「我離港前到過一間精神科醫院。當時有位病人禮貌地問,一個以作為世上最悠久民主政體而自傲的國家,如何能夠將此地交給一個政治制度非常不同的國家,且既沒諮詢當地公民,又沒給予他們民主的前景,好讓他們捍衞自己的將來。一個隨行同事說,奇怪,香港提出最理智問題的人,竟在精神科醫院。」彭定康 金融時報

“During a visit to a mental hospital before I left Hong Kong, a patient politely asked me how a country that prided itself on being the oldest democracy in the world had come to be handing over his city to another country with a very different system of government, without either consulting the citizens or giving them the prospect of democracy to safeguard their future. Strange, said one of my aides, that the man with the sanest question in Hong Kong is in a mental hospital.”Chris Patten Financial Times

Non Chinese literate friends, please simply switch to English Version provided by LOUSY Google Translation

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敬請參與在右下方的不記名訪客分佈調查問卷,你是: ?

Tuesday, August 27, 2013






Forest Gump Feather (main theme music)



《衝上雲霄II》在熱播中,又剛剛看完 the lone ranger 《獨行俠》,見到北美洲遼闊的平原,令 嗜悲 想飛和自駕遊。(剛剛 Check 完 CX Fanfares 三千幾可以到三藩市 maximum 14天,連稅都是 五千八不用六千元,但假期唔批可惜可惜,無緣去看看 Monument Valley!)



Monument Valley Sunrise to Moonrise (More ... )



各位飛長途遠程飛機可有留意得到,從香港由西至東到美加紐約多倫多,或從香港由東至西去歐洲倫敦法蘭克福,去程飛機航線經過那處,至於回程方向是否剛剛相反。若多留意,還會發覺來回程所需時間很大分別,那就要知道下面的一些航空資料。


Jet streams on earth (維基百科)



因為地球上有 Jet Stream 這個天文現象。


【ehow.com】The atmosphere is filled with constantly moving air streams, determined by the temperature differences in various areas of the earth. One of these is the jet stream, which runs east to west around the world.


The jet stream is a very fast current of air. It always moves faster than 57 miles per hour, and can reach speeds of around 200 miles per hour. It is located 6 to 9 miles above the surface of the Earth and moves quickest during the winter, where there is a greater temperature difference at the Earth's surface.

Flight Time
The jet stream is both used and avoided by aircraft. Because it so fast moving, flights that are heading east to west navigate around the jet stream in order to avoid it as a headwind, which can greatly reduce the speed of an aircraft and the flight time. However, flights heading east can use the jet stream to cut down their total flight time.

Fuel
By flying with the jet stream, aircraft can also use less fuel by allowing the fast-moving air to push them along. This also allows them to carry less fuel than usual, making them lighter. This will also help the aircraft move faster, reducing flight time even more.



Jetstream and Great Circle airplane routes (維基百科)


由東至西由西至東,便有了選擇途程需要,利用 Jet Stream Route 和 Great Circle Route 了。


【維基百科】The location of the jet stream is extremely important for aviation. Commercial use of the jet stream began on 18 November 1952, when Pan Am flew from Tokyo to Honolulu at an altitude of 7,600 metres (24,900 ft). It cut the trip time by over one-third, from 18 to 11.5 hours.

Not only does it cut time off the flight, it also nets fuel savings for the airline industry. Within North America, the time needed to fly east across the continent can be decreased by about 30 minutes if an airplane can fly with the jet stream, or increased by more than that amount if it must fly west against it.

Associated with jet streams is a phenomenon known as clear-air turbulence (CAT), caused by vertical and horizontal wind shear connected to the jet streams. The CAT is strongest on the cold air side of the jet, next to and just underneath the axis of the jet.

Clear-air turbulence can cause aircraft to plunge and so present a passenger safety hazard that has caused fatal accidents, such as the death of one passenger on United Airlines Flight 826.



根據 Great Circle 理論,如今蘇聯已經解體,俄國開放了領空給商業航機。


Great Circle and Polar airplane routes (維基百科)



【維基百科】The American Federal Aviation Administration defines the North Polar area of operations as the area lying north of 78 deg north latitude, which is entirely north of Alaska and most of Siberia.

The term "polar route" was originally more general, being applied to great circle routes between Europe and the west coast of North America in the 1950s. During much of the Cold War the Arctic region was a buffer zone between the Soviet Union and North America; civilian flights from Europe to the Asian Far East were unable to cross the Soviet Union or China and had to use a Middle East route or connect through Alaska across the Arctic region.

These Cold War tracks extended from the northern Alaskan coast across Greenland to Europe. Korean Air Lines Flight 902 was shot down in the USSR in 1978 after the crew made gross navigational errors attempting to fly the assigned polar route.

In September 1945, three American generals flew three Boeing B-29 Superfortresses from Northern Japan to Chicago in a record-breaking flight, using a great circle route which came very near the Arctic Circle.

The flight encountered dangerously icy conditions, but the possibility of future routine flights was announced, as was the possibility of hostile attacks through the Arctic Circle. Routine flights deep into the Arctic became possible only after the end of the Cold War, when the United States and Russia became less concerned about the possibility of a trans-polar attack.

Aircraft such as the Boeing 747-400 and the Airbus A340, with ranges of around 7,000 nautical miles (13,000 km), were also required to handle the distances between suitable airports. Before this era, all flights from North America to Asia were routed around the Communist bloc using a series of tracks between Alaska and Japan.

The main obstacle to flights across Russia was the inadequate Russian air traffic control system and a lack of English communication. To solve these issues RACGAT (Russian-American Coordinating Group for Air Traffic) was formed in 1993. By summer 1998 the Russian government gave permission to open four cross-polar routes, named Polar 1, 2, 3 and 4. Cathay Pacific flew the first polar flight into Siberia in July 1998.

Polar routes are now in common use by airlines connecting Asian cities such as Bangkok, Beijing, Dubai, Hong Kong, New Delhi, Seoul, Singapore, and Tokyo to North American destinations such as New York, Chicago, Detroit, Houston, Los Angeles, San Francisco, Toronto, Vancouver and Washington DC.



想飛?談何容易,但 嗜悲 身不由己,除了要申請大假外,去美加自駕游,要事先 pre-planning 不是一時三刻,就可以完成,不過發發夢還是可以的!






伸延閱覽:
Jet Stream Affect Flights ehow.com
Jet Stream/ Great circle Aviation 維基百科
Polar route 維基百科








2 comments:

chiseenjai said...

我飛多倫多, 都係 great circle.

第一次, 以為係東至西, 西至東, 後來諗番, 地球係圓...

依家又知道,飛 great circle, 係 "俄國開放了領空"...

haha :D

the inner space said...

慈善兄:去北美洲我搭過 UA CX AC SQ 的航機,分別:東岸 中西部 西岸 的城市,去程的直航路線必然是趁著 Jet Stream 來飛,一方面慳油航程時間,一般也是短一些。

回程時通常直航香港,也試過不是直航香港,因為沒有 Jet Stream 之利,航線用 great circle 或 polar route,很視附點與點的地理。

我最慘一次是本來直航回港,但逆風 head wind 超強勁,航機被被逼改道飛 Alaska 的 Anchorage 加油,幸好航機預了兩批服務員和足夠機師,不用因超過國際條例時限,需要停飛換班,結果也比預計多了 6小時。