chris mitchell
Well Known Member
Hi All,
I'd be grateful for thoughts on my recent Garmin G-5 installation in an RV-7. AS part of this work I took the opportunity to install a heated Garmin pitot and to re-plumb the entire dynamic and static system using the SafeAir/Dynon system of flexible tubing and connectors, and a new ASI (with appropriate speed marks for an RV-7 .
We flew an East-North-West-South course to calibrate the new ASI and plumbing with the ground speed taken from the Garmin 430. The results show that the calculated TAS taken from the ASI (corrected for altitude and temp) is within 1% of the ground speed, with the ASI slightly over-reading. So far so good. At least there are no pitot leaks!
However, the ASI and G-5 comparison is much less good.
The instruments agree at 110kts IAS, but at higher or lower speeds - 50kts up to 160 - the G-5 is reading up to 4 kts too low at both the higher and lower speeds.
Which to believe? Well the ASI agrees nicely with the ground speed calculations - so the G-5 is reading low.
I have read and re-read the installation procedure. Can't see anything to help. I did recheck the plumbing, looking for kinks etc but it all looked good. The G-5 is running on its internal GPS antenna - would that make a difference? I can't see that it would. Any other good ideas?
THe original reason for installing the G-5 was as an attitude indicator. I suppose the simple pressure driven ASI and Altimeter are highly unlikely to fail so maybe the easiest thing is to disable the ASI on the G-5, but having plumbed it I'm reluctant to do that. I'd much rather find the problem and fix it.
Many thanks
Chris
I'd be grateful for thoughts on my recent Garmin G-5 installation in an RV-7. AS part of this work I took the opportunity to install a heated Garmin pitot and to re-plumb the entire dynamic and static system using the SafeAir/Dynon system of flexible tubing and connectors, and a new ASI (with appropriate speed marks for an RV-7 .
We flew an East-North-West-South course to calibrate the new ASI and plumbing with the ground speed taken from the Garmin 430. The results show that the calculated TAS taken from the ASI (corrected for altitude and temp) is within 1% of the ground speed, with the ASI slightly over-reading. So far so good. At least there are no pitot leaks!
However, the ASI and G-5 comparison is much less good.
The instruments agree at 110kts IAS, but at higher or lower speeds - 50kts up to 160 - the G-5 is reading up to 4 kts too low at both the higher and lower speeds.
Which to believe? Well the ASI agrees nicely with the ground speed calculations - so the G-5 is reading low.
I have read and re-read the installation procedure. Can't see anything to help. I did recheck the plumbing, looking for kinks etc but it all looked good. The G-5 is running on its internal GPS antenna - would that make a difference? I can't see that it would. Any other good ideas?
THe original reason for installing the G-5 was as an attitude indicator. I suppose the simple pressure driven ASI and Altimeter are highly unlikely to fail so maybe the easiest thing is to disable the ASI on the G-5, but having plumbed it I'm reluctant to do that. I'd much rather find the problem and fix it.
Many thanks
Chris