CHAPTER IV
PLANNING A BIG AIRPLANE
As planned, the much-talked-of Air Derby around the world took placefrom Mineola Field, New York, on the 4th of July. A great crowd hadbeen attracted, owing to the extensive accounts of the affair in thebig newspapers for the past several months, and a thrilling hush fellover the assemblage as, at high noon, one after another of the famousflyers took off in various types of aircraft. There were four bigdirigibles, two of which started to cross the Atlantic at once, whilethe others took a northerly course with the intention of making thefinal hop from St. John's, Newfoundland, in accordance with severalprevious attempts of other aircraft. Besides these, sevenheavier-than-air machines started, all making for Newfoundland also.Four of these were flying-boats, two were seaplanes, and the other wasa double-propellered biplane.
Needless to say, the Ross boys and Bob Giddings and his father werepresent to see the machines off. They had arrived in the bigautomobile of the publisher, and were greatly interested in everydetail of the departure. Several of the contestants John Ross knew,having met them at some time during his flying periods, and it gave hima chance briefly to renew old acquaintanceship and personally to wishthem good luck on their long journey. Of course our friends would havegiven a whole lot to have been able to compete in the novel contestthemselves, but that was out of the question.
When the last machine had disappeared from sight, they took theirdeparture. Mr. Giddings left them at the office of the _DailyIndependent_, following which Bob drove Paul and John out to some ofthe city's beautiful parks. Late in the afternoon they again stoppedat the newspaper building and picked up Bob's father, thereupon turningthe car in the direction of Yonkers. Altogether they had passed a verypleasant holiday.
"Robert tells me that your plans for the new airplane, the Sky-Bird II,are just about finished, John," remarked Mr. Giddings, as they spednorthward along the smooth surface of Riverside Drive, with itsbeautiful greenery on the left and its fine residences at the right.
"Yes, sir," said John; "we have been devoting every spare moment tothem. Of course a good many changes had to be made to adapt conditionsfrom the little airplane to the big fellow, and to incorporate theextra pet features we all agreed upon were desirable. You know itnever pays to start building an important and costly affair like anairplane without having every detail thoroughly planned out, andperfect working drawings in hand. I think Paul will complete thedrawings early next week, including copies for accompanying thespecifications when we apply to Washington for patent rights. As soonas the drawings are done, we will drop in at your home in the eveningand show them to you."
"Good!" said Mr. Giddings. "I shall await them with great interest. Isuppose as soon as I approve these drawings, you fellows will all pitchinto the actual work."
"We surely will, sir," laughed Paul, while Bob, at the wheel in front,having caught some of the conversation, called back with energy:"That's just the size of it, dad."
"We have everything all ready," continued Paul. "The balsa-wood andspruce we ordered some time ago is on hand, and that will keep us busyuntil other needed materials arrive. We have repaired the bigexhibition building in the old fair-grounds, put on new double doorsand purchased a good Yale lock for them. John and I have taken ourworkbench and tools over there, and Bob has helped us rig up a nicelittle five-horse power motor and small handsaw, also a circular saw,home-made sand-drum, a small planer, and a boring-machine. Thatbuilding is dry, and has lots of room in it for housing the newairplane as it grows to maturity. When cold weather comes we caneasily install a couple of heating-stoves to keep ourselves comfortableand protect our materials and the machine from frost damage."
Mr. Giddings expressed himself as well pleased with these arrangements.As he noted the foresightedness of the young mechanics his confidencein them expanded.
"Don't hesitate to order anything you need, young men," he said warmly."Have them send the bills to me. If my trust in you is misplaced, I amwilling to stand the consequences. This is not only the best kind of apractical education for Bob, but it is good business training for allof us. Go ahead; go ahead!"
With such strong encouragement, is it any wonder that the three youngmen continued their operations vigorously? Not one of them scarcelywanted to stop long enough to eat and sleep, _a la_ Edison; and as itwas now summer vacation time, Paul and Bob were able to be with Johnall day long in the old exhibition building. Neighboring boys and evenolder people hung around the open doors to watch operations, but thebuilders were careful not to let them get close enough to gain anyideas which might be harmful to their interests.
On Tuesday evening of the week following the start of the Air Derby,John and his brother put on their best clothes and hied themselves overto the Giddings home. In Paul's hand was an envelope containing theprecious plans for the Sky-Bird II--completed at last by the youngdraftsman, and ready to be shown to the financial member of the quartet.
When they were all seated in the Giddings library a little later, Mr.Giddings scrutinized the plans with every evidence of satisfactionwritten upon his strong features. Now and then he would ask aquestion, as Paul explained view after view and detail after detail.At length he pointed to an oblong object situated in the pilot'scockpit just under the dashboard. "What is that?" he asked, curiously.
"That is what John and I call an 'automatic pilot,'" answered Paul."It is a new form of stabilizer, and made so as to overcome the defectsof others which are on the market. A stabilizer should automaticallykeep an airplane on a fairly level keel no matter how air conditionsare, even so steady that it will travel along on its course for aconsiderable distance with the pilot paying no attention to hiscontrols, perhaps eating his lunch or reading his orders."
"A mighty useful contrivance," commented Mr. Giddings. "I should thinkthat would also prevent lots of accidents in bad winds."
"It will--if it turns out as we expect," Paul remarked.
"Give me the full details of this," was the request. "Remember, I amnot much of an airplane man."
"Well," said Paul, "you know, sir, that it is far more difficult todrive an airplane than to guide an automobile, not merely because youhave two steering-gears or rudders to take care of, one for sidewiseand the other for up-and-down travel, but also because there aremovable planes in the wings of the machine, which have to be worked totip or 'bank' it when making a turn or to keep it on an even keel whena gust of wind strikes it. The 'rudder' is the vertical plane at thetail of the machine, and is used for steering sideways, while the'elevators' are the two horizontal movable planes just below therudder, which are used for steering up and down. Similar planes to thelatter, one situated in the back edge of each upper wing, are called'ailerons,' and one or the other is raised or depressed according towhether the aviator wishes to bank to the right or left.
"The driver of an automobile has nothing to do but watch hissteering-wheel, and be ready to touch a pedal when he wishes to slow upor go faster or stop. If he makes a curve he does not have to bank hismachine owing to his comparatively slow speed; but the aviator,traveling much faster through the air, must do this, bringing hisairplane to a steep angle if he makes a very short turn. If he doesnot calculate just right, he is likely to turn upside down and meetthis death in a nasty fall.
"While the careful automobilist can always see the road in front of himand avoid rough spots or obstacles before he reaches them, the aviatorcannot do this. It is true that he can see another airplane if it getsin his way, or a church steeple when he is flying low; but his greatestdangers are in the clear air itself, where they cannot be detected. Hemay suddenly drop into a 'hole,' which is really a downward current ofair, or he may get a terrific bump when he strikes a rising current. Afreakish whim of the winds may unexpectedly take away the air supportfrom under one of the wings, and he will lurch and dip sharply to oneside."
"And I suppose sometimes lose all control?" said Mr. Giddings.
"Yes, sir; that
has very often happened," put in John. "A flyer friendof mine took a nasty tumble that way near Cleveland last year, breakingthree ribs. It's a wonder he wasn't killed."
"The pilot is blind to these pitfalls," went on Paul. "He must controlhis machine largely by intuition and the sense of feeling, although theveteran airman, John says, can tell a good deal about what to expectfrom the nature of the earth or clouds below him."
"That's true," averred John. "The closer you are to the earth the moreyou will feel the 'bumps,' as we call them. They are a whole lot likethe waves of the ocean, only invisible, and there will be one straightover every protuberance or depression of size in the surface of theearth. Mountains, hills, houses, lakes, valleys, rivers, forests, allcause bumps or holes in the air up above them. At one thousand feetthey are pretty bad. At ten thousand feet they are scarcelynoticeable. That's why most pilots prefer to fly high whenever theycan."
"What causes the air to act in this way over such configurations?"propounded the publisher.
John looked helpless, and smiled. "You've got me there," he admitted."I haven't had the opportunity to study aerostatics the same as Paulhere. He can probably tell us."
"I'm not through my course yet," reminded his brother, "but I think Ican answer that. The air surrounding the earth is a great belt fortyor more miles through and is of an even thickness. As our globe sweepsthrough it, the lower stratum of air naturally sinks down into thevalleys and like depressions. This action pulls down the upperstretches of air, thus creating what are termed 'air-pockets' or'air-holes.' Very dangerous they are, too."
"That is plain enough," declared Bob. "Now, dad, let Paul go onexplaining this 'automatic pilot.'"
"If the aviator is enshrouded in fog or tries to sail through a heavybank of clouds, he is quite likely to lose all sense of direction,"continued Paul. "He will not know whether he is banking or travelingon an even keel. Sometimes pilots have come out of a low cloud to findthemselves dangerously close to the earth and in an awkward position,perhaps in a steep bank, a side-slip, or even in the terrifyingnose-dive, and they have not had time to right themselves beforecrashing to earth. So you see that before flying can become reasonablysafe, some way must be found of keeping the machine automatically on alevel keel.
"To operate this stabilizer of ours all the pilot will have to do is toguide the rudder with his feet. The automatic pilot works the elevatorand the ailerons. It takes care of 'bumps' and 'holes' and sees thatthe machine banks at just the right angle on the turns. This makes theoperation of an airplane containing the stabilizer even more simplethan running a motor-car, because you do not have to worry about goinginto different speed gears when climbing or descending. You willnotice on this drawing that strong piano-wires connect the instrumentswith all the necessary controlling planes of the machine."
"Instruments?" interrogated Mr. Giddings. "I thought there was butone."
"No; there are two stabilizers, as you will see,--here, and here," wasPaul's response, pointing his finger to the parts. "But, as each oneis exactly like the other in its construction, only the one has beendrawn in detail. The other stabilizer runs lengthwise of the cockpitand takes care of the elevator. Both of these are operated bycompressed air, which proceeds from a little tank, right here. Thetank is kept supplied by two tubes which lead into it, and each ofwhich joins a small pump operated by a fan which is right here on eachside of the fuselage where the onrush of wind will keep it humming asthe airplane travels.
"Each equalizer has a bore in it half-filled with mercury, working agood deal like a carpenter's level. If the airplane tilts to one sideor the other, the mercury will try to keep its level and willimmediately flow to the high side of the bore. At each end of thismercury tube there are electrical contact points. As one becomessubmerged in the mercury by a tilting of the plane, a connection ismade whereby two electro-magnets are energized on that side. One ofthese magnets closes an exhaust-valve, and the other opens aninlet-valve, in the compressed air tank. At once air is forced intothis double cylinder, which you see at the bottom of the stabilizer,filling the half which is to operate its own set of rudders; and apiston begins to work inside. The piston is connected to a toothedrack, as you will note, causing this to turn a sector engaging it. Thecontrol wires connect with this sector."
"Very clever arrangement; but I don't quite see how, in banking, theailerons can be brought back automatically to a neutral position assoon as the turn has been completed," ventured Mr. Giddings.
"John and I have provided for that, while Bob is responsible for theelectrical features I have just mentioned," said Paul. "You willnotice that at the top of the mercury channel there is a dividing wall.A tube runs from the left side of this wall to the right wing of theairplane, also from the right side of the wall to the left wing. Atthe end of each tube there is what we call a 'venturi tube.' This is akind of suction device operated by the wind. The wind which blowsthrough the left venturi tube sucks the air out of the right-hand sideof the mercury tube, and the right venturi tube sucks the air out ofthe left-hand side of the mercury tube. The stronger the wind, thegreater the suction. Now, when making a turn to the right the leftwing must travel faster than the right wing, and so there must be moresuction in the left venturi. This produces a greater suction in theright-hand side of the mercury tube, which draws the mercury up on thatside and down on the other, until the proper electrical contact isbroken and the ailerons are returned to neutral position."
"Can the mechanism be thrown out of gear when desired? I should thinksuch a feature might be desirable," remarked Mr. Giddings.
"Indeed it is desirable, sir," declared Paul. "No red-blooded pilotwishes to sit still and let his machine run itself all the time, nomore than an automobilist. That would spoil all the sport. By merelydisengaging the automatic pilot's wires here at the sector--the work ofa couple of seconds--the airplane is ready for hand control."
"How much does it weigh?" was the gentleman's next query.
"A trifle less than a hundred pounds."
"That oughtn't to handicap an airplane any."
"Not a bit," said Paul.
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