1. En Route Performance
CPL Performance

2. Aim
To introduce the performance aspects associated with the climb, cruise and descent segments of flight

3. Objectives State the factors effecting climb performance
Calculate the Climb Gradient
Calculate the maximum Rate of Climb (or descent) required to avoid controlled airspace
State the factors effecting cruise performance
Define Range and state how to fly for maximum range
Define Endurance and state how to fly for maximum endurance

4. 1. Climb Performance
We can describe climb performance as either Rate of Climb or Angle of Climb
Rate of Climb (RoC):
Altitude gained over time. Expressed in feet per minute (fpm).

5. 1. Climb Performance Angle of Climb (AoC):
Altitude gained over distance. Expressed as an angle.

6. 1. Climb Performance Types of Climbs
Whenever we fly we generally aim for a particular performance
For the climb we can choose from:
Best Rate of Climb (Vy)
Best Angle of Climb (Vx)
Cruise Climb

7. 1. Climb Performance Best Rate of Climb (Vy) Best Angle of Climb (Vx)
Cruise Climb
Cruise Climb

8. 1. Climb Performance
During your BAK studies we discussed factors effecting climb performance. A summary can be found below.
Factor Effect on RoC Effect on AoC
Power
Altitude
Weight
Flap
Wind
(Extended)
(Headwind)
N/A
(Tailwind)

9. 1. Climb Performance Climb Planning
In the POH for each aircraft you will find details about climb performance.
This will include the time fuel and distance required to climb to each altitude
It may be in the form or a table or a graph

10. 2. Climb Gradient
A measure of climb performance is the climb gradient which can be achieved
Climb gradient is a measure of the height gained per distance travelled expressed as a percentage
ie, Climb Gradient = 𝐻𝑒𝑖𝑔ℎ𝑡 𝑔𝑎𝑖𝑛𝑒𝑑 𝐷𝑖𝑠𝑡𝑎𝑛𝑐𝑒 𝑡𝑟𝑎𝑣𝑒𝑙𝑙𝑒𝑑 %

11. 2. Climb Gradient
For example, you climb 500ft while covering a distance of 8,000ft. What is your climb gradient?
Height Gained
500 ft
Distance Travelled 8000 ft
The climb gradient can be calculated as follows:
To Convert to percentage multiply by 100
0.063 x 100 = 6.3%
Climb Gradient = ℎ𝑒𝑖𝑔ℎ𝑡 𝑔𝑎𝑖𝑛𝑒𝑑 (𝑓𝑡) 𝐷𝑖𝑠𝑡𝑎𝑛𝑐𝑒 𝑡𝑟𝑎𝑣𝑒𝑙𝑙𝑒𝑑(𝑓𝑡) = = 0.063
That is, for each 1 ft travelled we climb 0.063ft

12. 2. Climb Gradient
We can also work out our climb gradient based on our current Rate of Climb and Groundspeed
Climb Gradient = 𝑅𝑎𝑡𝑒 𝑜𝑓 𝐶𝑙𝑖𝑚𝑏 (𝑓𝑝𝑚) 𝑆𝑝𝑒𝑒𝑑

13. 2. Climb Gradient
For example, you are climbing at 650fpm with a TAS of 110kts and a 10kt tailwind. What is your climb gradient?
650fpm
TAS +- Wind = Groundspeed
110-10=100kts
Climb Gradient = 𝑅𝑎𝑡𝑒 𝑜𝑓 𝐶𝑙𝑖𝑚𝑏 (𝑓𝑝𝑚) 𝑆𝑝𝑒𝑒𝑑
= = 6.5 %

14. 3. Avoiding CTA
When climbing (or descending) you may have a requirement to remain in a certain class of airspace Due to the structure of controlled airspace there are “steps” which you must be aware of
50nm
CLASS C
35nm
6000
CLASS G
25nm
4000
3000

15. 3. Avoiding CTA
When calculating a climb to remain outside of CTA the first thing to do is check if there is a limiting step A limiting step has the shallowest profile; least height gain for a given distance This is important as you may have to lower your climb rate or delay the climb.
50nm
CTA
35nm
6000
Non critical
25nm
4000
Critical
3000

16. 3. Avoiding CTA
Limiting Steps: we can see that the 10/1000 step profile is has a shallower profile than 15/2000, therefore if you wish to climb at a constant RoC you will need to determine a RoC which will not infringe this limiting step
Required RoC = 𝐻𝑒𝑖𝑔ℎ𝑡 𝑡𝑜 𝑐𝑙𝑖𝑚𝑏 𝑡ℎ𝑟𝑜𝑢𝑔ℎ(𝑓𝑡) 𝑙𝑒𝑛𝑔𝑡ℎ 𝑜𝑓 𝑠𝑡𝑒𝑝 x 𝑔𝑟𝑜𝑢𝑛𝑑𝑠𝑝𝑒𝑒𝑑 60
50nm
CTA
35nm
6000
Non critical
25nm
4000
Critical
3000
10nm/1000 step
15nm/2000 step

17. 3. Avoiding CTA
For example, the steps are as pictured below and you have a groundspeed of 120kts. What is the maximum rate of climb you can maintain without entering CTA?
Required RoC = 𝐻𝑒𝑖𝑔ℎ𝑡 𝑡𝑜 𝑐𝑙𝑖𝑚𝑏 𝑡ℎ𝑟𝑜𝑢𝑔ℎ(𝑓𝑡) 𝑙𝑒𝑛𝑔𝑡ℎ 𝑜𝑓 𝑠𝑡𝑒𝑝 x 𝑔𝑟𝑜𝑢𝑛𝑑𝑠𝑝𝑒𝑒𝑑 60
= x = 200fpm
50nm
CTA
35nm
6000
Non critical
25nm
4000
Critical
3000
10nm/1000 step
15nm/2000 step

18. 3. Avoiding CTA
The method is the same for calculating a descent profile to remain inside or outside of airspace When planning our descent we must also calculate where we will be starting the descent The formula we use for this is:
Distance on Descent = 𝑇𝑜𝑡𝑎𝑙 ℎ𝑒𝑖𝑔ℎ𝑡 𝑡𝑜 𝑑𝑒𝑠𝑐𝑒𝑛𝑡 𝑡ℎ𝑟𝑜𝑢𝑔ℎ (𝑓𝑡) 𝐶𝑎𝑙𝑐𝑢𝑙𝑎𝑡𝑒𝑑 𝑚𝑖𝑛𝑖𝑚𝑢𝑚 𝑅𝑜𝐷 x 𝑔𝑟𝑜𝑢𝑛𝑑𝑠𝑝𝑒𝑒𝑑 60

19. 3. Avoiding CTA 50nm 8000 CTA 35nm 6000 25nm Non critical 4000
3000
10nm/1000 step
15nm/2000 step
For example, the steps are as pictured above, you are cruising at 5500ft and you have a groundspeed of 130kts. You are planning to descent to 2000ft. What is the minimum rate of descent you require without entering CTA?
Required RoD = 𝐻𝑒𝑖𝑔ℎ𝑡 𝑡𝑜 𝑑𝑒𝑠𝑐𝑒𝑛𝑡 𝑡ℎ𝑟𝑜𝑢𝑔ℎ(𝑓𝑡) 𝑙𝑒𝑛𝑔𝑡ℎ 𝑜𝑓 𝑠𝑡𝑒𝑝 x 𝑔𝑟𝑜𝑢𝑛𝑑𝑠𝑝𝑒𝑒𝑑 60
= x = 216fpm

20. 4. Cruise Performance
Cruise performance data is presented in either tabular or graphical format. Both show fuel flow and TAS for conditions of engine RPM and percentage power, against cruise level and temperature Cruise performance assumes correct leaning of the mixture
PRESSURE ALTITUDE(FT)
RPM
20C - STANDARD TEMPERATURE
STANDARD TEMPERATURE
20C + STANDARD TEMPERATURE
%BHP
KTAS
GPH
6000
2600
--- 77
119
8.6 72
118
8.1
2500 73
114
8.2 69
113
7.8 66
112
7.4
2400
108 63
107 7 60
106
6.7
2300
103 57
101
6.4 55 99
6.2
2200 54 96
6.1 52 95
5.9 50 92
5.8
2100 49 90
5.7 47 88
5.5 46 86
8000
2650
121
120
8.7
117 70
111
7.1 58
104
6.5
100 53 97 6 93 91

21. 4. Cruise Performance
To use the tables find the desired % power for the intended cruise level then read off the TAS, fuel flow and RPM For example, if the planned altitude is 6000ft on an ISA day. What RPM should we use and what TAS and fuel flow should we expect if we want 65% power?
PRESSURE ALTITUDE(FT)
RPM
-20C STANDARD TEMPERATURE
STANDARD TEMPERATURE
20C +STANDARD TEMPERATURE
%BHP
KTAS
GPH
6000
2600
--- 77
119
8.6 72
118
8.1
2500 73
114
8.2 69
113
7.8 66
112
7.4
2400
108 63
107 7 60
106
6.7
2300
103 57
101
6.4 55 99
6.2
2200 54 96
6.1 52 95
5.9 50 92
5.8
2100 49 90
5.7 47 88
5.5 46 86
8000
2650
121
120
8.7
117 70
111
7.1 58
104
6.5
100 53 97 6 93 91

22. 4. Cruise Performance
When considering cruise performance we can elect to cruise in a number of different configurations based on our specific requirements
These requirements may be:
Travel the furthest distance for the fuel on board
Stay in the air for the longest possible time
Operate the aircraft at the lowest cost
Get to the destination at in the minimum amount of time

23. 5. Range
Range We may be given the requirement to “travel the furthest distance for a given amount of fuel” This is known as flying for Maximum Range Flying for maximum range is often a requirement if we need to carry the maximum amount of payload

24. 5. Range
Range
To fly for Maximum range we require the best ratio of TAS to fuel flow
For our aircraft the fuel flow relates directly to the PWR required
Pwr Reqd.
Power
Velocity (TAS)

25. 5. Range
Range
To find the best ratio of TAS to fuel flow (in nil wind) we plot a tangent to the PWR required graph which intersects at the origin
Pwr Reqd.
Power
Velocity (TAS)

26. 5. Range
Range
If we have any wind we must take this into account
To do this we move the point where we draw the tangent from to a location on the graph where the groundspeed is 0
Eg, if we have a 20kt headwind:
Pwr Reqd.
Power
20kt
Velocity (TAS)

27. 5. Range Range Pwr Reqd. Eg, if we have a 20kt tailwind: Power
Velocity (TAS)

28. 5. Range Range Pwr Reqd. Comparison of wind conditions on range Power
Headwind
Power
Nil Wind
Tailwind
20kt
20kt
Velocity (TAS)

29. 5. Range
Range
In practice we do not have a PWR required graph for our aeroplane so we must derive this information from the cruise performance tables
We need to determine the maximum distance we can travel for the minimum fuel
If we divide the groundspeed by fuel flow we can determine our Ground Nautical Miles per gallon of fuel
Ground Nautical Miles per gallon = 𝐺𝑆 𝐹𝑢𝑒𝑙 𝐹𝑙𝑜𝑤

30. 5. Range Range Here is a cruise performance chart for a typical C172
For nil wind conditions the GNMPG has been calculated
PRESSURE ALTITUDE(FT)
RPM
-20C STANDARD TEMPERATURE
STANDARD TEMPERATURE
%BHP
KTAS
GPH
GNMPG
6000
2600
--- 77
119
8.6
2500 73
114
8.2 69
113
7.8
2400 66
108
7.4 63
107 7
2300 60
103
6.7 57
101
6.4
2200 54 96
6.1 52 95
5.9
2100 49 90
5.7 47 88
5.5 16
8000
2650
121
8.7
118 70
112
7.1
106 55
100
6.2 6 50 93
5.8
Green Line shows best range in nil wind in ISA conditions
Occurs at higher altitude and 2300 RPM for 8000ft

31. 6. Endurance
Endurance If we have a requirement to “stay in the air for the longest time” This is known as flying for Maximum Endurance Flying for maximum endurance is often a requirement if we need to hold for weather

32. 6. Endurance Endurance Pwr Reqd.
To fly for Maximum Endurance we require the minimum fuel flow
For our aircraft the fuel flow relates directly to the PWR required
Pwr Reqd.
Power
Velocity (TAS)

33. 6. Endurance Endurance Pwr Reqd.
When PWR required is at a minimum fuel flow is at a minimum therefore that is the PWR required for maximum range
Pwr Reqd.
Power
Velocity (TAS)

34. 6. Endurance
Endurance
Wind has no significant effect on endurance as the distanced covered is not important
When flying for maximum endurance you should fly at the minimum altitude (safely!) as PWR required increases with an increase in altitude
The speed for maximum range corresponds to Vy