Originally Posted by
rhklenke
I did not think of it that way. When I read it, the phrase "closes with loss of power" implies a normally closed solenoid valve - a fuel pump does not "close" in the normal sense one thinks of "opening" and "closing".
You are right though in that the wording is ambiguous. I don't know what the intent was when the rule was originally written, but my guess is that, since most production turbine engines have (or have had, RAMs not withstanding), a fuel solenoid, that it was intended to require them, along with a manual valve.
For my part, I have never had a failure of a fuel solenoid, but in spite of myself, I quite often forget to check the manual shutoff before fueling, and I don't think that just a stopped fuel pump is enough to keep from flooding the engine during fueling - what with the high speed fueling pumps most of us use...
Bob
As one of the authors of the regulation I can say that the intent was for there to be a shutoff valve, just stopping the pump was discussed and ruled out.
You have to remember that at the time this was written JPXs where still flying (and may still be) and they had a servo operated shutoff valve, and most of the newer engines of the day had solenoid valves. So the regulation was written to allow these to operate and set a standard for future engines. The wording was left somewhat open to allow for new technology. Had the regulation said “solenoid valve”, if someone came up with, say a piezoelectric valve, it would not be compliant.
As to run away fuel pumps, I saw one at the Mississippi event many years ago. It resulted in a fire ball in the sky. There was no ECU operated shutoff valve, so the pilot could do nothing about it. This event is one of the contributors to the regulation.
Steven