Hi Francois,



How is the Mistral powered Piper coming? I am intensely curious about the strange oil cooling problem. Did they check the joint between oil pickup tube and
the oil pump? Also what is Peter (the test pilot) last

name at Embray Riddle? I would like to contact him directly and see if he wants to be on the newsletter.



Paul Lamar

François Badoux wrote:

Hi Paul,

We haven't opened up the engine yet as we wanted to do a few short flights to test the air side of the installation:  dP across the heat exchangers, so we
could fix things in parallel if needed.  This is now done and the results are excellent.  The engine will be removed and the oil pump checked next week while
we fully instrument the airplane (80 channels, 15 Hz) to gather a full set of flight data in the coming weeks.  I'll keep you informed.

Having said this, I checked how the oil pump was put together on the engine we are presently mounting on the bench here in Geneva.  Sure enough, it was
incorrectly put together.  As there are 32 possibilities to put the oil pump together, with only one correct according to Mazda's maintenance manual, chances
are that the oil pump on the Arrow is mounted incorrectly.  However, can someone tell me why Mazda puts those dots on the inner and outer rotors of the pump
and insists on having them aligned.  On first inspection, it does not seem to make a difference.  I think that the real problem happens if the intermediate
plate is mounted upside down, that would really screw up the flows.

There was no oil bypassing the cooler via the thermostat bypass in our oil gallery as we thought there might be.  The problem lies in the pump itself and in
an air leak either in the pickup tube or at the pump itself (we have to check the screw which holds the intermediate plate in place, if it's unsecured or
gone, then we don't have to look much further for our problem).  We also found out that the oil we were using has a tendency to foam, so we replaced it.
 Finally, our oil cooler is of the double-pass type with both lines at the bottom.  Its efficiency is therefore greatly diminished if it is only partially
filled, another thing to check.  Everything else looks in order, so we are pretty confident that the problem will be soon fixed.

Thanks for your time,

Francois

In the course of looking up the info on the oil pump I found some early flow data.
At 1000 RPM it is 5 liters a minute or 5.3 US quarts a minute.
or about 8 gallons per minute at 6000 RPM. This is a very early (1976) 13B so
perhaps later pumps pump more. Here is some stuff from the 13B Cosmo shop manual
on the pump.

You do need to line up the marks on the rotors with the marks on the housing.
Also the little screw holding the intermediate plate needs to be staked.

Here are some jpg's from the Cosmo manual. I'll send a copy of this to Peter.

Paul Lamar

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