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New instruments

 

I've done a little panel work on my tailwind the past few weeks
I've installed a GRT Mini II EFIS as a backup EFIS.? The Tailwind is now technically equipped for IFR (VOR/LOC/ILS).
It will take me a while to get current, and I'm not sure that I will yet, but the capability is there.
I've stumbled through the setup as there is no published documentation yet.? The two EFIS are coupled together so that most settings are shared between the units, but the air data and AHRS are independent.
I noticed on the initial flight that the indicated airspeeds are different between the units. Below 60mph they are identical and at 200mph they are about 5.5mph different.
The question then is which one is right?? I made a manometer based on an article by Jim Weir in Kitplanes and found that the new mini EFIS matches the theoretical, based on inches of H2O, very closely.? So it is my old EFIS that reads low at speed.? I'm asking GRT, but I don't think there is an adjustment to correct this, at least not accessible to the user.
Another issue I had was with the nav radio.? ?The MGL nav radio and Razor control head output SL-30 data to the EFIS with reversed VOR CDI deflection.? I notified MGL about this back in November and they have not issued a fix yet, so I programmed an Arduino Nano to intercept the serial data from the control head and correct it and send the corrected data to the EFIS.? This seems to work and I was even able to couple the VOR to the autopilot and fly a course with it.

PXL_20250316_035232856.jpg

 

Mike,
WOW!!? Very impressive!? ? I have a few questions/comments:
  • You mention that the air data and AHRS are independent for the two units.? What does that mean especially with the "air data"?? ?I am assuming the AHRS data is derived/displayed from the internal parts of each EFIS,? but for the pitot static data,? how is each unit "fed" that data?? Assuming you have each unit plumbed to a common pitot system and static line with some sort of a "wye" connector?? ?Or do you have them in series?? That is the line(s) come into one unit and then "T" off and go to the other?? I wouldn't think it would matter if the line was "split" some distance away from each unit or split "right on the unit".? There is no real "flow" of air so as long as there are no leaks in the fittings I would think that they should read the same.? ?I seem to recall there was some sort of setting on my GRT that had to do with airspeed although I don't remember where.
  • Does each unit read the same altitude?
  • Does your Operating Limitations document have the correct verbiage to include flying IFR as long as it is equipped with the proper instrumentation?? I don't remember the exact verbiage but when they did mine they accidentally left out the part that says that.? Mine just simply said something like "VFR day or night only".? ? When I called the FSDO they said it was an omission and they changed the OL to reflect that IFR flight was approved as long as the proper equipment was installed.? They actually issued a new Airworthiness Certificate along with the change in the OL.? Wasn't a big deal but glad I discovered it.
  • Do you have pitot heat?? If so,? how did you do it?
  • I am VERY impressed with your programming of an Arduino Nano to change the sensing.? Was the glideslope also reversed?
  • I see you have no steam gauges either.? ?I lost a little sleep originally because of all the "what if" scenarios (especially for airspeed) but glad I did it and haven't looked back.
  • Your panel looks nice and clean.? I see the one rectangular unit in the upper right.? ?Assuming that is an MGL something?? ?Is your com radio and transponder mounted remotely and controlled through the EFIS or does that rectangular unit do it all?
  • Get yourself a good CO detector? :)
  • It is no wonder your airplane is a major award winner!! Nice job.
Sorry for all the questions.? As an aside when you get to 200 MPH,? I would choose the display that is 5.5 MPH faster.? ?What the heck,? why not? :)? Sounds better.
Keith
 

That's a great looking layout Mike. These aircraft always have ramp appeal but you even wow the judges and bring home trophies! You are amazing ??
 

Hi Keith,

The two units are fed by a Y on the pitot and static just behind the panel.? I meant that the AHRS (gyros and accelerometers) and air data (altitude and airspeed sensors) are independent sensors in each unit. The challenge for me has been trying to determine what data is shared between the two EFIS over the data link and what is not.? The sensor data does not seem to be shared.? And GRT confirmed that the magnetometer data is not shared either.? I connected the magnetometer serial output to both units with a Y connection per their direction.? I had to calibrate the magnetometer independently in both units, but they agree very closely.? The altimeter calibration has both units agreeing very closely.? The IAS does not seem to be adjustable, but true airspeed can be calibrated.

My ops limits do allow for night and instrument flight, once properly equipped.

I do have a Piper blade-type heated pitot.

For the MGL nav, only the VOR is reversed.? The glide slope and localizer are correct.? This is probably because they use a stupid, intentionally backward CDI for the VOR on the control head display.? They use a moving airplane instead of a needle.? When the airplane is to the? right it means you are right of course.? With a traditional CDI when the needle is to the right it means you are left of course.? For me this is like trying to fly a localizer back course and is a poor human factors design, for someone who had learned on VORs? 48 years ago.?
As a side note, I decided to see what AI could do writing software.? Chat GPT wrote over 90% of the Arduino code for the converter (amazing, but scary).

I don't have any steam gauges, thus the backup EFIS..? The mini EFIS has an internal backup battery in case everything else goes dark.? The one thing that scares me is an overvoltage situation.? That could take out everything and for airplanes with electronic ignition, or fuel injection who knows what would happen.? I've done a lot to mitigate that possibility.? That might be worth a separate post.

The transponder, comm and nav radios are remote mounted.? The square unit in the upper right is the MGL Razor control head for the nav and comm.? The transponder is controlled by the EFIS.


I do have a handheld electronic CO detector, but I may need to replace it.

Thanks for the nice comments!

On Monday, March 24, 2025 at 07:01:36 AM CDT, Keith Klos via groups.io <kloskeith@...> wrote:


Mike,
WOW!!? Very impressive!? ? I have a few questions/comments:
  • You mention that the air data and AHRS are independent for the two units.? What does that mean especially with the "air data"?? ?I am assuming the AHRS data is derived/displayed from the internal parts of each EFIS,? but for the pitot static data,? how is each unit "fed" that data?? Assuming you have each unit plumbed to a common pitot system and static line with some sort of a "wye" connector?? ?Or do you have them in series?? That is the line(s) come into one unit and then "T" off and go to the other?? I wouldn't think it would matter if the line was "split" some distance away from each unit or split "right on the unit".? There is no real "flow" of air so as long as there are no leaks in the fittings I would think that they should read the same.? ?I seem to recall there was some sort of setting on my GRT that had to do with airspeed although I don't remember where.
  • Does each unit read the same altitude?
  • Does your Operating Limitations document have the correct verbiage to include flying IFR as long as it is equipped with the proper instrumentation?? I don't remember the exact verbiage but when they did mine they accidentally left out the part that says that.? Mine just simply said something like "VFR day or night only".? ? When I called the FSDO they said it was an omission and they changed the OL to reflect that IFR flight was approved as long as the proper equipment was installed.? They actually issued a new Airworthiness Certificate along with the change in the OL.? Wasn't a big deal but glad I discovered it.
  • Do you have pitot heat?? If so,? how did you do it?
  • I am VERY impressed with your programming of an Arduino Nano to change the sensing.? Was the glideslope also reversed?
  • I see you have no steam gauges either.? ?I lost a little sleep originally because of all the "what if" scenarios (especially for airspeed) but glad I did it and haven't looked back.
  • Your panel looks nice and clean.? I see the one rectangular unit in the upper right.? ?Assuming that is an MGL something?? ?Is your com radio and transponder mounted remotely and controlled through the EFIS or does that rectangular unit do it all?
  • Get yourself a good CO detector? :)
  • It is no wonder your airplane is a major award winner!! Nice job.
Sorry for all the questions.? As an aside when you get to 200 MPH,? I would choose the display that is 5.5 MPH faster.? ?What the heck,? why not? :)? Sounds better.
Keith
 

Mike,
Thanks for the answers.? You have a nice set up.? ?It is interesting about the MGL CDI.? ? I suppose they were trying to make it "more" intuitive for people that have never flown a VOR.? ? I wonder if when flying a back course, the little airplane stays on the correct side???
?
Have fun
Keith
?
?
 

BTW - GRT did respond.? They have added an indicated airspeed adjustment to their latest software.? I've attached the instructions they sent me.

On Tuesday, March 25, 2025 at 06:41:11 AM CDT, Keith Klos via groups.io <kloskeith@...> wrote:


Mike,
Thanks for the answers.? You have a nice set up.? ?It is interesting about the MGL CDI.? ? I suppose they were trying to make it "more" intuitive for people that have never flown a VOR.? ? I wonder if when flying a back course, the little airplane stays on the correct side???
?
Have fun
Keith
?
?

IAS Adjustment.pdf
IAS Adjustment.pdf

 

Mike and Keith,? all of this information is great and thank you for making it understandable.? Congratulations on the installation and the flying update with adjustments.??
Steven B
 

Building my panel also. Very nice! Might you post a straight-on photo of it? Would like to study it.
 

Kevin,
Not sure if you wanted a pic of mine or Mike's but here is mine.? GRT Sport EX EFIS in front of me.? Below that a GRT EIS.? In the center a Garmin 175 IFR navigator.? The EIS used to be there but I moved it below the EFIS so I would be able to more easily see the IFR navigator.? On the right is the Garmin GTR200 com radio with a King KT76A transponder below it.? Black box to the right of N number plaque is my CO detector.? Fuses rather than breakers except for the alternator field and main breaker.??
This layout works good for me now but could have been planned better.? ?When I first flew,? I had just an iPad mounted where the EFIS now is plus I didn't have the Garmin IFR navigator at that time.? ?I had to shift things around and was not able to make as efficient use of the space as I should have if I had planned ahead a little more.? The GRT autopilot servos are controled within the GRT EFIS so no extra stuff in the panel except for the switch.? The two black ports on either side of the switches in the middle are a twin USB port and the other is a 12 volt cigarette type outlet.? The USB port is pretty useless as I was too cheap and didn't by a good USB power supply.? It causes static in the radio.? When I need to charge something,? I have a pretty good portable USB charger that I plug into the 12 volt outlet.? Labels are just clear Dymo labels which have stood up better than I anticipated.? Not as nice as what Mike has but are not terrible either.
?
When I am flying,? I have 1/2 of the EFIS screen as? attitude/airspeed/altitude etc. and the other half shows the navigation map, weather and traffic.? ?For a bigger display for navigation/traffic and approach plates,? I have an iPad mounted via a suction cup mount on the left window just to the left of those red lights.? That is my primary visual reference for sectionals and traffic and weather info although it is shown also on 1/2 of the EFIS.? During an IFR approach it displays geo referenced approach plates.? The actual approach is flown via the IFR navigator which displays on the EFIS also.??
?
As an aside, note the two fresh air vents on each side and below the fuel tank.? I got them from Vans Aircraft for not a lot of money and they work really well.
?
Hope that helps
Keith

Keith_s Panel.jpg

 

Here is a straight on shot before I added the second EFIS.? I had the hole cut for it but put a cell phone mount and USB charger in it's place until I was ready to spend more $$.? I kind of miss the cell phone on the panel though.? I could pull up Avare with sectionals in addition to the map on the EFIS.?I bought a tablet to replace the cell phone, but I haven't found a good place to put it.? I try to keep it on my lap.
I reserved space below the N-number for a GPS-175, but I don't know if I will spend the money to add one.
BTW, the indicated airspeed adjustment that GRT provided works great.? The two EFIS read almost identical now.


On Monday, March 31, 2025 at 10:14:04 AM CDT, Kevin Southwick via groups.io <kevinsouthwick@...> wrote:


Building my panel also. Very nice! Might you post a straight-on photo of it? Would like to study it.

PXL_20230408_224904233.jpg
PXL_20250316_035214355.jpg

 

Thanks Mike and Keith for the photos!

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