Thanks to all who responded to my e-mail
for help.
Several people said that the VDO pressure
tranducer that comes on the engine is not
reliable, so we replaced it with a high
quality transducer mounted to the firewall.
The right angle molded into the hose just
before the pump inlet seemed a little soft,
right at the bend, suggesting the possibility
that the inlet hose might have been collapsing.
We wrapped safety wire around it to reinforce it
at the bend.
Now the oil pressure does not fluctuate
and never drops below 40 psi (when above
2000 rpm).
We are currently smoothing the cooling duct
inlet to help cooling , as suggested by Kim Prout,
and have cleaned up the duct exit area as
suggested by Bob Jacobsen.
We did some high speed taxi testing over the
weekend, and feel pretty comfortable with the
ground handling now. First flight may be only
days away at this point.
We hope to get our 40 hours flown off in time
to get up to the Arlington, Washington, Fly-In
next month.
Terry Seaver
A135, N135TD
>
> ----- Original Message -----
> From: Terry Seaver <terrys@cisco.com>
> Subject: Oil pressure fluctuations
>
> > Hi gang,
> >
> > We have been taxi testing our Rotax
> > 912S the past few weeks. Several times
> > the oil pressure would start out fine,
> > and after a few minutes would start
> > dropping, fluctuating between 10 and
> > 30 psi. (dropping to 0 for a few seconds
> > on one occasion). We thought it might
> > be a bad transducer, but had the same
> > problem after replacing it. We see the
> > same fluctuations with an ohm meter
> > attached to the transducer, so it is
> > not a problem with the instrument
> > or wiring.
> >
> > Has anyone else had problems like
> > this? Could be a collapsed inlet hose,
> > or a problem with the pressure relief
> > valve, or two bad transducers in a
> > row, or ?.
> >
> > On another note, on a cool day
> > (about 70 F) the water temp gets
> > up to 220 deg F after about ten
> > minutes of taxi. Is this typical for
> > an XS with a 912S? (The oil temp
> > was about 190-200 deg F).
> >
> > BTW, we got our FAA sign-off
> > yesterday. As soon as we get the
> > oil pressure problem fixed the plane
> > is ready for first flight. The pilot, on
> > the other hand, is not quite so ready.
> >
> > Terry Seaver
> > A135 / N135TD
> >
> >
|