The Aviator and the Weather Bureau

In order to qualify as meteorologist competent to confer with aviators, it seemed desirable to become personally acquainted with some of the conditions that confronted them. As a matter of professional acquirement therefore, I was glad to accept an invitation to go aloft after the necessary official arrangements had been made with Washington.

This trip was in line with the previous endeavors of applying practical meteorology to the science of flight and appropriately extended the work which was begun in San Diego with Chanute and the sea-gulls fifteen years before.

Object of Flight.—I wished to put myself in the student’s place and learn at first hand the practical facts he demanded from weather observations and to acquaint myself with everything possible that might be of value to an aviator. There were two definite things of which I desired knowledge: first, to determine the height of the upward trend of the sea-breeze over Point Loma which causes the mysterious “woolly” of a score of years’ acquaintance from a yachting standpoint; second, to observe the extent, form, and composition of the velo cloud which is the characteristic sun-cover of California.

Preparations for the Ascent.—Aviator Instructor Oscar Brindley (the 1915 winner of the Curtiss trophy), in military tractor No. 50, was assigned as pilot. It may be stated here that the accepted definition of aviator is a pilot of a flying-machine heavier than air. The airplane used in my first flight (see Fig. 13) was made in Los Angeles and is the present standard army model. This tractor has an 80-horsepower engine and 8-foot propeller. It is 21 feet long, has a wing-spread of 38 feet, supporting area 364 square feet, and a flying radius, with two persons, of 300 miles. The maximum altitude attained with this model at San Diego was 13,000 feet. Before being placed in service the machines are thoroughly gone over at the repair shop (see Fig. 22), and the motors are run at full speed for twenty-four hours, after which they are taken down and subjected to scrutiny for possible defects. All of the struts, guys, and wires are closely examined; the boltheads are all drilled, wired, and soldered so that no amount of vibration will loosen them. Regardless of the length of the flight, each machine, before going up again, is given a rigid inspection and not until the mechanicians have tested every part is it pronounced ready.

Not being prepared with a regulation aviation suit, I was loaned a leather jacket by one officer, face-goggles and safety helmet by others. I then took my place in the observer’s seat forward and was strapped into it with the safety belt (see Fig. 12). I was cautioned to let my body give way as the waist-controls were moved from side to side and not pay any attention to the steering rudder wheel which had a way of mysteriously revolving, advancing and receding.

In cranking an airplane, a certain formula is always gone through. The mechanician at the propeller calls out, “Close!” The aviator closes the switch and repeats the word. This short-circuits the ignition apparatus so that no spark occurs in the cylinders. The propeller is turned in order to introduce explosive mixtures into the cylinders. When ready to start the mechanician says “Open!” The aviator opens the switch and repeats the word. The charges in the cylinders then fire when the propeller is turned.

After the engine starts, the machine is “trimmed” by helpers and jockeyed for a favorable “take-off” into the air. (See Figs. 14, 15.) This model of airplane climbs on a gradient 1 to 7; its minimum speed is 41 miles per hour. In other words, if the speed is less than 41 miles per hour the machine will not fly horizontally.

The Ascent.—The tractor was headed into a 30-mile northwesterly wind so that the “take-off” was quick and easy; there were only a few seconds spent rolling over the field, when the airplane left the ground and I felt the never to be forgotten cushioning feeling of the air. For ten seconds there was experienced a decidedly weakening nervous chill, which occurred to me once before when making a high dive from a spring-board. It was the sort of physiological disturbance that can only be counteracted by immediately pulling one’s self together saying, “Well, here goes nothing!” The momentary depression was immediately followed by a corresponding elation of feeling which strange to say did not leave me during the trip and is always associated with thoughts of the journey. There was no dizziness, although I am peculiarly susceptible to the least change in balance. The earth did not recede as we progressed steadily upward; we seemed part of the earth, but not of it. Although the airplane reached an altitude of 3,000 feet in a comparatively few minutes, the barometer falling from 30.0 to 27.0 inches, the decreased bodily pressure was not at all noticeable.H

Next to the supporting quality of the atmosphere I had noticed the 70-mile blast of air as the airplane pushed its way steadily onward and upward. Naturally, the exhaust of the motor in addition to the roar of the wind made conversation impossible. Some airplanes have telephone communication between observer and pilot. (See Fig. 9.) During one flight in a machine not so equipped, the passenger noticed the breaking of some apparatus. Knowing that it was impossible to make himself heard he hastily scribbled the word “Accident!” on a bit of card, whereupon the pilot shut off his engine and glided to earth.

Two-thousand Feet above Point Loma.—Carrying out my suggestion as to investigating the “woolly,” the pilot drove the machine straight for Point Loma and those unseen aërial breakers. Suddenly there were two distinct “wallops” and I felt the fuselage beneath me respond as if struck by a stuffed club. There was evidently first a surge then a drop, and it was the descending current of air that deprived the airplane of the supporting medium, hence the shock. Point Loma itself, from this altitude, and seen directly from above, looked very like a barracuda’s backbone—long, low, and ugly. Although this peninsula (see Fig. 21) is less than 500 feet high it so effectively deflects the prevailing northwesterly wind that the upward surge has been noticed by aviators at an altitude of 4,000 feet. It is no wonder then that these descending winds, called “woollies” (from their churning the water into isolated masses which look like tufts of wool), are dreaded alike by yachtsmen and birdmen. They have been known to carry away topsails from too closely venturing schooners and student aviators always give the vicinity of Point Loma a wide berth.

No Winds Aloft.—We had not changed our direction since leaving the ground, but after passing over Point Loma the airplane was put sharply on a port course. I had been expecting this and must confess, somewhat dreaded it, innocently thinking that a 30-mile wind added to our 70-mile rate of speed would “heel” the craft to an uncomfortable angle when the course was changed from northwesterly to southerly. What was my astonishment to find that the putting about was unaccompanied by any of the nautical motions such as tilting or canting. Theoretically one may be ever so well grounded in physical laws but it seems to take actual experience to bring their truth home to us. Of course there can be no wind in the air; when we entered the air it was moving 30 miles an hour in relation to the earth but as soon as we were free from the earth the velocity of the wind had no effect on our flight. No matter how strong the gale, so far as it concerned the airplane, if the wind be steady no difficulty is experienced; the aviator is concerned only by wind-shifts.

The Velo Cloud Seen from Above.—In kindergarten days I remember that one of the first questions I asked was “Are clouds smoke?” And this early query was really first answered in the air. Fog on a mountain top may be cloud, but somehow cloud free from close proximity to the earth seems different.

The machine was put through the cloud blanket much as a horse takes a hurdle; it seemed unlike fog and more of a palpable substance. As we emerged, the sun was shining on it like a silvery sea with gently undulating surfaces and it looked for all the world as supportable as layers of cotton-wool. Many times have cloud-banks from mountain tops been observed, yet the upper side of the velo cloud from a flying-machine looked very different. The cloud was only four or five hundred feet thick and extended inland a few miles in irregular outline. The seaward edges of the velo cloud were not ragged, and apparently paralleled the coast for 10 or 15 miles.

Such was the exhilaration and confidence the air gave that I can understand how parachute jumpers confidently step off into space, for to them the air is a supporting medium no more terrible than a transparent sea to a good swimmer. I believe that the record parachute drop was made in 1916 by Colonel Maitland, of the English Royal Flying Corps, who descended in a parachute 10,000 feet from an airplane. Fifteen minutes was occupied in the descent.

Ease of Vision at 3,500 Feet Altitude.—At this altitude the ease of vision is most remarkable. At this height, with perpendicular vision, the eye is possessed of wonderful powers. In those “solitudes august with stars” men not only “mount up with wings as eagles” but are given the eagle’s unobstructed vision. Birds have been credited with much too keen vision. From this height of several thousand feet every object stood out with remarkable distinctness. Automobiles racing along the El Cajon boulevard to Lakeside were readily picked up with the unaided eye although 20 miles away. Looking down over the aviation field the long compass mark and the wind-direction pennant (Figs. 19 and 20) were easily distinguished. The bay and ocean, however, gave the most remarkable revelation, for the bottom of the bay and the shallow ocean shore were plainly discernible. The absence of water as well as air refraction explains why submarines cannot hide from an airplane: one of the army aviators told me that a submarine cannot ordinarily sink so low that it cannot be seen from an airplane.

Color of Landing-ground Important.—Owing to the absorption and reflection of sunlight, there is a distinct variation in the character of otherwise similar landing-ground. A field, dark from recent plowing (or burning), will heat the air over it faster than will a field of stubble, hence over the former field there will be the greater air disturbance, and this will affect the ease of landing. Air is heated by contact and convection. One of the aviators said that recently he was descending, and had all but reached the ground when a localized convectional current hurled his machine upward some distance but immediately afterward deposited him on the ground without damage.

Spiraling Down 3,000 Feet.—Speeding ever in wide circles the course lay southeast over the upper part of San Diego Bay. The city of San Diego presented the usual checkerboard appearance (Fig. 16), and even at this altitude it would seem easy to drop an orange at almost any point. The velo cloud was lifting and we could see the gradual disappearance as it melted rather than drifted from North Island. (See Fig. 17.)

The gliding descent was made from an altitude of 2,500 feet, starting above San Diego. As the aviation school was approached, we could see a number of machines in the air, three below and two above us, circling about like hawks. And, like soaring birds, these machines had their air-lanes, designated courses and levels being devoted to the different classes of machines. The landing was made without incident and the hour’s flight was ended.

Outline of Meteorological Work at the Aviation School.—At the close of the lecture detail, the attention of the student aviators was called to the importance of their having as thorough knowledge as possible of the fundamentals of meteorology. The application of these fundamentals to the analysis of air conditions met with in their daily flights was shown to be essential. Investigations as to varying wind direction were taken up by one of the staff instructors by the use of small parachutes to be dropped at different altitudes. (See Fig. 8.) Through the coöperation of the local official in charge of the San Diego Weather Bureau station, duplicate signal sheets were available from which the student officers made their local weather maps. From these maps and their own flights, they could arrive at some relationship between the actual and the theoretical 3,000- and 10,000-foot level maps prepared from the Bigelow formula, as used by the Bureau. Lectures were given on temperature and its distribution; winds, moisture, and clouds were also made part of the course, one of the papers of the BureauI being reprinted by the aviation school by permission of the Chief of the Bureau and used as a textbook. The Weather Bureau furnished the station with a standard set of meteorological instruments so that the student officers could become perfectly familiar with the regular equipment at the Weather Bureau stations.

Extending the Usefulness of the Bureau to the Aviators.—Practical utilization by the aviators of this district of the information possessed by the Bureau has received considerable impetus during the past six months. During the cross-country flights of April and May, 1916, the Los Angeles station was directed by the Chief of Bureau to furnish weather and flight conditions between San Diego and Los Angeles. With the aid of the general weather-map data from the regular stations, and special observations of wind, weather, and fog conditions on the immediate coast near Los Angeles, and on Mount Wilson, it was possible to issue satisfactory forecasts of flying conditions. The eye-observations of fog-heights as determined by the Weather Bureau coöperative station at the Mount Wilson Solar Observatory were especially valuable. From this mountain (6,000 feet elevation) it is possible on a good day to see the whole length of the coast from Point Firmin, San Pedro harbor to Point Loma, San Diego Bay. Knowing different levels, the observer at Mount Wilson was able to give actual thickness and extent of the fog-belt and its past twenty-four-hour history.