1. POWER GRAPHS
Performance

2. POWER 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

3. TOTAL DRAG
D
Ve
INDUCED DRAG
PARASITE
DRAG
TOTALDRAG
VMD
(max L/D
ratio)

4. MINIMUM DRAG SPEED
D
Ve
LOW
WEIGHT
PARASITE
DRAG
VMD1
HIGH
WEIGHT
VMD2

5. INFLUENCE OF WEIGHT
D
Ve
W = 20k
W = 10k
W = 30k
VMD1 VMD2 VMD3

6. INFLUENCE OF ALTITUDE
D
Ve
ANY LEVEL

7. INFLUENCE OF ALTITUDE
D
VTAS
SEA
LEVEL
10000ft
20000ft
DMIN = cte

8. SUMMARY
 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.

9. POWER REQUIRED
Pr
Ve
MINIMUM POWER
REQUIRED
MINIMUM DRAG
(MAX L/D RATIO)
POWER = DRAG x SPEED

10. INFLUENCE OF WEIGHT
Pr
Ve
W = 20k
W = 10k
W = 30k

11. INFLUENCE OF ALTITUDE
Pr
Ve
SEA
LEVEL
10000
ft
20000
ft
VMin PR

12. INFLUENCE OF ALTITUDE
Pr
VTAS
SEA
LEVEL
10000
ft
20000
ft

13. SUMMARY
 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.

14. POWER AVAILABLE
Pa
Ve
FULL THROTTLE
80 %
50 %

15. INFLUENCE OF ALTITUDE
Pa
Ve
SEA LEVEL
5000 ft

16. MIN & MAX SPEEDS
Pa
Ve
VMIN VMAX
EXCESS OF
POWER

17. MIN & MAX SPEEDS
Pa
Ve
VMin PR
EXCESS OF POWER
LACK OF POWER
SPEED IS
STABLE
SPEED IS
UNSTABLE