ESTIMATION OF CRITICAL MACH NUMBER AE-705 Introduction to Flight - PowerPoint PPT Presentation

Question No 1 ESTIMATION OF CRITICAL MACH NUMBER AE-705 Introduction to Flight Tutorial-05

Consider the NACA 0012 airfoil and its C p distribution @ AoA = 0 These are low-speed values measured in a wind tunnel at Re = 3.65 million Estimate M crit accurate upto three decimal places Solve the implicit equations Take intervals of 0.1, starting from M = 0.70 SOLVE !! AE-705 Introduction to Flight Tutorial-05

SOLUTION M crit = 0.737 AE-705 Introduction to Flight Tutorial-05

Question No 2 ESTIMATION OF WAVE DRAG AE-705 Introduction to Flight Tutorial-05

Consider Lockheed F- 104 supersonic fighter 4𝛽 𝐷 L = 𝑁 2 ∞ − 1 4𝛽 2 𝐷 D,wave = 𝑁 2 ∞ − 1 If it weighs 7260 kg and is flying level at Mach 2.2 at 11 km ISA, estimate the Wave Drag of the wings, if the wing reference area is 19.5 m 2 SOLVE !! AE-705 Introduction to Flight Tutorial-05

SOLUTION  T 11 = ? = 288.16 – (0.0065*11000) = 216.66 K  ρ 11 = ?  ρ 11 = ρ SL * {T 11 /T SL } 4.257 = 0.3648 kg/m 2  a 11 = ?  a 11 = ( γ RT 11 ) 0.5 = (1.4*287*216.66) 0.5 = 295.05 m/s AE-705 Introduction to Flight Tutorial-05

SOLUTION  V 11 = ?  V 11 = a 11 *M = 295.05*2.2 = 649.11 m/s  q 11 = ?  q 11 = ½ ρ 11 V 2 = ½*0.3648*649.11 2 = 76852.6 Pa  C L = ?  C L = L/qS ref = W/qS ref in level flight = (7260*9.81) / (76852.6*19.5) = 0.04752 AE-705 Introduction to Flight Tutorial-05

SOLUTION  Since F-104 has thin wings, and ignoring Lift produced by Fuselage : 4𝛽 𝐷 L = 𝑁 2 ∞ − 1  α = ? 𝛽 = 𝐷 L 𝑁 2 ∞ − 1  α = 0.04752 * 0.25*(2.2 2 -1) 0.5 4 = 0.02327 radians (i.e., 1.333 degrees) 4𝛽 2 C D,W = ? 𝐷 D,𝑋 =  C D,W = 4 * 0.02327 2 / (2.2 2 -1) 0.5 𝑁 2 ∞ − 1 = 1.1053 x 10 -3  D wave = ?  D wave = q 11 S ref C D,W = 76852.6*19.5*1.1053 x 10 -3 = 1656 N AE-705 Introduction to Flight Tutorial-05

D: The T-tail retained pitch A: Original F-104s had a B: The area C: The General Electric control at transonic speed. downward-firing ejector seat, in front of the canopy was J79-GE-11A afterburning This had been a problem in a feature more usually found painted black to reduce glare turbojet took up a lot of earlier designs flying close to in Soviet jets. for the pilot. fuselage length the sound barrier. E:The tiny 22-ft wing was H: The Starfighter was not optimized for Mach 2.2 F: Supersonic flying required G: 1 × 20 mm (0.79 in) M61 originally designed to have performance. The anhedral, new cutting edge technology Vulcan radar, a decision that was or downward angle, gave a at the intakes Gatling gun, 725 rounds soon changed. A simple very high rate of roll. range-only set was fitted. Question No 3 PLOTTING OF C L V/S M ∞ OF F-104 AE-705 Introduction to Flight Tutorial-05

 F -104 has a thin, symmetric airfoil with a thickness ratio of 3.5 percent.  Consider this airfoil in a flow at AoA = 5 deg.  The incompressible lift coefficient for the airfoil is C l = 2 πα , where α = AoA in radians  Plot C l v/s M for 0.2 ≤ M ≤ 2.0, in steps of 0.2 SOLVE !! AE-705 Introduction to Flight Tutorial-05

SOLUTION AE-705 Introduction to Flight Tutorial-05