　the　forward　end　ascends；

as　shown　by　the　dotted　line　A。



_Fig。　20。　Action　when　Propeller　ceases　to　pull。_



The　weight　a　having　now　ascended　as　far　as

possible　forward　in　its　swing；　and　its　motion

checked　by　the　banking　action　of　the　plan　it　will

again　swing　back；　and　again　carry　with　it　the

frame；　thus　setting　up　an　oscillation；　which　is　extremely

dangerous。



The　tail　E；　with　its　unchanged　angle；　does　not；

in　any　degree；　aid　in　maintaining　the　frame　on

an　even　keel。　Being　nearly　horizontal　while　in

flight；　if　not　at　a　negative　angle；　it　actually　assists

the　forward　end　of　the　frame　to　ascend。



APPLICATION　OF　THE　NEW　PRINCIPLE。Extending

the　application　of　the　suggested　form；　let　us　see

wherein　it　will　prevent　this　pendulous　motion　at

the　moment　the　power　ceases　to　exert　a　forwardly…

propelling　force。



_Fig。　21。　Synchronously　moving　Planes。_



In　Fig。　21　the　body　A　is　shown　to　be　equipped

with　the　supporting　plane　B　and　the　tail　a；　so

they　are　adjustable　simultaneously　at　the　same

angle；　and　the　weight　D　is　placed　below；　similar　to

the　other　structure。



At　every　moment　during　the　forward　movement

of　this　type　of　structure；　the　rear　end　of

the　machine　has　a　tendency　to　move　upwardly；

the　same　as　the　forward　end；　hence；　when　the

weight　seeks；　in　this　case　to　go　on；　it　acts　on　the

rear　plane；　or　tail；　and　causes　that　end　to　raise；

and　thus　by　mutual　action；　prevents　any　pendulous

swing。



LOW　WEIGHT　NOT　NECESSARY　WITH　SYNCHRONOUSLY…MOVING　WINGS。

A　little　reflection　will　convince

any　one　that　if　the　two　wings　move　in　harmony；

the　weight　does　not　have　to　be　placed　low；

and　thus　still　further　aid　in　making　a　compact

machine。　By　increasing　the　area　of　the　tail；　and

making　that　a　true　supporting　surface；　instead　of

a　mere　idler；　the　weight　can　be　moved　further

back；　the　distance　transversely　across　the　planes

may　be　shortened；　and　in　that　way　still　further

increase　the　lateral　stability。







CHAPTER　V



DIFFERENT　MACHINE　TYPES　AND　THEIR　CHARACTERISTICS





THERE　are　three　distinct　types　of　heavier…than…

air　machines；　which　are　widely　separated　in　all

their　characteristics；　so　that　there　is　scarcely　a

single　feature　in　common。



Two　of　them；　the　aeroplane；　and　the　orthopter；

have　prototypes　in　nature；　and　are　distinguished

by　their　respective　similarities　to　the　soaring

birds；　and　those　with　flapping　wings。



The　Helicopter；　on　the　other　hand；　has　no　antecedent

type；　but　is　dependent　for　its　raising

powers　on　the　pull　of　a　propeller；　or　a　plurality

of　them；　constructed；　as　will　be　pointed　out　hereinafter。



AEROPLANES。The　only　form　which　has　met

with　any　success　is　the　aeroplane；　which；　in

practice；　is　made　in　two　distinct　forms；　one　with

a　single　set　of　supporting　planes；　in　imitation　of

birds；　and　called　a　monoplane；　and　the　other　having

two　wings；　one　above　the　other；　and　called

the　bi…plane；　or　two…planes。



All　machines　now　on　the　market　which　do　not

depend　on　wing　oscillations　come　under　those

types。



THE　MONOPLANE。The　single　plane　type　has

some　strong　claims　for　support。　First　of　these

is　the　comparatively　small　head　resistance；　due

to　the　entire　absence　of　vertical　suppo