Red X over oil pressure while engine not running

[edwalker]

I have a Rotax 912 ULS with the standard Skyview EMS settings. After initial avionics installation we noticed that oil pressure was all over the place and took it to a Rotax authorized service center. Their Dynon rep noticed that we had the wrong oil pressure transducer selected on the sensor map. Switched it over, and problem solved!

There are no issues around accuracy of pressure indication; however, I noticed that when the Skyview powers up (and before engine start) the oil pressure sensor has a red X over it, after which it functions normally. Interestingly, it is the only sensor that does this. The Dynon-trained tech said I should download the latest sensor config file, but that doesn't seem to have made any difference.

Any explanation on why this is so, and is there a fix?

 

[dynonsupport]

Which pressure transducer are you using? Generically, tou'll see that X when the sensor is reporting an off-scale condition that is far enough off that SkyView believes the sensor is missing. I don't believe that we've had any other complaints about that, so it could be the sensor. It could also be that we have the limits for that particular sensor a bit to intolerant of real world sensor values.

 

[dynonsupport]

Actually, you may have teased an old bug. If you're not running the latest SkyView version (3.3), update to it. Also update the sensor file (it sounds like you've done this already).

 

[edwalker]

Honeywell P/N:MLH010BGB06E  0-145 psi range

Running 3.3 with current sensor file.

This is a new aircraft by Phoenixair manufactured in the Czech Republic, so the engine originated in that area. We had the plane inspected by the Lockwood Aviation Rotax team at Sebring just before bringing it back to Seattle. They had not seen this sensor before, and it was different from the one they had in stock for replacements (mostly wiring connections). The sensor operation was validated by a direct pressure test, and it appears to have functioned well after we selected the proper sensor definition in the Dynon hardware setup menu. The red X is the only hint that something is possibly still not right.

If you search on this part number a lot of references show up for TL Electronics which makes the default EFIS for this plane. I requested the Skyview instead. I wonder if it is shipped with the sensor to accommodate the TL EFIS or if it's standard on Czech versions of the engine? It's listed on the websites as an "active" sensor if that makes a difference.

I have current copies of the exported dfg and sfg files from this week if that will help.

c37_p6={
valid=1
name=OIL
id=ROTAX OIL PRESSURE (HONEYWELL)
alarm_type=OFF
range={
max_display=110
min_display=0
range1_valid=1
range1_top=29
range1_bot=0
range1_name=R1
range1_color=RED
range2_valid=1
range2_top=73
range2_bot=29
range2_name=R2
range2_color=GREEN
range3_valid=1
range3_top=101
range3_bot=73
range3_name=R3
range3_color=YELLOW
range4_valid=1
range4_top=110
range4_bot=101
range4_name=R4
range4_color=RED
range5_valid=0
range5_top=99
range5_bot=95
range5_name=R5
range5_color

 

[dynonsupport]

That sounds like a sensor that outputs the same as the Honeywell, but isn't actually it. In that case, the voltage it outputs might be different than the "actual" sensor. When it's X'd, what do you see under SETUP MENU > EMS SETUP > SENSOR DEBUG DATA for that pin/sensor on each column?

 

[edwalker]

Sorry for the delay, had to go out to the plane to get the data.

For engine off, red X in place for Oil Pressure, the following readings were found on the sensor debug output:

C37 P6
Name: Oil
Sensor ID: Rotax Oil Press
Raw: 402
Cal (V): 0.4917
Value: nan

Sensor input mapping for C37 P6:
Rotax Oil Pressure (Honeywell)

I surmise that nan stands for "not a number", signaling some undefined state for the sensor. Does this have anything to do with active vs passive sensors? This particular Honeywell is listed as active.

Here are the specs if that helps:

http://sensing.honeywell.com/index.php?ci_id=51394

 

[dynonsupport]

If the guys at Lockwood didn't recognize the sensor, it's not the Honeywell oil pressure sensor that comes on the Rotax engine, and therefore the above characterization is NOT the right one for it.

NaN is what you can get when the voltage that's coming off the sensor is way off scale. For reference, the Honeywell sensor that is supported bottoms out at about .8V at 0PSI and runs to about 4V at 145 PSI when it's connected correctly.

 

[edwalker]

It is the sensor that comes standard on the Czech version of the engine as delivered to the airframe factory. Is what you're saying that the preselected sensor input map (Oil Pressure Honeywell) that was chosen should not be used? If so, which one should I select?

According to the spec sheets (see link above) this particular sensor ranges from 4 mA to 20 mA. Is that compatible with any of the sensor definitions?

 

[dynonsupport]

Not sure how to answer this, precisely. If it's the sensor that is Rotax P/N 956413, then yes, you select the Honeywell sensor definition. If it's any other sensor, even a different Honeywell one, then that characterization will not work. From your part number above, it does look like that's a 10 bar sensor, which is 145 psi, so it should be the right one. I don't have the Honeywell part number for the "official" sensor handy to check for you though.

On the connection side, make sure that the sensor is connected to pin 6, and that the red wire on that sensor is actually getting 12V.