Da-20 Low Oil Temp High Oil Pressure.

[Slipzys]

Hey Guys got a questions that been stumping me for a while,

I'm working on my commercial cert right now and the flight school i fly out of uses da20s and 40s i fly the 20s for time building because its cheaper, but they have been doing some weird stuff recently and this is my first winter flying the DA-20s.

When starting the plane ill make sure to not use any rpm higher then 1000 until the engine oil temp is around 100 degrees. I then do my whole runup and everything is in the green oil temp and pressure. I start the take off roll and everything is still good but about 5-10 mins after once I'm at my cruise the oil temp is much lower then it was on the ground and the oil pressure is around 70-80 PSI. Which is freaky by itself I've never had this problem with these planes until it started to get colder out, but its still odd. I did my touch in go at an airport 50nm away and on the takeoff roll the oil pressure was red lining. I have no idea why this is happening and the flight school is acting like it is normal??? Again I am a newer pilot to da-20s and diamonds in general(fly c172s before) and I've never seen this happen with them. If anyone has any idea if this is safe as the flight school claims... anyone got an ideas?

[Steve]

Perhaps the flight school mechanics need to use a thinner weight oil in the winter, and/or partially block the oil cooler in the colder months...

[Rich]

AS with most (all) such engines the vernatherm acts like a thermostat for the oil. This excerpt from an AOPA article describes what might be your problem:

After a few minutes of operation, the Vernatherm valve senses warm oil temperatures and will seat, directing warm engine oil to the cooler. If the cooler hasn't been preheated, this warm oil will run into exceedingly viscous cold oil in the cooler. If it's really cold, the oil in the cooler will be congealed (solid)

Much more likely if your school is using straight-weight 100 oil. Just how cold is it?

[Rich]

The other possibility, of course, is the vernatherm is not functioning properly. I had a coolant thermostat in a motorcycle fail like this, resulting in a cold-running bike and substantially compromised fuel economy.

[Slipzys]

Thanks for the response,

Its not too cold at all its about 0 degrees C (32F)

I really want to say and hope that the flight school switched the oil to an oil that's better in the cold but im not sure. I just wanted to make sure that this wasn't some kind of operational problem on my part. I was assuming not, but still better be safe then sorry. Im going to hope that someone tries to fix it because super high oil pressure surely cant be good for the engine and ive been doing these flights at night so an engine failure would not be great

I also did this flight with 4 and a half quarts of oil which is above the amount needed but getting close to the lower side of it. Ive had the problem before and thought that more oil could just make the pressure more intense?

[Rich]

If you look at the POH for the DA20, 0 degC is below the minimum temperature recommended for the W100 (SAE 50) straight-weight. Depending on the biases of those doing your maintenance, they might be using W100 (cheaper) and not have bothered to change for the change of season. The higher oil pressure may or may not be a problem in itself, but it would tend to somewhat inhibit its flow to various internal parts and the numbers you're showing do exceed the limits depicted in the POH. You should check these out. The Continental in the DA20 shows to be more finicky than the DA40's Lycoming.

[Slipzys]

Yes its a very concerning topic. I do hope that something is done about the problem. I will be trying my best to push it on them to look into it.

Thank you very much for you help Rich.

[Kesk]

Are they using the 100W oil? This causes issues in winter as people have said. If it's an IO-240-B32B we run 15-W50 year round.

Are you using any assortment of the plates for the cowlings? Only one set should be installed i.e. inlet baffle plates or the bottom ones near the drain lines

[Spinner]

As Kesk mentions there are baffles for the engine cowlings both inlet and outlet. Service Bulletin No.: DACi-71-03 Rev 0 talks about the installation of baffles.

http://support.diamond-air.at/techpubs+ ... 73ab0.html

The SB says:

A new winterization kit has been developed, consisting of the existing
winterization kit cowling outlet blocks plus new cowling inlet blocks.
This kit improves engine operating temperatures at low outside air
temperatures. Below 32"F (O"C) the inlet and outlet blocks may be
used together. Between 32"F (O"C) and 54"F (12.5"C) either the inlet
or outlet blocks may be used. Above 54"F (12.5"C) both blocks must
be removed.

I have found the temps a little high we usually remove all baffles when the temperature hits 0 Celsius and temps stay fairly normal.