New Panel Test Flight Questions...

[James Turner]

Hi All,

I have just completed the first couple of test flights with my new avionics suite:-

PA24-180 (sn 24-82)
Aspen PFD
JPI 930 EDM
GNS 480

I wish I could say everything was perfect from the outset however this is not the case. I'm hoping for some help...

1. After calibrating the Aspen as per the install manual everything looked great on the ground. All headings within 2.5 degrees and a good stable attitude. The flight test calls for a turn from East onto South (southern hemisphere) and again East onto North. They ask you to note the heading on roll out and then again after the heading stabilises. My headings varied by over 15 degrees which is double the allowable limit of 7 degrees. Also it was at this stage that I noticed that the wind was indicating ~80 kts when this was definitely not the case. The base map was also skewed by up to 30 degrees from what the GPS and the real world was indicating. Obviously something is wrong. Any ideas??

2. I always knew that cylinder #3 was the hottest but it is actually quite a bit hotter than the next hottest and limits me during climb out. I struggle to keep the CHT below 400 degrees on anything over ISA. Baffles are OK, not great but certainly passable. Any ideas on how I might reduce CHT #3 a little?

3. Lastly, I keep getting high fuel pressure warnings (over 6psi) with the electric fuel pump off (and on for that matter). It is either a faulty sensor or maybe the pressure is too high??

Sorry for all the questions but any and all help is appreciated.

Cheers,

James.

[Michael Rath]

James,

1. In dealing with the aspen, you need to get with the shop that installed it. Sounds like it needs some more work to make it right.

2. I just installed a JPI and all the information is overwhelming. CHT is mostly about baffling. Also, carberated engines are always going to have a bigger temp spread than injected engines. My 0-540 has a few cylinders that are running very close if not right up to 400. That is a little hot but is within limits. Rember, climbs below 5000' should be done full rich. I know if I try to lean in the climb below 5000' I will exceed the 400 limit I have set.

3. Is 6 psi a factory limit or a JPI set limit? You also might be able to adjust the JPI fuel pressure filter so it will take the spikes out of the data. I don't have the fuel pressure option but I know for the fuel flow option with a carberated engine you can adjust the filter so it evens out the data.

[Kory Kearney]

I thought about putting an aspen in mine, and in doing so talked to my local avionics guy. He told me the aspens are tricky in a comanche becasue the antenna is so incredibly picky about magentisim. He pointed out that the trim cables run past the magnet in the overhead speaker, and therefore carry a flux through the upper fuse. He aslo told me that any tools used to mount the antenna have to be de-magnitized, other wise anything magnetic near the antenna ruins it.

Needless to say I bought a standby vac system.

[James Turner]

Hi Kory,

That is what the problem turned out to be; magnetic interference from the trim cables. When we mounted the RSM (antenna) we carried out the magnetic interference test as per the IM but never thought to move the trim system through the whole range whilst conducting the test... The upshot was that the RSM calibrated perfectly on the ground but in flight (with the trim in a different position) was all over the place

Long story short; we moved the RSM to the starboard side just behind the beginning of the vertical fin extension; degaussed everything and it works fine. I should also say that I replaced the cabin speaker with a much smaller unit and will monitor the degaussing requirements over the next few months/years... The other option is to get a bottom mounted RSM; no backup GPS with that though...

Michael; the JPI issue is looking like dodgy pinning in the supplied JPI wiring harness. Even before the first test flight I had to have the power and grounds re-pinned to good quality gold pins just to get the thing to power up correctly. I'm now having to pull it all out and have all the other connectors re-pinned to try to solve the other issues like the fluctuating Fuel Pressure... Expensive, certified crap in my opinion but I do love it...

Regarding the #3 CHT. I can't help but think the 2in hole directly behind the #3 cylinder that serves as the intake for the Carb Heat manifold has something to do with the issue? I'd love to temporarily disconnect the SCAT tube, block up the hole as see if that helps??

Cheers,

James.