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2017-06-20 22:18:44[媒体名称] bbc [新闻日期] 2017/6/20
[网址] 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.
凤凰城今日天气预报指出气温可能会上升至120F(摄氏49度)
超过某些小飞机所能飞行的最高气温(48度) 因此必须取消这些航班
该地高温历史纪录则为1990年六月创下的 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.
当温度升高的时候 空气密度下降 因此机翼能产生的升力也会减少
ICAO去年就有警告气候变迁造成的高温可能对飞机起飞时造成负面影响
高海拔或较短的跑道也会限制飞机的载重
因此许多中东国家或南美高海拔的机场倾向把长途航班排在较凉的傍晚或晚上
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".
大一点的飞机例如747或空中巴士就能承受比较高的温度 故此次在凤凰城并未受到影响
美国航空声称这些机种应该可以承受到摄氏53度
不过这个温度似乎正是某些地区(Furnace Creek)今天预期会达到的...