AOA calibration and pitot static leak test
I am embarrassed to say that I have determined that the issues with my AOA were the result of my errors and not Garmin instruments or equipment. After spending multiple consultations with g3xperts and vansairforce builder supporters, I have located leaks in my pitot system which caused erroneous calibration information to the GSU25. I thought I had thoroughly tested every leg of the system and had secured or determined all legs were leak free. I still had leaks at the pitot probe. I read in the manual that the probe was allowed a certain amount of leaking but I was sure that had to be the culprit. As I removed the probe I thought I discovered a leak where I had allowed a flared aluminum fitting from the pitot probe to become loose where it connected to the flexible nylon tubing. I removed the probe and discovered leaks coming out of the epoxy filled area where the wiring and aluminum tubes exit the probe. I reinstalled the probe and made certain my flared fittings were secure. Fortunately, some of our experts (Walt and Steve, great guys) (which we are lucky to have on our forum), advised me that if a check of the complete system failed to hold airspeed constant or within the acceptable parameters, then I still had leaks. If I still had leaks, my AOA calibrations may not be accurate or valid.
I performed one last leak test with a manometer and by taping/securing the drain holes and AOA hole under the probe. I was surprised that even with the leaks that I found in the probe (videos available by email if desired), the airspeed held absolutely constant, indicating a leak free system.
The weather co-operated early in the AM with smooth air and I was able to calibrate all functions of the AOA. I still have to fine tune the settings and learn how the AOA will work best for me but it works. The heated GAP26 pitot/AOA probe and the GSU25 both operate correctly. I have learned a great deal about the G3X system and will be very aware of a technician that is testing my pitot-static and transponder on the bi-annual certification.
I am very thankful for the expertise, contributions and patience of our members to this forum.
HERE ARE A COUPLE OF SUGGESTIONS THAT I LEARNED IN THIS PROCESS .
BE CAREFUL WHEN PRESSURE TESTING. Read the manual to discover the cautions set forth before pressure or leak testing. I was afraid that I, or a technician not familiar with G3X or our experimental EFIS systems may have caused damage to my AOA sensor. I have had three calibrations and transponder bi annual test performed prior to installing a Touch system with AOA cababilities. I have learned that these are very sensitive. I also learned that the push to connect connectors can be very reliable. I purchased mine from SteinAir and a local company that sells Parker connectors (both stainless steel and quality plastic). None of my connectors leaked.
1. I constructed a very easy and cheap manometer using a ½'’ vinyl tube (lowes) after looking at the multiple post on this forum. I was not necessarily looking for precise measurement but changes which would occur from leaks.
2. I first disconnected my nylon tubing from instruments and tested each leg if the line had tees or connections to non instruments (GSUs and G5) to make sure all connections were leak free. It also helped me to make sure I was not over pressurizing so that when I connected legs with the instruments (GSU73 and GSU25) that I did not over pressurize.
3. When I determined that the all legs and connectors were leak free including all attachments to instruments, I reattached the tubing to each connector by cutting the end so that the nylon tubing at the connectors had a fresh end to be reconnected in the fitting. I previously had a two screen non touch and I replaced with single screen touch and added a G5 so the tubing had been removed and reinserted probably multiple times.
4. Be sure to tape/secure all drain holes or the hole under the pitot/AOA probe before any pressure is applied
This procedure is really not as hard as I had convinced myself that it would be.
Thanks also to g3xperts who have patiently helped me install, trouble shoot and configure all the garmin instruments.