Originally Posted by sky9
1 If there is sign of cavitation in the pumps, I presume that it involves wear on the impellers. What happens to that wear or debris; does it travel downstream or is there a filter to capture it before it enters the cans?
Cavitation does not necessarily cause abrasion, it may in mild cases only "dent" the surface.
Having said that, there is a high-pressure filter specifically to prevent debris from the HP pump to enter the engine and damage it permanently. It also has no bypass: if the HP pump fails, the engine would not work anyway.
2 When the propeller on my boat cavitates the RPM increases but the boat goes nowhere; the prop effectively stalls. Does the same happen to the fuel pumps?
The HP pump is a gear-type pump, not impeller-type. If it cavitates, it will still work, although slightly less efficient, because the liquid with bubbles in it is now compressible, unlike the completely liquid fuel it normally pumps.
3 If temperature of fuel is an issue why hasn't anyone restricted the altitude or fuel temp of the 777 as a "safety first" prudent measure or are they looking for another incident to verify their research?
Fuel temperature is almost certainly not an issue here. There is no need for a general altitude restriction, because fuel temperature is monitored. Warning is given well above critical temperature. Countermeasures to keep the fuel from cooling further exist, such as increasing mach number (cruising speed) or descending to lower flight levels if and when necessary. Both measures increase fuel consumption.
There are fuel temperature limits, but just how far above the known freezing point would you consider "prudently safe"? Is 13 degrees C enough?
In this incident fuel temperature was still very far in the "safe" region. Freezing point according to spec would have been -47C or lower, actual freezing point was -57C, lowest recorded fuel temperature was -34C.
Bernd