My 10,000 Flights in Untried Planes (Oct, 1931)
My 10,000 Flights in Untried Planes
By Frank T. Courtney
CAPTAIN FRANK T. COURTNEY began flying in England in 1911. During the war, he served as a member of the Royal Flying Corps. In 1919, an accident destroyed his chance of making the first nonstop flight across the Atlantic. In 1928, he attempted to fly the Atlantic from east to west. The engine caught fire in mid-ocean and he drifted for twenty-four hours. He is a famous racing pilot and has tested more new planes than any other flyer.
JUST for fun, the other evening, I jotted down a list of the planes I have ridden into the sky on their initial tests. It totaled more than a hundred different types.
For fifteen years, I have been a freelance test pilot in England, on the Continent, and in America. During that time I suppose I must have made 10,000 test hops—possibly more than any other pilot in the world.
My most fascinating adventure in test flying began one fall day in London. A relatively unknown Spaniard, Juan de la Cierva, invited me to lunch. He had brought a strange “flying windmill” from Madrid, and asked me to fly it in its early tests. That was in 1925. For eighteen months afterwards, I did all the flying on the five experimental machines that led to the present autogiro. The inside story of those early days has never been told.
One of our early problems was getting the vanes spinning for the take-off. The windmill of the autogiro is not braced like the wings of an airplane. The vanes, free to move up and down, are held rigid during flight by centrifugal force pulling them outward. Aloft, the rushing air keeps the vanes spinning at sufficient speed to maintain this invisible bracing. But on the ground, the vanes must be spun up to 100 revolutions a minute artificially before the take-off can be made. This is now done through a drive from the motor.
IN THE beginning, I had to taxi back and forth across the field to start the windmill going. Then Cierva attached knobs to the underside of the four vanes. Mechanics wound a long rope outside these knobs then ran with the end, spinning the vanes as a boy spins a top. One of the “mechs” who didn’t get much fun out of running suggested tying the end of the rope to a stake and taxiing the ship away, spinning the vanes in this manner.
It sounded all right and we tried it. I opened the throttle and the ship moved down the field faster and faster, the vanes streaking around over my head.
They were spinning at more than a hundred revolutions a minute when the end of the rope whistled through the air. There was a loud splintering crash. The ship rocked and trembled. I cut the gun and stopped. The end of the rope, whipping through the air, had sliced through the fin and rudder as cleanly as a knife!
Another accident in those early days taught us an important lesson. The first autogiro I flew had the windmill simply mounted on an old Avro fuselage with the landing wheels comparatively close together.
IN THE early part of 1926, I was giving * an exhibition with this machine at Paris. The sky was ugly when I took off from Villacoublay field. The wind was blowing in gusts. Only the fact that a large assemblage of dignitaries was present made us go on with the demonstration. As I circled the field, the strength of the wind increased. It was a howling, forty-mile-an-hour gale when 1 came down to land.
The ship sat down in the teeth of the wind, not a hundred feet from the cameras. It landed squarely on both wheels. Then a side gust struck the spinning vanes, rocked the ship on its narrow landing gear, heeled it over. The long, flail-like arms threshed into the mud, Hinging it away like sparks from an emery wheel. Then the craft crumpled, lay still.
I crawled out, muddy but unhurt.
As a result of that spectacular crack-up, the wide landing gear, giving greater ground stability, was adopted as part of the design of modern autogiros. Another improvement resulted from a hair-raising crash at Southampton, England, a few months later. Two vanes of the rotor fell off in mid-air.
About 150 feet up, I noticed excessive vibration in the vanes. Picking out a long line of trees, I steered directly above them. They would break my fall in the event of a crash. At the end of the line, the vibration was no worse and I swung over the field at 125 feet. Suddenly the vibration increased. The vanes were shaking violently. I started down. At that instant, there was a loud crack above my head.
The steel main spar of one of the vanes, crystallized by the vibration, had snapped. The long blade of the windmill broke free, whirled into space. I had one glimpse of it fluttering off like a broken blade of grass. After that, I saw nothing. The uneven jerking of the remaining blades rattled me about in the cockpit like a pea in a tin can. My shoulders were battered black and blue. Fifteen feet up, a second blade tore away from the reeling craft. It fell like a stone.
While I was in the hospital, mending half a dozen broken bones, vertical hinges in addition to horizontal hinges were fitted to the vane spars. This prevents vibration on modern machines and makes impossible a repetition of my accident. Today, the autogiro is less likely to break in the air than an airplane.
BY BRINGING out weak points, revealing needed improvements, and helping adjust and alter new machines, the test pilot plays an important part. Most of the work we do, however, is not with radically new designs like the autogiro. It is with slight variations of well-known types. In the air, the test flyer must note every peculiarity of a new craft. And he must be able to trace the peculiarity to its mechanical source. Of necessity, he must be not only an expert flyer but a trained engineer as well.
I started in aviation in 1913, working without wages at the old Claude Grahame-White factory, near London. At that time, the greatest test pilot in England in my opinion was Fred Raynham. His narrow escapes would fill a book. One of them gave me the first rule I always observe in the testing of all new machines.
Raynham was up in a twin-engined Avro bomber at Brooklands, in the spring of 1914. High in the air, he closed the throttles to glide down for a landing. Instantly the tail dropped, the nose reared skyward. He slapped on the engines again, just in time to prevent a stall. Half a dozen times, the same thing happened. The ship hadn’t been weighed for balance and had taken off tail-heavy. When the engines were wide open, the gale from the propeller gave sufficient lift to the elevators to hold the craft level. But as soon as the blades slowed down, the tail of the plane sank.
In this particular machine, the pilot sat far at the nose of the fuselage; the observer back behind the wings. The two tractor propellers were set close together, their glittering circles almost touching the narrow top of the dragon-fly body. Later, measurements showed that these deadly disks whirled so close together that less than three inches clearance on either side would be given a man crawling along the fuselage top. And the tip of a spinning propeller will shear through the body of a man as cleanly as a razor cuts a cotton thread.
THE observer, watching from the rear cockpit, realized this. He also understood why Raynham couldn’t go down. Pulling himself out of his cockpit, this unsung hero of the air clung batlike to the upper surface of the fuselage while the big ship rushed at top speed through the sky. An inch at a time, he dragged himself toward the tiny “tunnel” between those whirling knives. Flattened to the canvas, he edged between, praying the rocking ship wouldn’t lurch in a gust or down current. When he dropped into the forward cockpit beside Raynham, his weight balanced the plane and permitted a landing.
Raynham described to me his feelings at the time and ever since, I have never hopped off for a test flight without weighing a ship to be sure it is properly balanced.
This is comparatively easy. The two landing wheels and the tail skid are placed on scales. The readings of these instruments, taking into account their distance from the center of lift of the main wings, on which the plane is balanced like a seesaw while in flight, shows whether the ship is properly balanced. Once, I weighed up a very light pursuit plane in this way. A mistake had been made in construction and it was 100 pounds tail-heavy. If I had taken the plane into the air, I would have been piloting flying dynamite.
Besides weighing up a new ship, I observe a number of other rules. First, I climb into the cockpit and make sure the controls are working properly.
NOT long ago, a $20,000 plane was wrecked at a Long Island field because the pilot failed to “waggle” his stick before the test flight. Had he done so he would have found that the ailerons had been hooked up backward. In another case, a huge air-liner was washed out in New Jersey on its first test flight. A careless mechanic had attached the elevator control wires in reverse and the pilot hadn’t noticed it until he tried to take off.
Another thing I do is adjust the controls until there is no friction or play. Not one plane in a hundred has the controls in perfect adjustment. When I recently made tests of the huge Curtiss “Condor” at St. Louis, Mo., I altered the rudder several times by a method I devised and have used for several years. To save expense, I rigged up a plywood box which I bolted to the rudder in different positions, one time adding area to the balancing surface ahead of the point where the rudder was pivoted, and again to the rudder itself.
Each time I would hop off and fly the plane, noting how it steered. When I found the best adjustment, -a new control surface having the same ratio of balance area and rudder area was constructed. This saved the expense of building a whole series of new rudders in order to discover which would give the best results.
BEFORE I even start the engines on a testing job, I may spend hours sitting in the cockpit. I go over the instruments, get familiar with my surroundings, practice just what I will do in every emergency I may meet in the air. I cut the switch and shut off the gasoline a hundred times, until the movements become subconscious. Such practice has paid for itself a dozen times over.
For instance, not long after the war, I took off on a test flight from a small English field in a de Havilland bomber with twin Liberty engines. At the right of the pilot’s seat, five fuel pipe lines met, with stopcocks that let the pilot regulate the fuel flow.
Four hundred feet in the air, just over the edge of the field, one of these stopcocks broke off. A one-inch jet of high-test gasoline shot from the end of the broken pipe. In an instant, the floor of the cockpit swirled with explosive fuel. The slightest spark would have made the ship a roaring furnace.
Choking in the fumes and half-blinded by spray on my goggles, I instinctively found the switch and cut the roaring engines. I had just sufficient height to swing in a half-circle, push the landing wheels through the bordering hedge, and sit down in the field. Twenty feet less height would have spelled a certain crash.
That narrow squeak emphasizes another rule I since have followed: Have a big field for a test flight. Then if the unexpected happens, there is plenty of room in which to maneuver.
One ship I tested turned into a mechanical broncho high in the air. If I had not had a big field to land in, I would have washed it out in getting down. The elevator flaps had balancing areas which extended ahead of the point where the elevator pivoted. Their purpose was to make the controls easy to operate. In this plane too much area had been allowed for this purpose.
AS LONG as the engine raced at full throttle, the slipstream from the propeller, which passed over the elevator surface but not over the balancing tips, gave the elevator more power per square foot than the balancing tips. But as soon as I throttled down at the top of my climb, the stick jerked out of my hand. The balancing surfaces, out of proportion, rocked the elevator up and down. The ship reared and plunged in the sky. I shoved open the throttle. The plane flew smoothly again. I was bewildered. The only thing I could do was to land with the motor on and trust to luck when I cut it.
Only three or four inches up, I skimmed the field going 120 miles an hour. Then I cut the pun. The plane bounced all over the field. A tire blew out. The ship slewed into a ground loop and stopped in a cloud of dust, only slightly damaged. Only a big field made a landing like that possible.
The longest time I ever spent on a test job was on a large triplane bomber in which two 500-horsepower motors, housed in an engine room in the cabin, drove four propellers out on the wings through gears. Running these gears in the flexible structure of an airplane was a very different thing from running them in the engineering shop, and gear trouble was always cropping up. It was two and a half years before tests were completed.
The shortest time I ever spent on a test job was in trying out the world’s ugliest plane. It was named “The Ape.” A high grasshopperlike landing gear permitted rough landings and variable wings and tail allowed a thousand and one experiments to be made with the queer “flying laboratory,” which was designed for researches by the Royal Flying Corps. All I was required to do was to get it off the ground.
BUT probably the queerest machine I ever tested was a strange “cube lift” biplane. A rich enthusiast designed it to revolutionize flying. As engineers know, there is a limit to the size of big planes. As they grow larger, the wing surface advances as a square while the increased weight advances as a cube. So the ratio of weight to wing surface is increasingly greater the larger the plane is built. On the other hand, dirigibles advance in lifting volume as a cube and in head resistance as a square, so they become more efficient as they grow in size.
This designer maintained he had found a way to build large wings so their increase in lifting power kept pace with their increase in weight. All he had done was decrease weight by leaving out bracing struts and building his wing tips perilously thin. In the air, these tips flapped and fluttered, ready to fold up in the first hard gust. When I flew the plane, I heaved a sigh of relief when I got down alive.
Fortunately, before I made that flight I waited for a perfectly calm day. That is another of my rules that has paid rich dividends. I never go up on a first flight in a strange ship in gusty weather. Only once have I broken this rule. That was in an emergency in 1919 and afterward I wished I hadn’t.
A big twin-motored distance plane had been built for me to fly the Atlantic nonstop in a race with Harry Hawker and Capt. John Alcock, the first man to achieve the honor in a heavier-than-air machine. Both their planes were already in Newfoundland when my machine was finished. Time was precious. A mean cross-wind was blowing at the Norwich field, but we decided to go ahead with the tests. I had just left the ground when the upwind motor cut out. The other engine, combined with the wind, pulled the ship around before I could jerk back the throttle. There was no time to straighten out. The plane crashed, wiping out the landing gear, wrecking the lower wing, and destroying my chances of being the first airplane pilot to bridge the Atlantic in a single hop.
SOMETIMES testing a new fitting is more dangerous than trying out a whole new plane. I remember once an inventor hired me to test an “air brake” to slow down a plane quickly on landing. It was a flap that popped above the main wing like a jack-in-the-box when I pulled a lever in the cockpit. The sudden added resistance slowed down the plane close to the danger point.
The idea sounded all right, but I was skeptical. I climbed to 10,000 feet before I pulled the release lever. In a flash I was hurled forward against the double safety strap I always wear in testing planes. The ship dropped like a stone. I have no idea how far we fell before I found the lever and pulled the flap inside. It had worked too well. As you know, the upper surface of a wing contributes two thirds of the lift and the under surface one third. This is the result of air currents forming a partial vacuum above by the wing curve. The flap had disturbed these lifting currents as well as formed sudden added resistance. If it had popped out near the ground in landing, the ship would have dropped like a lead pancake.
The effect of this flap was exactly opposite that of the Handley-Page wing-slots which I tested early in 1922. These narrow auxiliary wings in front of the main supporting surfaces keep the air currents going steadily over the top of the wings even at low speeds. This prevents the pilot from losing control and going into a tail spin that may end in a crash.
AS I look back on my fifteen years of test flying I think one of the biggest scares in all my experiences was over something that never happened.
I was testing the “Awana,” a giant troopship, after the war. This folding-winged monster could carry more than twenty soldiers at a load. On the test flight, we placed 120-pound bars of lead in the cabin to represent the men, and one bar in the pilot’s compartment to take the place of the navigator. On the last test, a speed run, the chief engineer went along. With throttles wide open we roared down the field 200 feet above the ground. Going two miles a minute, we heard a terrific crash behind us. We thought the main wing spar had broken. I cut everything. Each breath, I expected the wings to crumple and hurl us to the ground. We were in a cold sweat when the wheels touched and we were safe. The instant the plane stopped rolling, we piled out, going over the wings, fuselage, and tail. Nothing was wrong.
We were on the point of ordering the pulling apart of the wings so we could look inside—meaning a loss of thousands of dollars—when we stumbled on the secret of the sound. The bar in the cockpit had broken free and during the speed trial the vibration from the thundering engines worked it back along the floor. Between the cockpit and the cabin there was a five-inch step. As we raced at full speed, the 120-pound bar had made the drop to the wooden floor below, the sound reverberating in the cabin like the crash of a giant timber and naturally giving us a fine scare.
A TEST pilot, who risks his life in untried planes, must be prepared for anything. The surprise may be a false alarm or a desperate crisis. In the world of flying men, he plays a role replete with thrills and drama, which he has to treat as ordinary mechanical happenings. He is using the sky for his laboratory in work that plays its part in bringing better planes.
MORE fine articles on the way from this great flying man. Watch for them in early issues of Popular Science Monthly. —The Editor.
Capt. Courtney’s FIVE RULES FOR TEST FLYING
1. . . Weigh the plane to be sure it is in perfect balance before trying to take off.
2. . . Sit in the cockpit, switching on and off the ignition and fuel until these emergency movements become instinctive.
3. . . Make sure the controls are hooked up correctly by “waggling” the stick.
4. . . Select a large field for the initial tests so there will be plenty of room to maneuver in an emergency.
5. . . Never take an untried plane up unless the air is calm.