At 9 o'clock in the evening of May 27, 1919, the NC-4, the giant flying boat of the United States Navy, landed at Lisbon, Portugal, completing the last lap of the trans-Atlantic flight from Newfoundland to Portugal. Interested watchers had crowded the hills overlooking the harbor ever since news of the start from the Azores had been received, although they knew very well that they would have many hours to wait before the ship could reach Lisbon. Their patience was finally rewarded by the appearance of the NC-4, which glided down to the water and was quickly moored to the mother ship. This last lap of the flight had been accomplished without difficulty, and had proved conclusively that a trans-Atlantic flight was within the range of human possibilities.
In thus completing the first transoceanic flight, the NC-4 had been successful where various competitors had failed. The NC-1 and the NC-3, which left Newfoundland with the NC-4, had been forced down, when near the Azores, by adverse weather conditions, and had been unable to continue the flight. After the crew had been taken off the NC-1, an attempt was made to tow the craft to Florta, but the tow-line broke, and the machine finally sank.
The NC-j, after being adrift for 60 hours in a severe storm, made Ponta Delgado under her own power, but was too badly damaged to proceed further on the flight.
On May 18, 1919, while the fate of the NC-3 was still in doubt, Hawker and Grieve made their unsuccessful attempt to fly a Sop- with biplane from Newfoundland to Ireland, and were forced down by engine trouble when only 1200 miles out. Fortunately, they were picked up by a tramp steamer, but the plane was a complete wreck.
The C-5, a United States Navy airship of the non-rigid type, had been specially equipped for a trans-Atlantic flight, to compete with the NC flying boats. After flying from Montauk Point, L. I., to St. John’s, Newfoundland, the C-5 broke away from its moorings during a severe storm, was blown to sea and wrecked.
The record of the NC-4 was not long to stand alone. On June 14 and 15, 1919, Messrs. Alcock and Brown, in a two-motored Vickers-Vimy bombing plane, made a non-stop flight from Newfoundland to Ireland, breaking all non-stop records for heavier- than-air machines, and accomplishing the first non-stop transoceanic flight.
The next flight across the Atlantic was made by the R-34, a British airship of the rigid type, which arrived at Mineola, L. I., on July 5, 1919, after a flight of 108 hours duration from East Fortune, Scotland. Stiff head winds were encountered throughout the course, which accounted for the more than four days required for the trip. After a few days at Mineola for refueling and inspection, the return flight was made. Weather conditions were more favorable, and the time required for the return trip was only 75 hours. The record of the R-34 in making a round trip air voyage across the Atlantic still stands alone.
After the completion of the trans-Atlantic flights described above, attention was naturally turned to a consideration of flights across the Pacific. It was well known that such a flight would involve difficulties not met in the trans-Atlantic flight, but the extent of these difficulties was not known.
The following study of the possibilities of a trans-Pacific flight has been made in the attempt to collect all the available information regarding the conditions upon which such a flight would depend. These flight conditions may be grouped under the following heads:
1. Types of machines available.
2. Distribution and physical conditions of possible landing places.
3. Distances to be flown.
4. Meteorological conditions.
The routes to be followed in such a flight would depend almost entirely on the above conditions; for that reason, the discussion of possible routes will be based on a study of these conditions.
1. Types of Machines Available
Four types of machines could be considered as available for such a flight. They are airplanes (land machines), seaplanes of the flying-boat type, non-rigid airships and rigid airships. The two types first named are heavier-than-air machines and the airships are lighter-than-air craft. The non-stop flight record for all types of aircraft is held by the rigid airship. It is reported that during the war a German rigid, the L-53, which was dispatched from Bulgaria to carry ammunition and medical supplies for the relief of the troops in German East Africa, was recalled by wireless after reaching Khartoum, in southern Egypt. The total distance flown, in the neighborhood of 4000 nautical miles, was covered in 100 hours, and it is reported that sufficient fuel remained on board for an additional 60-hour flight.
The heavier-than-air non-stop record, as noted previously, is held by the Vickers-Vimy bomber, flown by Alcock and Brown in the flight from Newfoundland to Ireland, a distance of 1680 nautical miles. The seaplane record is held by the NC-4, made in the flight from Newfoundland to the Azores, a distance of approximately 1200 nautical miles. An F-5-L flying boat, tested at Hampton Roads, flew for over 20 hours at an average airspeed of 55 knots, covering in that time something over 1100 nautical miles.
The non-rigid airship record is probably held by the C-5, which in its flight from Montauk Point to St. John’s, referred to previously, covered a distance of approximately 1200 nautical miles. This flight was accomplished in 25 hours and 50 minutes. The endurance, as calculated just before getaway at Montauk Point, was 47 hours at a cruising speed of 40 knots, or 1880 nautical miles.
From the records given above, with a choice based on radius of action and reliability, the machines would be classed, in the order of their merit: (1) Rigid airship; (2) non-rigid airship; (3) flying boat. The experience of Hawker and Grieve in their attempted trans-Atlantic flight indicates that a land machine is not safe for long distance flights over water. If a seaplane of the NC or F-$-L type were used, it probably would be found necessary to refuel at sea from a destroyer, unless it were found possible to follow the coast around the North Pacific from the United States to Japan and China.
It is possible to find at any of the American cities along the Pacific coast suitable landing places for both land machines and seaplanes of the heavier-than-air type, and for all types of lighter-than-air machines. The cities which most likely would be chosen as starting points for such a flight would be San Francisco and Seattle; these cities are well provided with suitable landing fields and harbors.
At Honolulu there are good facilities for landing all types of machines. The large harbor provides a landing for all types of seaplanes, and the parade ground at Fort Schofield provides excellent landing facilities for land machines and lighter-than-air craft.
Landing fields between Honolulu and the Asiatic coast are not numerous, nor of the best for any type of machine. Possible harbors for seaplanes could be found at Jaluit, in the Marshall Islands; at Ponape or at Truk, in the Carolines ; at Guam ; at Yap ; at Cebu and at Manila, in the Philippines; and at Hongkong or at Canton, along the south China coast.
In following the North Pacific coast from Seattle, landings could be made by seaplanes at Sitka, at Kodiak and at Unalaska, in Alaska; at Petropavlovsk, on the Kamchatka peninsular; at Nemuro, Yokohama and Nagasaki, in Japan ; and at Shanghai, on the China coast.
Very few, if any, of the places enumerated in the two preceding paragraphs would provide suitable landing fields for land machines. The small islands of the Pacific are in general only coral reefs, and would, in all probability, be rough and unsuitable for landing purposes. Those of the islands which are of volcanic formation are simply high, rocky projections which would be entirely unsuited for landings. At a few points it is probable that landings could be made, particularly at Guam and at Manila, where there are parade grounds maintained by the United States forces stationed there. On some of the islands, it would be possible to erect mooring towers for lighter-than-air craft, but the work involved would he very great. Along the North Pacific coast the greater part of the land is such that it would be difficult to find a field large enough and sufficiently smooth for the landing of a land type machine.
3. Distances to be Flown
I he shortest distance in a direct line from any point on the west coast of the United States, exclusive of Alaska, to the nearest point of any commercial importance on the Asiatic coast is the distance from Astoria, Oregon, to Yokohama, Japan, a distance of approximately 4200 nautical miles. The minimum distance at any point between the American continent and the Asiatic continent is between the northwest extremity of Alaska and the most northeasterly point of Siberia, a distance of approximately 25 miles. Because of location and of weather conditions, a flight across this short space would hardly be considered.
For comparison with distances across the Pacific, the distance covered by Alcock and Brown in their trans-Atlantic flight was 1680 nautical miles, the record for any type of heavier-than-air machine; the distance flown by the NC-4 from Newfoundland to the Azores was 1200 nautical miles, the record for seaplanes. It should be noted however, that the range of action of the NC-4 as equipped for this flight was approximately 1400 nautical miles. The distance from San Francisco to Honolulu, which is the nearest landing point to the Pacific coast, is 2090 nautical miles, an increase
The U. S. Navy “F-5-L” Flying Boat.
One of these boats flew on a non-stop flight of over 20 hours, and covered slightly more than 1100 nautical miles of 410 miles over the greatest distance covered thus far by a heavier-than-air machine in a non-stop flight. The distance from Honolulu to the Asiatic coast at Hongkong is 4900 nautical miles, and from Honolulu to Yokohama, is approximately 3400 miles. The distance from Sitka across the North Pacific to the Alaskan Peninsula is approximately 1000 nautical miles, and from the Alaskan Peninsula across Bering Sea to Kamchatka, approximately 1260 miles.
These figures show that the proposed flight across the Pacific will involve non-stop runs which greatly exceed any which thus far have been accomplished in any type of heavier-than-air machine, unless the northern route is followed. The total distance from Mineola to East Fortune, Scotland, flown by the R-34, was approximately 2700 nautical miles. This exceeds by 30 per cent the distance from San Francisco to Honolulu. The flight from Honolulu to Hongkong of 4900 miles could be broken up into three shorter flights, landings being made at Jaluit and at Guam, and, if desirable, at Manila. The flight of the German Zeppelin referred to previously would indicate that this type of machine could cover any non-stop run necessary in the trans-Pacific flight.
4. Meteorological Conditions
The meteorological conditions which must be considered in a study of the possibilities of this flight are winds, fogs, temperatures, calms and storms. All must be favorable before a flight is attempted.
The prevailing winds are due to several more or less constant conditions of atmospheric pressure which prevail over certain portions of the Pacific. These are the North Pacific high, the South American high, the Asiatic high and the Aleutian low. Of these, the North Pacific high has the greatest effect in the regions which probably would be covered in this flight. The others tend, in certain portions of the ocean, to modify the conditions which result from the North Pacific high.
the North Pacific high is confined in position to limits between 310 and 450 north latitude and 1350 and 150° west longitude. The direction of the winds around this region of high pressure is anti-cyclonic, or clockwise.
The South American high is practically fixed in position at latitude 30° south and longitude 1000 west (approximate). The direction of the winds around this region is cyclonic, or counterclockwise.
The Asiatic high prevails off the Asiatic coast from October to April. It extends along the coast from Shanghai to north Korea, and eastward as far as 1550 east longitude. It disappears in the spring and reappears in October. The direction of the winds around this region is anti-cyclonic, or clockwise.
The Aleutian low centers over Bering Sea, the Gulf of Alaska and the Alaskan Peninsula, and prevails from September to June. The direction of the winds around this region is cyclonic, or counter-clockwise.
Due to these conditions of atmospheric pressure, certain prevailing winds are found. These are the northeast trades, the southeast trades, the westerly winds, and the summer and winter monsoons.
The northeast trades arc practically continuous throughout the year and extend from a few miles off the coast of the United States almost to the Philippine Islands. Their limits move north and south, between the equator and the 36th parallel, north latitude, following the change in position of the North Pacific high. In winter and spring they merge with the winter monsoons along the south Asiatic coast. For a distance of approximately 200 miles off the American coast, the winds may be variable, but beyond that limit the trades prevail.
The southeast trades cover the Pacific between the position of the South American high, as given above, and the equator. Their limits are practically fixed. Between the regions covered by the northeast trades and the southeast trades is a narrow zone, centering at about 10° north latitude, in which the winds arc variable, northeast, east or southeast.
Due to the North Pacific high and the Aleutian low there are strong westerly winds covering that portion of the Pacific between Japan and Canada. These winds center between 450 and 50° north latitude, and prevail during all months of the year except June, July and August.
Due to the Asiatic high, the winds prevailing along the Asiatic coast during the winter months, known as the winter monsoons, are from the northeast. These winds often blow with storm force, and, in general, cause thick, rainy weather, and make navigation along the coast difficult. During May, June, July and August, the winter monsoons disappear and the summer monsoons take their place. These winds are in general from the southeast, and are not as strong or as constant as the winter monsoons.
The south Asiatic coast and the Philippine Islands are subject to frequent and severe typhoons—sudden tropical storms of great violence, originating in the Pacific Islands near the equator, and travelling west, northwest and northeast across the Philippines and the China coast. The number and severity of these storms is a maximum during the months of July, August and September, when there may be four to six per month, and a minimum during 30 February, during which month less than five have been reported during the last 22 years.
During the months from December to July inclusive, there may be severe storms originating along the Asiatic coast and moving in a generally northeasterly direction to the Aleutian Islands, the Alaskan and Canadian coasts. These storms may be of from six to eight days duration.
The Central Pacific is practically free from severe storms travelling along extended tracks, but is subject to severe local storms which may occur during almost any month of the year.
The effects of these winds and storms on flight along the different routes to be considered will be shown in the tables of meteorological conditions for each route.
A study of fog conditions shows that throughout the year fogs prevail along the west coast of America from San Francisco to Seattle and Sitka, the number of days of fog during the month varying from 5 to 40 per cent, depending on the season of the year. From Sitka to the Alaskan Peninsula and the Aleutian Islands, fog prevails during all months of the year except October, November and December. Across the North Pacific from the Aleutian Islands to Kamchatka, and south to Japan, fogs prevail during the months of June, July, August and September; from 30 to 50 per cent of the days of these months are with fog.
The most southerly mid-ocean limit of the region of fog is the Midway Islands, 28° north latitude, where during the month of May 15 per cent of the days are with fog. The portions of the ocean between the 28th parallel, north latitude, and the equator are free from fog throughout the year, except along the American coast.
The temperatures which prevail over the Pacific Ocean are such that they would cause no difficulties to aerial travel, except in the extreme north, in the neighborhood of Alaska and Kamchatka. The southerly limits of the average monthly temperatures which are below freezing arc found during the months of December and January along a line extending through north Korea, north Japan, south Kamchatka, the Alaskan Peninsula and Sitka. During the month of July the average temperature along the line extending across north Kamchatka and the Bering Sea is 450 F. That portion of the ocean from Honolulu to the Marshall Islands, and west to the Philippine Islands, has an average monthly temperature of from 750 to 8o° F. throughout the year.
Discussion of Possible Routes
After a study of the landing places which could be used in the trans-Pacific flight, routes have been laid out which show the greatest possibilities for this flight. These routes are shown on the accompanying sketch, and will be described under the headings as given on that sketch.
The description of these routes, with tables giving detailed information regarding distances, courses to be flown and all meteorological data, follow.
Route 1—the Northern Route—follows a path from Seattle to Sitka, thence to Kodiak, to Unalaska, to Petropavlovsk, to Yokohama, to Nagasaki and finally to Shanghai. The total distance covered in this flight would be 5415 nautical miles. The particular features of the landing places to be used in following this route may be described briefly as follows:
Seattle.—Has excellent harbor facilities, and has suitable fields for land machines within a short distance of the city. Supplies of all kinds are available. The temperature range is from a maximum of 96° F. in June to an extreme minimum of 30 F. in January.
Sitka.—Has numerous anchorages which are more or less protected, but has no good docking facilities. Supplies are limited. The temperature range is from a maximum of 87° F. to a minimum of 20 F. It is uncertain whether a suitable landing field for a land machine could be found here. (United States territory.)
Kodiak.—Has good harbor facilities at St. Paul harbor on the northwest side of the island, where good anchorage could be found for mother ships to provide supplies for seaplanes. General supplies are very limited at Kodiak. The temperature range is very similar to that of Sitka, the minimum average monthly temperature of 28° F. obtaining in February. (United States territory.)
Unalaska.—Has several good anchorages and is open to navigation at all seasons of the year. General supplies are available here, but no suitable landing places could be found for land machines. The average monthly temperatures are very similar to those of Kodiak, the minimum of 30° F. obtaining during December, January and March. (United States territory.)
Petropsvlovsk.—There is an excellent harbor available, but unfortunately the harbor is closed by ice from November to May. The temperature range is from a maximum of 740 F. to a minimum of — 70 F. During winter months, as much as 20 feet of snow has been reported. General supplies are available here, and there is a well-equipped wireless station at this point. (Siberian port.)
Yokohama.—Excellent harbor facilities are available, open at all seasons of the year. The temperature range at Tokio, which is approximately 20 miles north of Yokohama, is from a maximum of 970 F. to a minimum of 40 F. The country in the immediate vicinity of Yokohama would not be suitable for landing fields for a land machine, but it is probable that good landing facilities could be found in or near Tokio. (Japanese port.)
Nagasaki.—Provides an excellent harbor open at all seasons of the year, and abundant general supplies are available. The temperature range at Nagasaki is from a maximum of 98° F. to a minimum of 230 F. The country surrounding Nagasaki is very mountainous, and it would be difficult to find a suitable landing field for a land machine. (Japanese port.)
Shanghai.—There are excellent harbor facilities at Shanghai both on the Whangpo River, directly in front of the business section of the city, and in the outer harbor at the mouth of the Yangtse River. Supplies of all kinds are available at Shanghai. The temperature range is from a maximum of 105° F. to a minimum of 90 F. (Chinese port, with international settlement.)
The tables1 for Route 1 show the meteorological conditions which obtain in each of the sections of the route which would be covered in a non-stop flight, for each month of the year. These tables also show the distances to be covered between landing places. A study of the distances to be flown shows that each section of the route is well within the range of flight of several of the types of aircraft already constructed. The longest sections are from Una- laska to Petropavlovslc, and from Petropavlovsk to Yokohama. If it appears desirable these may he divided into shorter sections. Between Unalaska and Petropavlovsk is the island of Attu. If a stop were made at this point it would divide the 1260 nautical miles from Unalaska to Petropavlovsk into two sections, one of 765 nautical miles, between Unalaska and Attu, and the other, 525 nautical miles, between Attu and Petropavlovsk.
Attu Island.—A wild rocky island at the extreme end of the Aleutian Island chain. There are two small harbors which afford good shelter for vessels of less than 14 feet draft. The island would offer no landing places for land machines. No supplies would he available at Ibis point. (United States possession.)
The section of the route from Petropavlovsk to Yokohama could be divided by making a landing at Nemuro in northern Japan. This would make two sections, one from Petropavlovsk to Nemuro, of 825 nautical miles, and the other, from Nemuro to Yokohama, of 605 nautical miles.
Nemuro.—Has good harbor facilities, but is subject to extreme changes of temperature. The temperature varies between a maximum of 90° F. in July and a minimum of— 8° F. in February. General supplies would be available at this point, and a wireless station is located at Otchisi, a few miles to the southeast of Nemuro. (Japanese village.)
In studying the tables for Route 1 it is seen that for a flight from the American coast to the Asiatic coast, head winds would be encountered along the section of the route from Unalaska to Petropavlovsk throughout the months from January to April inclusive, and from October to December inclusive. During the remaining months of the year the winds are variable. During the months of May, June, July, August and September, there are very high percentages of days with fog, varying from a minimum of 15- per cent in the month of May to a maximum of 50 per cent in the months of June and July. These two conditions, and the extreme low temperatures encountered at Petropavlovsk from November to May, would tend to make this northern route very undesirable for any type of machine which has thus far been constructed.
Route 2—the Central Route—is from San Francisco to Honolulu, thence to Jaluit, to Guam, to Manila and to Hongkong. The total distance to be flown in following this route is 7690 nautical miles. The landing places may he described briefly as follows:
San Francisco.—Has excellent harbor facilities and landing fields for all types of machines, both lighter-than-air and heavier-than-air. The temperature range is from a maximum of 100° F. in June to a minimum of 290 F. in January. Fogs are likely to prevail over San Francisco Bay in any month of the year. The days of fog are a minimum during the winter months of December, January, February and March.
Honolulu.—As has been stated before, Honolulu provides excellent landing facilities for all types of aircraft. Supplies are abundant, and the temperature range is from a maximum of 86° F. in August and September to a minimum of 57° F. in January. (United States possession.)
Jaluit.—Provides good harbor facilities with plenty of depth, but probably would not provide good landing fields for land machines. The harbor is in the form of a lagoon, surrounded by low coral islands. Coal, water and ships’ provisions are available, but other supplies are limited. The temperature range is very much the same as that of Honolulu ; maximum and minimum figures are not available, but the average monthly temperatures are 80° F. and 810 F. throughout the year. (Originally German possession, awarded to Japan by Peace Treaty.)
Guam.—Provides anchorages for all classes of vessels, and at Port Apra, on the west coast, has mooring buoys for the use of United States naval vessels. General supplies and water can be obtained, but coal facilities are not good. A United States naval radio station is established here. Maximum and minimum temperatures are not available, but the average monthly temperatures vary from 78° F. to 82° F. (United States possession.)
Manila.—Excellent harbor facilities are available for all types of vessels, and landing fields for land machines and lighter-than-air craft. Supplies of all kinds are available. The temperature range is from a maximum of 102° F. in May to a minimum of 63° F. in January and February. (United States possession.)
Hongkong.—Has excellent harbor facilities for all types of water-craft, and could probably provide, in the public parks, landing fields for land machines and lighter-than-air craft. Supplies of all kinds are available. Temperature range is from a maximum of 970 F. in August to a minimum of 320 F. in January. (British colony.)
The tables for Route 2 show the weather conditions for different sections of that route. It will be noted that the distance to be flown from San Francisco to Honolulu is 2090 nautical miles, and from Honolulu to Jaluit, 2150 nautical miles, exceeding the distance covered thus far in any non-stop flight with heavier-than-air machines. The only machines which have covered greater distances in non-stop flights are the rigid airships of the types of the German L-49 and L-53, and the British R-34. The distance from Jaluit to Guam, may, if necessary, be divided into shorter sections, because of the fact that the course passes over the Marshall and the Caroline Islands, where several landing places could be found in case of need. In the section from Guam to Manila, suitable landing places could be found, in case of .need, among the most easterly islands of the Philippine group, by making only a slight deviation from the course.
The portions of this route from San Francisco to Honolulu, to Jaluit and Guam are within the region covered by the northeast trades. With very few exceptions, the northeast trades prevail throughout each of these sections during the entire year. These winds vary in strength from 15 to 24 nautical miles per hour, and could be counted on to give material aid in the flight from San Francisco to Honolulu and from Honolulu to Jaluit. In these sections of the route the course followed is almost directly in line with the direction of the northeast trades. In the sections from Jaluit to Guam and Guam to Manila, the course would be across the direction of the winds. From Manila to Hongkong the winds are variable, due to the changes from winter monsoons to summer monsoons, and vice versa.
This route is practically free from fog at all periods of the year. The only portion of the route subject to fog is that in the region of San Francisco. The fogs here extend a few hundred miles out to sea, and it would always be possible to choose a day for starting from San Francisco when fog conditions would not interfere with flight.
A study of the conditions which arc found on Route 2 would indicate that at the present time there is no type of heavier-than-air machine which could accomplish the flight from San Francisco to Honolulu, or from Honolulu to Jaluit, without refueling somewhere en route. This would limit this course for heavier-than-air machines to some type of seaplane, probably of the NC type, or something larger when larger machines are constructed. It would be possible to accomplish this flight with lighter-than-air machines of the rigid airship types mentioned previously, either the German L-53 or the British R-34. Under certain conditions, it is probable that the non-rigid airship of the type of the C-5, which was wrecked at Newfoundland while being prepared for the trans-Atlantic flight, could cover the distances required, for this route. This question will be discussed later.
Route 3—the South Central Route—follows very closely Route 2. Starting from San Francisco the course is laid to Honolulu, thence to Johnston Islands, to Jaluit, to Truk in the Caroline Islands, to Yap in the Pelew group, to Cebu in the Philippines, to Manila and to Hongkong. The total distance covered in this flight is 7899 nautical miles, an increase of 209 miles over that of Route 2. The advantage of this route in comparison with Route 2 is that the distances to he covered in non-stop flight are made much less, because of making use of a greater number of landing places. The landing places on this route, other than those described in connection with Route 2, have the following characteristics:
Johnston Islands.—A coral reef about eight miles in length, and coral ledges, enclosing a lagoon. The coral ledges, extending in a northeasterly direction, are well defined by breakers. The lagoon forms an anchorage which is well sheltered from the northeast trades, but is exposed to winds varying from east to southwest. No supplies of any kind would be available at this point. The only possibility of use of the islands would be to form an anchorage for a mother ship from which supplies for seaplanes could be obtained. No landing facilities for land machines or lighter- than-air craft would be available.
Truk (also known as Hogulu).—A small group of islands consisting of 10 lofty basaltic islands and numerous coral islands inclosing a lagoon about 46 x 40 miles in extent. The lagoon provides good anchorage in any portion. No supplies would be available, and it is reported that the natives on some of the islands are inclined to head-hunting. Here again, the only landing facilities would be for seaplanes where supplies could be obtained from a mother ship. (Formerly a German possession, awarded to Japan by Peace Treaty.)
Yap.—A small island of volcanic origin with a maximum elevation of 1050 feet. Good harbor facilities are provided on the west coast, and coal and water are available. From November to May the island is in the track of the northeast trades, during the remainder of the year it is subject to occasional typhoons. The average monthly temperature range is from 80° F. to 82° F. (Formerly German possession, to be awarded to United States of America by Peace Treaty.)
Cebu.—An important commercial port on the east coast of the island of Cebu, provides an excellent harbor and has facilities for all kinds of repairs. A marine railway is available here which would make possible the docking of seaplanes of the NC type in case of need. The surrounding country has numerous sugar plantations, and it is probable that a land machine could be brought down without entirely wrecking the plane, if a suitable landing field could not be found in the city. (United States possession.)
The tables for Route 3 show the meteorological conditions which obtain in all sections of the South Central Route. Conditions vary very little from those which have already been described for the Central Route—Route 2. As has been noted previously, the main advantage of this route over Route 2 is in the shorter distances to be covered in non-stop flight. The only lap which is not shortened is that from San Francisco to Honolulu.
If provisions could be made for the refueling of seaplanes at sea it would be possible for flying boats of the NC type to cover the distance from San Francisco to Honolulu with one refueling. Distances between landing places beyond Honolulu could be covered by machines of this type in non-stop flight.
Route 4—the North Central Route—deviates quite considerably in the central portion from Routes 2 and 3. As with Routes 2 and 3, the first section would be from San Francisco to Honolulu : from Honolulu the route would be to the Midway Islands, from the Midway Islands to Wake, thence to Guam, to Yap, to Cebu, to Manila and Hongkong. The total distance covered in following this route would be 7811 nautical miles, practically an average between the Central and the South Central Routes. Here again, the advantage in comparison with the Central Route would be a decrease in the distance to be covered in non-stop flight. Another advantage would lie in the fact that all landing places, except Hongkong, would be at points either belonging to or under the control of the United States Government.
Those landing places not already described in connection with the routes discussed previously will be described as follows:
Midway Islands.—A group of islands offering good harbor facilities during the summer months, but too small and too uneven to offer landing facilities for land machines, or for lighter-than-air machines unless moored to a mast. A few supplies would be available, but the main purpose of the use of this island as a landing place would be to offer shelter for a mother ship from which supplies could be obtained. There is always a rough westerly sea and from October to April there are only occasional days of fine weather. (United States possession.)
Wake Island.—A low coral island about eight feet above normal sea level, inclosing a large lagoon which would offer shelter for anchorage except in most severe weather. During severe storms the sea breaks completely over the island. No supplies or provisions are available, and the only advantage of landing at this point would be to obtain supplies from a mother ship anchored in the lagoon. (United States possession.)
I he meteorological conditions obtaining along the North Central Route are shown in the tables for Route 4. As has been noted previously, the only advantages of this route in comparison with Route 2 are a decrease in the distances to be covered in non-stop flight, and the fact that all landing places except one are under the control of the United States Government. This latter consideration is probably the only advantage that Route 4 would show in comparison with Route 3.
Route 5—The Lighter-Than-Air Route—at the present time available for lighter-than-air craft only, would be from San Francisco to Honolulu, thence to Guam, to Manila and to Hongkong. The total distance covered would be 7440 nautical miles, 250 miles less than the distance flown along Route 2. Meteorological conditions would vary very little from those previously described for that route. The longest non-stop flight would be from Honolulu to Guam, a distance of 3400 nautical miles. Detailed meteorological data are unnecessary.
The study of the information available regarding the five routes which have been outlined for the trans-Pacific flight shows certain characteristics which should be considered in choosing a route to be followed:
First.—The Northern Route, while offering the advantages of short distances to be covered in non-stop flight, is subject to the disadvantages of extreme cold during months from October to May and subject to extreme fog conditions during the months from May to September inclusive. These two conditions make an attempt at flight following this course inadvisable. If the only object of such a flight were to win fame and a cash prize, it is possible that, by watching until conditions were right, the flight could be accomplished, following this route, by some type of seaplane. The route is not suitable for land machines unless a flight were accomplished during the winter months when landings could be made on the ice. This ice condition, however, is very uncertain at some of the proposed landing places, and the possibility of a successful flight being made with such a machine is very small. Commercially, the route would have little value.
Second.—Route 2, because of the long distances to be covered in non-stop flight, is unsuited for any type of heavier- than-air machine which has been thus far constructed. It might be possible to accomplish flight following this route if provisions were made for refueling machines of the NC type at sea. Flight along this route could be accomplished by a rigid airship of the R-34 type.
Third.—Routes 3 and 4 offer advantages of shorter nonstop flights, as compared with Route 2. It should be noted, however, that there is no way of decreasing the distance from
San Francisco to Honolulu, and any machine capable of flight between these points could cover the distances necessary for the flight between all other landing places in Route 2. Route 4 has the advantage of all landing places, except Hongkong, being under United States Government control. It might be desirable to make a combination of Routes 2 and 4, the courses being laid from San Francisco to Honolulu, to Midway, to Wake, to Guam, to Manila and to Hongkong.
Fourth.—Route 5, due to the long non-stop flights to he accomplished, would be suitable for large lighter-than-air craft only. Several rigid airships are now in use in Europe which could cover these distances. This route has the advantage of all landing points, except Hongkong, being under United States control. It might be feasible to make this a main route, with emergency mooring towers located at Midway Islands, at Yap (if this island becomes United States property) and at Cebu. The station at the Midway Islands might also be used as a landing point on flights from Honolulu to Yokohama, a total distance of 3400 nautical miles.
A study of the weather conditions along Route 2 shows that during the months of January, February and March the northeast trades are practically constant in velocity over the entire course from San Francisco to Guam. This is a period of the year when typhoons are a minimum, so that the course from Guam to Manila and from Manila to Hongkong would be practically free from the influence of these storms. These months, and particularly the month of February, would be the most suitable for attempting a flight following this course. This flight could easily be accomplished with a rigid airship of the R-34 type, and it is probable that it could be accomplished by a non-rigid airship of the C-5 type, if especially equipped for the flight. The following calculations, based upon information obtained from an article published by Commander Hunsaker in Aviation of September 1, 1919 show the possibilities of the C-5 type non-rigid airship in accomplishing this flight.
The endurance of the C-5 as equipped for the flight from Montauk to Newfoundland was 47 hours, at a cruising speed of 40 nautical miles per hour. This gives a cruising range of 1880 nautical miles. This range is somewhat less than the distance to be covered between San Francisco and Honolulu, and between Honolulu and Jaluit. If, however, the assistance due to the northeast trades, which have a constant velocity through the month of February of 20 nautical miles per hour, be counted upon, we find that the cruising range would be increased from 1880 to 2820 nautical miles. This gives a cruising range more than sufficient to accomplish the flights mentioned above. The following calculations have been made to determine the time necessary for the flight for each section of this route. It is found in each case that the time of flight is much less than the endurance of the machine, because of the assistance of the northeast trades.
In case the fuel supply should be exhausted, because of adverse winds, or for any other reason, it would be possible for the airship to summon a destroyer by wireless, and refuel and replenish water ballast and gas from the destroyer at sea.
In calculating the times listed above, allowances have been made in all cases for both the direction and the velocity of the winds that would prevail over the different sections of the course. These, of course, would vary during different days of the month, but it is probable that the calculated time would not be more than 10 per cent in error.
It should be noted that the wind velocity given in the tables and used in the above calculation, are those that prevail at water level, as shown by the monthly pilot charts for the North Pacific Ocean, published by the Hydrographic Office. Wind velocities and directions at high altitudes may be very different. In general, wind directions gradually change with increase of altitude, so that for altitudes of 1 mile it is found that all winds are from the west of north or south, and above 2 miles, all winds are decidedly from the west. (Report 13, National Advisory Committee for Aeronautics.) This would indicate that for flights from America to Asia, low altitudes should be kept, to take advantage of the northeast trades; and for flights in the opposite direction, maximum altitudes consistent with the design of the machine should be attained.
As has been noted previously, the main advantage of Routes 3 and 4 in comparison with Route 2 is in having shorter distances to be accomplished in non-stop flight. These routes would not be suitable for land machines, because of no landing facilities being available at the intermediate stopping points. They could be used only for seaplanes, and would require a refueling at sea, at some point between San Francisco and Honolulu, for any type of sea-plate yet constructed.
The conclusion reached through the study of the possible routes as described previously is that there is no type of heavier-than- air machine in use at the present time which could accomplish the trans-Pacific flight, without refueling at sea, unless Route 1 were followed. Flight over this course does not appear advisable, because of adverse weather conditions. Temperature conditions are favorable along all routes except Route I. Fog might, delay flight along the Central Routes only at San Francisco.
Lighter-than-air craft could accomplish the flight following Routes 2 or 5, and the month in which weather conditions would be best for this flight would be in the month of February. It would not be wise to attempt flights with lighter-than-air machines during the months of June, July, August and September, because of the frequency and severity of typhoons likely to be encountered between Guam and Manila, and between Manila and Hongkong. A lighter-than-air craft of the type of the R-34, having cruised over Route 2 or Route 5 during the month of February, could, by going inland a short distance from Hongkong, work its way up the China coast to Shanghai, and then across to Japan. Following a course practically along the 45th parallel, north latitude, it would find, during the month of March, westerly winds which would make it possible for the ship to accomplish a non-stop flight from Japan to Seattle or Vancouver. The distance to be covered in this flight is approximately 4200 nautical miles. This distance is approximately the same as that covered by the German rigid airship mentioned previously, in the flight from Bulgaria to Khartoum and back, without regassing or refueling. By going to higher altitudes to avoid storms, flights as just outlined could probably be accomplished by lighter-than-air craft at any season of the year.
It might be interesting to note that the distance from San Francisco to Charlotte Bay, on the north coast of Australia, following the course from San Francisco to Honolulu, to Jaluit and to Charlotte Bay, is 6215 nautical miles. The distance from Jaluit to Charlotte Bay is 1965 nautical miles, less than the distance from San Francisco to Honolulu. This would indicate that any type of machine which could accomplish the flight from San Francisco to Jaluit could continue the flight from Jaluit to Australia without special difficulty. There are possibilities of landing places being found between Jaluit and Charlotte Bay, among some of the Solomon Islands, or at some point on the coast of New Guinea. The Aerial Age of February 9, 1920, reported that an officer of the British Royal Flying Corps is at present making preparations for a flight from Australia to San Francisco, following this route reversed.
Another possible route would be across the South Pacific from Valparaiso, Chile, to Townsville, Australia. This route would be divided into four sections: (1) From Valparaiso to the Easter Islands, a distance of 2000 nautical miles; (2) from Easter Islands to Tahiti, in the Solomon Islands, a distance of 2200 nautical miles; (3) from Tahiti to Suva, in the Fiji Islands, a distance of 1830 nautical miles ; and (4) from Suva to Townsville, also a distance of 1830 nautical miles. The total distance to be covered in such a flight would be 7860 nautical miles. While Easter Islands do not afford very desirable landing facilities, it probably would be possible for a large rigid airship to accomplish this flight without particular difficulty.
The distance from Townsville, Australia, to Cebu, in the Philippines, is 2270 nautical miles, and from Cebu to Hongkong is 910 miles. This makes the total distance, following the air routes outlined from Valparaiso to Hongkong, just over 11,000 nautical miles. It is very possible that with the development of the rigid airship type of the lighter-than-air machines, a route following this general course might be of considerable commercial importance.