GI 275 Calibration

[flyboy0681]

I attempted to place the ADI through a heading calibration and when I pressed the Start button to proceed with the process, I keep getting the message "Invalid motion" and it won't countdown to the first move. No matter what I do or what heading I taxi into, it keeps giving me this error. Any ideas?

[StevenL757]

You may want to have someone familiar with the calibration process (like a shop tech) sit on your right while you maneuver the aircraft.  He or she can manipulate the instrument while you focus on maneuvering correctly.  It needs to be done on a level surface away from large metal buildings, and preferably on a calm-wind day.  Any adverse motion - save for the running engine - will give this error and won't allow the countdown to initially start.

I've done this procedure probably 5 or 6 times in 2 airplanes.  The turns should be slow, done at a consistent speed, yet stable-enough to stop the airplane on the headings warranted for the calibration to successfully complete.

[flyboy0681]

1 minute ago, StevenL757 said:

You may want to have someone familiar with the calibration process (like a shop tech) sit on your right while you maneuver the aircraft.  He or she can manipulate the instrument while you focus on maneuvering correctly.  It needs to be done on a level surface away from large metal buildings, and preferably on a calm-wind day.  Any adverse motion - save for the running engine - will give this error and won't allow the countdown to initially start.

I've done this procedure probably 5 or 6 times in 2 airplanes.  The turns should be slow, done at a consistent speed, yet stable-enough to stop the airplane on the headings warranted for the calibration to successfully complete.

That's just it, all of your suggestions were followed.

[StevenL757]

Understood.  The first data point on the 275's calibration procedure is always the most difficult to obtain - largely-due to the vibration of the engine.  Some airplanes exhibit this more than others, and the instrument is surprisingly very responsive to any vibration that it doesn't "like".  The good news is once that initial data point is captured, the rest of the process generally goes smoothly.  A few suggestions in addition to what you've tried...

• Shut the engine down and start it back up again.  Sounds crazy (like someone telling you to "just reboot your computer - it fixes everything"), but it may help allow the instrument to sense a smoother running engine.
• Not desirable at all and I don't ever recommend it, BUT - as a one-time fix - you could start the airplane with the avionics powered and then attempt the calibration process.
• This has been known to produce very good results, but if your methods tried so far + the above don't work, you would work with two other people to hand-tow the airplane through the range of headings required to calibrate properly.  You could do this with or without a power supply attached (probably ok if you have a small power supply and a long-enough extension cord) and can keep the airplane far-enough away from any large metal buildings (think massive hangars).  Without a power supply (battery power only), pull any breakers for equipment that doesn't need to be running, then turn on your Master (your GI275 should turn on with the Master switch on - it shouldn't be on the avionics master), and run through the calibration process that way.  You would be in the left seat, one person would be in the right seat manipulating the instrument and calling out the headings, and the third person will tow the airplane.  Obviously, make sure the mags are off and you have a long-enough tow bar to allow the person towing to remain clear of the prop.

Best of luck...hope some of this is helpful.

[carusoam]

Great detailed response Steven!

Thanks for sharing it all.

Best regards,

 -a-