Reference Line for Level Flight

[Snork]

We are fabricating the bracket for the Dynon AHRS, but having difficulty finding the reference for level flight in the BH4. The AHRS must be mounted so that it is close to level when the aircraft is in level flight. Anyone? Bueller? Thanks in advance!

[rodsmith]

I would think that it is the thrust line shown on page 1 of the plans. The lower longeron below the front doors is parallel to it.

[Snork]

Thanks, Rod!

[Pbruce]

You probably knew this, but the instrument can also adjusted for level at a selected pitch attitude if desired (I used cruise power and speed).

What is really critical is that the instrument MUST be mounted within a degree or two of the magnetometer level, or vice versa. (At least it was for my old D180- I assume a remote Dynon AHRS would be similar

). I found this out the hard way: bought a second hand RV and discovered that both the heading and attitude didn’t work. Sent it back to Dynon in the belief that it had once worked properly. Dynon said they fixed the unit, at a cost $750, but it still didn’t work. We noticed that it must be more than 2 degrees out relative to the magnetometer, and tried to correct that. It still didn’t work. It turned out that our iPhone level was the culprit. We shimmed it with a bubble level and it worked mostly (it still registered a bank when pure yaw was induced-I learned to live with that)

It could never have worked for the original builder. The guy could have saved me a lot of time and expense if he had just said so. Sigh. Maybe that’s why he had 3 GPS’s in the plane. I have no idea what Dynon fixed. They didn’t say. You are doing the right thing by insuring that everything is bang-on during the setup.

[robcaldwell]

I mounted my ADHRS under the pilot side front seat. Works great!