power graphs intro
TRANSCRIPT
POWER GRAPHSPOWER GRAPHS
PerformancePerformance
POWER GRAPHSPOWER GRAPHS
TOTAL DRAG (thrust required)
• Minimum drag speed
• Influence of weight
• Influence of altitude
POWER REQUIRED
• Minimum power required speed
• Influence of weight
• Influence of altitude
POWER AVAILABLE
• Influence of altitude
• Minimum and maximum speeds
TOTAL DRAGTOTAL DRAG
D
Ve
INDUCED DRAG
PA
RA
SIT
E D
RA
GTOTA
L D
RA
G
VMD
(max L/D ratio)
MINIMUM DRAG SPEEDMINIMUM DRAG SPEED
D
Ve
LOW WEIGHT
PA
RA
SIT
E D
RA
G
VMD1
HIGH WEIGHT
VMD2
INFLUENCE OF WEIGHTINFLUENCE OF WEIGHT
D
Ve
W = 20k
W = 10k
W = 30k
VMD1 VMD2 VMD3
INFLUENCE OF ALTITUDEINFLUENCE OF ALTITUDE
D
Ve
ANY LEVEL
INFLUENCE OF ALTITUDEINFLUENCE OF ALTITUDE
D
VTAS
SE
A L
EV
EL
1000
0 ft
2000
0 ft
DMIN = cte
SUMMARYSUMMARY
Induced drag decreases with speed, whilst parasite drag increases.
Flying at the minimum drag speed, parasite drag equals induced drag.
The minimum drag speed corresponds to max. L/D ratio speed.
If weight is increased, the minimum drag speed will be higher.
In terms of EAS, the minimum drag speed does not change with altitude.
In terms of TAS, the minimum drag speed increases with altitude, but the minimum drag value remains constant.
POWER REQUIREDPOWER REQUIRED
Pr
Ve
MINIMUM POWER REQUIRED
MINIMUM DRAG
(MAX L/D RATIO)
POWER = DRAG x SPEED
INFLUENCE OF WEIGHTINFLUENCE OF WEIGHT
Pr
Ve
W = 20k
W = 10k
W = 30k
INFLUENCE OF ALTITUDEINFLUENCE OF ALTITUDE
Pr
Ve
SEA LEVEL
1000
0 ft
2000
0 ft
VMin PR
INFLUENCE OF ALTITUDEINFLUENCE OF ALTITUDE
Pr
VTAS
SEA LEVEL
10000 ft
20000 ft
SUMMARYSUMMARY
The minimum power speed is lower than the minimum drag speed.
More weight obviously increases the power required.
Although the minimum power required increases with altitude, the minimum power required speed (EAS) remains constant.
Both minimum power required speed and minimum drag speed increase with altitude in terms of TAS.
POWER AVAILABLEPOWER AVAILABLE
Pa
Ve
FULL THROTTLE
80 %
50 %
INFLUENCE OF ALTITUDEINFLUENCE OF ALTITUDE
Pa
Ve
SEA LEVEL
5000 ft
MIN & MAX SPEEDSMIN & MAX SPEEDS
Pa
VeVMIN VMAX
EXCESS OF POWER
MIN & MAX SPEEDSMIN & MAX SPEEDS
Pa
VeVMin PR
EXCESS OF POWER
LACK OF POWER
SPEED IS STABLE
SPEED IS UNSTABLE