The fuel metering unit has direct inputs via
- only the EEC
- the EEC and the fire control handle
- the EEC, fire control handle and the engine master switch
Explanation
The fuel metering unit receives its normal scheduling commands from the EEC, but for guaranteed shutoff it also has direct inputs from the engine fire control handle and the engine master (fuel) switch. These hardwired inputs let the crew cut fuel independently of the EEC, so all three feed the metering unit directly.
sasna asking:
EEC directly controls FMV, fire handle and master s/w is directly connected to SOV.
Community Comments (3)
D
dimky Posts: 514 12.08.2013 / 21:40
I'm not sure about what I'm writing in this comment but I'll try. :)
Here is short quote from cfm56-5a training manual:
The HMU has:
- two electrical connectors to ECU channels A and B
- an electrical connection between the shut-off solenoid and the A/C
So, fuel metering unit (in case of cfm56-5a it is called fuel metering valve, is inside HMU), is controlled not only by EEC (ECU). In different engines fuel system will have some differences so it is not easy to say definitely.
Absolutely not sure about that. I hope someone will explain more correctly.
Here is short quote from cfm56-5a training manual:
The HMU has:
- two electrical connectors to ECU channels A and B
- an electrical connection between the shut-off solenoid and the A/C
So, fuel metering unit (in case of cfm56-5a it is called fuel metering valve, is inside HMU), is controlled not only by EEC (ECU). In different engines fuel system will have some differences so it is not easy to say definitely.
Absolutely not sure about that. I hope someone will explain more correctly.
S
sasna Posts: 20 27.08.2013 / 22:16
since the que says FMU and not FMV, so the answer may be correct if SOV is a part of FMU.....FMV part of FMU is directly connected to EEC
R
rwm1273 Posts: 4 12.07.2016 / 07:05
This question is specific to a particular style of engine. Not all systems work this way. Many aircraft have a separate valve connected to the fire control handle, and not connected in any way to the EEC, fuel metering device (HMU,FCU), or master switch. P&W engines (both turboprop and turbofan) are often this way.
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