AE 2350 Lecture Notes

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AE 2350 Lecture Notes 10

• May 14, 1999

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TOPICS TO BE STUDIED

• Take-off and Landing Performance
• Introduction to Aircraft Stability and Control

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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.

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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.
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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)
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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)
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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.
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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.