120 GI275/Ipad Panel Upgrade
Posted: Tue Oct 15, 2024 10:27 am
After about 500 hours of mostly xc flying in four years, I had plenty of time to contemplate my dream panel for my 120.
The first couple hundred I kept it old school with paper charts and my compass. No gps or vor installed in Ava. After a while though I decided I'd proved to myself I could do it and began using the Avare app on my phone to simplify my life.
A couple years ago I was flying alongside my cousin in his Luscombe 8E, and I was outrunning him! Curious, I always thought the Luscombes were faster. My cousins opinion was that my tachometer was off. I privately thought he might be right.
At last years annual, it was confirmed. It was about 100rpm low in the cruise range. Also I was starting to see drips of oil coming from the tach case. The original instrument from 1947 had served well.
Now, there are much more economical ways to address this issue. I'm sure there are good shops who could overhaul the tach and return it to its original glory, keeping the panel original and pure.
However the culmination of my daydreaming about the future panel settled on a digital engine instrument/monitor and an iPad for navigation. I had done some preliminary work and thought it all would just fit.
My friend Rafael at Air Plains in Wellington KS is a Garmin dealer and they've been doing a lot of avionics work lately, so I had great help available. The plane already has a Garmin comm and transponder. Rafael took measurements of the old panel and worked in CAD to develop a new one.
I decided to go with the Garmin 275 EIS and use the Guardian Avionics ipad mini dock. The fit is *tight*. The top of the 275 is just below the u channel on the underside of the dash. I actually had to cut away one corner of the ipad dock to avoid interference with the fixed panel cutout. We first made a wood test panel to make sure it would all fit.
I decided it would be good experience for me to make my own wiring harness. Besides the minimum required oil temp and pressure sensors I also added spark plug gasket CHT proves, EGT, carb temp, and fuel flow.
The oil temp probe is hard wired, which would mean that each oil change would require twisting the wires to check the screen. Therefore I added the TAFL spin on oil filter adapter and removed the screen. Oil pressure sensor mounted to the firewall with the original pressure line re-routed and adapted into it.
I had to manufacture new flexible fuel lines and route them for the fuel flow. I used a PMA bracket for the 172 that Dynon makes to mount the meter on one of the engine mount tubes.
EGT and CHT was straight forward although I had one time consuming side track with CHT. Somehow somewhere I came under the impression that the fuel injection ports on the cylinder could be used for cht probes. It also just so happens that the threads on those ports match the standard spring loaded probes! It wasn't until I was installing them that I realized there was no way this would be accurate, so I fell back to spark plug probes.
I spent a lot of time routing wires and tidying things up the best I could. It turned out pretty good especially firewall forward.
The probes feed data into the Garmin GEA24 brain box which then communicates with the 275. Rafael made a really nice bracket to mount the GEA24 on the firewall above the copilot rudder pedals. All the wires came through the same holes that oil pressure and tach cable used. There are 4 connectors on the 24, one of which is output to the 275. There is also a connection from the 275 to the Garmin USB port I already had installed for software updates.
I borrowed crimp tools and nice wire strippers from a few hangar neighbors and built up as much of the wiring harness on my bench as I could. The install manual is comprehensive but took some time. Then I finished up connecting to the sensor wiring already on the plane.
What I thought would take one hard day of work took five to do all the under panel wiring and routing etc. My back really appreciated day 6 when I didn't have to lay upside down under the panel anymore!
Power is provided to the GEA24 and 275 separately. I had to add 2 breakers. The old Ammeter is replaced with a Garmin shunt that mounted behind the fixed panel, just left of the copilot yoke. I had some mixup on connector locations for the shunt sensor wires (batt amps vs generator amps) and i had to swap all the cht pins. The Garmin wiring diagram didn't include the Alcor spark plug cht probe I used and it wasn't clear to me which color was hi vs lo. I guessed and was wrong, so when testing the probes with a heat gun, the indicated temp went down, not up. Oops!
The only other gremlin was i had to redo the thread sealant on the oil pressure sensor.
As part of this project, I moved the compass up onto the dash. Half of a day was spent re-routing the wiring for the nulite ring lights on the remaining instruments.
The Guardian dock has built in charging ability with a cord that plugs into the USB port i already had. It also has a cooling fan incorporated.
As I put it all together I realized a major mistake! On the test wooden panel I had only checked the fit of the 275 and ipad dock, and hadn't installed the other instruments. Well my old VSI had its adjustment screw and bump at the 6 o'clock position and interfered with the dock! I scrambled around the airport and traded for a newer vsi with the bump in the 730 position. Whew.
The ipad with Garmin pilot will bluetooth to the 275 to provide real time graph readout of the engine parameters which has already proved useful in diagnosing a stuck valve. I also discovered that the Delco GCU wasn't working properly and I was getting nearly 16 volts output at cruise. A new Zeftronics GCU now has the system properly regulated.
Post install testing with all the electronics on, including led beacon and nav lights, show a total system draw of 7 amps. My Concorde 35 amp-hr battery and 30 amp generator are more than adequate!
I really like the look of the finished product and have enjoyed about 15 hrs with it so far.
The weight change ended up being a gain of about 4 lbs. The 275 offset the weight of the removed engine instruments and Hobbs meter closely. Adding the engine sensors and especially the oil filter led to the weight gain. The next projects will focus on weight and drag reduction!
The first couple hundred I kept it old school with paper charts and my compass. No gps or vor installed in Ava. After a while though I decided I'd proved to myself I could do it and began using the Avare app on my phone to simplify my life.
A couple years ago I was flying alongside my cousin in his Luscombe 8E, and I was outrunning him! Curious, I always thought the Luscombes were faster. My cousins opinion was that my tachometer was off. I privately thought he might be right.
At last years annual, it was confirmed. It was about 100rpm low in the cruise range. Also I was starting to see drips of oil coming from the tach case. The original instrument from 1947 had served well.
Now, there are much more economical ways to address this issue. I'm sure there are good shops who could overhaul the tach and return it to its original glory, keeping the panel original and pure.
However the culmination of my daydreaming about the future panel settled on a digital engine instrument/monitor and an iPad for navigation. I had done some preliminary work and thought it all would just fit.
My friend Rafael at Air Plains in Wellington KS is a Garmin dealer and they've been doing a lot of avionics work lately, so I had great help available. The plane already has a Garmin comm and transponder. Rafael took measurements of the old panel and worked in CAD to develop a new one.
I decided to go with the Garmin 275 EIS and use the Guardian Avionics ipad mini dock. The fit is *tight*. The top of the 275 is just below the u channel on the underside of the dash. I actually had to cut away one corner of the ipad dock to avoid interference with the fixed panel cutout. We first made a wood test panel to make sure it would all fit.
I decided it would be good experience for me to make my own wiring harness. Besides the minimum required oil temp and pressure sensors I also added spark plug gasket CHT proves, EGT, carb temp, and fuel flow.
The oil temp probe is hard wired, which would mean that each oil change would require twisting the wires to check the screen. Therefore I added the TAFL spin on oil filter adapter and removed the screen. Oil pressure sensor mounted to the firewall with the original pressure line re-routed and adapted into it.
I had to manufacture new flexible fuel lines and route them for the fuel flow. I used a PMA bracket for the 172 that Dynon makes to mount the meter on one of the engine mount tubes.
EGT and CHT was straight forward although I had one time consuming side track with CHT. Somehow somewhere I came under the impression that the fuel injection ports on the cylinder could be used for cht probes. It also just so happens that the threads on those ports match the standard spring loaded probes! It wasn't until I was installing them that I realized there was no way this would be accurate, so I fell back to spark plug probes.
I spent a lot of time routing wires and tidying things up the best I could. It turned out pretty good especially firewall forward.
The probes feed data into the Garmin GEA24 brain box which then communicates with the 275. Rafael made a really nice bracket to mount the GEA24 on the firewall above the copilot rudder pedals. All the wires came through the same holes that oil pressure and tach cable used. There are 4 connectors on the 24, one of which is output to the 275. There is also a connection from the 275 to the Garmin USB port I already had installed for software updates.
I borrowed crimp tools and nice wire strippers from a few hangar neighbors and built up as much of the wiring harness on my bench as I could. The install manual is comprehensive but took some time. Then I finished up connecting to the sensor wiring already on the plane.
What I thought would take one hard day of work took five to do all the under panel wiring and routing etc. My back really appreciated day 6 when I didn't have to lay upside down under the panel anymore!
Power is provided to the GEA24 and 275 separately. I had to add 2 breakers. The old Ammeter is replaced with a Garmin shunt that mounted behind the fixed panel, just left of the copilot yoke. I had some mixup on connector locations for the shunt sensor wires (batt amps vs generator amps) and i had to swap all the cht pins. The Garmin wiring diagram didn't include the Alcor spark plug cht probe I used and it wasn't clear to me which color was hi vs lo. I guessed and was wrong, so when testing the probes with a heat gun, the indicated temp went down, not up. Oops!
The only other gremlin was i had to redo the thread sealant on the oil pressure sensor.
As part of this project, I moved the compass up onto the dash. Half of a day was spent re-routing the wiring for the nulite ring lights on the remaining instruments.
The Guardian dock has built in charging ability with a cord that plugs into the USB port i already had. It also has a cooling fan incorporated.
As I put it all together I realized a major mistake! On the test wooden panel I had only checked the fit of the 275 and ipad dock, and hadn't installed the other instruments. Well my old VSI had its adjustment screw and bump at the 6 o'clock position and interfered with the dock! I scrambled around the airport and traded for a newer vsi with the bump in the 730 position. Whew.
The ipad with Garmin pilot will bluetooth to the 275 to provide real time graph readout of the engine parameters which has already proved useful in diagnosing a stuck valve. I also discovered that the Delco GCU wasn't working properly and I was getting nearly 16 volts output at cruise. A new Zeftronics GCU now has the system properly regulated.
Post install testing with all the electronics on, including led beacon and nav lights, show a total system draw of 7 amps. My Concorde 35 amp-hr battery and 30 amp generator are more than adequate!
I really like the look of the finished product and have enjoyed about 15 hrs with it so far.
The weight change ended up being a gain of about 4 lbs. The 275 offset the weight of the removed engine instruments and Hobbs meter closely. Adding the engine sensors and especially the oil filter led to the weight gain. The next projects will focus on weight and drag reduction!
