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AE 2350 Lecture Notes #10

AE 2350 Lecture Notes #10. May 14, 1999. TOPICS TO BE STUDIED. Take-off and Landing Performance Introduction to Aircraft Stability and Control. Take-Off Performance. FAA has a number of regulations called FAR that the aircraft should meet.

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AE 2350 Lecture Notes #10

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  1. AE 2350 Lecture Notes #10 May 14, 1999

  2. TOPICS TO BE STUDIED • Take-off and Landing Performance • Introduction to Aircraft Stability and Control

  3. Take-Off Performance • FAA has a number of regulations called FAR that the aircraft should meet. • e.g. Total Takeoff Distance including a clearance of 35 foot structure at the end of the runway. • One engine out condition. • Figure 15.26 and figure 15.29 in the text give curves for the total takeoff distance, for all engine operation, and one engine out condition, respectively. • Compute these for your fighter and ensure they are below 6,000 ft. • Use Cl,max = 1.7, • Here L is the wing sweep computed as sweep of the line joining the midchord at the root and the midchord at the tip. The above equation (13.4) empirically corrects for sweep and aspect ratio.

  4. Takeoff Performance Theory We attempt to compute the ground roll as accurately as possible. Add an extra 20% distance to account for transition and climb. Transition and climb 20% of total takeoff distance, from experience Ground Roll 80% of total takeoff distance, from experience.

  5. Ground Roll Let v be the aircraft speed. dv/dt = a where a= acceleration of the vehicle a= (All horizontal forces acting on the aircraft) / (Mass of aircraft) Integrate: v = at Velocity at lift-off vLO = a tLO Integrate again: d = 1/2 a t2 dLO = 1/2 a t2LO = v2LO/(2a)

  6. Ground Roll (Continued) From the previous slide, the total roll distance is dLO = 1/2 a t2LO = v2LO/(2a) a = Acceleration of the aircraft due to horizontal forces on it. These forces are: Thrust, Drag, Ground Friction Thrust far exceeds the other two factors during takeoff. Thus, a = T/(Aircraft Mass) = T g/ (GW) Then, total roll distance is dLO = v2LO/(2a) = v2LO. GW/(2Tg)

  7. Ground Roll (Continued) Total roll distance dLO = v2LO. GW/(2Tg) The pilot usually lifts off at 1.2 times stall velocity. Stall velocity VStall is defined from: 1/2 r V2Stall CLmax S= GW V2Stall= GW/(1/2 r CLmax S) v2LO =(1.2 VStall)2 = 1.44 GW/(1/2 r CLmax S) Then, dLO = v2LO. GW/(2Tg)= 1.44 (GW)2 / (TgrS CLmax) Multiply this by 1.25 to include transition and climb The result, after additional factors of safety, is figure 15.26 in text.

  8. Landing Performance Use figure 15.35, which was derived using arguments similar to take-off performance. There is considerable scatter in landing distances due to use of spoiler, brakes, reverse thrust, human factors ground conditions : wet runway , dry runway Use the dotted line in figure 15.35 in the text.

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