1. Temperature Datum System
Author: Kev Mc Henry

2. Identify the components and their location
Describe the system
Identify the components and their location
List significant specifications
Describe the system interface
Objectives

3. Temperature Datum System
The Temperature Datum (TD) system is used to electronically trim the fuel to the engine.
The TD system will:
a. Provide over-temperature protection during start and in flight.
b. Maintain a selected temperature in flight.
The Temperature Datum (TD) system is used to electronically trim the fuel to the engine.
The TD system will:
a. Provide over-temperature protection during start and in flight.
b. Maintain a selected temperature in flight.
Temperature Datum System
TD system requirements 2

4. Temperature Datum System
Components in the TD system are:
The Speed Sense Control.
The Thermocouples.
The TD Control switch.
The TD amplifier.
The TD valve.
The Co-ordinator/Discriminator.
The electronic Fuel Correction lights.
The components in the TD system are:
1. The Speed Sense Control.
2. The Thermocouples.
3. The TD Control switch.
4. The TD amplifier.
5. The TD valve.
6. The Co-ordinator/Discriminator.
7. The electronic Fuel Correction lights.
Temperature Datum System
Photo of TD components 3

5. TD Overview

6. Temperature Datum System
Co-ordinator/
Discriminator
Speed
Sense
Control TD
Valve
Show the location of the following:
The Speed Sense Control.
The Co-ordinator/Discriminator.
The TD valve.
Temperature Datum System
Photo of TD components 4

7. Fuel System Tubing TD system Operation
This slide and the next will explain the ‘Cross-over’ bump.
Crossover occurs at 66o throttle position. The TD system changes from Temperature Limiting to Temperature controlling. This change is effected by a micro-switch in the Co-ordinator /Discriminator.
Fuel System Tubing
TD system Operation 18

8. Temperature Datum SystemTD
Amplifier
Thermocouples
Show the location of the following:
The Thermocouples.
The TD amplifier.
Temperature Datum System
Photo of TD components 5

9. Temperature Datum System
Electronic Fuel
Correction Lights
TD Control
Switches
Show the location of the following:
The Electronic fuel correction lights.
The TD control switches.
Temperature Datum System
TD valve 6

10. Temperature Datum Valve
Corrected
Fuel Out
Null Orifice
Bypass
Valve
Motor/
Generator
Take Reset
Solenoid
Venturi
Recap the basic component parts of the TD valve.
20% Take
Stop
50% Take
Stop
Bypassed Fuel
(5% - 70% of input fuel)
120% of Required
Fuel in from FCU
Temperature Datum Valve
Bypass valve - null 7

11. Temperature Datum Valve
Corrected
Fuel Out
Null Orifice
Bypass
Valve
Motor/
Generator
Take Reset
Solenoid
Venturi
20% Take
Stop
50% Take
Stop
Bypassed Fuel
(5% - 70% of input fuel)
120% of Required
Fuel in from FCU
Temperature Datum Valve

12. Bypass Needle NULL (always bypass 20%) 120% in 100% out
Explain the standard bypass rate of 20% when the needle is in NULL.
Bypass Needle
Bypass valve - Max put 8

13. Bypass Needle NULL (always bypass 20%) MAX PUT + 15% (bypass 5%) 120%in
100%
out
120% in
115%
out
Explain the bypass rate when the needle is at MAX PUT.
Bypass Needle
Bypass valve - Max take 9

14. Bypass Needle NULL (always bypass 20%) MAX PUT + 15% (bypass 5%)
MAX TAKE - 20%/50%
(bypass 40%/70%)
120% in
100%
out
120% in
115%
out
120% in
80%/50%
out
Explain the bypass rate when the needle is at MAX TAKE. (50% up to 94% RPM and 20% above that).
Bypass Needle
TD system Operation 10

15. TD Valve Adjustment

16. Temperature Datum Amplifier

17. TD Amp Installed

18. 3 things affect the operation of the T.D. system:
Position of the TD control switch. (NULL - LOCKED - AUTO).
Engine RPM. (<94% & >94%).
Throttle position (<66O & >66O).
3 things affect the operation of the TD system:
1. Position of the TD control switch.
(NULL - LOCKED - AUTO).
2. Engine RPM. (<94% & >94%).
3. Throttle position (<66O & >66O).
T. D. System Operation
TD system Operation 11

19. T. D. System Operation - Null
TD Control switch to NULL:
If the TD control switch is in the NULL position, the TD Valve will remain in 20% bypass position.
In NULL, the Fuel Correction lights behave in the same manner as for AUTO but the TD valve will not move.
NB: In ‘NULL’, > 66o throttle, there is NO Overtemperature protection if 1077o is exceeded.
TD Control switch in NULL:
If the TD control switch is in the NULL position, the TD Valve will remain in 20% bypass position.
In NULL, the Fuel Correction lights behave in the same manner as for AUTO but the TD valve will not move.
T. D. System Operation - Null
TD Controlling check 23

20. “NULL” TD System OFF

21. T. D. System Operation - Start Limiting
TD Control switch in AUTO:
Starting:
LSGI selected:
RPM <94%.
TD system in Start Limiting mode.
Maximum permitted TIT - 830oC.
Maximum ‘Take’ capability - 50%. (Fuel is taken [trimmed] if temp >830oC).
Electronic Fuel Correction light - ON.
TD control switch in AUTO:
Starting:
LSGI selected:
RPM <94%.
TD system in Start Limiting mode.
Maximum permitted TIT - 830oC.
Maximum ‘Take’ capability - 50%. (Fuel is taken [trimmed] if temp >830oC).
Electronic Fuel Correction light - ON.
T. D. System Operation - Start Limiting
TD system Operation 12

22. Start Limiting

23. T. D. System Operation - Normal Limiting
TD Control switch in AUTO:
Starting:
NGI selected:
RPM >94%.
TD system in Normal Limiting mode.
Maximum permitted TIT oC.
Maximum ‘Take’ capability - 20%. (Fuel is taken [trimmed] if temp >1077oC).
Electronic Fuel Correction light - ON.
TD control switch in AUTO:
Starting:
NGI selected:
RPM >94%.
TD system in Normal Limiting mode.
Maximum permitted TIT oC.
Maximum ‘Take’ capability - 20%. (Fuel is taken [trimmed] if temp >1077oC).
Electronic Fuel Correction light - ON.
T. D. System Operation - Normal Limiting
TD system Operation 13

24. Normal Limiting

25. TD Control switch in AUTO:
On Speed, >66o throttle:
crossover 820oC (+/- 20oC).
Temperature scheduled from 820oC to 1077oC between 66o and 90o throttle position.
Maximum ‘Take’ - 20%.
Maximum ‘Put’ - 15%.
Electronic Fuel Correction light - OUT.
TD control switch in AUTO:
On Speed, >66o throttle:
crossover 820oC (+/- 20oC).
Temperature scheduled from 820oC to oC (1067oC oC) between 66o and 90o throttle position.
Maximum ‘Take’ - 20%.
Maximum ‘Put’ - 15%.
Electronic Fuel Correction light - OUT.
T. D. System Operation
TD system Operation 15

26. T. D. System Operation - Controlling
TD Control switch in AUTO:
As the throttles are advanced through 66o (crossover), the TD system normally ‘cuts back’ the fuel to set 820oC (+/- 20oC). This is known as the crossover bump.
Between throttle settings of 66o & 90o , a specific temperature is scheduled. The TD valve will either ‘put’ or ‘take’ fuel to achieve the required temperature.
TD control switch in AUTO:
As the throttles are advanced through 66o (crossover), the TD system normally ‘cuts back’ the fuel to set 820oC (+/- 20oC). This is known as the crossover bump.
Between throttle settings of 66o & 90o, a specific temperature is scheduled. The TD valve will either ‘put’ or ‘take’ fuel to achieve the required temperature.
T. D. System Operation - Controlling
TD system Operation 16

27. Controlling (Sel Temp 820 - 1077°C)

28. TD Control switch in LOCKED:
The crossover ‘bump’ can be an inconvenience, especially during formation and tactical flying and also during take-off in very cold weather.
To overcome this, the TD valve is electronically locked in position and will alter the fuel hydro-mechanically with throttle selection.
The TD valves are normally locked in pairs, above crossover.
TD Control switch in LOCKED:
The crossover ‘bump’ can be an inconvenience, especially during formation and tactical flying and also during take-off in very cold weather.
To overcome this, the TD valve is electronically locked in position and will alter the fuel hydro-mechanically with throttle selection.
The TD valves are normally locked in pairs, above crossover.
T. D. System Operation
TD system Operation 20

29. T. D. System Operation 18O MAX TORQUE = 19600’’/LBS 66O 20000 1077oC
18000
16000
14000
12000 T O R Q U E
820oC
10000
8000
6000
4000
This slide and the next will explain the ‘Cross-over’ bump.
Crossover occurs at 66o throttle position. The TD system changes from Temperature Limiting to Temperature controlling. This change is effected by a micro-switch in the Co-ordinator /Discriminator.
2000
600oC 0O
10O
20O
30O
40O
50O
60O
70O
80O
90O
T. D. System Operation
THROTTLE
TD system Operation 18

30. T. D. System Operation 18O MAX TORQUE = 19600’’/LBS 66O 20000 1077oC
18000
16000
Torque, Fuel flow
and TIT reduce at
Crossover
14000
12000 T O R Q U E
820oC
10000
8000
Crossover
‘BUMP’
6000
4000
The TD system causes a temperature of 820oC +/- 20oC to be scheduled. Generally speaking the TD system will have to cut back the amount of fuel going to the burners to achieve the desired temperature. This cut-back can be seen on the TIT, torque and fuel flow gauges along with the Fuel Correction lights going out.
2000
600oC 0O
10O
20O
30O
40O
50O
60O
70O
80O
90O
T. D. System Operation
THROTTLE
TD system Operation 19

31. Locked In Correction

32. Overtemp Release

33. T. D. System Operation 18O 34O 66O 100% 94% 90% 80% 70% 60% R P M 50%C R O S V E
40% G R O U N D F L I G H T
30% I D L E I D L E
20%
This and the next 3 slides give a graphic representation of the operation of the TD system.
10% 0% 0O
10O
20O
30O
40O
50O
60O
70O
80O
90O
T. D. System Operation
THROTTLE
TD system Operation 25

34. T. D. System Operation 18O 34O 66O 100% 94% 90% GROUND IDLE 80% 70%
START
TEMP
LIMITING
MAX TEMP
830OC
MAX TAKE
50%
NO PUT
EFC
LIGHT ON
60% R P M
50% C R O S V E
40% G R O U N D F L I G H T
30% I D L E I D L E
20%
Ground Idle - Throttles in Ground Idle detent - RPM < 94%.
Start Temp limiting - 830oC.
Max take 50%, No put capability.
Electronic Fuel Correction light ON.
10% 0% 0O
10O
20O
30O
40O
50O
60O
70O
80O
90O
T. D. System Operation
THROTTLE
TD system Operation 26

35. T. D. System Operation 106% 18O 34O 66O 100% NGI 94% 90% GROUND IDLE
NORMAL
TEMPERATURE
LIMITING
UP TO 1077OC
OVERTEMP
PROTECTION
@ 1077OC
MAX TAKE
20%
NO PUT
CAPABILITY
EFC
LIGHT ON
80%
70%
START
TEMP
LIMITING
MAX TEMP
830OC
MAX TAKE
50%
NO PUT
EFC
LIGHT ON
60% R P M
50% C R O S V E
40% G R O U N D F L I G H T
30% I D L E I D L E
20%
NGI up to 66o throttle, RPM > 94%.
Normal Temp limiting oC (1067oC to 1083oC), Overtemp protection.
Max take 20%, No put capability.
Electronic Fuel Correction light ON.
10% 0% 0O
10O
20O
30O
40O
50O
60O
70O
80O
90O
T. D. System Operation
THROTTLE
TD system Operation 27

36. T. D. System Operation 106% 18O 34O 66O 100% NGI 94% 90% GROUND IDLE
NORMAL
TEMPERATURE
LIMITING
UP TO 1077OC
OVERTEMP
PROTECTION
@ 1077OC
MAX TAKE
20%
NO PUT
CAPABILITY
EFC
LIGHT ON
TEMPERATURE
CONTROLLING
820°C OC
SCHEDULED
AT 90O THROTTLE
MAX TAKE
20%
MAX PUT
+15%
NO OVERTEMP
PROTECTION
IN AUTO
EFC
LIGHT OUT
(UNLESS O’TEMP
IN LOCKED)
80%
70%
START
TEMP
LIMITING
MAX TEMP
830OC
MAX TAKE
50%
60% R P M
50% C R O S V E
40% G R O U N D F L I G H T
30% I D L E I D L E
20%
> 66o throttle, RPM 100%.
Temp Controlling - 820°C oC (1067oC to 1083oC) scheduled, NO Overtemp protection unless LOCKED has been selected.
Max take 20%, Max Put +15%.
Electronic Fuel Correction light OUT (unless O/Temp in LOCKED).
10% 0% 0O
10O
20O
30O
40O
50O
60O
70O
80O
90O
T. D. System Operation
THROTTLE
TD system Operation 28

37. TD Control switch in LOCKED:
The TD valve will only unlock if an over-temp occurs (>1077oC), or if ‘NULL’ or ‘AUTO’ is selected.
The Fuel Correction lights will remain in the state they were in when locked was selected.
If locked was selected above crossover, when an overtemp occurs the Fuel Correction light will come on to advise that controlling action has occurred.
TD Control switch in LOCKED:
The TD valve will only unlock if an over-temp occurs (>1077oC), or if ‘NULL’ or ‘AUTO’ is selected.
The Fuel Correction lights will remain in the state they were in when locked was selected.
If locked was selected above crossover, when an overtemp occurs the Fuel Correction light will come on to advise that controlling action has occurred.
T. D. System Operation
TD system Operation 21

38. TD Control switch in LOCKED:
If it is required to re-lock the TD valves, the throttles must be selected back above crossover with the TD switches in AUTO then LOCKED re-selected.
TD Control switch in LOCKED:
If it is required to re-lock the TD valves, the throttles must be selected back above crossover with the TD switches in AUTO then LOCKED re-selected.
T. D. System Operation
TD system Operation 22

39. ANY QUESTIONS?