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Question: a boeing 747400 cruises at mach 086 at an altitude...

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A Boeing 747-400 cruises at Mach 0.86 at an altitude of 35,000 feet. At mid- cruise the aircraft weight is 3.20 MN and the total thrust from four engines is 185 kN 6 (a) Determine the lift coefficient and lift-to-drag ratio (L/D) if the wing area is 510 m2. Data at 35,000 feet: static temperature and pressure are 219 K and 23.8 kPa. Compare your calculations with the flight data for the 747-400 shown in Figure Q6a. With reference to the boundary layer, explain why the lift-to-drag ratio reduces significantly as the Mach number increases from 0.86 to 0.88 (b) 19 0.86 Man sevoto て 16 Flight Mach No 0.88 Boeing 747-400 Cruise Data at 35000 ft 14 Figure Q6a (left) and Q6b (above) 12 0.2 0.3 04 0.5 06 07 0.8 Lift coefficient Due to fuel burn, the weight of the 747 reduces to 2.4 MN when it lands with a sea-level airspeed of 60 m/s using mechanical high-lift devices. (c) Determine the lift coefficient at landing. Also, sketch typical boundary layer velocity profiles for aerofoils employing the mechanical high-lift devices shown in the Figure Q6b. With reference to the boundary layer, discuss how these slats, vanes and flaps increase lift. (d) Sketch, qualitatively, a plot of lift coefficient versus angle of attack for (i) a typical plain, cambered aerofoil;) one with a leading-edge slat; and (ii one with both slats and trailing edge flaps. In October 1995 NASA conducted Mach 1.6 flight tests using an F16-XL with a titanium suction panel on the port (lef) wing, as illustrated in Figure Q6c. With reference to the boundary layer, discuss the purpose of these experiments. (e) ntanium Suctian Panel Figure Q6c Air ducted

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