A fully loaded Boeing 747 “Jumbo Jet” would depart on an ordinary long-distance flight at about 160 knots (184 mph). The length of the runway, weight, and environmental factors are used to calculate takeoff speeds. A 747 “Jumbo Jet” would typically land at 145 kts to 150 kts depending on the landing flap setting (166mph-172mph).
Engine Thrust
Most airlines and airplanes have the option to de-rate power for takeoff (or utilize assumed temperatures). This occurs on runways where the aircraft is operating at a high performance level, such as when it can take off without using the entire runway. Large commercial airplanes rarely use their full engine power during takeoff since the majority of runways at big airports are long enough to tolerate a drop in thrust. Up to 75% of the maximum force could be used for the takeoff thrust.
Less thrust during takeoff lowers the temperature to which the engine’s various parts are exposed. In consequence, this can significantly lessen engine wear and Tᴇᴀʀ, minimize maintenance costs, and ultimately increase engine life.
Additional Speed for Landing
The flap setting should be higher the slower the takeoff and landing speed. Most jumbo planes land on flaps 25 or 40. To give a speed “buffer” in case of any velocity fluctuations, pilots often fly the approach speed quicker than the touchdown speed. When the nose is elevated just before touchdown, the surplus speed reduces, or to put it another way, it is “bled off” during the flare. In low wind conditions, we would increase the approach speed by 5 kts; in high wind conditions, we might increase it by 20 kts. Maximum takeoff weight for the B747 is 396,000 KGS (or 875,000 LBS).
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Video resource: Captain Boeing
