Vibration induced airlock?
Some years ago, a particular aircraft type with which I was involved, was experiencing false fuel indications. I observed research into this, which involved a transparent vessel of fuel being vibrated at various frequencies to represent vibration levels and frequencies seen in-flight.
When the vibration level was varied, it was possible to create what can only be described as a 'black hole', into which bubbles dissolved air from the surrounding fuel would head. Slight variation of the vibration level could make the 'black hole' move up or down in the fuel.
The supposition for our investigation was that if such a black hole occurred in a fuel probe stillwell, this could lead to a loss of signal and hence the erroneous level reading.
As I recall, the vibration levels in this case pretty well matched those seen when the aircraft throttled back from climb to cruise RPM, which tied in with the in-flight occurrences.
What I'm wondering is if a particular vibration level and rate of change could have caused a similar 'black hole' to occur near the fuel pick up point.
The fact that this event occurred on the final part of the flight, after the fuel had been 'degassed' of air in the cruise, would suggest not, and it seems highly improbable that it would occur in both wings at the same time, but if the system is symmetrical, who knows?
Last edited by Mechta; 9th Aug 2008 at 18:42.