The قطار Diaries
A variable geometry wing is usually improved in flight to a different shape. The variable-sweep wing transforms concerning an economical straight configuration for takeoff and landing, to the lower-drag swept configuration for top-pace flight.گوتارد اکسپرس، سوئیس، ۱۸۹۷ آغاز به کار قطارها به سدهٔ ۱۵۰۰