There Are a Variety of Routes Between the Continental United States (CONUS) and South East

THE Routes to AND FROM southeast asia

GO THROUGH vietnam

by

kurt priessman, msgt, usaf (ret)

table of contents

Military and Military Contracted Aircraft - A Discussion of Distances related to AIRCRAFT Capability

C-130E Hercules

C-141 A Starlifter

KC-135R Stratotanker

C-5A Galaxy

DC-8

DC-10

Boeing 707

WeATHER -A Discussion of Trade Winds and Jet Streams

The Trade Winds

The Jet Streams

Polar Jet

SubtropicalJet

NAVIGATION - Discussion of the Great Circle

The Great Circle

DISCUSSION - Distances, JETSTREAMS, & the great circle

The Great Circle Route

The Northern Route

The Northern Jet Stream Route

The Jet Stream Route

The Southern Jet Stream Route

The Commercial Flight Route

Appendices

1 - USAF Military Aircraft information

2 - Commercial Aircraft Information

Tables

1 – Aircraft and Distance Information

Notes

Bibliography

There are a variety of routes between the continental United States (CONUS) and South East Asia (SEA), considering the type of aircraft, the aircraft’s speed and range, prevailing winds at flight altitude, aircraft payload, and crew duty limitations, all which limit the distance of each leg or hop of a flight. Another factor is the season, as it affects prevailing winds, and therefore the route that may be taken.

Air refueling of civilian and military personnel transport carriers was not routinely if ever done, since those resources were primarily used to refuel bombers and fighters in direct support of the battle in Vietnam, Laos, and Cambodia.

Military and Military Contracted Aircraft -

A Discussion of Distances related to AIRCRAFT Capability

As discussed in the opening paragraph, there are limitations to the distances or maximum ranges aircraft can reasonably be expected to fly without refueling. These limitations are based on the aircraft’s weight, the amount of fuel, the weight of cargo and passengers, flight altitude, and the weather to include temperature, winds, etc.

There are also limitations on the crew flying the aircraft, basically limiting the amount of time the crew can participate in flying, even when there is an “augmented crew”. The crew-duty limitation is usually ten and fourteen hours which includes from pre-flight briefing to at a minimum debriefing the maintenance personnel concerning aircraft write-ups.

For this discussion, the USAF military aircraft used for transport circa the Vietnam War (1963 – 1975), are the C-130A Hercules, the KC-135 Stratotanker, the C-141A Starlifter, and the C-5A Galaxy. Commercial aircraft of the era were the DC-8, the DC-10, and the Boeing 707. Boeing later purchased McDonnell-Douglas. Please refer to the Appendix 1 for U.S. Air Force Fact Sheets and Federated American Scientist Military Analysis Network used to compare or verify missing facts on the military aircraft and Appendix 2 for Boeing’s Information on the commercial jet transports.

C-130E Hercules

The C-130E was introduced in 1962. The aircraft’s airspeed was 345 miles per hour (mph) and its ceiling was 19,000 feet at a weight of 42,000 pounds. Its range at maximum normal payload was somewhat less than at 35,000 pounds, therefore using the latter pay load; its range was 1,438 miles.1

In the early 1960s, the C-130 was used for intra- and inter-theater transport of cargo and personnel as well as other missions. However, in 1966, contract transportstook over airlifts for the 5-day R&R program, and by 1968, the Military Airlift Command (MAC) and contract transports were hauling 150,000 passengers and 45,000 tons of cargo monthly to and from SEA. At first MAC flights flew regularly only to Tan Son Nhut but later flew to other bases. Also to concentrate C-130 resources for use in Vietnam, in April 1968, the Assistant Secretary of Defense ordered overwater flights of C-130s discontinued.2

C-141 A Starlifter

The C-141A was introduced in 1964 and became operational in 1965. The aircraft’s airspeed was 500 mph, its ceiling was 41,000 feet, and its range was 2,500 miles. The range was obtained from the Federation of American Scientists (FAS) founded by the scientists of the Manhattan project.3

KC-135R Stratotanker

The KC-135 Stratotanker was first deployed in 1956. Although its primary mission was refueling, occasionally military personnel would “hop” on the aircraft to get to a designated location. The aircraft’s maximum airspeed was 530 mph at 30,000 feet. Its ceiling was 50,000 feet, and the aircraft’s range listed varies from 1,500 miles to 11,015 miles based on configuration.4

C-5A Galaxy

The C-5A Galaxy first operational C-5A was delivered in June 1970 and its initial fights to Vietnam were only to Cam Ranh Bay. Its speed is 518 mph; its ceiling was not provided in the Air Force Fact Sheet; however, the Federation of Scientists lists the ceiling at 34,000 feet with a range of 5,940 miles empty.5

DC-8

The DC-8 was the first Douglas jet-powered transport introduced in September 1959. Its cruising speed was 570 mph, its ceiling was 35,000 feet and its range was 4,773 miles in the DC-8-63 configuration.6

DC-10

The McDonnell Douglas DC-10 was introduced in 1968 and first delivered in 1971. Its cruising speed was 587 mph with a ceiling of 42,000 feet. According to Boeing, its range was 3,800 miles but the “20” series used by Northwest Orient was 5,750 miles.7

BOEING 707

The Boeing 707 was the competitor to the DC-8, and was introduced in 1957. It is the commercial addition to Boeing after the Air Force had Boeing build the KC-135. Its speed was 600 mph its ceiling was 41,000 feet. Initially built as a mid-range transport it was soon flying across the ocean and continent.8

The statistical information for the aircraft and distances between Air Force bases in the Pacific are on Table 1.

WeATHER –A Discussion of Trade Winds and Jet Streams

The Trade Winds

In latitudes north of 30º (in both the northern and southern hemispheres), the heating of land and water cause the westerly winds called the “trade winds” or “westerlies”. These winds are predominant between 30º and 50º latitude. Above the 50º latitude the cooling of the earth cause the predominant winds to be from east to west and are called the “polar easterlies”.9

Please click on the picture for better resolution! (38K)

The Jet Streams

The jet streams are fast flowing, relatively narrow air currents found in the atmosphere at around 11 kilometers (36,000 ft) above the surface of the Earth, just under the tropopause. They form at the boundaries of adjacent air masses with significant differences in temperature, such as of the polar region and the warmer air to the south. The jet stream is mainly found in the Stratosphere.

The major jet streams are westerly winds (flowing west to east) in both the Northern and the Southern Hemispheres, although in the summer, easterly jets can form in tropical regions. The path of the jet typically has a meandering shape, and these meanders themselves propagate east, at lower speeds than that of the actual wind within the flow. The theory of Rossby waves provides the accepted explanation for propagation of the meanders; Rossby waves propagate westward with respect to the flow in which they are embedded, but relative to the ground, they migrate eastward across the globe.

The 50°-60° N/S region is where the polar jetis located, with the subtropical jet located around 30°N latitude. Jet streams vary in height of four to eight miles and can reach speeds of more than 275 mph. The actual appearance of jet streams result from the complex interaction between many variables - such as the location of high and low pressure systems, warm and cold air, and seasonal changes. They meander around the globe, dipping and rising in altitude/latitude, splitting at times and forming eddies, and even disappearing altogether to appear somewhere else.

Jet streams also "follow the sun" in that as the sun's elevation increases each day in the spring, the jet streams shift north moving into Canada by summer. As autumn approaches and the sun's elevation decreases, the jet stream moves south into the United States helping to bring cooler air to the country.10

The figure below depicts latitudes of the polar and subtropical jet streams.

Polar Jet

Marked by a concentration of isotherms and strong vertical shear, this jet is the boundary between the polar air and the subtropical air. It often divides into two branches, the north and the south, and marks the high speed core of the prevailing westerlies. It is associated with the location and motion of the high and low pressure areas of the middle latitudes, and therefore, is variable in position, elevation, and wind speed. Its position tends to migrate south in the Northern Hemispheric winter and north in the summer, and its core winds increase during the winter and become less strong in the summer.11

SUBTROPICAL JET

Marked by a concentration of isotherms and vertical shear, this jet is the boundary between the subtropical air and the tropical air. It is found approximately between 25° and 35° North latitude and usually above an altitude of 40,000 feet. Its position tends to migrate south in the Northern Hemispheric winter and north in the summer.12

NAVIGATION–A Discussion of the Great Circle

The Great Circle13

A great circle is a circle on the surface of a sphere that has the same circumference as the sphere, dividing the sphere into two equal hemispheres. Equivalently, a great circle on a sphere is a circle on the sphere's surface whose center is the same as the center of the sphere. A great circle is the intersection of a sphere with a plane going through its center. A great circle is the largest circle that can be drawn on a given sphere.Great circles serve as the analog of "straight lines" in spherical geometry. See also spherical trigonometry and geodesic.

The great circle on the spherical surface is the path with the smallest curvature, and hence an arc (an orthodrome) is the shortest path between two points on the surface. The distance between any two points on a sphere is known as the great-circle distance. While this is the shortest distance between two points, if one was to travel along one it would be hard to manually steer as the heading is constantly changing (except in the case of due north or south or along the equator).

When long distance aviation or nautical routes are drawn on a flat map (for instance, the Mercator projection), they often look curved. This is because they lie on great circles. A route that would look like a straight line on the map would actually be longer.

On the Earth, the meridians are on great circles, and the equator is a great circle. Other lines of latitude are not great circles, because they are smaller than the equator; their centers are not at the center of the Earth -- they are small circles instead. Great circles on Earth are roughly 40,000 km in length, though the Earth is not a perfect sphere; for instance, the equator is 40,075 km. Some examples of great circles on the celestial sphere include the horizon (in the astronomical sense), the celestial equator, and the ecliptic.

Great circle routes are used by ships and aircraft where currents and winds are not a significant factor. For aircraft traveling westerly between continents in the northern hemisphere these paths will extend northward near or into the arctic region, while easterly flights often flew a more southerly track to take advantage of the jet stream.

This discussion is critical and essential to understanding the routing of military and military contracted flights between the Continental United States (CONUS) and Southeast Asia (SEA). It graphically illustrates why many veterans indicate that when flying to SEA they indicate stops in Alaska and Japan; specifically Eielson or Elmendorf Air Force Bases in Alaska, and Yokota, Kadena, or Naha Air Force Bases in Japan. These stops were along the Great Circle Routes and not only shortened the distance, but also utilized the “polar easterlies” for “pushing” the aircraft past normal aircraft range limitations.

It shows that military and military contracted aircraft returning from SEA would try to use flight paths as close as possibleto the trade winds and jet streams which move from west to east.

DISCUSSION- Distances,JETSTREAMS, & the great circle

While Great Circle Routes are of great use in aviation, it did not mean that they are always used, particularly during certain seasons. Prevailing winds often necessitate or make it useful to use the jet stream or other prevailing winds, particularly based on the latitudes of ports of embarkation and destination and the range of the aircraft.

Most of the bases in SEA were in the southern latitudes and therefore below the 30° N latitude. This meant that to use the Subtropical jet stream, flights flew a southerly route more often in winter and a more northerly route in summer. Later discussion will point out those routes which utilized both prevailing winds and bases used for refueling as aircraft “hopped” across the Pacific Ocean. The following Air Force Bases are in these latitudes:

LocationLatitude

U-TapaoAB, Thailand12°40′40″N, 101°00′33″E

Tan Son NhutAB, Vietnam10°81′87″N, 106°65′18″E

Clark AFB, Philippines15°11′09″N, 120°33′37″E

Kadena AFB, Okinawa26°21′20″N, 127°46′03″E

Yokota AFB, Japan35°44′55″N, 139°20′55″E

Anderson AFB, Guam13°35′N, 144°55′E

Wake Island19°18′0″N, 166°38′0″E

Midway Island28°13′N, 177°22′W

The atoll lies about 2,800 miles west of San Francisco and 2,200 miles east of Japan.

Hickam AFB, Hawaii21°19'50" N, 157°57'59" W

Elmendorf AFB, Alaska61°15'11" N, 149°47'38" W

Travis AFB, California38°15'46" N, 121°55'39" W

As an example; the C-141A used in the Vietnam War, had a maximum range of approximately 2,500 miles, flew at an altitude of 25,000 – 41,000 feet, with a speed of 500 miles per hour. The distance between Clark AFB, in the Philippines and Anderson AFB, in Guam is 1,633 miles, well within the range of the C-141A.

However, the distance between Clark AFB and the next possible landing field, Wake Island is 3,044 miles form Clark, outside the normal distance of the C-141A; unless the aircraft is able to fly at an altitude where the prevailing easterly wind is of sufficient speed to make up at least 500 – 600 miles. If the flight normally takes 5:32 hours, the prevailing wind would have to be approximately 100 miles per hour at a significant altitude to make up the time within safety parameters.

Other examples of typical flights follow:

Travis AFB, California to U-Tapao RTAFB, Thailand is 7,966 miles and would take 13 hours and 51 minutes non-stop. The following shows a picture of the Great Circle Route.

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The Great Circle Route

The following picture and tables show the first of several routes to and from SEA to CONUS to SEA.

The Northern Route

From / To / Initial
Heading / Distance / Time
VTBU (12°40'48"N 101°00'18"E) / VVTS (10°49'08"N 106°39'07"E) / 107° / (E) / 403 mi / 0:42
VVTS (10°49'08"N 106°39'07"E) / RPLC (15°11'10"N 120°33'37"E) / 70° / (E) / 984 mi / 1:43
RPLC (15°11'10"N 120°33'37"E) / RJTY (35°44'55"N 139°20'55"E) / 35° / (NE) / 1832 mi / 3:11
RJTY (35°44'55"N 139°20'55"E) / PAED (61°15'05"N 149°48'23"W) / 36° / (NE) / 3475 mi / 6:02
PAED (61°15'05"N 149°48'23"W) / KSUU (38°15'46"N 121°55'39"W) / 130° / (SE) / 1989 mi / 3:27
Total: / 8683 mi / 15:05
Code / Source / Location
VTBU / DAFIF / Rayong [U-Taphao Intl], TH
VVTS / DAFIF / Ho Chi Minh City (Saigon) [Tan Son Nhat Intl], VN
RPLC / DAFIF / Luzon [Diosdado Macapagal Intl (Clark Intl, Clark AB)], PH
RJTY / DAFIF / Tokyo [Yokota AFB], Honshu, JP
PAED / FAA / Anchorage [Elmendorf AFB], AK, US
KSUU / FAA / Fairfield [Travis AFB], CA, US

As one should notice, “the Northern Route” mimics the Great Circle Route almost exactly. Please note the time and distance of the route. Alternative routes could be made to make stops at Kadena AFB, Okinawa, Taipei, TainanAB, or Ching Chang Kang (CCK), Taiwan (Republic of China). It would generally be used in a westerly direction, in other words, from CONUS to SEA.

There are alternative routes required by the maximum ranges of the aircraft shown in the next twopictures. The below route will be called “the Northern Jet Stream Route”.

The Northern Jet Stream Route

From / To / Initial
Heading / Distance / Time
VTBU (12°40'48"N 101°00'18"E) / VVTS (10°49'08"N 106°39'07"E) / 107° / (E) / 403 mi / 0:42
VVTS (10°49'08"N 106°39'07"E) / RPLC (15°11'10"N 120°33'37"E) / 70° / (E) / 984 mi / 1:43
RPLC (15°11'10"N 120°33'37"E) / RJTY (35°44'55"N 139°20'55"E) / 35° / (NE) / 1832 mi / 3:11
RJTY (35°44'55"N 139°20'55"E) / PMDY (28°12'13"N 177°22'46"W) / 89° / (E) / 2573 mi / 4:28
PMDY (28°12'13"N 177°22'46"W) / PAED (61°15'05"N 149°48'23"W) / 21° / (N) / 2613 mi / 4:32
PAED (61°15'05"N 149°48'23"W) / KSUU (38°15'46"N 121°55'39"W) / 130° / (SE) / 1989 mi / 3:27
Total: / 10393 mi / 18:04
Code / Source / Location
VTBU / DAFIF / Rayong [U-Taphao Intl], TH
VVTS / DAFIF / Ho Chi Minh City (Saigon) [Tan Son Nhat Intl], VN
RPLC / DAFIF / Luzon [Diosdado Macapagal Intl (Clark Intl, Clark AB)], PH
RJTY / DAFIF / Tokyo [Yokota AFB], Honshu, JP
PMDY / FAA / Sand Island [Henderson Field], Midway Atoll, UM
PAED / FAA / Anchorage [Elmendorf AFB], AK, US
KSUU / FAA / Fairfield [Travis AFB], CA, US

Except for the deviation above the 50° N latitude this route is similar to the jet stream and might be flown in order to utilize the polar jet stream.

The next route was also flown if weather conditions were suitable. For naming purposes the route will be called “the Jet Stream Route” as it utilizes the trade winds and the sub-tropical jet stream. A variation for a C-5 or military contracted transport would be to Hickam AFB, Hawaii or Elmendorf AFB, Alaska then onward.