Topics in Category: Model 550 Citation Bravo - Rotate.Aero Wed, 24 Jan 2018 09:56:47 +0000 MYOB /media/kunena/images/icons/rss.png Topics in Category: Model 550 Citation Bravo - Rotate.Aero en-gb ATA 79-31, Oil Temperature vs Resistance Chart (Garrett TFE731) - by: Mark Temp(C)---Ohms 090.38 2097.31 40104.60 60112.28 80120.36 100128.85 130142.40

If simulation is needed for troubleshooting, a decade box should be your weapon of choice. B)

Cessna 550 Bravo AMM 79-31-02-2
ATA 79 Oil Sun, 11 Jun 2017 21:58:32 +0000
ATA 79-31, Oil Pressure Indication (Garrett TFE731) - by: Mark
Engine left forward section. Oil Pressure Transmitter on the left and the Oil Differential Pressure Switch on the right.

From the maintenance manual I found a chart which showed how the indication was derived. I originally thought it was resistance based, but I discovered it's DC Voltage driven system.

From the chart:

0 --- 0.0
50 --- 1.0
100 --- 2.0
150 --- 3.0
200 --- 4.0
250 --- 5.0

Cessna described a test harness that could be built to simulate the voltages (From AMM revision 27, 79-30-00-1, Pages 1-2). From what I saw, their harness would not work at all. The four pins on the transmitter plug are "A" 28VDC, "B" Signal +, "C" Signal -, and "D" Ground. Their harness did not tie into pin "A" so how was a simulated voltage to be achieved???

They wanted you to connect into pins "B" and "C" only. Their drawing was similar to the one below.

With this set-up, you're only going to get a variable resistance. They called for a 500 ohm potentiometer. I have absolutely no idea what the switch is for.

Instead of all this Mickey Mouse crap, it looked like I could use a battery to simulate this voltage. All the indicator wanted to see was a positive and negative DC signal. I wasn't sure if it would work, but I gave it a shot anyway.

I had this on the indicator (1.5 VDC equalled approximately 75PSI)

This would of been a whole bunch easier with a variable DC power supply or a battery holder pack in which more batteries could be added in to increase the voltage.

I'm betting all Garrett 731's use the same system.

Model 550 Bravo AMM 79-31-01-2
AWM 77-10-01-01
ATA 79 Oil Fri, 09 Jun 2017 01:15:17 +0000
ATA 33, Panel Lights - by: Mark ]]> ATA 33 Lights Fri, 24 Feb 2017 00:37:47 +0000 Precipitation Static - by: Mark
We checked every static wick with a Meg-Ohm Meter and found one on the left elevator out of tolerance. Most likely not the problem , but at least worth checking.

We then started to look at panel bonding and straps. Those were checked visibly and with the milli-ohm feature of the meter linked above. Two items popped right out. The right gear door and the front right baggage door had broken straps.

Any poorly grounded panel will cause static. Hopefully the repair of these two straps will cure this aircraft's problems.

New terminal installed. Old broken terminal still attached (covered in paint).

ATA 23 Communication Fri, 02 Oct 2015 21:38:32 +0000