Carl Pattinson wrote:
>For the record our original fuel flow tests (with the sender in situ )
exceeded the maximum flow required by over 100%. On the rotax 912, 25
litres per hour (maximum flow) equates to 416 millilitres per minute. From
memory our fuel system was delivering in excess of 1200 millilitres per
minute (72 litres per hour). This was with both pumps working (ie:
electrical and mechanical),
and shutting down the electrical pump made very little difference to the
readings. We have a fuel pressure sensor on the carb side of the flowmeter
and never experience low pressure readings (ie: below 4psi).<
It is easy to get 72 litres/hr but I would be very surprised if you can
do
it whilst delivering 4psi. The real test is what the electrical pump can
provide on its own with a failed mechanical pump as the valves in the
mechanical pump add a restriction of their own. With unrestricted flow I
managed between 80 and 90litres/hr. To maintain 2.25psi the flow dropped
to
about 40litres/hr with the Floscan. Paddy and I both have the 912S so we
used 30 litres/ hr as the max flow therefore needing a minimum of 36
litres/hr at 2.25psi to give the 20% safety margin stipulated by the PFA.
The Benwick sender with its small aperture (1/16" is pretty small) created
enough pressure drop to make the above figures impossible to achieve.
Removing the sender from the line restored the flow rate above that required
so it was the sensor limiting the flow rate. I already had the Floscan so
Paddy changed to that and was easily able to attain the required numbers.
I am sure you have had no problems but the real test would be whether you
would get full power during the climb or on a go around with the mechanical
pump failed. I hope you never have to find out especially with a 912 on
a
hot day. It may be that with the slightly lower fuel flow of the 912 you
might just achieve the required figures but there is no way I can see that
you will get 72 litres/hr whilst maintaining 2.25psi. If you can achieve
30
litres/hr at 2.25psi then it indicates that the Benwick sender would be
just
suitable for the 912 but not for any engines with higher fuel flow.
Tony Renshaw wrote:
>I know from my enquiries that it is near impossible to get a Floscan out
of
Floscan! The only suitable model is called a 264PB-15 and if you tell them
it is for a plane, forget it. So, don't tell them that, but it seems this
range is very limited and mostly sold to the likes of Blue Mountains, and
Rocky Mountains Instruments.<
I went direct to the company whilst in Seattle (3016 NE Blakely Street,
Seattle, WA 98105). They sold me one with no problems. I think it is either
a case of it depends who you talk to or, as you say, just let them think
you
are using it for a boat (which is their main market). By the way the sensor
reference recommended by Rocky Mountain Instruments is the 201 A type. The
reference numbers that came with mine were 201 A-6 & 201-031-00.
Nigel Charles
Broadband from an unbeatable 15.99!
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