[媒體名稱] bbc [新聞日期] 2017/6/20
[網址] http://www.bbc.com/news/world-us-canada-40339730
As temperatures climb in Phoenix, Arizona, more than 40 flights have been
cancelled - because it is too hot for the planes to fly.
The weather forecast for the US city suggests temperatures could reach 120F
(49C) on Tuesday.
That is higher than the operating temperature of some planes.
American Airlines announced it was cancelling dozens of flights scheduled to
take off from Sky Harbor airport during the hottest part of the day.
The local Fox News affiliate in Phoenix said the cancellations mostly
affected regional flights on the smaller Bombardier CRJ airliners, which have
a maximum operating temperature of about 118F (48C).
The all-time record for temperatures in Phoenix is just slightly higher, at
122F, which hit on 26 June 1990.
The cancelled flights were scheduled to take off between 15:00 and 18:00
local time.
鳳凰城今日天氣預報指出氣溫可能會上升至120F(攝氏49度)
超過某些小飛機所能飛行的最高氣溫(48度) 因此必須取消這些航班
該地高溫歷史紀錄則為1990年六月創下的 122F (50C)
Why can't planes fly?
At higher temperatures, air has a lower density - it is thinner. That lower
air density reduces how much lift is generated on an aircraft's wings - a
core principle in aeronautics.
That, in turn, means the aircraft's engines need to generate more thrust to
get airborne.
It's a well-known problem - a 2016 report from the International Civil
Aviation Organization (ICAO) even warned that higher temperatures caused by
climate change could "have severe consequences for aircraft take-off
performance, where high altitudes or short runways limit the payload or even
the fuel-carrying capacity".
Those problems are why many countries in the Middle East, and some
high-altitude airports in South America, tend to schedule long flights for
the evening or night, when it is cooler.
當溫度升高的時候 空氣密度下降 因此機翼能產生的升力也會減少
ICAO去年就有警告氣候變遷造成的高溫可能對飛機起飛時造成負面影響
高海拔或較短的跑道也會限制飛機的載重
因此許多中東國家或南美高海拔的機場傾向把長途航班排在較涼的傍晚或晚上
Bigger aircraft like Boeing 747s and Airbus models have a slightly higher
operating temperature, and have not been affected by the heat in Phoenix.
An American Airlines statement provided to The Arizona Republic newspaper
said those jets should be fine up to 126-127F (53C) - just a little higher
than what is expected.
Those temperatures, however, are forecast for the aptly named Furnace Creek
in Death Valley, in California, with some areas expecting new temperature
records on Tuesday.
The Death Valley National Parks Service has issued a warning to visitors to
avoid hiking after 10am, and to "travel prepared to survive".
大一點的飛機例如747或空中巴士就能承受比較高的溫度 故此次在鳳凰城並未受到影響
美國航空聲稱這些機種應該可以承受到攝氏53度
不過這個溫度似乎正是某些地區(Furnace Creek)今天預期會達到的...