TRACKING AND DODGING STORMS

Evening Post, Volume CXXIII, Issue 67, 20 March 1937, Page 10

TRACKING AND DODGING STORMS

ELABORATE REPORTING NETWORK

The commencement of a flying-boat service across the Pacific to J\ew Zealand has brought into the circle of immediate interest several aspects of aviation to which even air-minded New Zealanders have hitherto paid little attention—for want of information. Foremost among these is the specialised study of meteorology, the conversion to practical use of some branches of weatherlore that, in the absence of highly-developed aviation, have been almost academic. The product of this meteorological research, which goes on from hour lo hour throughout the day, is very different from the weather forecast that can be condensed into a phrase such as "fair lo fine."

The greater part of the business of flying—not Saturday afternoon flying— is done from the ground, and of the ground organisation the meteorological work is at least as important as any. It is a full partner with the flying, the radio, and the navigation sections. The weather system of the South Pacific has still to be tied together, as plans work out in practice and as experience dictates during the next few months of exploratory flying, for the period of survey flights is required more for the gaining of knowledge of weather conditions than of the knowledge of bases or aeroplane performance. A mile is a mile, and an aeroplane's performance is constant, north or south of the equator, but the weather of the upper air over the South Pacific to be flown is so far almost unknown, and that knowledge can be gained only by repeated observation and experience. However, a start is being made at the New Zealand end of the airline of the South Pacific from a much,better position than scratch, for, as Mr. Harold Gatty and Mr. Albert Francis, the company's meteorologist at Auckland commented, the New Zealand Meteorological Office had patterned its work, using thoroughly modern methods, to meet future and not merely immediate requirements, so that when air services, by whatever company or interests established, commenced operation to New Zealand from overseas the skeleton plan might be filled out quickly, with a substantial basis of preliminary work done. Observations of upper air conditions, for instance, were commenced at Apia some years ago, and similar work has been done at Wellington and Auckland. The first observations made by the observers at Apia were directed solely to the general study of meteorological conditions and upper air movements, and extraordinarily interesting results were obtained, about winds that regularly changed in direction by a full 180 degrees—as from north-east to south-west—as the marker balloon rose I from one layer of moving air to a higher and contrary wind. Day aftei day this reverse movement was observed and measured, and the facts were added to the general knowledge of air movement, with, at that time, no idea of aviation. When the Tasman service was confidently proposed the upper air work at Apia took on a new importance, and, of course, such knowledge of South Pacific air masses and the experience gained in methods of observation will assist in the services for internal aviation. REPORTS FOR AND FROM AIRCRAFT. The necessity for far more detailed weather facts, particularly about the upper air, for the guidance of aviation, and the capacity of aviation to supply weather data, go together splendidly. The flying crew must have detailed, up-to-the-moment weather advice, and the flying-boat, at 150 miles an hour and closely in touch with the base behind and the base ahead by radio, passes through, and can detail by radio, bands of weather extending over 1000 or 1500 miles in a single day. This detailing of conditions to be expected and of the conditions actually met, and the comparison of forecast and fact are the first duties of the meteorologist-radio officer combination, and a mass of data is built up by the messages exchanged on each flight, so voluminous that when it is turned over to special staff men to analyse, their work takes longer than the actual ocean flight. But it does add'to knowledge of the air over ocean distances, the origin and track of storms, and the why and the wherefore of calm weather or foul. Plans have been outlined for co-opera-tion between the New Zealand Meteorological Office and the company's meteorological staff in New Zealand and along the route to the Northern Hemisphere, and if such plans can be applied the present meteorological net, comprising New Zealand land stations, the present limited upper air work, reports from Australia and the Southern Pacific, from the Apia, Fiji, headquarters, and ships at sea, may be greatly widened. IN THE NORTHERN HEMISPHERE. This wider network may not stretch so wide as the service of the Northern Hemisphere, where data for the Pacific area are gathered from eight separate Governments; the Straits Settlements, French Indo-China, Siberia, China, Japan Canada, the United States, including Alaska, and Mexico act in full co-operation under international agreement, and broadcast their summaries for the common assistance of all and of all aviation services. In -the Northern Hemisphere weather data are available twice daily, morning and evening, over a vast land and ocean area (ships also co-operating) well over one-half way round the hemisphere. On ai average day as many as fifty ships may supply weather data to the common fund, and certain of them are equipped for taking observations of the upper air. to heights of 30.000 ft 1 when conditions are favourable. Particular reports are received by PanAmerican Airways from their observers at the island bases along the North Pacific route—Honolulu, Midway. Wake. Guam, and Manila—and from the official Governmental summari-> , the ships, upper air, aeroplane and island base reports the meteorologists—or aerologists—draw special charts to meet the particular needs of the air service, and issue their forecasts in the forms devised for rapid communications to aeroplanes and stations ahead. Two of these general ocean airway forecasts divided by stage sections are made daily, whether or not an aeroplane is flying, for from this repeated observation, repeated analysis, and repeated comparison of forecast with the weather experienced the meteorologist's knowledge and experience are built up, so that when similar combinations are reported from a set of observers he may forecast with conviction that this or that is likely to follow A STREAM OF REPORTS. When an aeroplane is flying the weather service is far more intricate: it becomes particular for each section, find the interchange of advice between bases and aeroplane is almost conliirious. The longer ocean stages, for instance. Uio Alamoda-Honolulu stage. j»410 miles, is divided into five zones, each of about. 500 miles. Forecasts are made for each zone and.for four clil-

ferent levels, 500, 4800, 7800, and 11,800 feet (of barometric pressure). The forecasts are still more detailed, because fo;- each stage three courses may be flown. The ideal course is the great circle, that is, the shortest air distance between the two points, but if the weather is unfavourable —heavy weather or head winds—a course may be taken either north or south of the ideal line. For each course the zone and '■ c four level forecasts are made out, but in practice they, of course, overlap, and once the general section chart is drawn, and ledrawi. and redrawn again as reports come in, the northerly or southerly ourse advice is amended rapidly. The cabled account ot the flight of the survey clipper between Alameda and Honolulu particularly mentioned that Captain Musick had not flown a direct course, but had detoured and flown at various levels to obtain weather data for comparison with the forecasts made and with the experience of the Hawaiian clipper, flying at the same time a more direct route. ROUND, OVER, OR UNDER. There is always some way to get round, to get over, or to fly under a storm on an ocean air line, if the way round or over or under is known. The meteorologist's chart, if he has sufficient data to draw it from, will give an almost certain line of general guidance as to the way past, yet a final decision may have to lie with the pilot in charge, and it may, probably will, not be just as to the way past the weather, but how to profit most from it for on one side or the other there will be a tail wind, and though in an air line run of a hundred or so miles tail winds are possibly not worth the chasing, they do on great distances justify and pay for a detour from the shortest course on map miles, for tail winds shorten those miles and head winds add to them. Schedules are maintained so long as it can be seen that the aeroplane will not get into really bad conditions, but if there is a doubt that the weather ahead is such as to present possible trouble the trip is cancelled, or, if the storm is not extensive, the course ordered "will swing the aeroplane past the danger area. Unlike land flying, ocean flying is largely done at low altitudes. Over land routes machines, on long stages, may go through at between 8000 and 12,000 feet, and higher than that over mountainous country, but ocean flights are as a rule made below 8000 feet, unless trade or reverse trade winds determine otherwise, and when the least turbulent air is at the surface the flying boats may skim the water, comparatively speaking.' The two German flying boats which: crossed the North Atlantic last September flew a great part of the distance within ten feet of the water. NO RECORDS. Records are not attempted. The idea is to maintain a steady schedule time over the full journey and over the several sections, but in practice this is difficult, for head and tail winds will greatly affect flight time. Captain Edwin Musick on. one occasion made such a sorry job of maintaining schedule time between Alameda and Honolulu, in the course of which he detoured to gain the best weather conditions and so flew 2550 miles, that he apologised. He was 60 seconds ahead of time. But there are not so many Musicks. Between Alameda and Honolulu flight'times have varied between 13 hours 57 minutes, fastest time, to 22 hours 48 minutes, against heavy winds, but average times are between 16 and 18 hours, without going over standard cruising speeds, for at such- speeds the fuel and oil economy is far greater than if the motors are opened up. A big reserve of power is always held, that the head-winds, which cannot always be avoided, will not upset schedule time seriously and engine power will always be available to discount storm power. A big margin of fuel is also carried, for the Bureau of Commerce has laid down a rule that no ocean flying-boat shall land. with less than four hours' fuel in her tanks, and the company has added a 50 per cent, margin over this again. On no occasion has the four-hour rule been waived, and only once has a 'plane landed, with less than six hours' fuel on hand. The period during which exploratory flights will be continued in the South Pacific has not been indicated. When the North Pacific line was inaugurated these flights continued for almost a year before a passenger was carried. The South Pacific service is to commence by December 31 of this year, but it may be considered necessary to make only a limited number of preliminary, flights, and the decision upon that point will rest largely upon the requirements of the meteorological stalls at Honolulu, on the floating base at Kingman Reef, at Pago Pago, and Auckland, and the success of the plans made for co-operation with New Zealand Australian, Pacific, and possibly further weather stations in the collection, analysis, and reading confidently the accumulating mass of data tor future guidance and value to the Dominion and Commonwealth Meteorological Offices as well as to the company.