Monthly Archives: April 2023

Magnetometer and AHARS Calibration

Tonight I worked to calibrate the magnetometer and the AHARS. It was rather windy when i got to the airport, and you need good GPS data to calibrate both, so i had to wait until the storms passed. First up was the AHARS calibration. This was pretty easy. Basically level the aircraft in flight attitude and let the G3x figure out pitch and roll offset. I also needed to do a vibration test on the AHARS once the engine was running. Next I did a magnetic interference test. Basically you start and turn off all the various electrical gizmos that could cause interference and manipulate the controls etc. You do this in 10 second increments. The magnetometer (which is in the left wing tip) passed the interference test.

I taxied to an open part of the airport and used my compass to ensure I was facing due north. I guess you can do the magnetometer calibration with the engine running and just taxi it. But I chose to shut down and just push the tail around. Basically all you have to do it rotate the plane 360 degrees and 30 degree segments. The display tells you what to do and when. Dirt simple. And I got a successful calibration.

Now with the aircraft warmed up, I taxied back to the hangar, tied her to my truck and did a full power run-up for the AHARS vibration test. This also passed. So now I have a fully tested and calibrated AHARS and magnetometer.  I also setup all the airspeed marking limitations tonight in the EFIS.


First Taxi Test & Brake Wear In

Tonight I set about taxiing for the first time! My goal was two fold. First, I wanted to taxi test that everything was working, and break in the brakes. Second, I wanted to use the taxi test as an engine warm up for a static run-up to adjust max RPM if required. Idle RPM is still not quite perfect either.

There’s not too much to note. The aircraft taxis like a dream. I’m by no means an experienced tailwheel pilot, but of the taildraggers I have taxied – this is the easiest and most maneuverable. It was definitely a wide grin moment for me!

For the brake check-in, I just ran the rpms a little high and periodically used the brakes to control speed.

The static run up wasn’t successful because I cannot get above 2400 RPM without the tail coming up, despite full nose up stick aft. I’ll probably just have to dial this in during flight testing.

OH, and I almost forgot. I also wanted to test that the cowling fit properly with the engine running and during the torque of starting. With the 200hp angle valve engine, the fit is TIGHT. Everything went perfectly!

Post first start corrections

After the first start, there were a few squawks we discovered. First, in the third startup we were not able to get the prop to cycle. Research after the fact showed folks reporting that a higher RPM is required to get the oil flowing on first start for the whirl wind props. 2000 – 2300 RPM were suggested. Tonight I set about testing that – sure enough it worked! The prop now cycles appropriately.

Amazingly I had not put a gasket under the magneto! Yikes! And I had two sitting on hand. So I had to remove the magneto, install a gasket, and retime. I did my best to mark the magneto position and lock the gear in place, but I still had to verify the timing. I got it spot on.

Also found the oil cooler scat tubing is rubbing on my oil dipstick. I put a couple solutions in place, but I fear neither are long term solutions. I will need a more secure method of holding it in place.

The baggage door lock had been problematic during first start. The latch came apart due to a fault bushing I had damaged carelessly closing the baggage door previously. So for first start up I had to tape the door shut. It was an easy fix tonight and the baggage door was good as new.

I also went over the plane with a fine tooth comb looking for any loose items or other fixes.