Correct response - wrong circumstance
Warning: I'm non-professional; not crew, not engineer - just guest here, thanks.
In an earlier post I asked the following but no one has answered. Can anyone assist?
"An article on smartcockpit, written by an Airbus employee about Low Fuel Temperatures, has a table listing the Minimum Inlet Temperatures for engines from various manufacturers. RR has temp of 3C (This figure seems generalised for RR).
What happens next if the fuel heat exchange systems cannot raise the fuel temperature to, or above, 3C?"
I'm interested in the answer because:
1) as far as I have read, no one on the thread has explicitly discussed the systems designed to protect the engines in the event that fuel quality/quantity is below operating standard.
2) I also wonder if there has been a failure in applied logic, meaning, the aircraft systems did exactly what they were designed to do but under the wrong, or unforeseen, circumstances, namely in this case, about to land.
3) It's intriguing to me that some form of self-limiting system operated to reduce the engine speed to just above flight idle. Presumably (?) all of the ways in which an engine can be throttled back are fully known, that the actions are 'programmed' and follow some logic pathways developed during the design stage of the engines/aircraft. If so, the examination of the cause of incident would start by examining these logic pathways and associated systems. Of course, I'm assuming that an engine is never, under any circumstances, allowed to be un-controlled unless there has been some catastrophic failure.
And so, combining 1 to 3 above, and while reading about the 3C minimum fuel temperature, I wondered what the engines are designed to do under such circumstances. Leaving aside the provisions made for starting engines on the ground in freezing conditions, under what other conditions would designers have reasoned an aircraft’s fuel would be about to enter the engines below 3C and what should the engines do to protect themselves and the aircraft?
Could it be that the designers thought that those conditions are ‘only’ to be met at high altitude in very cold air, in which case, the best option is to command the engines to throttle back, to protect themselves, and force the aircraft to descend to warmer air?
But, suppose fuel below 3C was about to enter the engines on flight BA038 at very low altitude; what would the engines do?
You see my point – planned/designed response but wrong circumstances!
By the way, I’ve discussed the 3C temp. issue because that is what triggered my thoughts but you engineer types can probably think of other issues. But the issue must result in some system commanding a throttle back.
Okay, heading for bunker ….
Thanks in advance.
Regards, Tanimbar