On 31/07/2012 22:27, klinefelter.kevin@gmail.com wrote:
>
> Snip ....
/.....//I was chatting with Rob Seaton ( of Rotech in canada)//. He said
he learned how too small a fuel line and/or tortured routing can cause
"cavitation" at the pumps. So maybe your fuel filter(s), on the suction
side of the pump,are causing cavitation in the pump(s). Maybe due to the
size (restriction of flow) of the filter, even if they are clean./
/........//Snip/
Kevin, I think Rob Seaton may be on the money with this one.
A year or so back, I experienced a dead cut while flying a friend's 914
powered Europa on a hot day. Nifty application of fuel pump restored the
noise, but once safely back on the ground, I checked the filters (all
clean). This aircraft was fitted with Europa specified Purolator glass
shrouded filters that allow you to see the fuel flowing. At low RPM, the
filter appeared full, but as power was increased, the filter began to
fill with what I thought was air. My first action was to check the
pipework and security of connections - but everything seemed fine - it
was definitely not drawing in air from anywhere. I then concluded that I
had experienced vapour lock and left it at that.
Curiosity got the better of me and I started researching cavitation and
stumbled upon this very stilted, but interesting presentation on
Youtube. Take a look at the first minute from 00.20 - in particular, the
glass venturi. This was exactly what I saw in the Purolator filters.
http://www.youtube.com/watch?v=K_w3gcvA87I
My conclusion is that the Purolator filter has the correct mesh size to
trap contaminants, but the filter capacity is too small and creates a
pressure drop in the fuel line.
Nigel
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