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Absolute Ceiling

The document discusses aircraft performance and static stability, focusing on thrust available versus thrust required, and the power needed for level, unaccelerated flight. It also covers the effects of altitude on power required, rate of climb, and the concepts of absolute and service ceilings. Key equations and relationships are presented to illustrate these aerodynamic principles.

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kgt.jayasooriya
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52 views29 pages

Absolute Ceiling

The document discusses aircraft performance and static stability, focusing on thrust available versus thrust required, and the power needed for level, unaccelerated flight. It also covers the effects of altitude on power required, rate of climb, and the concepts of absolute and service ceilings. Key equations and relationships are presented to illustrate these aerodynamic principles.

Uploaded by

kgt.jayasooriya
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
Available Formats
Download as PDF, TXT or read online on Scribd
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AIR CRAFT PERFORMANCE AND

STATIC STABILITY
Thrust Available and Maximum Velocity
 Thrust Required→ phenomenon associated with the
airframe
 Thrust Available → phenomenon associated with the
engine

2 AERODYNAMICS
Power required for level, unaccelerated flight
 Recall the definition of Power
 Power = Force x Velocity = F .V
 For an aircraft in level unaccelerated fight, power
required
PR = TRV
 Considering relationships derived in previous sections,

2W 3CD2 1
PR =  3
  SCL 3
C L2 / CD

3 AERODYNAMICS
Power required for level, unaccelerated flight

4 AERODYNAMICS
 CL2 
PR = TRV = DV = q S  CD , 0 + V
 eAR 

2
C
PR = q SCD ,0V + q SV L
eAR
Parasite power Induced power
required required

5 AERODYNAMICS
 Aerodynamic conditions that hold at PRmin

C D , 0 = 13 C D ,i

6 AERODYNAMICS
 Draw a line through the origin and tangent to the PR
curve→ Corresponds to TRmin (L/D max)

 The point of tangency corresponds to a minimum slope→


a minimum value of PR
V

 Mathematically,
d ( PR / V ) d (TRV / V ) dTR
= = =0
dV dV dV
Power available and maximum Velocity
 Propeller driven aircraft

PA = P

 Jet engines
PA = TAV

8 AERODYNAMICS
9 AERODYNAMICS
Effects of Altitude on the Power Required
 For sea level conditions,
2W 2W 3CD2
V0 = PR , 0 =
 0 SCL  0 SCL3
 For the given altitude,

2W 2W 3CD2
V alt= PR ,alt =
SCL SCL3

10 AERODYNAMICS
1
 0 
2

Valt = V0  
  

1
 0 
2

PR ,alt = PR ,0  
  
RATE OF CLIMB
 How fast can an airplane climb?
 How long does it take to reach a certain altitude??

14 AERODYNAMICS
Airplane in Climbing Flight

L


 Forces parallel to the flight path:

T = D + W sin 

 Forces perpendicular to the flight path:


L = W cos
TV − DV = Excess Power
Pexcess
RC =
W
Variation of ROC with Density Altitude
Time to Climb
 Rate of climb→ vertical velocity → rate of change of
distance→
dh
R/C =
dt

dh
dt =
R/C
 Time to climb from one altitude h1 to another altitude h2:
h1
dh
t=
h2
R/C
GLIDING

22 AERODYNAMICS
 Forces along the flight path
D = W sin 

 Forces perpendicular to the flight path


L = W cos
 Glide angle 1
tan  =
L
D
ABSOLUTE AND SERVICE CEILINGS
 Absolute Ceiling
 The maximum altitude above sea level at which an aircraft or
missile can maintain horizontal flight under standard
atmospheric conditions
 The altitude at which maximum rate of climb=0

 Service Ceiling
 Altitude at which rate of climb = 100ft/min
 Represents the practical upper limit of steady, level flight
Absolute Ceiling
Service Ceiling

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