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Troubleshooting a mag heading error

April 9, 2010 1 comment

The weather in Albuquerque has really been all over the place this winter and spring. We have been having a lot of winds blowing and several storms coming through. Between the storms I got the chance to take my airplane up to Santa Fe Aero to have all of the last squawks cleared. They went through all of them and before I knew it the airplane was ready. I arrived to pick up the airplane to fly back to Double Eagle. Everything was working well except for a few intermittent cross check attitude messages that continued to arise from time to time. The attitude solution was always good when compared to the MFD and mechanical back-up on my aircraft. (yes, I do have triple redundancy on my airplane!)

I decided that I would use my airplane as a test bed for trying to figure out what these pesky messages were all about. We made several flights to take some data and decided that we would replace the RSM and recalibrate the headings to see if we had an RSM that might be close to the limits. In the Aspen AHRS solution the magnetic heading information is used by the filtering routines that determine the attitude, and therefore if there are inaccurate or inconsistent headings from the RSM, this could affect the solution enough to trigger a message. The really nice thing about the Aspen system is that it provides this indication to assure the pilot that they have the necessary indications to crosscheck attitude when it detects anything that isn’t expected from the sensors. So, one early morning our A&P mechanic came out and made the necessary modifications and we headed out to the tarmac for a compass swing to re-calibrate the headings.

As I am sure many of you know and that I have mentioned in previous postings of this blog, the magnetometer technology is very dependent on adjacent magnetic structures of equipment in the airplane and how accurate the compass swing is. All in all this was a very interesting experience as it gave my a lot of insight into what the dealers perform when they install an Aspen system. After this was done we went up for a flight test. We did not see any cross check attitude messages and the system worked flawlessly. I have since taken the airplane up on several other flights and everything has been nothing short of perfect. This includes first flight for our welsh corgi dog to see how she handled being in an airplane, which she did very well!

I have decided that I will take my airplane to Sun-n-Fun to experience a long cross country with the Aspen System. I just recently finished instrument ground school and will also take the chance to get some simulated instrument flying. I will be taking a CFII with me so the trip besides being a lot of fun will also be instructional. We plan on leaving on Sunday and arriving in Lakeland on Monday. We will be parking at the Aspen GA parking area and I invite all of you to come by and see the airplane. I will be spending as much time out there as possible so I also look forward to meeting with other pilots and answer any questions regarding Aspen or my experiences. I look forward to seeing you there.

Categories: Post installation

Clearing the squawks (part 2)

March 24, 2010 2 comments

Pat brought along his technician and adjusted the throttle quadrant. We went up for a flight and confirmed the throttle was fixed. We also confirmed the intermittent crosscheck attitude on the PFD. The MFD worked perfectly. We spent some time checking the data between attitude and heading between the PFD and MFD. During the crosscheck attitude on the PFD the data matched very close so whatever was causing the display of the message was intermittent in nature and minor. We also checked out the TAS and it appeared that the TAS was not picking up all of the targets.

After landing we discussed the installation. The only thing we could think off was that the PFD RSM, which is installed on the top of the fuselage, was installed using stainless steel crews. The installation allows for the use of stainless steel screws but Aspen provides brass screws. Since my installation had a large shim installed due to the curvature of the fuselage, the brass screws provided did not fit (see this post for picture of shim). It was possible that the stainless steel screws became magnetized and could be affecting the magnetometer. Pat agreed to replace them with brass. In addition we decided to return the TAS and replace as it appeared the interrogator was not working well. We both agreed that the best place to do this was in Santa Fe and I agreed to bring the airplane back up as soon as possible.

In the meantime with the throttle quadrant fixed and the crosscheck attitude only intermittent and only on the PFD I decided that since I have the EFD1000 MFD which provides me full redundancy of AHRS I would take the airplane up to the practice area over the next couple of days to become more familiar with the system. The weather in Albuquerque was going to be great over the next several days.

Categories: Flying, Post installation

Clearing the squawks (part 1)

March 24, 2010 Leave a comment

After landing at Double Eagle following my flights, I contacted Pat at Santa Fe Aero to discuss what we had seen. I really did not have a lot of squawks for an initial flight so I was pretty pleased. We discussed the crosscheck attitude, heading lead lags as well as some issues with the interface between the TAS and the Aspen MFD. I also had some issues with the idle setting on my throttle quadrant being too high. This incidentally creates an interesting situation because the DA 40 with its long wings tends to float down the runway on landing if I flare at too high a speed. I have found it necessary to really concentrate on flying the airplane down to the ground and not relaxing until the mains and the nose are down more so than I had experienced when flying a high wing airplane. The extra speed produced by the higher than normal idle setting made it even more challenging. While it was an easy landing I did learn some good things about landing hot!

In any case Pat agreed to come down to Double Eagle and work the throttle quadrant and to fly with me to investigate the cross check attitude, heading and TAS issues. I thought this was a pretty big deal and was a bit unexpected. Just another example of the strong customer focus the people have up at Santa Fe Aero! The following day Pat flew down the Santa Fe Aero Navion B, which by the way is equipped with a beautiful two tube Aspen system in it. The aircraft is a beautiful airplane as you can see by the picture below. Santa Fe Aero does excellent work as you can see from the picture of the cockpit!

Navion Panel with dual Aspen displays

Santa Fe Aero's Navion

Categories: Flying, Post installation